All in One Solar Street Lights: The Ultimate Guide (Updated in 2023)

All in one solar street lights installed in the remote countryside

All in one solar street lights installed in the remote countryside

Are you looking for a solar-energy-based illuminating solution for either your own courtyards or some public sites, such as playgrounds, pathways, parking lots, plazas, etc?

Or, you are upset about the short autonomy of your current solar street lights with traditional technology, which, sometimes, especially during monsoon, have to subsist on the national electricity grid?

(some hybrid solar street lights systems are grid-tied systems, they are designed to connect to the national electricity grid. When their own battery bank runs out of power, they will switch to the electricity grid.)

However, things can be worse.

Your projects could be located in some remote rural areas or isolated islands, where no electricity can reach. How can your solar-powered street lights survive a spell of raining weather?

You may say we should increase the size of both battery bank and solar panels. Well, this sounds plausible in engineering respect, but when it comes to the project budget, this also means the raising of outlay significantly since the cost of battery accounts for a larger part.

Then, why not adopt the ones with advanced technology, all in one solar street lights.

Without further ado, let’s dive right in:

Chapter 1. What is all in one solar street lights?

All in one solar street lights are one type of integrated solar street lights, which integrates into a product the four main components: solar panel, light source, battery, solar energy cables, and solar controller.

Now let’s go through the details of each module one by one

30w explosion drawing

30w explosion drawing

The major modules

# Monocrystalline Solar Panel

Monocrystalline and polycrystalline solar panels are two different solar panels which are widely applied in the solar industry.

Generally speaking, monocrystalline performs better than polycrystalline, especially in cold weather they have higher energy conversion rates than polycrystalline. To data, Sunpower monocrystalline solar panel can reach as much as 24.1% conversion rates.

So, Monocrystalline panels are installed in all in one solar street lights due to its limited size.

These solar panels act as the role of energy collecting and conversion, in the daytime, they collect energy from the sun and then convert them into electric power which will be stored in batteries as chemical energy.

# LED Light source

Suffice it to say, as light sources LEDs are prevailing among illuminating market, for its high performance in energy-saving. It definitely can be counted as a new generation of lighting solution.

LED types vary in size and watts, such as 3528, 3030, 5050, 5630, to adapt to different applications.

Our S2 series integrated solar street lights is with Philips LUXEON 3030 SMD, which has almost 190 lumens per watt. A LED module is formed by these single 3030 SMDs which are soldered to an aluminum substrate in advance.

4 pieces of LED modules in 60w all in one solar street lights

4 pieces of LED modules in 60w all in one solar street lights

Furthermore, an aluminum heatsink is always applied to the rear side of the led modules to help dissipate the heat generated by LEDs. This is very important, for although manufacturers claim that LED has a lifespan of more than 50,000 hours, its light depreciation can be abnormally high if it is working in a temperature larger than 70 Celsius. So we must make sure that the LED junction temperature is under 70 Celsius.

# Lithium-ion Battery

Rather than car batteries, which are designed to discharge a large amount of energy in a short period of time, renewable energy industries prefer deep-cycle batteries, for their excellent characteristics in the enduring power supply, deep discharges and far more cycle times, 3000 times, twice or three times more than that of car batteries.

Batteries cycle times is also affected by the depth of discharge(DoD), we will talk more in Chapter 5.

There are two main types of deep-cycle batteries existed in the solar battery market: lead acid and lithium.

Why do all in one solar street lights use lithium-ion battery?

5 reasons:

  1. Flooded lead-acid batteries require maintenance, say, equalization
  2. Although sealed lead acid batteries are maintenance free, they are pretty expensive than flooded ones
  3. Both two types of lead-acid batteries occupy too much space to be set up in all in one solar street lights, which is compact design and with small spaces inside.
  4. Lithium batteries have longer lifespan than lead-acid batteries, six times the number of cycles compared to a lead-acid
  5. Lithium is capable of surviving irregular discharging and maintenance free.

However, manufacturers often use two types of lithium-ion battery

  • ternary lithium battery, 18650
  • lithium iron phosphate (LiFePO4) battery, 26650

Difference between them?

Part Number Typical voltage The typical voltage of battery package price Working temperature Declared cycle times
Ternary lithium battery 18 65 18650 3.7v 11.1v cheaper -30 to 65 Celsius 1500 times
LiFePO4 lithium battery 26 65 26650 3.2v 12.8v almost twice the price of 18650 -10 to 75 Celsius 1200 times
Lithium Iron Phosphate (LiFePO4) Battery (LEFT) VS Ternary Lithium Battery (RIGHT)

Lithium Iron Phosphate (LiFePO4) Battery (LEFT) VS Ternary Lithium Battery (RIGHT)

What kind of lithium-ion battery should I use in my projects?

What we have learned, from the comparison table above, is that LiFePO4 battery is more expensive, but its chemical substance inside is more stable, which makes it kind of high-temperature resistance, while ternary lithium battery is relatively low-temperature resistance, for its materials are more active and can work under 0 Celsius.

So, if your project is in the tropics, LiFePO4 battery is recommended. But if the project is in northern countries, we advise ternary lithium battery.

# MPPT Solar Charge Controller

There are 2 types of controller: PWM and MPPT in the market.

All in one solar led street lights adopts MPPT, for, in this case, PWM will waste some energy collected by panels, while MPPT can convert all the solar energy collected into chemical energy

As the main functional component, MPPT solar charge controllers have some basic functions as below

1. Dusk to dawn control

The controller is always monitoring the voltage of the solar panel, which increases or decreases with the intensity of the sunlight. When it is lower than 5v, towards dusk, the control will switch on the LED lights. And when it is towards daybreak and the voltage is larger than 5v, the LED lights will be turned off.

2. Time control

The solar controller can also control the power output according to the time schedule, for instance, you want

  • 70 percent brightness from 6:00 pm to 7:00 pm,
  • 100 percent from 8:00pm to 10:00pm,
  • 30 percent from 11:00 pm to 5:00 am.

Commonly, a controller has around 5 time-slots you can use to set according to different requirements of projects.

Time control is often used in conjunction with motion sensor control. For example, from 11:00 pm to 5:00 am, there are few people on the road, so you can set only 30% power during this period, meanwhile, only capitalizing on the motion sensor to raise power to 100% when a passer-by is detected.

By doing this, we can save a lot of energy to boost the duration of off-grid solar street lights and ramp up the days of autonomy.

3. Motion sensor control

A controller can take action when it receives a signal from the motion sensor to increase LED brightness when someone is in sensor area, and then revert to the former level of brightness when it moves out of the area.

4. Preventing overcharge and Low voltage disconnect(LVD)

Either overcharge or over discharge can dramatically reduce the lifespan of batteries, although batteries modules themselves have this sort of protection, solar charge controllers usually have the same function analogous to that of battery modules. But be rest assured, the two are not conflicting with each other, for they function in different dimensions.

Motion sensor and solar charge controller

Motion sensor, solar charge controller

# Infrared(PIR) Motion sensor

Infrared and microwave motion sensor are two popular types in all in one integrated solar street lights, the infrared motion sensor detects heat source movement, while microwave ones send microwave radar and receive the bounced signals to analyze the changes in bounced signals.

Our all in one solar street lights incorporate infrared types, which have a 120-degree working angle and can detect a squat cone space under the lights.

We do not prefer microwave ones, although they have a larger working angle, they are rather too sensitive and more likely to respond to some wrong movements, such as swaying trees, fluttering birds and flapping flags. Those wrong response could consume lots of gratuitous battery energy, and that’s what we do not expect.

Above is the introduction of the primary components.

However, as integrated solar street lights, all in one solar street lights can also integrate some other functioning modules, such as Bluetooth, CCTV(Closed Circuit TV), or even wireless monitoring system, which enables end-users to monitor the status of each lights or even to control every lights by PC or mobile phone at any places where there are internet services.

Then, How do all these modules work as a complete system?

We will talk about the working process in 2 aspects:

Chapter 2. How does an all in one solar street light work?


Auto-charging during the day

Auto-charging during the day

First, the solar charge controller will turn off LED lights towards dawn once solar panel voltage rise to 5v, which is accounted for a little sunlight in the morning.

When there is enough sunshine during the day, the solar panel will work together with the solar charge controller to collect the solar energy.

Commonly, in a 12v solar system, with the effect of insolation, the voltage of its solar panel will rise to around 18v so as to charge the 12v battery bank. Meanwhile, the solar charge controller will prevent overcharge to protect the batteries.


LED turns on automatically at night

LED turns on automatically at night

When there is not enough sunlight towards dusk and solar panel voltage drops to a value under 5v, the LEDs will be turned on accordingly.

“Time control mode” and “Motion sensor control mode” will be working during discharging at night.

As primary function, Time control is used to customize different brightness in different time slots. For example:

  • Time slot 1: 6:00 pm – 7:00 pm, 50% brightness
  • Time slot 2: 7:00 pm – 8:00 pm, 70% brightness
  • Time slot 3: 8:00 pm – 10:00 pm, 100% brightness
  • Time slot 4: 11:00 pm – 2:00 am, 50% brightness
  • Time slot 5: 3:00 am – 5:00 am, 30% brightness

And so on.

Motion sensor function

Motion sensor function

a motion sensor is used as a minor function which can be recognized as an energy-saving mode

The LEDs’ brightness will rise to 100% when someone is approaching the lights and then revert to the previous level of brightness 20 seconds after the man leaves.

Chapter 3. Why should we use all in one solar street lights?

Why traditional solar street lights were not that popular?

In the past, why people do not tend to choose solar-powered street lights is due to three major reasons,

1. Lighting bulbs are energy consuming

Both MH(metal halide) and HPS (high-pressure sodium), which were used as light source in streetlights at that time, are with the relatively obsolete lighting technology (60-80 lumens/w) compared with that of the LED. those bulbs/lamps usually require a large amount of energy per day from its battery bank, which is considered as a downright burden to its battery capacity.

2. The LED technology is newly-developed and pretty expensive

In those days, although LEDs had been on the market in commercial outdoor lighting for a few years, the technology was still not mature. Their lighting efficiency was only 100 lumens/watt (now, in 2019, it can be up to 200 lumens/watt). Furthermore, since LEDs were newly-developed at that time, the cost was rather expensive and the average man on the street could not afford to buy.

3. Lithium-ion battery technology is not well developed

The third reason is the solar battery. The lithium-ion battery has the longest lifespan as one kind of deep cycle batteries, but they were not stable and would fail to work under 0 Celsius. (now, the working temperature of ternary lithium battery: -30 to 65 Celsius)

However, Things have changed over years.

New technologies are applied to solar street lights?

The size of both batteries and lighting sources is increasingly small nowadays.

Thanks for the technological breakthrough in both the lithium-ion battery and LED lighting. These developments make it possible for the solar lighting industry to develop integrated solar street lights.

1. Battery

Compared with lead acid batteries, lithium batteries are lighter, smaller, with longer lifespan and larger DoD, what is more important is that lithium batteries are with larger capacity at the same volume.

Lead acid batteries VS. lithium-ion battery

Lead acid batteries VS. lithium-ion battery

2. Light source

Compared with MH/HPS bulbs, LED takes up far less space in the lamps

MH/HPS bulbs VS. LED

MH/HPS bulbs VS. LED

What can we benefit from the latest technology?

1. No wiring, and easy to install within a few minutes

there is no complex wiring process, even if you are the end-users, you do not have to be with an engineering background or skills of setting electrical equipment, all you need to do is fixing the product with 12 pieces of fastening screws. Your family will stand to benefit from the free solar energy all the time.

Installation: former design VS All-in-one design

Installation: former design VS All-in-one design

2. 60% less energy consumption, which also means more days of autonomy

The light sources of most conventional solar street lights were Metal Halide(MH) or High-Pressure Sodium(HPS), which luminous efficacy is only 60-80 lumens per watt. However, nowadays, the cutting-edge LED lighting technology has dramatically boosted it up to about 200 lumens per watt. People can get the same brightness at night by consuming much less energy from solar batteries.

