The best battery equalizer function is very important for the battery management system of electric vehicles (EV) because it can increase the mileage of the vehicle and ensure the safe operation of the battery of the electric vehicle. In addition, the battery balance function is also used to correct the imbalance of the battery itself. Due to mismatch problems in the manufacturing process or operating conditions, after a period of use, all batteries (including batteries in electric vehicles) will have unbalance problems, which will lead to varying degrees of aging of each battery cell.

Even if other battery cells still have a lot of power remaining, the entire battery pack can only be charged after its weakest battery cell is fully discharged. Therefore, balancing the battery cells can increase the capacity of the battery pack to a greater extent, and ensure that all the energy in it can be used, thereby increasing the battery life. Using this technology for electric vehicle batteries can increase driving range. In addition to increasing the battery capacity to a greater extent, the best battery equalizer function can also prevent battery cells from overcharging and over-discharging (both of which will cause accelerated battery degradation and potentially dangerous operating scenarios), thereby ensuring safe battery operation.

There are two common methods to achieve best battery equalizer: active balance and passive balance. Active battery cell balancing uses a DC/DC converter to charge low-power battery cells, thereby redistributing the power of the battery cells. Nowadays, battery cell manufacturing and classification technology has made significant progress, greatly reducing the degree of mismatch of battery cells in the battery pack. Therefore, it can be avoided that a larger battery balancing current is used to balance each battery cell with a severely mismatched power level at the beginning of operation. Regular battery balancing with a smaller balancing current can manage any mismatch problems that gradually arise during operation.

Passive balancing consumes more battery cells (usually through heat dissipation) until the power of all battery cells reaches the same level. The key difference between passive balancing and active balancing is that passive balancing does not distribute energy, but consumes energy so that all battery cells with a higher initial power are finally matched with battery cells with a lower power. Because passive balancing is simpler and cheaper, it is more commonly used.

The battery power is usually expressed by the state of charge, which indicates the percentage of the battery charge level and the battery capacity. Figure 1 illustrates the differences between the various types of best battery equalizer.