Brief description of active balancing methods for lithium-ion battery packs

An individual lithium-ion battery will encounter the problem of imbalance of power when it is set aside and imbalance of power when it is charged when it is combined into a battery pack. The passive balancing scheme balances the lithium battery pack charging process by shunting the excess current gained by the weaker battery (which absorbs less current) during charging relative to that gained by the stronger battery (which is capable of absorbing more current) to the resistor, however, the The "passive balance" does not solve the balance of each small cell in the discharge process, which requires a new program - active balance - to solve.

Active balancing abandons the passive balancing method of consuming current and replaces it with a method of transferring current. The device responsible for the charge transfer is a power converter, which enables the small cells within the battery pack to transfer charge whether they are charging, discharging, or in an idle state, so that dynamic balancing between the small cells can be maintained on a regular basis.

Since the charge transfer efficiency of the active balancing method is extremely high, a higher balancing current can be provided, which means that this method is more capable of balancing lithium batteries when they are charging, discharging and idle.

1.Strong fast charging capability:

The active balancing function enables the small cells in the battery pack to reach equilibrium more quickly, so fast charging is safer and suitable for higher rate charging methods with higher currents.


Even if each small battery has reached the equilibrium state of charging, but due to different temperature gradients, some small batteries with higher internal temperatures, some small batteries with lower internal leakage rate will make each small battery internal leakage rate is different, test data show that the battery every 10 ° C, the leakage rate will be doubled, the active balancing function ensures that the small batteries in the unused lithium battery packs are "constantly" re-balanced, which is conducive to the full use of the battery packs of the stored power can make the battery packs end of the working capacity of a single lithium battery with a minimum of residual power.


There is no lithium battery pack with 100% discharge capacity, because the end of the working capacity of a group of lithium batteries is determined by one of the first small lithium batteries to be discharged, and it is not guaranteed that all small lithium batteries can reach the end of the discharge capacity at the same time. On the contrary, there will be individual small LiPo batteries keeping unused residual power. Through the active balancing method, when the Li-ion battery pack is discharged, the internal large-capacity Li-ion battery will distribute the power to the small-capacity Li-ion battery, so the small-capacity Li-ion battery can also be fully discharged, and there will be no residual power left in the battery pack, and the battery pack with active balancing function has a larger actual power storage capacity (i.e., it can release the power closer to the nominal capacity).

As a final note, the performance of the system used in the active balancing method depends on the ratio between the balancing current and the battery charging/discharging efficiency. The higher the unbalance rate of a group of LiPo cells, or the higher the charge/discharge rate of the battery pack, the higher the balancing current required. Of course, this current consumption for balancing is quite cost-effective compared to the additional current gained from internal balancing, and moreover, this active balancing also contributes to the extension of the life of the lithium battery pack.

Post time: Jan-25-2024