All in one solar street lights with this kind of light source easily realize 5+ days autonomy, making it possible to work normally in places with rainy seasons or less insolation.

3. Better hurricane/typhoon resistance ability

All in one integrated solar street lights are designed with compact structure, compared with that of split-types, which solar panel are separated from the lamp. This kind of structure has better performance in withstanding hurricane/typhoon.


After Super Typhoon Mangkhut in 2018

After Super Typhoon Mangkhut in 2018

Split-type solar street light will not withstand such inclement weather since its separated solar panels are more likely to be shredded by storms.

4. Lower transportation cost benefits from compact structure and all-in-one design

If you are a businessman, compact design means a lot to your profit margin.

The whole container loads of solar street lights could be twice or even three times more than before, in the meantime, the rent of the warehouse can cost much less than before.

Besides, due to the convenience of installation, which we talked in #1, your company will save even more local labor costs.

And more…

Chapter 4. All in one solar street lights VS. Traditional solar street lights

Conventional solar street lights VS all in one solar led street lights

Conventional solar street lights VS all in one solar led street lights

In this chapter, we will go through a concrete example by presenting a comparison table between them, so you can figure out the pros and cons more easily.

Traditional solar street lights All in one solar LED street lights
basic type Split type All-in-one type
Light source MH (Metal Halide) LED (Philips 3030 SMD)
energy saving mode no yes
connect to the electricity grid grid-tied off-grid
cables With cables No cables
request wiring skills yes no
performance autonomy days 3 days 3 days
brightness 3000 lumens 3000 lumens
consumed power 50 watts  17 watts
light efficacy 60 lumens / watts 180 lumens / watts
working hours 10 hours per day 10 hours per day
battery type sealed lead-acid lithium-ion
battery size 156 Ah 27 Ah
solar panel size 280 watts 50 watts

the same brightness, working hours, and days of autonomy,

But it is obvious, the upfront cost of all in one solar led street lights is fairly low,

it only needs 27Ah battery and 50 watts solar panel, whereas traditional solar street lights require 156 Ah and 280 watts, let alone other extra wiring costs that are entailed in installation.

Chapter 5. How to get a qualified all in one solar street lights?

needless to say, the quality of products is very important to businesses, sometimes, is crucial for winning tenders.

But can you always get a qualified all in one solar street light? I doubt it.

You might encounter problems:

  • even if you have been in this business for years, but you still have no idea about what exactly standards for an eligible product?
  • you might have learned the standards, but how to achieve? What factors affect the quality?

Let’s dive in the content with these questions you may have.

For almost all kinds of integrated solar street lights,  QC mainly focuses on the following items:

  • CCT & CRI
  • LM80 standard
  • Battery cycle times
  • 3 transportation testing for lithium batteries
  • Ingress Protection standard
  • Working temperature

Let’s review each one in detail.


CCT & CRI are important optical factors for illuminating

Various CCT (correlated color temperature)

Various CCT (correlated color temperature)

CCT stands for correlated color temperature.  lower value tends to yellow, while larger value tends to white and even with a little blueish color, refer to 8000K in the picture.

3000K looks like the sunlight at dusk or daybreak, the sunlight at noon is around 5000K, 6500K is called natural white, compact fluorescent lamp commonly has 6000-7000K.

Nowadays, nature white(6000-7000K) is always using in solar street lights.

Different CRI (color rendering index)

Different CRI (color rendering index)

Color rendering index (CRI) indicates how well a light source allows the substance to reflect its real color, the higher the CRI, the more an object can reflect its real color under this light source. Refer to the CRI 80 VS CRI 90

However, larger CRI also means more brightness loss as compensation. Namely, when we use the same chips to produce LED, if we make it with higher CRI, its brightness will be relatively dimmer than the one with lower CRI, so we commonly apply CRI 70 to the solar street light industry to get somewhat equilibrium.


integrating sphere

integrating sphere

With the help of the integrating sphere, we can easily get the two optical parameters when inspecting the incoming raw materials. In fact, integrating sphere can also help to get even more electrical parameters, such as illuminance(brightness), lighting efficacy and so on.

LM80 Standard


TYPICAL LM-80 DATA UP TO 10,000 HOURS, Source: Lumileds

LM80 is related to the lumen maintenance of LED, this standard requires the LED to meet the following table

Working time(hours) brightness depreciation(%)
1,000 0
3,000 <1%
10,000 <3%
50,000 <30%

Since human eyes will not perceive the depreciation until it drops to 30%, an LM80 certified LED can definitely walk you through 50, 000 hours without becoming dim sensorily


Full Vektrex IESNA LM-80 System

Image credit: Vectrex, Full Vektrex IESNA LM-80 System

Some types of equipment are specially designed to do this test accordingly, although it is very expensive.

If you do not want to invest such huge and expensive facilities, our advice is to complete the job in a third party laboratory with little payment.

Battery cycle time

DoD vs. Cycle times

DoD vs. Cycle times

Battery seems to be the most vulnerable part, they have the higher failure rates than the others, its lifespan depends on not only the materials and workmanship but also how we use it, for examples, how many proportions of power is discharged before next charging, specifically, the depth of discharge (DoD)

In solar street lights systems, the larger proportion the batteries are discharged every day, the shorter its cycle times will be.

Batteries manufacturers declare the cycle times of their lithium battery to be 1000 – 1500 times, which is based on the scenario that the battery is almost fully discharged each time.

However, we need to verify this data by ourselves so as to be responsible for the quality


Battery Cycle Time Test Equipment

Battery Cycle Time Test Equipment, Credit: U-powerful

Use an instrument like this one can help to record the testing data automatically, some of them have UPS(Uninterrupted Power Supply) function to guarantee a complete testing process and the data integrity.

UN38.3 transportation testing for lithium batteries

Solar batteries are on fire

Solar batteries are on fire

UN38.3 is for the safety of transportation of batteries or products with batteries, it includes 8 test items

  1. Altitude Simulation
  2. Thermal Test
  3. Vibration
  4. Shock
  5. External Short Circuit
  6. Impact
  7. Overcharge
  8. Forced Discharge

Over those procedures, UN38.8 requires there is no leakage, no venting, no disassembly, no rupture, and no fire.

These are more extreme test conditions compared with normal working conditions, products which have passed UN38.3 are definitely able to perform better.

Detailed reports?

You can check the PDF file to see how we test our products according to UN38.3 directives

Ingress Protection standard

Outdoor lighting fixtures

Outdoor lighting fixtures

All in one integrated solar street lights are outdoor lighting, so they have to withstand a hostile environment where they may fail to work because of dust or rainfall.

Ingress Protection(IP) rating is used to define the grades of resistance against dust and water.

Outdoor lighting fixtures are usually with an IP65 rating, which is the highest protection level for outdoor luminaire except for underwater luminaire. The first digit 6 is for dust and the second digit 5 is for water.

Though there is waterproof seals set between the enclosure over the final assembly, those interior components themselves are watertight too. For instance, the wiring connectors are all waterproof, and the controller is IP67 rating.


IP65 testing equipment

IP65 testing equipment

Apparently, referring to the picture above, a mimic raining environment is necessary for final testing, and it is more useful during the stage of design or pilot production.

If you do not have a spacious site for this kind of voluminous facility, we also suggest seeking a third party laboratory to help you with this work.

Working temperature

Outdoor temperature varies with location or season, the working temperature will directly affect the performance of each component or even lifespan in some extreme situations.

So either respective modules or assembled products needs testing and monitoring.

Engineering and QC take in charge of these jobs in a factory, when:

  • new product design,
  • pilot production,
  • raw material changes,

As with others, these processes also rely on special tools.


Climate Environmental Test Equipment

Climate Environmental Test Equipment

The equipment is used to imitate various working environments to test the tolerance of electronic products. The technician can also set worse working temperature than a real condition to check whether the electronic modules could survive from the testing.

Chapter 6. All in one solar street lights applications

The regions with sufficient sunshine is a must for a solar-powered facility to work normally.  The same principle applies to all in one solar street lights. Furthermore, as an off-grid solar-powered product, all in one integrated solar street lights can be used in remote areas where there is devoid of the infrastructure of the power station, such as islands, famous mountains surmounted by beauty spots, or some countryside.

However, as lighting products, all in one integrated solar street lights are mainly installed in the outdoor sites where illumination is required at night.

These sites are generally classified into four different areas as below:



1. Roadways

Fixtures: roadway lighting, street lighting

Locations: highway, road, motorway, lane,

Roadways represent a variety of ways for vehicle traffic. These ways require narrow beam angle across the road and wide beam angle along the road, for this can increase pole spacings and reduce the numbers of streetlights on it.

Recommend light distribution types:

Type II, Type III

Open Areas

Open Areas

2. Open Areas

Fixtures: parking lot lighting, park lighting, playground lighting, airport lighting, outdoor security lighting(sometimes with cameras)

Locations: airport, park, garden, parking lot, playground, tennis court, outdoor basketball court, intersections

Open Areas often connect vehicle traffic to pedestrian traffic, including the locations with public activities, such as the park, garden, and the places where security monitoring is always processing, such as parking lot, intersections.

these areas need illumination solution at night for either human activities or the scrutiny of the safety and security.

Recommend light distribution types:

Type II, Type III, Type V,

Pedestrian Areas

Pedestrian Areas

3. Pedestrian Areas

Fixtures: pathway lighting

Locations: plazas, courtyards, and pathways

Pedestrian areas indicate the transition between the building and its surrounding sites since these transition areas cover irregularly shaped spaces, more lighting distribution types may require for this kind of projects.

Recommend light distribution types:

Type II, Type III, Type IV, Type V,

Site Perimeter

Site Perimeter

4. Site Perimeter

Fixtures: Perimeter lighting, site lighting,

Locations: factory perimeter, industrial zone perimeter

Some sites, for instance, your villa, require illumination around its perimeter and exclude illumination onto the site itself, for at night you do not expect the street light trespass on your private space, especially bedroom.

Recommend light distribution types:

Type II, Type III, Type IV,

Type II lens for all in one integrated solar street lights

Type II lens for all in one integrated solar street lights

In the MH/HPS ages, this kind of lighting bulbs have to rely on reflector cup to shape special light distribution types on the ground, those cups usually installed above the bulbs, this is another reason why old street lights are too big to be integrated.

Whereas in LED ages, engineers only need to have a thin lens installed onto the LED to realize various light distribution types.

Chapter 7. how to design a project with all in one solar street lights(Case study)

Here is a real-life inquiry from Oman.

First email

First email

Since there is lack of detailed information for designing a project, so we ask for more information, and the customer sends them in attachments

Second email

Second email

We spent some time to study and organize the information from the emails

At last, the customer’s requirements are listed below

  1. 100w rated wattage, all in one solar led street lights for a roadway project
  2. The road is 12-meter width
  3. Mounting height 10 meters
  4. minimum required illumination level at the ground: 5 lux
  5. 12 hours/day, full power operation
  6. 5 days of autonomy
  7. materials are suitable for continuous 55 Celsius (the testing method is in Chapter 5)
  8. IP65 waterproof.

The engineering process started firstly from checking the existed IES files to guarantee the 5 lux optical requirement on the ground

let’s go through the steps one by one

design a project with all in one solar street lights

design a project with all in one solar street lights

Step 1: check IES datasheet

Our 100w happens to be tested at the mounting height 10 m ( MH = 10 m), and it central illuminance can reach around 8 lux,

(tips: if the mounting height is 7 meters in your project, you need to multiply factor 2.041 in the right column to get relevant lux data on the ground)

100w road surface isolux diagram

100w road surface isolux diagram

Step 2: adjust the distance between the poles

Solar street lights throng one side of the street

Solar street lights throng one side of the street


After adjustment

After adjustment

In the course of simulation of engineering, IES files and Dialux can help engineers to get appropriate pole distance pretty easily.


