The voltage and capacity of the lithium wall mounted battery pack, simply from the perspective of the voltage and capacity of the lithium battery pack, have no direct relationship between them, and there is no relevant calculation formula.
The voltage and capacity of powerwall 20 kwh lithium battery pack have been determined during battery design. Lithium battery packs with the same voltage can be made into products with different capacities. The nominal voltage of lifepo4 powerwall battery is 3.2V, the terminal charging voltage is 3.6V, and the terminal discharge voltage is 2.0V. Because the quality and process of the positive and negative electrode materials and electrolyte materials used by various manufacturers are different, their performance will be somewhat different.
The capacity of lithium iron phosphate battery packs varies greatly, and they are divided into three categories: small ones with a few milliampere hours, medium ones with tens of milliampere hours, and large ones with hundreds of milliampere hours. There are some differences in the same parameters of different types of batteries.
Although there is no direct relationship between the two, there are other variables related to voltage and capacity, making them related, that is, the discharge platform of lithium battery pack. When the battery pack is discharged, the voltage will gradually decrease with the passing of current, and the slope is large. Therefore, sometimes the voltage can be used to estimate the remaining capacity of the home battery energy storage. When the voltage is lower and lower, the remaining capacity of the lithium battery pack may be less and less.
However, this estimation method will still be affected by many external factors, and the estimation results will vary greatly.
For example, if the same lithium battery pack has the same residual capacity, the voltage value will change due to the discharge current. The higher the discharge current, the higher the battery voltage; When there is no current, the voltage is not affected by the current, so the highest voltage will be displayed. Temperature also affects the voltage. The lower the temperature, the lower the voltage of lithium battery pack with the same capacity.
The cycle has a major impact on the unloading platform. As the cycle progresses, the discharge platform of the lithium battery pack tends to deteriorate, and the voltage will continue to drop, which is also a major factor in reducing the power supply time of the lithium battery pack.
Some operations during use will also cause voltage fluctuations and differences, resulting in abnormal capacity display of power wall lithium battery pack. For example, a temporary high current consumption connected to a high power load will lead to a rapid drop in the voltage of the lithium battery pack. At the same time, the displayed battery pack capacity will decrease more than the actual capacity. If the large current is removed, the voltage of the battery will rise, resulting in an unreasonable increase in the capacity of the lithium battery pack