How to Choose Lithium Battery Type for Solar Street Light ?

The lithium ion battery development for many years, today let us talk about the lithium ion battery for solar street light.

Litium Batteries Cell

Table of Contents

12v lithium ion battery Introduce

This type of batteries is rechargeable, so it also called rechargeable lithium batteries. And we know that the rechargeable batteries are wide used in portable electric products, mobile, electric cars, etc. So there are difference from the shape and the specification of this kinds of batteries,

The mobile phone battery is a piece of 3.7v specially designed flat battery. And in other use like camera also used this type designed for the product. In high-power usage scenarios, such as electric cars, solar energy storage battery which will use a battery package made up of batteries cells. These battery cells are the basic unit of the battery pack.

The voltage of a lithium ion battery cells is 3.2-3.7V, so the term of 12v lithium ion battery is 3 series or 4 series battery cells in one package. And the voltage of the batteries is 11.1V or 12.8V, the 12V is a the industry term.

What are the components of a 12v lithium ion battery?

The 12v lithium ion battery pack made up of a plenty of battery cells, protect the circuit board, Insulation board, and plastic package.

The battery cells are welded together by conductors. But the battery after series and parallel connection is not directly output or input. They must pass a suitable circuit protection board to work. When the voltage is higher than 4.2v, the circuit will automatically stop charging. Otherwise, when the voltage is lower than 2.75v, the circuit automatically stops discharging.

Overcharging, over-discharging and short-circuiting will seriously damage the performance of the battery and may lead to risks of use. 

Therefore, there will be an elongated protective circuit board in the battery pack to prevent these risks.

There are many benefits to adding Insulation boards to the battery pack. It will make the battery pack look flat and improve the appearance. The insulation board has the dual function of electrical insulation and heat insulation which improved safety and performance.

Plastic package are usually thermoplastic with blue color. It shrinks under the action of heat, thus tightly wrapping and fixing the entire battery.

The battery cells specification

The lithium ion battery cells can be divided into the following types according to their shape:

14500, 18500, 18650, 22650, 26650, 32600, 32650, 32900, 32675, 38120, 42110, 42120

But what do these numbers represent?

For example, the 18650, “18” means the diameter of the cell is 18mm, “50” means the height of the cell is 50mm, and the last “0” means the cell shape is round.

Generally, the most used for 12v lithium ion battery for solar power are 18650 and 26650.

There are two main types materials of 12v lithium ion battery.

LFP Lithium Battery

Lithium iron phosphate (LFP) is an inorganic compound with the formula LiFePO4.

It is a gray, red-grey, brown or black solid that is insoluble in water. The material has attracted attention as a component of lithium iron phosphate batteries.

The LFP batteries most use cells type is 26650. There is a term is energy density. It described the energy with the weight. The LFP energy density is 120Wh per kilogram. In general, a LFP battery cell is 3.2V, around 2200mAh. The 12v lithium battery pack will use a 4 series connection. So the void load voltage will be 12.8V. So the same capacity of the batteries, a LFP cell size greater than a ternary battery cell.

In 2022, more and more solar applications use the LFP battery such as all in one solar street light, because long life span and stability.

The charging cycle more than 2000 times. It means that even if on cycle is completed every single day, the life time will reach 5.4 years. Moreover, it won’t reach a cycle per day in the actual scenario.

And the life span will be 5-8 years.

In addition to long life span and excellent charge and discharge performance, the biggest advantage of LFP batteries lies in their safety. LFP battery has stable chemical properties and good high temperature stability. The decomposition temperature of the LFP battery is as high as 750 Celsius degrees. Since there are no active elements, it will not burn violently in the case of impact, acupuncture, and short circuit.

Nevertheless, the price of the LFP is the most expensive of all type of the lithium ion batteries.

Ternary Lithium Battery

Ternary lithium battery refers to a lithium battery containing transition metal lithium intercalation oxide, the transition metal lithium intercalation oxide contains nickel, cobalt and manganese, which can be expressed as LiMnxNiyCo1-x-yO2 (0 <x <0.5, 0 < y <0.5). 

The material combines the advantages of lithium cobalt oxide, lithium nickelate and lithium manganate, and forms a ternary synergistic effect of the three materials, and its comprehensive performance is better than any single combined compound.

Compare to the LFP battery the Ternary lithium battery use more is 18650. 

Of course, the type of 14450 is also common. The energy density is 200Wh per kilogram. The density is high. And the cell is 3.7V, a 12v battery pack made up of 3 series connection. So the void load voltage is 11.1V.

This type of batteries also wide use in solar products. The price is moderate and cost-effective, so this type lithium batteries is a strong competitor of LFP.