  1. load the 100w IES file into software Dialux
  2. Set the pole position: both sides or only one side?. (in this case, only one side installation is allowed)
  3. Input basic parameters: road width, mounting height, preliminary pole distance, and the number of lamps per pole.
  4. Try a different value of pole distance on the basis of using minimum streetlights, until you get “minimum 5 lux on the ground”
Installed at one side - diaLux simulation

Installed at one side – diaLux simulation

In the end, we decide 25 meters is the best pole distance. And at this time, the minimum illuminance is about 7 lux.

Step 3. Calculate the battery size

So far, optical parameters and installation positions have all been determined.

Next, we need to size the solar battery according to requirements, 12 hours/day and 5 days backup

  1. The LED modules in this 100w model require working current 1.34A.
  2. 12 hours full power operation consumes battery power 1.34A x 12H = 16.08AH
  3. for 5 days backup, we need (16.08AH x 5 = 80.4 AH)
  4. So we select an existed battery size: 84AH for this model.

Step 4. Calculate the solar panel size

The final step is to size the solar panel according to battery size 84AH and the peak sun hours

  1. The solar irradiance in Sultanate of Oman is sufficient, its peak sun hours is about 6.5 hours
  2. 84AH / 6.5 = 12.92 A, so we need 12.92A current from solar panel for 6.5 hours
  3. For LifePO4 lithium battery, the charging voltage is 18v
  4. 18V x 12.92A = 232.62 W, that means we need about 230 w energy from solar panel per day theoretically
  5.  Since the battery is not always totally empty, so we usually multiply a coefficient, 0.7
  6. 232.62 W x 0.7 = 162.84 W

Our 100w model is equipped with a 170w monocrystalline solar panel.

100w model, 10 000 lumen, and with 5 days of autonomy

100w model, 10 000 lumens, and with 5 days of autonomy

So, finally, we prepare the products with recommended parameters as below

  • 170W monocrystalline solar panel
  • 84AH LifePO4 lithium battery
  • 100w rated LED model
  • 10 000 lumen
  • IP65

check here to check the datasheet in details.


All in one solar street lights is a new trendy type of solar street lights, And this trend will be strengthened as the development of sodium-ion batteries, which is even powerful than current lithium-ion batteries.

Although it may take some time for sodium-ion batteries to go out from the laboratory to real-world applications, it is worth expecting. And at that time, solar street lights will be powerful enough to replace all streetlights.

Delivery by sea solar street lights

solar street lights delivered by sea

Interested in estimating your potential projects with the help of our experts?


plan to replace traditional solar street lights with our all in one integrated solar street lights?


you do not want to miss out on the benefits to illuminate your own factory zone, and even courtyards or backyards?

Feel free to contact us with your detailed requirements. (as detailed as possible)


4 Simple Ways to Find True Solar South for Aligning Solar Panel Correctly in Few Minutes (2019, Step by Step)

True Solar South vs. Magnetic South

Contractor is finding the True Solar South

It has been known that south-facing solar panel (In the Northern Hemisphere) can get the most out of sunshine.

And when it comes to orienting solar panels, most people will simply choose the south which the compass points to.


this approach is absolutely wrong.

Because you will only be able to find out the magnetic south with it.


In any PV system related project, we tend to set up solar panels to face the solar south rather than the magnetic south.

Although doing this only brings about a 3% improvement in energy collection, it will be a big deal if your solar array is huge or your extreme condition requires getting as much energy conversion as possible.

Now, the questions are:

  • How can we ascertain the true solar south?
  • What’s the difference between “True Solar South” and “Magnetic South”?

Well, today I am going to make it easy for you

Basic Knowledge: True Solar South vs. Magnetic South

Before we talk about the methods of finding true solar south, let’s go through the basic knowledge quickly

  • What is “True Solar South”?
  • What is Magnetic South?
  • Is there any difference between them?

This can be easily understood with the help of the following image (pic.1):

True Solar South vs. Magnetic South

pic.1 True Solar South vs. Magnetic South

In fact,

There is a giant magnet in the earth.

Its magnetic South Pole is around the Earth’s South Pole, while its magnetic North Pole is around the Earth’s North Pole (Refer to pic.2).

This big magnet rotates along with the Earth. However, its axis is not aligned with the Earth’s, although they are pretty close to each other. The declination is approx. 14 degree.

For better understanding:

When the compass needle points at the south, it is actually aligning with the Magnetic South Pole and not the true South Pole.

the earth poles vs magnetic poles

Pic. 2: the earth poles vs magnetic poles

We often refer to the direction of the Earth’s South Pole as the true south or the true solar south, while the direction of the magnetic south pole is referred to as the Magnetic South.

In the solar energy-related industry, accurately locating the true south means a lot to the solar PV system.

Lucky for you,

we have 4 proven practical methods you can use today to help you when adjusting your solar panel to ensure you find the right direction and improve the efficiency of your solar powered system.

Now, Let’s dive into the content step by step.

Method #1: The shortest shadow method

The shadow of an object will be shortest when the Sun is highest at noon, and at this moment, the direction of the shadow line is the true solar south.

This method involves simply finding out the shortest shadow at noon according to this theory,

Now, let’s dive into the steps

The shortest shadow method

Simple steps:

1. Set a straight stick on a flat ground in the morning, toward noon – it is important that the straight stick is set perpendicular to the horizontal, and the ground should be as flat as possible, because a tilt-mounted stick or uneven ground will produce a faulty result of the shortest shadow.

Tips: A plumb bob could efficiently help you put up the stick vertically on the ground.

2. Mark the shadow end on the ground every few minutes – as time passes by, the shadow cast by the stick will move. You need to leave a mark at the end of the shadow on the ground every 10 – 20 minutes, these marks will finally form a curve.

Tips: the interval is not necessarily the same, as long as we can get the moment when the shadow starts becoming longer, instead of shorter.

3. Find out the shortest shadow line – draw a line to connect those marks to the point where the stick touches the ground. By now, the shortest line is evident.

4. Reveal the true solar south – now that we have marked that special line we concluded in the third step, the direction of the Solar South has been revealed. You could then adjust your solar panels to align with this direction.

Method #2: Using a shadow at solar noon

This could be the simplest way – it takes far less time than Method #1

Let’s start with the question: what is solar noon?

Solar noon is the local time when the sun rises to its highest point at your location, and at this time, the sun is crossing your local meridian.

Instead of spending several hours standing outside and measuring the shortest shadow, in method #2, all you have to do is to find out your local solar noon, then go out at that time to check the direction of the shadow of an upright object on the ground.

Using a shadow at solar noon to find out true south

Here, you may still need to raise a straight stick vertically on the ground, but you can refer to Method #1 Step 1 for that.

We will introduce 2 feasible ways to calculate your local solar noon.

  1. A)
  2. B)

Now, let’s dive right in.

Online solar noon calculator A

Simple steps:

1. Visit the website and input your location, longitude and time zone (I will use my location, Shenzhen, China as an example)

solar noon calculator

2. Get your longitude – open the Compass APP on your phone as below – you can see my location is Shenzhen and Longitude is 113° 56’ 27” E

Compass APP on your phone

3. Fill in the form with the required data and click on Display Calculator

solar noon calculator

4. You will be redirected to the page below. Click on “continue”

solar noon calculator

5. The solar noon calendar would be generated as below – this special calendar has listed all the solar noon for each day of the year. Assuming your team would go out to carry out this task on Nov 30th, 2018, the solar noon on that day is 12:14 pm

solar noon calculator

Online solar noon calculator B

Follow the simple steps below:

1. Visit the website

solar noon calculator alternative

2. Drag the red mark to your address on the map. The solar noon will be displayed on the right side simultaneously.

solar noon calculator alternative

3. Select the date, for instance, Nov 30th, 2018

solar noon calculator alternative

4. You will get the same solar noon 12:14 as from calculator

solar noon calculator alternative

Since both calculators, A and B, show the same time 12:14, then your team can go outside at that time to mark the true solar south easily.

Try the steps above, and let me know if the two calculators also generate the same results in your city.

Method #3: The magnetic declination method

Seeking out truth south according to magnetic declination may be the most accurate method.

As we know, the magnetic south that a compass points to slightly deviates from the true south – the direction that is along a meridian towards the South Pole. The deviation angle between them is called magnetic declination.

The magnetic declination changes every year because magnetic poles are shifting each year. However, the Earth’s pole is not moving. Chances are we should go to authority online database to obtain up-to-date data of declination.

Let’s go through the simple steps:

1. Visit the authority site NOAA, and fill in the required data – taking my city Shenzhen as an example, my latitude and longitude are 22.40 N and 113.56 W respectively (refer to the images above). Select Nov 30, 2018, as the date, since my team plans to do this job on that day, and click on the calculate button.

magnetic declination calculator

2. Your magnetic declination would be displayed – from the results, you can see that my declination in Shenzhen China is 9.02 degree East.

magnetic declination calculator

3. Prepare the compass – we need a compass with degree scales. Place it on a horizontal surface, and adjust the needle to align with the south-north scale as below. Its black hand will point to the magnetic south

compass with scale

4. Rotate the compass horizontally according to the declination – my declination is 9.02° East, so we rotate 9.02 degree counterclockwise. Now, the ‘S’ on the scales will point to the true solar south. (Refer to picture below)

compass with scale

Tips: If your declination is 9.02 degree West, then rotate clockwise instead.

Method #4: the Polaris method

If you live in the northern hemisphere, you can also use the Polaris to locate the true north or south.

The Earth’s imaginary rotation axis always passes through the Polaris, so you may find she does not move in the sky, and the direction towards the Polaris is always the true north.

The Earth's imaginary rotation axis and the Polaris

With the basic knowledge above, let’s walk down the simple steps:

1. Identify the Polaris – Commonly, finding the Polaris requires the help of “Big Dipper” and “Little Dipper” in the northern sky. Below are 3 helpful clues

  • The Polaris belongs to “Little Dipper”, together with 6 other stars
  • The Polaris doesn’t move
  • The “Big Dipper” constellation revolve around the Polaris all year round.
Big Dipper and Little Dipper in the northern sky

“Big Dipper” and “Little Dipper” in the northern sky


Big Dipper and Polaris

Big Dipper and Polaris

2. Set up the solar panel – line up the seam between 2 solar panels with the Polaris as instructed in the following picture, and the solar panel will be facing the true south

the Polaris method

Some people like the Polaris method most, because it neither requires any calculation nor marking shadow for a few hours.

Which one do you think is the best method? And do you have any other more efficient method(s)?

We love to hear from you in the comments.

Polycrystalline vs Monocrystalline Solar Panel, Which one is better?

Polycrystalline vs Monocrystalline Solar PanelEvery day, a better and improved solar technology is being researched to effectively harness the sun’s energy.

The current solar technologies aren’t as efficient as we want, particularly as regards the solar panels used. Currently, there are just 2 popular types of solar panels, in spite of their inadequacies we need to know what each of them offer and how you can benefit from either one in your next solar purchase.

In this post, we covered extensively 2 types of solar panels. At the end you’d get to know their characteristics and compare both to help you in making the right decision.

Let’s get to it…

What are the Major PV Solar Panel Technologies?

There are different types of solar panel available today in the world and new ones are constantly being developed to ensure the inexhaustible energy of the sun does not go untapped.

The first of all solar cells ever created is the monocrystalline cell which was discovered in 1935 by Calvin Fuller and Gerald Pearson. This solar panel is by far the most developed of all solar panel technologies that could be employed.

Next is the arrival of the cost-effective polycrystalline cells which also has ever-since being improved.

There are other technologies such as the thin film solar panel which is suitable for regions with high temperature. In this article we shall stick with the most developed solar PV technologies. Which are the polycrystalline and the monocrystalline PV technologies.

What is a polycrystalline solar panel?

Polycrystalline materials are materials made out of several crystals (rocks) of silicon.

All crystalline PV panels are made of silicon. Scientists say it is the second most abundant element on the earth crust. Silicon is obtained from rocks and at all times it is found in its combined state as silicon dioxide.

How polycrystalline panels are made?

The process of making a polycrystalline PV panel can be quite tasking.

