The solar photovoltaic energy storage system is the market’s most widely used energy storage system. Lithium battery packs are important components in off-grid photovoltaic energy storage systems. So how to match the lithium battery pack?

The solar photovoltaic energy storage system is the market’s most widely used energy storage system. Lithium battery packs are important components in off-grid photovoltaic energy storage systems. So how to match the lithium battery pack?

12V system

At present, the voltage of many photovoltaic energy storage systems is 12V, especially off-grid solar energy systems, such as solar street lights, solar monitoring equipment, small portable photovoltaic energy storage power supplies, and so on. Most of the solar photovoltaic energy storage systems using the 12V series are energy storage systems with a power of less than 300W.aic energy storage power stations.

3V/6V/9V system

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

24V system

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

Basically, the calculation is considered from two aspects, one is the power supply time of the energy storage system; the other is the sunshine time from the solar panel and charging.

1- Consider the power supply time to determine the capacity of the lithium battery pack

For example, a 12V series photovoltaic energy storage system and a 30W power solar street light need to have 10 hours of lighting time every day, and it is necessary to consider the situation that it cannot be charged on three rainy days.

Then the calculated lithium battery pack capacity can be 30W*10h*3 days/12V=75Ah. We can match the 12V75Ah lithium battery pack to support this photovoltaic energy storage system. The calculation formula is:

Working wattage × working time ÷ working voltage = capacity required by the battery

However, on cloudy and rainy days, because it cannot be charged, it is necessary to consider increasing the corresponding spare capacity.

No.2 Considering the solar panel and charging sunshine time to determine the capacity of the lithium battery pack

For example, for a 12V series photovoltaic energy storage system, the output power of the solar panel 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 within one day. How to match the capacity of the lithium battery pack?

The calculation method is 100W*5h/12V=41.7Ah. In other words, for this photovoltaic energy storage system, we need at least a lithium battery pack with a capacity of 12V41.7Ah to fully store the energy converted by the solar panel during the sunshine period.

Of course, it is very important that we cannot ignore that the above formula is only applicable when there is no loss in a perfect state. In actual use, our circuit system will have different degrees of loss. When calculating, the loss rate needs to be considered.

Another point to note is that different types of lithium battery packs have different calculated platform voltages. For example, if a 12V system lithium battery pack uses ternary lithium batteries, 3 batteries are required in series, and the platform voltage will be 3.6V*3 String = 10.8V; and the lithium iron phosphate battery pack will use 4 series in series, then the voltage platform will become 3.2V*4=12.8V.

Therefore, a more accurate calculation method must consider the system loss of the specific product and the corresponding platform voltage to calculate, which will be more accurate.

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