Multi-series Lithium Ion Battery Pack Equalization

In today market, there are two balancing methods for a multi-series lithium ion battery pack, including traditional passive balancing and automatic balancing. There is some controversy about whether the battery management circuit should have a balancer function. Here are some shares about it.

If the production and storage time of a lithium ion battery pack composed of multiple series cells is relatively long, due to the different static power consumption of the management circuit and the different self-discharge rate of each cell, the voltage of each string of the battery pack will be inconsistent, and there will be a significant voltage difference. In order to ensure the consistency of capacity, the equalization circuit has a balanced cell voltage effect on the battery pack, and realizes full charge and complete discharge of the battery pack to maximize its effect.

Many people believe that the equalization circuit works only when a lithium ion battery pack is used to the middle and late stages. In fact when the battery pack is used to the middle and late stages, the capacity difference due to the different capacity loss of each cell can not be compensated by the equalization circuit. Therefore, we should understand that what the equalization circuit balances is the voltage, while the capacity can not be compensated.

A lithium ion battery pack with less than 4 strings is recommended not to be equipped with an equalization function. But it is necessary to strictly match the composed cells and try to achieve the consistency of cell capacity and internal resistance. Lithium ion batteries are not afraid of use but storage! They should be stored as single cells rather than the whole battery packs. After the battery pack is completed, it should be delivered to consumers for use as soon as possible.

When a multi-series lithium ion battery pack is charged, it should be ensured that each cell is charged equally, otherwise the performance and life of the entire battery pack will be affected during use. There are commonly used equalization charging technologies including constant shunt resistance equalization charging, on-off shunt resistance equalization charging, uniform battery voltage equalization charging, switched capacitor equalization charging, step-down converter equalization charging, inductance equalization charging, etc.

Multi-series Lithium Ion Battery Pack Equalization