It starts by first extracting silicon from the rock by means of a very hot furnace of over 2,000oC. The furnace melts the rock into liquid, and this is then poured into a cooling machine. The result of this cooling is a pure silicon rock which is ready for processes to become a PV panel.

Silicon in its pure state is just a semiconductor which does not conduct easily because of its atomic structure. A material conducts when it has free electrons or free holes, but pure silicon does not have any. However, this can be improved by adding impurities to this silicon. The process whereby impurities are added to a pure element is called doping and the added elements are called dopants.

The dopant and the silicon rocks are mixed in a 3 ft x 3 ft square-shaped mold and the mold is inserted to a large furnace of temperature of about 2500oF. The mold stays in the furnace for about 20 hours for a proper melting process. It is removed after this period and allowed to cool for a day or two.

After the cooling a solid silicon block (ingot) is obtained. This ingot is sliced into a thin and fragile square shaped solid called wafer.

There are two stages when it comes to cutting an ingot; the first stage is where the entire solid is cut into a column of the required size but a very long width and the second stage is where the width is removed by cutting the column into the desired thin sheets -the wafer.

Though we’ve obtained the wafer the process is yet incomplete, unless the thin sheets are carefully collected and separated for the cleaning process.

Due to the fragility of these solids, hands are used to separate the solids individually and since hands are involved our material becomes more prone to contamination, because of this the wafers are washed properly after the collection.

Lastly is the addition of the last chemical unto the already washed wafers, this is then baked to obtain a fusion of the two materials.

Other finishing touches will be; addition of anti-reflective clothing on the panel, addition of chemicals to help the panel to better conduct electricity out of the panel, addition of aesthetic value to make it more visually appealing and addition of electrical contacts to help convey out the converted electricity.

What is a monocrystalline solar panel?

It is called monocrystalline because of how it is made or more appropriately, how what it is made from i.e. it is made out of a single crystal (of silicon).

How monocrystalline solar panels are made?

Unlike the polycrystalline panel which is gotten from many silicon crystals obtained melted and directly cooled, the production of a monocrystalline panel involves a more complex process ‘the Czochralski Growth’

After obtaining the silicon rocks from its parent rock, it is melted in something like an enclosed flask called the ‘Czochralski Growth Apparatus’. This flask has a heater in its innermost layer with a graphite bowl that contains the silicon rocks. The innermost layer is succeeded by another layer called the heat shield located in a space called the chamber.

Once the silicon is melted, a certain material called the ‘seed crystal’ is dipped into fluid and is pulled back up while rotating. The seed crystal continues to rotate as it moves up, while the graphite bowl simultaneously lowers itself, thus creating a solid cylindrical ingot of silicon around the seed crystal. The ingot might be larger than the desired diameter, but it can be trimmed to a desired size.

Large-sized ingot would not do us any good. Therefore, the ingot is sliced into thin layers using a 100-200-micron thick high-grade steel wire connected to rotating rollers cuts the ingot into roughly-surfaced wafers. To remove the rough surfaces several wafers are lapped on both sides in between to counter-rotating pad, this is called ‘lapping’. Though lapping helps to smoothen the surface of the wafer, it degrades the crystal structure of the silicon surface of the wafer. However, a process called ‘etching’ is employed to restore this and improve the crystal structure. Etching is done by immersing the wafer into any suitable etchant such as; KOH or HF.

The surface of the panel is then polished using an ultra-fine slurry to obtain a smooth wafer.

Having discussed how the various Crystalline panels are made we have a good ground to discuss the major differences between them. As we move on we would consider different points in analyzing the two types of technology.

Monocrystalline VS Polycrystalline Solar Panels

In the previous sections, we have gone through all of the processes required to make a crystalline solar panel, we shall proceed to analyzing several points that must be considered in placing proper value on each solar panel.

At the end of this section, you would be able to identify what solar panel is best for you based on their characteristics.

●     Appearance Difference

How the different panels are made contributes to how they eventually look.

For instance, the monocrystalline panel is made out of a single crystal of silicon and thus it has a uniform color throughout the entire material. Whereas, the polycrystalline panel would have varying color differences across the entire material due to the fact that its ingot is gotten from several crystals of silicon.

Most times monocrystalline panels are black or dark blue in color and each cell (finished wafer) has a rounded edge. Do not forget that we have seen that the ingot obtained from melting the silicon rocks looks like a rounded cylinder and thus the individual wafers originally are rounded and needs to be cut into square shape to meet up with the required standard, but this would waste a whole lot of the monocrystalline silicon.

Therefore, it is then cut so that, part of the rounded part of the circular wafer does not waste. Hence, the reason for its rounded edge.

Polycrystalline panels have a bluish color and appears as though there are particles (looks more like rocks) are present inside the panel. Each cell has a square shape because it was cut out of a square shaped ingot.

●     Module Convert Efficiency

How efficiently the panels would be able to convert solar energy into electricity greatly depends on the molecular structure of each material.

The monocrystalline panel because of its consistent make-up allows electrons to flow freely, but the polycrystalline would not as much as a monocrystalline panel would owing to the same reason of molecular structure. The conversion efficiency of the monocrystalline panel is from about 15% to about 20%

●     Temperature Factor

The conversion efficiency of the panel also depends on the temperature, such that an increase or decrease in temperature above a threshold of 25oC causes an increase or decrease in the efficiency of any of the panels (be it monocrystalline or polycrystalline).

However, how much temperature affects the efficiency of the panel (temperature coefficient) varies between different brands e.g. a certain type of panel may have a temperature coefficient of about -0.123% per oC which means for every increment of 10C the efficiency reduces by 0.123%.

It has been observed that generally polycrystalline panels can withstand more heat than the monocrystalline panel

●     Shading Factor

No solar panel works well when it is completely shaded. However, because of some particular reasons the monocrystalline panel functions better in cases where there’s no extreme shade.

●     Cost

The monocrystalline panel costs more than the polycrystalline solar panel. This is due to the cost of producing the mono panel which costs approximately 20% more than the cost of production of polycrystalline panel.

The cost of production of mono panel is more of a function of the wastage procured during the reduction of the shape of the ingot to a rounded square shape.

●     Space Efficiency

If you need a panel that efficiently converts and you’re willing to trade cost for space, the monocrystalline panel is your best bet. Though it’s not impossible to get polycrystalline panels of the same efficiency as a mono, but since the conversion efficiency of the polycrystalline panel is less one would need a large poly to match the required efficiency.

So, for less space and great efficiency the monocrystalline panel works well.


Let’s look at a summary of what was explained through this post, you can choose based on your need.

Pros Cons
Monocrystalline PV panel
  • They have very high conversion efficiency
  • They also have high space efficiency
  • They perform better in shady places than a polycrystalline panel would.
  • They are very costly to produce and to purchase
Polycrystalline PV panel
  • They have a relatively low cost of production and hence, are cheaper to purchase
  • They have proved to have more heat tolerance than monocrystalline panels (though very minute)
They tend to be large and may not be used in houses with small space

They have. a small conversion efficiency compared to that of monocrystalline panel.



Solar Energy Advantages and Disadvantages

Solar Energy Advantages and Disadvantages

set up solar panel

Why should I invest in solar energy?

What is in it for me?

Is solar energy a perfect option? What about its faults?

These questions would be clearly explained through the course of this post.

Let’s start with the basics of solar energy.

you could also download the PDF file here

solar energy advantages and disadvantages pdf

Solar Energy Technology

Solar energy simply means the energy derived from the Sun. This energy can be used to generate electricity and heat.

For this post we’d focus mainly on electricity generated from the Sun.

How is this done?

To convert solar energy into electricity, a device called solar cell or Photovoltaic (PV) cell is used.

Once sunlight falls on the PV cell, it is converted into electric current. The electric current gotten (direct current) is then inverted to alternating current – used by electrical appliances.

The electricity gotten from the PV cells is also stored in batteries to save energy for the night or days of little sunlight.

With that cleared, let’s move on to see the pros and cons of solar energy.

Solar Energy Pros and Cons

Currently, the entire process of harnessing solar energy isn’t 100% efficient, It still has disadvantages and setbacks.

However, the advantages of using solar energy overwhelms its disadvantages. Also, most of the disadvantages already have known solutions, thus, solar energy still standing out as one of the best energy sources.

OK! Let’s get right into the pros of solar energy.

Solar Lights

Solar Lights

Advantages of Solar Energy

No Monthly Bills

Once you have a solar power system installed, it goes running for years, and as statistics have it, the system might not need any prior change at least not in the next 25-30 years after installation.

Really, the first advantage of owning a solar power system is the fact that you get to own your own electricity not paying dues to anyone.

This means you’ll be able to determine how much energy you expend each month or yearly as you so wish.

Inexhaustibility of Fuel Supply

The fuel in this case is the sun, and it is inexhaustible. This is unlike other energy sources like coal, natural gas, uranium and the likes.

It is argued by scientists that the sun is about 4.6 billion years old and will die in about 10 billion years to come. But this doesn’t matter anyways (who’s probably going to be here at that time).

Therefore, you’d have unlimited supply of sun throughout your lifetime, which can be converted for electricity.

Low Maintenance Cost

Solar power system needs very little maintenance and the major part of that is to clean the dirt and rubble that may be found on it. You don’t have to do this everyday or every month, but just a few times in a year.

This is exceptional because other power generating systems require maintenance frequently as they contain moving parts.

No Negative Environment Impact

If you ever lived beside an industry that runs 24-7 on big generators you most probably know what I’m talking about.

Asides the unwanted noise generated they also pollute our environment, endangering our lives and also increasing the rates at which global warming occurs.

Solar power system does not produce pollution be it air or noise. Thereby reducing the rate at which our ozone layer is depleted, while it generates power.

Source of Income

If you end up generating more energy than you need, you could sell those excess energy off and you’d get paid in cash.

Services such as net metering and feed-in-tariff also known as FIT enable everyone who owns a solar power system to do this.

Value-Added Property

Your home gets more value and could attract a higher price when you want to sell because of the presence of the solar power system.


Some people believe that the addition of a solar panel to their house increases how visually appealing their house could be. This is arguable as it is not true in all cases.

No Wasting of Space

with solar panels put on the rooftops of the house, you get to generate the needed energy without loss of land.

This available space could be used to do other things that you have in mind.

Improving Technology

The technology of solar system improves daily. Solar energy has a very competitive market, this competition brings about an increase in effectiveness of the designs of solar panels and also reduce cost.

Shared Solar

It is possible for some group of houses to come together and establish their own power generating station together.

This is majorly for places that do not have too much space with their houses  close to one another causing shading on these solar panels.

Improves the Economy

The use of solar panel system in a country helps reduce the rate at which the fuel is imported from other countries.

Everyone knows that imports are subtracted from a country’s GDP not added, and to reduce this one has to develop his own country to stand on its own. Solar power system is very important in helping the country’s economy.

Availability of Jobs

As statistics have shown that the solar power generating section of the country employs more staffs than any other power generating section.

As this section improves, it shall continue to bring about more employment opportunities.

Investing in solar energy is a great deal. However, you’d face some issues like;

Solar Panels

Solar Panels

Disadvantages of Solar Energy


The major issue with cost is the higher start-up cost of installation, which is really very high, I mean real high and could weigh more than the cost of building the house with which it would be used.

Costs of installing an effective solar panels varies from $10,000 – $20,000 or maybe more. The cost of batteries too poses serious problem in the usage of solar power system.

It Is roof Dependent

Solar panel doesn’t work for every kind of roof e.g. houses using slates or cedar tiles. The installation could also be hindered by rooftop additions and skylights.


Although installation of solar panel on some building adds beauty to it,uc this is however not true in all cases. It does happen that addition of solar panel to buildings makes it less beautiful to behold.


This is the one of the key disadvantages of solar power system. You must note that since the sun doesn’t shine in the night, the solar panels do not produce any electrical energy during this time.

Also, during times of winter when sun doesn’t shine as much, you’d have reduced returns during these periods, but these problems are reduced by the use of batteries which helps to store electrical energy generated.

