How to calculate and match lithium battery pack for solar energy storage system?

Solar energy storage systems are currently the most widely used energy storage systems in the market. In off-grid energy storage systems, lithium battery packs are very important components. So how to match the lithium battery pack?

1. First determine the voltage platform series of the solar energy storage system
At present, many energy storage system voltage platforms are 12V series, especially off-grid energy storage systems, such as solar street lights, solar monitoring equipment energy storage systems, portable energy storage power supplies, and so on. Most of the solar energy storage systems using 12V series are energy storage systems with a power of less than 300W.

Some low-voltage energy storage systems include: 3V series, such as solar emergency lights, solar small signs, etc.; 6V series, such as solar lawn lights, solar signs, etc.; 9V series of energy storage systems are also many, introducing Between 6V and 12V, some solar street lights also have 9V. Solar systems using 9V, 6V, and 3V series are basically small energy storage systems below 30W.

solar lawn light

Some high-voltage energy storage systems include 24V series, such as football field solar lighting, and medium-sized solar portable energy storage systems. The power of these energy storage systems is relatively large, which will be around 500W; there are also 36V and 48V series of energy storage systems. The power of the system will be larger, basically more than 1000W, such as home energy storage system, outdoor portable energy storage power supply, etc., the power will even reach about 5000W; of course, there are larger energy storage systems, the voltage will reach 96V, 192V series, these special high-voltage energy storage systems are basically large-scale energy storage power stations.

2. Matching method of lithium battery pack capacity
Taking the 12V series with the largest batch in the market as an example in the field of technology products, we will share the matching method of lithium battery packs.

At present, there are basically two aspects to match, one is the power supply time of the energy storage system to calculate the match; the other is the solar panel and the charging sunshine time to match.

Let’s talk about the method of matching the capacity of a lithium battery pack according to the power supply time

For example, the 12V series of energy storage systems and 50W solar street lights need to have 10 hours of lighting time per day, and it is also necessary to consider the situation that they cannot be charged on 3 rainy days.

Then the calculated lithium battery pack capacity can be 50W*10h*3 days/12V=125Ah. We can match the 12V125Ah lithium battery pack to support this energy storage system. The calculation method is to divide the total number of watt-hours required by the street lamp by the platform voltage. Among them, if it cannot be charged on cloudy and rainy days, it is necessary to consider increasing the corresponding spare capacity.

Country Solar Street Light

Let's talk about the method of matching the capacity of the lithium battery pack according to the solar panel and the charging sunshine time

For example, it is still a 12V series of energy storage systems. The output power of solar panels is 100W, and the effective sunshine time for charging is 5 hours per day. The energy storage system needs to fully charge the lithium battery pack within one day. How to match the capacity of the lithium battery pack?

The calculation method is 100W*5h/12V=41.7Ah. That is to say, for this energy storage system, we can match the 12V41.7Ah lithium battery pack.

The above calculation method ignores the loss. In the actual use process, it can be calculated according to the specific loss conversion rate. There are also different types of lithium battery packs, and the calculated platform voltage is also different. For example, a 12V system lithium battery pack uses a ternary lithium battery and needs 3 series connected, then the platform voltage will be 3.6V*3 strings=10.8V; The lithium iron phosphate battery pack will use 4 in series, so the voltage platform will become 3.2V*4=12.8V.

A more accurate calculation method needs to add the system loss of the specific product and the corresponding specific platform voltage to calculate, which will be more accurate.