With the technology development, today the ternary lithium battery performance is more stable.

As battery burning accidents often broke out in the past few years, then battery manufacturers are more concerned about safety. They optimized the internal design and test and classify battery cells before use. The safety in use is greatly improved.

Actually, Ternary battery has better high temperature resistance. It can still run well above 40 Celsius degrees. The self-discharge loss can reach two years at no load.

Batteries Package for Solar Lights

The solar power has developed for tens of years. And as the storage battery of the solar energy, there are many rechargeable batteries options. Usually, we use lead acid batteries or lithium ion batteries for solar lights.

The low cost of lead-acid batteries is the most important reason that has not been eliminated.

In fact, it is already facing serious environmental problems. Heavy metals and acid pollution directly lead to large areas of groundwater being polluted.

Why choose Lithium-ion battery for solar street light ?

Compared with traditional battery technology, lithium-ion batteries charge faster, have a longer life, and have a higher power density, resulting in a longer battery life in a lighter package. When you understand how they work, they can work better for you.

It’s eco-friendly. Compared with lead-acid batteries, lithium batteries are less likely to leak. When the battery life expires, a recycling company will recycle it. Because the value of reuse is also high.

Lithium-ion is long life span. The performance of lead-acid batteries will drop sharply after two years. However, the lead-acid battery can still stabilize above 75% capacity or even higher after 3 years.

12v lithium system or 24v lithium system, how to choose?

12V lithium system is 3 series or 4 series cells. 24 lithium system is 6 series or 8 series.

As we know rated power is equal to rated voltage multiplied by current ( P=UI ).

So the higher the voltage at the same power, the lower the current. Theoretically, 24v lithium system has a small calorific value so the efficiency is high.

But actually the 12v lithium system is very common for solar application. Because the 12v lithium solar application system components are cheaper.

Generally, the output power of solar products is only tens of watts. And the current is only several amperes. The difference in efficiency is not very obvious. And there are more accessories on the market that can be used for 12v lithium systems.

In the application of high-power products, 24v lithium system efficiency is definitely higher than 12v lithium system. For example, electric cars have begun to use the 48v system.

If you want to improve efficiency and are not afraid to spend money, choose 24v boldly.

How to configuring your battery?

The capacity of the batteries should be matched the solar power lights system. 

For example, if your solar panel is 70W, and effective sunlight for 4.5 hours. Thus, the solar panel can generate 70×4.5=315wH electricity. 

If you use the 12v lithium batteries. E=PT=UIT. So the capacity will be 315/12=26.25AH.

And it says the capacity must be greater than 26.25AH to be enough to store the electricity generated by solar panel. 

In fact, I’ll recommend you use a batteries 1.2 to 1.5 times than this capacity or even 2 times. There are 2 main reasons.

Barrel Effect of lithium iron battery

Because of the batteries pack made up of single cells, so when the cells capacity uneven, there will occur barrel effect. The cell with the smallest capacity determines the overall batteries capacity.

When we use pale of 3.7v 2200mAH cells made up a battery pack. But one of the cells actual capacity only 1800mAH, the barrel effect will occur.

When the battery pack in charging, the 1800mAh cell will reach the cut-off voltage 4.2v first. So the protect circuit board will stop charging. So the rest of the 2200mAH cells actual were only charged 1800mAH. This is wastable. 

Vice versa, when the battery pack in discharging, The 1800mAh cell will reach the discharge cut-off voltage 2.75V. The discharging process will be stop prematurely.

In a conclusion, When use a 1.2- 1.5 times capacity battery pack, the issue will be resolved. Even if the barrel effect occur, the capacity in the barrel effect situation still enough. According to the previous example, 1800➗2200✖1.2=0.98. Increment effectively makes up for the loss.

Cycle Times of lithium iron battery

Charge lithium-ion battery no need to let it discharge 100% before recharging. lithium-ion batteries work in charge cycles. 

You complete one charge cycle when you’ve used (discharged) an amount that equals 100% of your battery’s capacity — but not necessarily all from one charge. For instance, you might use 75% of your battery’s capacity one day, then recharge it fully daytime. If you use 25% the next day, you will have discharged a total of 100%, and the two days will add up to one charge cycle. It could take several days to complete a cycle.

The capacity of any type of battery will diminish after a certain amount of recharging. With lithium-ion batteries, the capacity diminishes slightly with each complete charge cycle.

But when use the greater than 1.2 times capacity of batteries, that will hold at least 80% of their original capacity for a high number of charge cycles, which varies depending on the product.

The design principle is that batteries should not be completely discharged, the cycle will be extended accordingly, and the life span will be longer.