Low Efficiency

Solar panels have low efficiency of about 15-20 percent. This means that only about 20 percent of the sunlight that falls on it is converted to solar power. Also, solar panels are very fragile and may damage easily.

Waste of land

In some cases where solar panels are not placed on rooftops, it happens that the solar panels tends to take more space because the amount of energy trapped increases with the area of the solar panel.

Untrustworthy Local Installers

Due to high competition in market, local installer pull all sort of tricks to entice house owners to sign all sorts of long-term contracts before explaining the details of the contract.

Dependency on Latitude

Some countries are more exposed to sun’s rays more than the other, for example countries like Senegal and Mauritania will enjoy enough solar energy as they ought to. Because of the closeness to the equator.


Solar energy is worth your investment, you’d enjoy absolute energy independence and several other benefits. Even with the disadvantages, solutions can be provided for most. Contact us at to discuss your solar energy needs.



Peak Sun Hours: Important Factor of the Average Daily Solar Insolation

Peak Sun Hours

Peak Sun Hours, Source:

In the course of designing an off-grid solar street lighting system, you’re often faced with an initial challenge of factoring the Peak Sun Hours of your location to experience maximum energy from your solar PV system.

If you’re not a PV technical personnel, understanding the peak sun hours and factoring it could be a difficult task.


Not to worry, in this post we’ve made the process as simple as possible for you to understand and apply the same to your PV installation.

To start,

Let us take a clear look at the term itself.

What is Peak Sun Hours?

In simple terms,

Peak Sun Hours is the number of hours in a day when the Sun is at its maximum radiation.

The value of PSH varies per location, this is due to some certain factors that will be discussed shortly.

Before then, let’s break down the technicalities; because there’s more to the definition.

Average radiation from the sun measured on the surface of the earth during a clear day or noon is about 1000W/m2. (This value is standard for all PV tests & measurements.)

The number of hours in a day that a location experiences this value of radiation is called Peak Sun Hours.

1 Sun Hour is equivalent to 1000 W/m2 of the sun’s radiation collected in 1 hour.

3 Sun Hours is equivalent to 1000 W/m2 of the sun’s radiation collected in 3 hours.

The unit of measurement is therefore kWh/m2. It is also expressed as kWh/m2 day, this refers to the total Peak Sun Hours in a day.

As stated earlier,

Based on your location, there are couple of factors that affect the value of the Peak Sun Hours.

What are they?

Factors that Affect the Peak Sun Hours of a Location?

It is important to note that your PV module has no effect on the Peak Sun Hours, rather, the factors are more environmental.

The 3 major environmental factors that affect the Peak Sun Hours include:

1.   Position relative to the Sun:

Regions of the world that are closer to the equator have more intense radiation from the sun compared to those further away from the equator. The Peak Sun Hours is more in those regions closer to the equator.

Therefore, if you’re installing a solar power system in these regions, you’d have more energy produced from the solar PV system and vice versa.

2. Cloudiness

The presence of clouds in the atmosphere diffuse the solar radiation, thereby reducing the Peak Sun Hours. The cloudiness of a location is more of a daily factor; where rainy or cloudy days have less PSH, and clear days have more PSH.

3. Climatic Seasons

During some seasons, PSH is bound to reduce based on the sun’s position on those times. For instance, there’s more Peak Sun hours during summer seasons compared to winter seasons.

Knowing the PSH of your location is very important when installing a solar PV system. This would allow you to estimate the energy the PV system can produce maximally.

To estimate the energy your PV can produce, follow the simple steps below.

How to calculate the Energy produced by your solar system using Peak Sun Hours.

In 2 simple steps, you’re done.

Firstly, determine the power rating of your solar PV system.

Then you multiply the value by the PSH of your location. This gives you the estimate of the total daily energy that can be produced by your solar PV system.

For example,

Suppose I install a solar PV system of 5 m2 in California, where the PSH is 5.5 kWh/m2, the total energy the system can produce daily is

5 (m2) × 5.5 (kWh/m2 day) = 27.5 (kWh)

The higher the PSH, the greater the energy produced from a solar PV system.

What if your location has a low PSH, what do you do?

How to improve your solar PV energy production for low Peak Sun Hours Areas.

Even during cloudy days, your solar panel would still produce power only that it would be about 25-40% less than the expected. To minimize this, the following can be adopted:

  • Use solar modules made for low PSH regions, they are usually designed with greater efficiency.
  • Use a sun tracking solar panel.
  • Tilt the angle of PV module to effectively capture the sun’s radiation based on your location. This is the most popular solution used for areas with low PSH. Depending on your location, the angle optimum angle is calculated relative to the latitude, which now determines the angle the PV modules will be tilted.

You might need the service of a technical personnel on this method.

To round up, we’d share a couple of online resources that would help you to determine the PSH of your location.

Available Online resources to know the peak sun hours for my location.

For locations in America, these resources can be very helpful to determine PSH of your location

For locations in Europe and Asia, the link below would help in making several solar calculations, including the optimum tilt angle for your location.

For locations in Australia, this document would give adequate information to the PSH values of your location.

Other helpful resources for other cities can be found in the link below. You can also check this link to help in estimating the optimum tilt angle for your PV module.


Solar Battery Calculation: How to Size the Battery for Solar Street Lights

solar power street lights

Solar led street lights

In the course of designing solar led street lights,

just like many,

you’d often encounter the problem of accurately sizing the battery.

This is because,

when the battery is undersized, the street light won’t be able to sustain for up to 3 rainy or cloudy days.

Also, if the battery is oversized, you’d face the problem of sulfation, especially if it’s a flooded battery bank.

Well, we have decided to completely solve the challenge of accurately sizing your battery.

No need racking your head anymore on this task. By the time you’re done reading this, it’ll be such an easy task.

We’ve compiled a detailed breakdown and a step by step guide to sizing the battery for your solar led street light.

Best battery type for off-grid solar system: Deep cycle battery

For your information,

the Battery type used for off-grid solar streetlights are commonly deep cycle batteries.

What do I mean?

Not just any kind of battery can be suitable for off-grid solar street lights;

Deep cycle battery

Solar battery, Deep cycle battery

Since off-grid solar streetlight is a stand-alone solar power system, all of its power supply is from batteries (not from electricity utilities), this requests that the batteries must be able to undergo repeated and deep discharges, deep cycle batteries partake of these requested characteristics


it’s very important that you clearly understand some related terms of solar batteries. This will help you understand the battery sizing process.

Essential terms need to know:

1. Battery Capacity & Power

The Power rating is the amount of energy that can be supplied by a battery at one time, it is measured in Watts. Let’s assume that a 12V battery supply 2Amps current to the solar system, we can say the battery can supply 24Watts.

Power(W) = Voltage(V) x Current (Amps) = 12V x 2A = 24W

The battery capacity is the total amount of energy that can be stored by the battery, its unit is KWh, if the battery can supply 24W for 100 hours totally, we will say, its capacity is 2.4KWh.

Capacity(Wh) = Voltage(V) x Current (Amps) x Time(Hours) = 12V x 2A x 100h /1000 = 2.4KWh

LiFePO4 battery

LiFePO4 battery

2. Amp-hour

the Amp-hour is another expression of the battery capacity.

if the battery nominal voltage is 12V, and it can totally continue to release 2Amps current for 10hours,

we can see its capacity is 12 x 2 x 10 = 240Wh, or 20Ah.

solar led lights

Solar led lights

3. Depth of Discharge

Depth of Discharge(DoD) refers to the available amount of energy that can be used in a battery when it is processed from a fully charged state to a fully discharged state.

if the battery’s capacity is 100KWh, only 60KWh can be released to power the solar system, its DoD is 60%.

Therefore, the DOD is a very important factor in the calculation of sizing the battery for solar street lights.

as we known, a LiFePO4 battery type’s DOD is 80 percent, while GEL battery DOD is 50 percent.

We covered a detailed explanation of Depth of Discharge in the following link

30 percent DoD depth of discharge

30% Depth of Discharge

4. Battery Working Temperature

This refers to the ideal environmental temperature for a battery. The ideal temperature is 27°C (80°F) because a battery’s internal reaction is optimal at this temperature.

If the temperature is lower, the battery’s efficiency will be reduced.

higher temperature improves the efficiency only if it’s a little above 27°C and for a shorter time.

battery does not work in cold weather

Battery does not work in cold weather


Solar battery calculation: step by step

Let’s go through an example to explain the battery sizing process step by step.

Step 1: Prepare the data that is required.

  • Rated LED power,
  • Rated working voltage of LED
  • LED brigthness settings during night
  • days of autonomy
  • battery type and its DoD

Let’s assume

the rated power of the LED lamp in a solar streetlight is 30W at 12V.

LED brightness at night will be set as: 1 hour 60% + 5 hours 100% + 6 hours 40%

3 days of autonomy, in others ways, it can support 3 raining/cloudy days

battery type is LiFePO4 batteries, the DoD would be 80%

Step 2: Calculate daily energy consumption of LED lamp

the current consumption of the LED lamp = 30/12 = 2.5Amps

the total power consumption in a day = 8Hours at 100% brightness

so the daily power consumption = 2.5 x 8 = 20Ah.

Step 3: Considering the 3 days’ autonomy

if we design the solar-powered streetlights can sustain for 3 raining/cloudy days, then we should multiply daily power consumption by days of autonmy

that will be, 20Ah x 3 = 60Ah.

Step 4: Considering the depth of discharge.

in this example, our battery type is LiFePO4, and Its DoD is 80%

so the battery size should be 60Ah/80% = 75Ah

Light distribution types to guide solar streetlights design

The IESNA (Illuminating Engineering Society of North America) has defined various light distribution types. Light fixtures are designed to fall under one of the types defined, and lighting designers use this a guideline when selecting lighting for a particular area. Incorrectly selecting light fixtures can result in glare and light trespass into unwanted areas, such as onto the property of someone else.


Type I


Type 1 distribution have a very narrow and long lighting area. This is useful when selecting a light fixture to light up a narrow area, such as a pathway or very narrow roadway. Type 1 fixtures would normally be placed along the center of the pathway.

Type II


Type 2 distribution is used for wider pathways and narrow roadways (single lane),. Type 2 fixtures are usually placed off to the side of the pathway or roadway, since they are able to provide a small degree of forward light throw.

Type III


Type 3 distribution is used primarily for roadway lighting, and is placed off to the side of the road. The forward throw on these fixtures allow light to product outwards, illuminating multi lane roadways.

Type IV


Type 4 distribution is used to light up parking lots as well as very wide roadways. Type 4 fixtures throw more light forward than they do to the sides, thus is not practical for lighting long roadways, as fixtures will need to be spaced closer together. Wall mounted fixtures such as wallpacks also commonly use type 4 distribution to throw light in front of an exterior entrance door to a building.

Type V / Type VS


Type 5 fixtures throw an equal amount of light in all directions around the fixture. This is usefull for lighting up parking lots, where the light fixtures are placed away from perimeter of the lot. Type V fixtures provide light in a circular pattern, where as Type VS provides light in a square pattern around the fixture. Both however have very similar distribution patterns.

What Is Depth of Discharge (DoD), How Does It Affect a Battery?

deep cycle batteryA solar power system(solar street lighting) is a reliable solution to harness and use energy obtained from the sun. And a solar battery is an indispensable part of this system, as it converts solar energy into battery chemical energy, which we can utilize in our daily life.

Solar batteries are deep-cycle batteries, which are capable of surviving deep discharges, namely, Deep-cycle batteries allow to discharge large proportion of a battery’s capacity. Some of them can reach 90% DoD.

What is DoD?

Before the explanation of DoD, let’s first go through another relevant term, battery capacity.

What is Battery Capacity?

Battery Capacity is the total electrical energy that a battery can store, which is measured in kWH.

For instance:

If the battery can sustain 500 watt loads of power consumption in your house for a total of 60 hours, then its capacity would be 0.5×60=30kWH. During that period, the battery goes from being fully charged, to a state of being completely discharged.

In the real world, completely discharging a battery could result in irreversible loss to its lifespan and capacity. We have another article to explain why this damage could happen:

Above is an extreme example of over discharging, 100% DoD (Depth of Discharge)


what is DoD and how does it affect a battery’s lifespan?

Let’s explain, one by one:

What is DoD?

DoD stands for Depth of Discharge, which measures how deeply discharged a battery is, assuming the battery has a nominal capacity of 100 kWh, which discharges 30kW in 1 hour. Its DOD would be (30x 1)/100 = 30%.

30 percent DoD depth of discharge

30% Depth of Discharge

Since over discharge can dramatically damage a rechargeable battery, a concrete request on maximum DoD is defined by manufacturers.

This data is very useful for you when you are designing an off-grid solar power system – you can set up the LVD (Low Voltage Disconnect) function on the solar charge controller to disconnect the battery from loads before reaching the limited DoD, established by the manufacturer.

off-grid solar power system

off-grid solar power system

Flooded lead-acid usually has 50% DoD, while lithium-ion can reach up to 80% DoD.



LiFePO4 performs better than any other lithium-ion battery and can reach up to 90%, and our advanced integrated solar street lights have adopted the LiFePO4 battery.

Some other manufacturers may describe the data as SOC.

What is SOC?

SOC is the acronym for the State of Charge. Just like the depth of discharge, SOC is a term of measurement in batteries. In fact, SOC is the direct opposite of DOD – while DOD is at 100%, SOC is at 0%; when DoD is at 40%, SoC is at 60%.

Depth of Discharge vs Cycle Life

Why is DoD important to battery?

We can equate battery cycle life with battery lifespan. Manufacturers commonly declare the cycle life at a certain value of DoD; for example, LiNCM declares the cycle life to be 1900 @ 80% DoD.

The larger the DoD every cycle, the smaller the available cycle times will be.

We can see that DoD affects the life expectancy of a battery directly, and this theory applies to most rechargeable batteries: lithium-ion, lead-acid or nickel-iron.

DoD vs. Cycle times



From this graph, we can see a dramatic disparity: the battery’s cycle life is up to 7000 times at 10% DoD, while only 500 times at 100% DoD.

Besides Depth of Discharge, the working temperature also has a great impact on battery performance.

Battery capacity and working temperature

The charge and discharge of a battery depend on chemical reactions inside, while the chemical reaction of the battery has a great relationship with the temperature.

Its nominal capacity is measured at warm 27°C (80°F) since its chemical reaction performance is most efficient at that temperature.

a battery does not work in freezing weather

Batteries do not work in freezing weather

Low temperatures can reduce the activity of electrolytes in a battery. A battery that provides 100% capacity at 27°C will typically deliver only 40% at –20°C.

Although warmer or higher temperature improves performance slightly, prolonged exposure will evaporate electrolytes and result in the permanent capacity loss.


When sizing the battery for an off-grid solar system, we need to consider that DoD and working temperature are the most important factors.

Use a solar charge controller with LVD (low voltage disconnect) function to ensure that the discharging battery does not exceed the limited DoD, which is advised by the manufacturer, so as to guarantee battery lifespan.

Consider temperature compensation to your battery size when the working temperature is not at nominal capacity temperature, since battery size is not “the bigger the better.”

We have another article explaining why…


What is the difference between solar street lights and traditional street lights


streetlights harness solar and wind energy

With the development of photovoltaic technology, the conversion efficiency of solar panels has improved significantly: from 5% in 1945 (the solar panel’s inception) to 20% in 2015.

Solar panels also stirred a big commercial change all over the world, especially in the Middle East, where Dubai Awards $3.9 Billion Solar Energy Contract couple of months ago.

Indeed, more and more municipal projects choose to use solar street lights to replace traditional streetlights.

But what are the benefits of replacing traditional halogen streetlights with solar streetlights?

And what are the differences between them?

Let’s dive into the useful information!

solar panels array

solar panels array in the rural area

Types of solar streetlights

Typically, there are two types of solar streetlights: off-grid and grid-tied.

Off-grid solar streetlights are disconnected from the electric utility company and stand alone like a small solar lighting system unit. They convert solar energy into battery storage during the day, then illuminate the road at night.

Commonly, they are designed to sustain 3 cloudy days, when there is little solar power to convert.

So, if your location has seasonal rainy days that last more than 3 days, you may consider going with grid-tied solar panel streetlights.

grid-tied electricity energy utility

grid-tied electricity energy utility

Vice versa, grid-tied solar panel streetlights are connected to an electric utility company, and will only use electricity as a backup in case there is a period of prolonged cloudy weather.

Design and installation of streetlights

When it comes to a solar streetlight design and installation,

in order to get optimal results, both off-grid and grid-tied types should consider several engineering parameters: local weather conditions, panel size, light source watts, battery bank size, days of autonomy, lux level on the ground, beam angle and light posts distance.

Traditional halogen streetlights consider little about these parameters.

install 100w solar streetlights

install 100w solar streetlights

LED technology dramatically benefits solar streetlights

Nowadays, with the development of LED lighting technology, all types of streetlights are switching their light sources to LED, because LED provides great lighting efficiency: >150lumen per watt and a long lifespan (>35000 hours), which means there is no maintenance cost for over 7 years.

Meanwhile, rather than traditional halogen bulb lights, which emit diffused light and require a reflector cup on its upper side to reflect light downwards, LED lights emit directional lights, so a reflector cup may not be essential.

Furthermore, it is more feasible to apply a lens on an LED light source to meet different street lighting distribution requirements;


Type III streetlight distribution

for instance, the Type III distribution is meant for roadway lighting, general parking areas and other areas where a larger area of lighting is required.

Additionally, LED lights provide the same brightness as bulb lights, while using less battery energy  (commonly, LED lights only need 1/5 to 1/2 watts compared to halogen lights).

enkonn all in one solar street light 30w front view

30W all in one solar street light front view

enkonn solar street light rear view

30W solar street light rear view

This is important information for solar street lights.

When designed, a solar street system requires a smaller solar panel and a smaller solar battery than before in halogen age. This means that people can integrate solar panel, light source, battery and charge controller into one structure when designing a compact structure for solar street lights.

Finally, new compact solar streetlights, also called all-in-one solar streetlights, have become popular in recent years.

We have another article that provides more information about the advantage of these kinds of streetlights:

But what do we get in comparison?

If your projects relate to grid-tied types, switching to LED is the most viable solution to reduce your power consumption. Furthermore, grid-tied projects can use solar panels to harness solar energy to reduce, even more, the electricity bill every month.

If your projects are new, or are in a rural area where it is impossible to bring in municipal electricity, then off-grid solar streetlights are the best option.

Impact on the Environment

Suffice it to say, solar panel streetlights, which harness green and free energy from the sun, have less or no impact on the environment, while traditional streetlights use the electricity, which is produced from non-renewable energy. Moreover, the use of non-renewable energy also results in the production of greenhouse gas – carbon dioxide.

grid tied electricity and pollution

grid tied electricity and pollution

Initial investment and future cost

The initial investment of solar streetlights is higher than conventional halogen streetlights because of the higher cost of solar panels and batteries. But since it harnesses free solar energy, future savings will offset the upfront investment. In the long term, solar streetlights are more cost-effective, for sure.

go solar upfront payment

go solar upfront payment


The kind of streetlights one should select is based on the concrete requirements of projects and one’s budgets. Switching to LED fixtures will lower the power consumption and system loads. We should also expect the technology of the graphene battery, which could be the revolutionary energy storage technology in the future. Also, we think the graphene battery technology will benefit solar lighting dramatically as LED technology since a powerful battery will ensure longer days of autonomy at the same battery size level.

Let’s expect the new battery technology.

What do you think? I hope to hear your comments :)

Solar Charge Controller: The Definitive Guide

Chapter 1: What is a solar charge controller?

A solar charge controller, or solar charge regulator, is an important instrument in almost all solar power systems that use batteries as a chemical energy storage solution. It is used in stand-alone or hybrid solar power systems but not used in straight grid-tied systems, which don’t have rechargeable batteries.

stand-alone solar power system

Stand-alone solar power system

Its two basic functions are very simple:

  1. Prevents batteries from overcharging
  2. Blocks the flow of reverse current.

Overcharging can result in battery overheating, or, in an extreme possibility, a fire. Overcharged deep-cycle flooded batteries could also emit gas of hydrogen, which is explosive. What’s more, overcharging will quickly ruin the battery, thus shortening its lifespan dramatically.

Burned lead-acid battery

Burned lead-acid battery

Solar charge controllers can preclude the flow of reverse current from batteries to solar panels at night when the voltage of solar panels is lower than that of batteries.

Furthermore, solar charge controllers have other optional features, such as battery temperature sensor & compensation, Low-voltage disconnect (LVD), Load control (dusk to dawn), Displays, remote monitoring and diversion load control.

Let’s dive into the article to check these functions & features one by one.

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Chapter 2: Charging a battery: Multi-stage charging

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But before we dive directly into Chapter 3: Functions and features of a solar charge controller, we’d better take a look at necessary information about charging a battery.

If you are already quite familiar with this piece of information, you could jump to chapter 3 from here.

Pour water into cup

Pour water into a cup

2.1 Brief interpretation

Imagine pouring water into a cup – at the beginning, you will pour at a faster rate; when the cup is close to full, water flow slows down so that the water will not overflow from the cup. On the contrary, if you keep pouring water at a faster rate, it’s hard for you to stop the flow in time at the end, and water will overflow from that cup.

Charging solar battery

Charging solar battery

The same theory applies to charging a battery:

  • When the battery is low, the charge controller delivers lots of energy for a quick charge
  • When the battery is close to full, it slows the charger by regulating its voltage and current.
  • When the battery is full, it sends only a trickle of power to keep a full charge.

This is the so-called multi-stage charging.

2.2 Example: 3-4 Stages

Set Points:

In order to make sure you can easily understand the following content, which refers to an example of multi-stage charging (3-4 Stages), let’s firstly explain the jargon “set points.”

In brief,

the solar charge controller is set to change its charging rate at specific voltages, which are called the set points.

Set points are usually temperature compensated, and we will discuss this topic after the example of multi-stage charging.

Now, let’s go through the example in detail

The following is an example from MorningStar, which has 4 stages of charging.

MorningStar 4 stages of charging

Source: MorningStar, 4 stages of charging

2.2.1 Stage 1: Bulk Charge

At this stage, the battery bank is low, and its voltage is lower than the absorption voltage set-point. So, the solar charge controller will send as much available solar energy as possible to the battery bank for recharging.

2.2.2 Stage 2: Absorption Charge

When its voltage reaches the absorption voltage set-point, the output voltage of the solar charge controller will keep a relatively constant value. Steady voltage input prevents a battery bank from over-heating and excessive gassing. Commonly, the battery bank could be fully charged at this stage.

2.2.3 Stage 3: Float charge

As we know, the battery bank is fully charged at the absorption stage, and a fully charged battery cannot convert solar energy into chemical energy anymore. Further power from the charge controller will only be turned into heating and gassing, as it is overcharging.

Trickle from tap

Trickle from tap

The float stage is designed to prevent the battery bank from long-term overcharging. At this stage, the charge controller will reduce the charging voltage and deliver a very small amount of power, like trickles, so as to maintain the battery bank and preclude further heating and gassing

2.2.4 Stage 4: Equalization charge

The equalize charge uses a higher voltage than that of absorption charging, so as to level all the cells in a battery bank. As we know, batteries in series or/and parallels constitute a battery bank. If some cells in the battery bank are not fully recharged, this stage will make them all fully recharged and complete all the battery chemical reactions.

Boiling water

Boiling water

Since it follows stage 3 (when the battery bank is fully recharged), when we raise the voltage and send more power to the batteries, the electrolytes will look like they are boiling. In actuality, it is not hot; it is hydrogen generated from the electrolytes, producing a lot of bubbles. These bubbles stir the electrolytes.

Stirring the electrolytes regularly in this way is essential to a flooded battery bank.

We can consider it a periodic overcharge, but it is beneficial (sometimes essential) to certain batteries, such as flooded batteries and not sealed batteries, like AGM and Gel.