Working Environment

The lithium ion batteries working temperature -20- 50. However, the performance of the lithium battery will generally decrease when it is lower than 0℃, and the discharge capacity will be correspondingly reduced. 

Therefore, the operating temperature for the full performance of the lithium battery is usually 0~40℃.

As the lithium battery pack has been waterproofed to a certain extent, the general wind and rain are no problem. But it cannot be used soaked in water.

Top 10 Lithium-ion Battery Brands in the World

This is a global top 10 lithium ion battery manufacture brand index below.

Samsung SDI
#1 Brand Index 9.6
#2 Brand Index 9.5
#3 Brand Index 9.4
LG Chem
#4 Brand Index 9.3
#5 Brand Index 9.2
A123 Systems
#6 Brand Index 9.1
eCobalt Solutions
#7 Brand Index 9.0
#8 Brand Index 8.9
Contemporary Amperex Technology
#9 Brand Index 8.8
Johnson Controls
#10 Brand Index 8.7

Top 10 Lithium-ion Battery Brands in the China

#1 BYD  

Rating: 84.06%

Shenzhen BYD Lithium Battery Co., Ltd., BYD IT, a well-known brand of lithium batteries, the world’s largest manufacturer of rechargeable batteries, nickel-cadmium batteries / mobile phone lithium batteries, a high-tech enterprise with strong research and development capabilities.

#2 BAK

Rating: 88.18%

The number of employees in Chinese companies established in 2001 has reached more than 8,000. The company’s products are mainly mobile phone batteries, laptop batteries and power batteries. It has become one of the world’s largest professional manufacturers of lithium batteries. Low cost and high quality have become BAK’s business philosophy. BAK’s business market has already covered the whole country and has gradually become a global development trend.


Rating: 72.73%

Established in 1983, Desay Group is already in the forefront of the top 100 Chinese electronic information companies, focusing on automotive electronics, new energy batteries, LED optoelectronics and other fields, and is committed to providing customers with the highest quality products. The development is already a large-scale enterprise whose annual sales can reach 10 billion yuan.

#4 OptimumNano

Rating: 87.37%

Shenzhen OptimumNano Battery Co., Ltd., a supplier of energy storage system solutions, an early domestic enterprise that developed lithium iron phosphate new energy vehicle power batteries, vehicle starting power supplies, etc.


Rating: 86.21%

China’s well-known lithium battery brand, Tianjin local famous brand, and China’s representative lithium battery brand. The company was established in 1997 and is a subsidiary of Tianjin Lishen Battery Co., Ltd. and is one of the professional manufacturers of lithium-ion batteries in China.


Rating: 94.28%

Scud (Fujian) Electronics Co., Ltd., a well-known battery brand, a famous brand in Fujian Province, a famous brand in Fujian Province, one of the professional lithium-ion battery module manufacturers with the strongest design capabilities and complete supporting capabilities.


Rating: 96.48%

The brand of BEILIANG is a subsidiary of Shenzhen LIANGPIN Electronic Technology Co., Ltd. It is a professional manufacturer of secondary rechargeable batteries, battery chargers, mini fans. Button batteries have no popular consumer market. From development to product design and production, the whole process is strictly followed. Every detail, to ensure environmental protection standards and quality requirements, to ensure safety and quality.


Rating: 66.2%

Hefei Guoxuan High-Tech Power Energy Co., Ltd., a supplier and service provider of battery materials, battery cell design technology, etc., is an enterprise specializing in the research and development, production and operation of new lithium-ion batteries and their materials.


Rating: 40.74%

AVIC Lithium Battery (Luoyang) Co., Ltd., a well-known brand of lithium batteries, the core drafting unit of industry standards, a leading domestic professional manufacturing company for large-capacity, high-rate, long-life lithium-ion power batteries, a national 863 project undertaker, and Chengfei Integrated Holding Company.


Rating: 90.31%

Harbin Coslight Group Co., Ltd., a well-known (famous) battery brand, a high-tech enterprise, a well-known brand in Heilongjiang Province, a famous brand product in Heilongjiang Province, a leading brand in the domestic battery market share, and one of the largest domestic battery manufacturers with the most advanced technology and equipment.

Final words

This article details the 12v lithium ion battery used in the solar street light system. 

In fact, this lithium battery is also widely used in other products. China is already the largest battery producer, if you need to buy such products, you can contact us. If you are interested in such content, you can also subscribe.

Judy Deng

Judy Deng

A blogger interested in solar and LED lighting. He studies how to make people's lives greener and more environmentally friendly. Also served as a faculty member for non-profit organizations.

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