Commonly you could find in battery specifications how long the equalization charge should last, and then set the parameter in the charge controller accordingly.

2.3 Why flooded battery banks need equalization

In short,

to preclude the sulfation of a lead-acid battery.

chemical reaction of discharging

The chemical reaction of discharging

The chemical reactions of battery discharging generate soft lead sulfate crystals, which usually are attached to the surface of the plates. If the battery keeps working in this kind of condition, as time passes by, the soft sulfate crystals will multiply and become even harder and harder, making them pretty difficult to convert back to soft ones, or even further activate materials that were a part of the electrolyte.

The sulfation of lead-acid batteries is the scourge of a battery failure. This issue is common in long-term, undercharged battery banks.

If charged completely, the soft sulfate crystals can be converted back to active materials, but a solar battery is seldom fully recharged, especially in a not well-designed solar PV system, where either the solar panel is too small or the battery bank is oversized.

Sulfation of lead-acid battery

Sulfation of lead-acid battery

Only a periodic overcharge at high voltage can solve this problem; namely, equalization charging, which works at high voltage, generates bubbles and stirs the electrolyte. That’s why stage 4 is essential to a flooded battery bank. In many off-grid solar systems, we usually use a generator + charger to equalize the flooded solar battery periodically, according to the battery specification.

2.4 Control set points vs. temperature

Since absorption set-point (stage 2), float set-point (stage 3) and equalization set-point (stage 4) all can be compensated for temperature if there is a temperature sensor, we would like to spare some words for this little topic.

In some advanced charge controllers, multi-stage charging set-points fluctuate with the battery’s temperature. This is called a “temperature compensation” feature.

The controller has a temperature sensor, and when the battery temperature is low, the set point will be raised, and vice versa – it will adjust accordingly once the temperature gets higher.

Temperature sensor probe

Temperature sensor probe

Some controllers have built-in temperature sensors, so they must be installed in proximity to the battery to detect the temperature. Others may have a temperature probe that should be attached to the battery directly; a cable will connect it to the controller to report battery temperature.

If your batteries are applied to a situation where temperature fluctuation is larger than 15 degrees Celsius every day, adopting a controller with temperature compensation is preferable.

2.5 Control set points vs. battery type

When we come to battery type, another article about solar batteries is recommended.

Most solar power systems adopt a deep-cycle, lead-acid battery, of which there are 2 types: flooded type and sealed type. A lead-acid flooded battery is not only economical, but also prevalent in the market.

Various solar battery types

Various solar battery types

Battery types also affect the design of set-points for solar charge controllers; modern controllers have the feature to allow you to select the battery types before connecting to a solar power system.

2.6 Determining the ideal set points

Finally, we come to the theory about determining the ideal set points. Frankly speaking, it is more about equilibrium between quick charging and maintenance trickle charging. The user of a solar power system should take various factors into consideration, such as ambient temperature, solar intensity, battery type and even home appliance loads.

It is necessary to only cope with the top 1 or 2 factors; that is enough in most cases.

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Chapter 3: What is the function of solar charge controller?

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3.1 Preventing overcharge

When a battery is completely charged, it cannot store more solar energy as chemical energy. But if power is continuously applied to the fully charged battery at a high rate, the power will be turned into heat and gassing, which would present as a flooded battery with a lot of bubbles from the electrolytes. That is the hydrogen gas, which is generated from a chemical reaction. These gases are dangerous since they are explosive. Overcharging also accelerates battery aging.  And then we need a solar charge controller.

Damaged battery due to overcharge

Damaged battery due to overcharge

The main function of the solar charge controller is to regulate the voltage and current that is generated by solar panels going to the batteries to prevent batteries from overcharging and guarantee the batteries a safe working condition and a longer lifespan.

There are 3 types of regulators:

1. Current regulator

A current regulator acts like a switch. It simply switches the circuit on or off to control the energy flow to the battery bank, just like stage 1 bulk charging. They are usually called shunt controllers, which are no longer used due to their obsolete technology.

2. Pulse width modulation (PWM)

Shunt controllers shut down the current completely, while the PWM controller reduces the current gradually. PWM is more similar with stage 3 float charging.

We will have an in-depth discussion about PWM and MPPT when we start the topic: PWM VS MPPT which one is better.

3. Voltage regulator

Voltage regulation is common. The solar charge controller regulates the charging in response to the battery voltage. It is quite simple. When the voltage of a battery reaches a certain value, the controller protects the battery from overcharging by reducing the power. When the voltage of a battery drops because of a large sum of power consumption, the controller will allow bulk charging again.

3.2 Blocking reverse current

The second main function is to prevent reverse current flow.

At night, or whenever there is no sunlight, the solar panel does not have power to convert into electricity, and, in a solar power system, the voltage of the battery bank will be higher than the voltage of the solar panel, since we all know electricity flows from high voltage to low voltage. So, without a charge controller, the electricity will flow from the battery bank to the solar panel, which is a waste of power, as the solar power system takes efforts to collect energy during the day but wasting a little of them at night. Although the loss is only a little in proportion to the total energy collected, it is not hard to solve.

Blocking Reverse Current at night

Blocking Reverse Current at night

A solar charge controller can deal with this problem.

Most controllers allow the flow to go only from solar panel into a battery bank by designing into the circuit a semiconductor, which only passes currents in one direction.

Some controllers have a mechanical switch, which is also called a relay. When the relay clicks on and off, you will hear a clatter sound. When the voltage of the solar panels is lower than that of the battery bank, it detects and then switches off the circuit, disconnecting the solar panels from the battery bank.

3.3 Load control

Some solar charge controllers are designed with load control, allowing you to connect a DC load, such as an LED lamp (a concrete example is on our website all-in-one solar LED street lights), direct to the solar charge controller, and the load control will turn the lamp on and off according to its pre-settings (the voltage of battery, photocell sensor, or a timer).

Solar charge controller in solar street lights

Solar charge controller in solar street lights

For example, there commonly are timers in LED solar street lights, and the load control will read the time from the timer and then execute the command: turn the LED on at 7:00 pm at dusk and turn it off at 6:00 am the next morning. Or the load control will read information from the photocell sensor and then control the LED on and off according to the brightness of the ambient environment.

3.4 Low voltage disconnect (LVD)

Imagine that you are boiling water in a pot and you forget to turn off the fire until the boiling water is totally evaporated; no longer any water in the dry pot and the pot overheats. The pot is destroyed permanently. In the same way, discharging a solar battery completely will result in permanent damage to a battery.

Burned pot

Burned pot

Deep cycle batteries are widely used in solar power systems. The Depth of Discharge (DOD) could be as large as 80%; however, they are susceptible to permanent damage if discharged up to 90% or, even worse, 100%.

If you wait to switch off the DC load from your batteries until you find your lights dimming, the battery damage could have already happened. Both battery capacity and life expectancy will be decreased every time when over-discharge happens. If the battery were set to work in this kind of over-discharge state for a period of time, it would be ruined quickly.

The only practical solution to protect batteries from over-discharge is to switch loads (such as appliances, LED lights and so on) off and on, provided that the voltage has recovered from bulk charging.

Typically, if a 12V battery drops to 10.9 volts, the battery would be on the verge of over-discharging. In the same way, 21.9 volts for a 24V battery.

Low voltage disconnect

Low voltage disconnect

If your home solar system has some DC loads, the LVD feature is necessary. Some LVDs are integrated into charge controllers while others aren’t.

3.5 Overload protection



When the input current flow is much higher than what the circuit can safely deal with, your system overloads. This can lead your system to overheat or even cause a fire. Overload can be caused by different reasons, such as a wrong wiring design (short circuit), or a problematic appliance (a stuck fan). Commonly, a push-button reset is designed for the overload protection circuit.

However, there is a built-in overload protection in each solar charge controller; large solar power systems usually require double safety protection: fuses or circuit breakers. If the wire carrying capacity is smaller than the overload limit of the controller, then setting up a fuse or breaker in your circuit is a must.

3.6 Displays

The displays of solar charge controllers vary from LED indicators to LCD screen displays, with information of voltage and current. Displays to solar power systems are what console dashboards are to cars. They provide you with detailed data so that you can monitor the state of your battery bank: how much energy you are using or generating.

Solar charge controller with LED indicators

Solar charge controller with LED indicators

If your system already has a self-contained monitor, then the display feature would not be important. Even the cheapest monitor would include basic meters, just as controllers have.

Solar charge controller with LCD Screen

Solar charge controller with LCD Screen

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Chapter 4: PWM charge controller

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4.1 Need-to-know glossaries

At the beginning, we will go through some glossaries – refer to the following table.

Nominal Cells Voc Vmp
12V 36 22V 17V
20V 60 38V 30V
24V 72 44V 36V
  • Voc, open-circuit voltage, is the maximum voltage across a PV cell, when you measure a solar panel in theoretically standard test conditions (STC) with only a voltmeter connected. The voltage the meter receives is the Voc.
  • Vmp, voltage at maximum power, is the output voltage of solar panels when connected with the PV system.
  • Nominal Voltage is a reference voltage used to categorize solar equipment in an off-grid system. In a grid-tied system, the nominal voltages (12v, 24v and 48v) are meaningless.
120W nominal 12V Monocrystalline solar panel with 36 pieces of silicon squares

120W nominal 12V Monocrystalline solar panel with 36 pieces of silicon squares

Although charging a battery requires higher voltage, nominal voltages can help you find out corresponding equipment (such as a battery bank) with which a solar panel can match.


a 12V solar panel actually has Voc of 22V and Vmp of 17V, with 36 pieces of silicon squares on the front side.


the 24V solar panel has Voc of 44V and Vmp of 36V, with 72 pieces of silicon squares.

You might be wondering: why a 12-volt panel is not 12 volts?

here’s the deal.

4.2 Why 12-volt panels are 17 volts

A fully charged 12V battery is actually approximately 12.6 volts; to charge a 12V battery, we need higher input voltage – about 13.7-14.4 volts from a solar panel. But why did we design the solar panel Vmp to 17V and not just 14V?

A Voc of a solar panel is measured under Standard Test Conditions or STC, and Vmp is also measured under STC, where the ambient temperature isn’t too hot, the intensity of sunshine is perfect – no clouds, no haze. However, we are not always that lucky. If we encounter some bad weather – for example, hazy or cloudy days – the voltage of a solar panel will drop; so, the panels should be designed with some extra voltage so that your system can still receive enough voltage, even if the weather is not ideal; i.e. no sunlight.

4.3 Charge controller types:

There are 3 types of solar charge controllers:

  • Shunt controllers
  • PWM
  • MPPT

Shunt controllers: We mentioned shunt controllers when we talked about current regulation – they act just like a switch, turning on and off the flow of current to a battery. You may still see a few on old systems, although they have already been taken off the market. PWM and MPPT are the 2 main types that prevail today.


Let’s go into PWM first.

4.4 What is PWM solar charge controller?

PWM (Pulse Width Modulated), literally, works by modulating its current pulse width.

PWM sends to the battery intermittent charging pulses rather than a steady power output. It operates more like stage-3 float charging that generates trickles of currents to battery.

But how fast (frequency) and how long (width) the pulse should be produced is determined by the state of the battery it detects. If the battery is already fully charged, and the loads in the system are not working, the PWM will only send a very short pulse every few seconds; for a discharged battery, the pulses would be near to continuous. This is the basic working principle.

Although PWM is less expensive than MPPT, because of the sharp pulse the PWM generates, when processing a rapid on and off switch during working, your TV, radios or telephone signals may often be interfered with. That’s the inherent downside of PWM.

When your system chooses PWM as the charge controller, it is important to make the nominal voltage of solar panels the same as the nominal voltage of a battery bank;


PWM in 12V system

PWM in 12V system

if your battery bank is 12V, you must select 12V solar panel as well.

PWM in 24V system

PWM in 24V system

And if your battery bank is 24V, then you must use a 24V solar panel, or wire two 12V solar panels in series, to make it a 24V.

PWM in 48V system

PWM in 48V system

But if your battery bank is 48V, then you need to wire four 12V solar panels in series, or two 24V solar panels in series, to get 48V.

And so on.

Meanwhile, make sure the PWM specifications match that of your battery bank, too.

4.5 How big of a solar charge controller do I need: PWM

How to size a PWM when we design an off-grid PV system?

Step 1, Get the Isc (Short Circuit Amps) and the Voc (Open-Circuit Voltage) solar panel from its nameplate, and figure out how many strings in parallel are in the solar array.

solar panel nameplate

Solar panel nameplate

From the nameplate,

we read the Voc 22.1V and Isc 8.68A, and we confirm that it is a nominal 12V solar panel from Voc.

Let’s start with a simple example and assume we only have 1 string in parallel.

Step 2, Multiply Isc by the number of strings in parallel.

8.68Isc x 1 string = 8.68A

Step 3, multiply by 1.25 safety factor. (Why the factor is 1.25: refer to NEC 690.8(A)(1) Photovoltaic Source Circuit Currents)

8.68Isc x 1 string x 1.25 = 10.85A

So, we can choose a PWM that’s current load capacity should be larger than 10.85A.

PWM in 24V 2 strings system

PWM in 24V 2 strings system

Now, let’s check another example with 2 strings in 2 parallels using the same 140w panel mentioned just now.

But do remember – we are using a PWM charge controller, so we need to pay attention to how many panels are in strings so that the voltage of the solar array matches the voltage of the battery bank.

In this example, we have 2 parallel strings and 2 panels in series, so the solar array is for 24V battery system.

8.68Isc x 2 strings x 1.25 = 21.7A

A 25A PWM solar charge controller would be enough.

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Chapter 5: MPPT charge controller

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5.1 How does a MPPT solar charge controller work?

What is the meaning of MPPT?

MPPT is the acronym for Maximum Power Point Tracking, which is a type of electronic digital tracking.

MPPT is more sophisticated – and also the more expensive – of the two. MPPT has around 94% – 98% conversion efficiency. That is power in (from the solar panel) almost equals power out (to battery bank).

The MPPT charge controllers read the output of solar panels and the voltage of batteries to figure out the best power point to draw from solar panel; then, the MPPT turns the voltage down to meet the battery charging voltage while raising the current. By doing this, the MPPT can increase energy that we finally get from solar panels by almost 40%, compared with PWM, since PWM cannot increase current to track the maximum power point.

Unlike PWM, which requires the voltages match with both sides, MPPT can be applied to the PV system, which voltage of solar array is higher than that of the battery bank. This feature brings the MPPT many advantages, which we will discuss in Chapter 6


let’s move on to the examples so that you can catch the point quickly.

5.2 How to size mppt solar charge controller?

Remember the nominal 20V panels with 60 pieces of cells?

In the PWM circuit, they are too large to match a 12V battery bank and too small for a 24V battery bank, but the MPPT can solve this embarrassing situation.

The 20V panel has 30Vmp and 9A Imp, and its rated power = 30 x 9 = 270W.

Assume the 20V panel applies to the 12V battery. The MPPT will convert 30V down to around 14V to charge the battery, and increases the current so that it can draw maximum power from the solar panel.

If we take 30V down to 14V, the decreased rate is

30/14 = 2.14.

Then the increased current is

9 x 2.14 = 19.28A.


30 x 9 = 14 x 19.28 = 270 watts (power in equals power out);

since the output current is 19.28A, we multiply by 1.25 safe factor.

We get

19.28 x 1.25 = 24.1A.

So, it will be good that we choose an MPPT with a current capacity larger than 24.1A.

Another example with 2 strings in 2 parallels using the nominal 20V panel to charge the 12V battery: the total power in is

270 x 4 = 1080 W.

The current output would be

1080 / 14 = 77.14A.

Multiply by 1.25

77.14 x 1.25 = 96.43A.

So, we are going to choose a 100A MPPT.

5.3 Charge controller sizing: the voltage of the controller

One more thing we need to pay attention to when sizing a solar charge controller is the voltage. Make sure the controller is capable of carrying input voltage from the panels. A 150V charge controller can only carry three 20v nominal panels in series. You may wonder…3 x 20 = 60V? That is far away from 150V!


That is because the actual voltage that solar panels generate could be much higher than 20V; sometimes, higher than the Vmp 30V. So, we use Voc to do the calculation. Voc = 38V.

3 x 38 = 114V

Then three nominal 20V panel in series is 114V

NEC table 690.7

NEC table 690.7

Since panel voltage will increase in the cold weather, refer to the NEC Table 690.7. Then we pick up the safest factor, 1.25, multiply 114v by 1.25,

we get

114 x 1.25 = 142.5V.

Now you can understand why a 150V controller can only support three 20V in series, especially in winter.

Nowadays, newly developed controllers could have much higher voltages; some models even support as much as 700V input. This is very important when your solar array is settled far away from your battery bank.

Let’s explore the reason in chapter 6.

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Chapter 6: PWM vs. MPPT

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6.1 PWM vs. MPPT: Which one is better?

We have learned about the features of both controllers (PWM & MPPT) in previous chapters. We well noted that PWM does not convert extra voltage into currents, which results in low power conversion rates. In other words, PWM doesn’t transfer all energy that is collected by solar panels to batteries, but MPPT is always tracking the maximum power point from the panels and adjusting its currents and voltage accordingly so that it can transfer all energy collected by solar panel to battery.



A concrete example will explain this clearly:

The basic physical formula:

Power (watts) = V (Volts) x I (Amps)

If we use a nominal 12V, 100W solar panel to charge a 12V battery system, the actual Vmp is 17V, and we can calculate its current output:

I = Power / V

I = 100 / 17 = 5.88 amps

Now we know the panel output is 17V and 5.88A.

Scenario 1: The photovoltaic system is with PWM solar charge controller.

PWM will drag the voltage down to battery charging voltage – approximate 14V. After going through the PWM, the solar energy only remains 14V and 5.88A.

That is:

P = V x I = 14 x 5.88 = 82.32 W

Scenario 2: The photovoltaic system is with the MPPT solar charge controller.

The MPPT not only drags the voltage down to 14V, but also increases the current, so that the power almost equals to power out.

So, if the voltage decreases by 17/14 = 1.21

Then the current to battery increases by 1.21, we get

5.88 x 1.21 = 7.11A

Total power out

P = 14 x 7.11 = 99.54 W

In this example, the power wasted by PWM is

99.54 – 82.32 = 17.22W

Almost 20% energy was not converted to battery chemical energy. If we consider the scenario in a large solar array, the loss could be tremendous.

So, it’s better to use MPPT for large solar array.

6.2 The strengths of MPPT

a) High conversion efficiency

If your photovoltaic system comes with a large solar array, MPPT would be the best choice to boost the solar energy conversion, especially in cold weather, since the panel voltage will rise as the temperature drops. The MPPT conversion rate could rise from 20% to 40%. That’s green and free energy that really saves money on your bill.

Solar panel array in distance

Solar panel array in distance

b) Lower energy loss in cables or lower cost for purchasing cables.

Please remember Ohm’s law formula

V (Volts) = R (Ohm) x I (Amps)

Output power  P(Watts) = V (Volts) x I (Amps)


Resistance loss  PR(Watts) = R (Ohm) x  I2 (Amps)

Then, if your PV panels are installed a long distance from your battery bank, the power loss of cable resistance is considerable ( PR = R x I2  ). Here R represents the resistance of cables. R increases as cable length increases:

Cable resistance formula

Cable resistance formula

But if we double the Voltage of the solar array by wiring them in more series, according to P = V x I, there is no change of total power outputP, so the current through cable I should be half.

Finally, the resistance PR(Watts) = R (Ohm) x  I2 (Amps) will be a quarter than before.

In fact, with MPPT, you could raise the voltage of the solar array even higher to reduce the current flow.

In this case, we increase the panel’s voltage to reduce the resistance loss through cables, and since we are using MPPT, which always tracks to harvest maximum power from panels, we have no voltage waste as PWM may have.

We could review this topic from another aspect. If you cannot raise the panels voltage, then you have to find out some solution to reduce cable resistance, as resistance = resistivity × length / area, it seems the only way is to use cables with large transverse areas, and that will be another huge sum of money to spend.

To recap, when it comes with small systems, PWM is a good solution since it is inexpensive, but for large systems, in order to improve conversion rates and not waste the solar panel capacity of harnessing solar energy, MPPT is preferable. MPPT would always be applied to higher power systems.

6.3 Pros and cons

Learning knowledgeable information from the previous content is necessary before making the decision to purchase a solar charge controller for your PV system. A comparison table, listing the difference between PWM and MPPT, is also suggested. So, we put their pros and cons together to make it more convenient for you to review.

Pros Cons
  • PWM technology has been available in PV systems for a long time and is a relatively stable and mature technology
  • They are cost-effective and are affordable for most consumers
  • PWM can withstand up to 60 amps load currently
  • Most PWMs have a reasonable heat dissipation structure that allows them to work continuously
  • PWM comes in different sizes to suit a wide range of applications
  • If PWM is applied to photovoltaic solar systems, the voltage of the solar panel has to match that of the battery bank
  • The current load capacity of a single PWM has not been developed and is still only up to 60 amps
  • Some smaller sized PWM charge controllers cannot be UL listed due to their poor structure design
  • Some smaller sized PWM do not have fittings of conduit
  • PWM has signal interference problems sometimes. The controllers generate noise in TV or radios
  • PWM limits the expansion of photovoltaic solar systems to some extent
  • It cannot be applied to high voltage off-grid solar arrays
  • MPPT maximizes the conversion of solar energy from PV panels, and the rates can be 40% more efficient than PWM
  • MPPT can be used in cases where the solar panel voltage is higher than the battery voltage.
  • MPPT can withstand up to 80 amps load current
  • MPPT features longer warranties than PWM
  • MPPT does not limit the expansion of solar panels in the system
  • MPPT is the only solution for a hybrid solar power system
  • MPPT are more expensive than PWM. The pricing of some models is double that of a PWM charge controller
  • Since MPPT has more components and functions, its physical size is larger than PWM.
  • MPPT are more complicated, so most time, we need to follow a guide when sizing the solar array
  • MPPT solar controller constantly compels the solar panel array wired in strings

6.4 Does every solar PV system need a charge controller?

The answer is no.

Generally, if your solar panel is less then 5 watts for every 100 amp hours battery, then you do not need a solar charge controller.

Here is a formula we can use:

Quotient = Battery Capacity (Amp Hour) / Imp of solar panel (Amps)

If the quotient is larger than 200, you don’t need a controller; otherwise, you’d better install a controller.

For example, if you have a 200AH battery and 20W panel, the quotient would be 200/1.18=169.5; in this case, you need a controller.

If you have 400AH battery and 10W panel, the quotient would be 400/0.59=677.9; in this case, you do not need a controller.


  • Set Points: The specific voltages that were set for charge controllers to change charging rates.
  • DoD: Depth of Discharge, the proportion of battery capacity (amp hours) removed from a fully charged battery. For example, if total battery capacity is 100 Ah and 40 Ah is already discharged, then the DoD is 40%.
  • Deep Cycle Battery: Lead-acid battery, which can always be deeply discharged to a low state-of-charge. Deep cycle batteries have high DoD.
  • Imp: Current at maximum power; the quotient of maximum power by Vmp.
  • STC: Standard test conditions, ideal conditions in a laboratory where a fixture is tested.
  • Voc: Open-circuit voltage, the maximum voltage across a PV cell, when you measure a solar panel in theoretically standard test conditions (STC) with only voltmeter connected. The voltage the meter gets is the Voc.
  • Vmp: Voltage at maximum power, the output voltage of a solar panel when it is connected to the PV system.
  • Nominal Voltage: A reference voltage used to categorize solar equipment in an off-grid system. In a grid-tied system, the nominal voltages (12v, 24v and 48v) are meaningless.
  • Isc: Short-circuit current, the maximum current across an external circuit that is without any loads or resistance.

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