CR2032 button cell

Briefly describe the active balancing method of CR2032 button cell packs

When individual lithium-ion batteries are combined into battery packs, they will encounter the problem of unbalanced power when they are idle and unbalanced power when they are charged. The passive balancing solution balances the charging process of the lithium battery pack by diverting the excess current obtained by the weak battery (absorbing less current) during the charging process relative to the strong battery (capable of absorbing more current) to the resistor. However, "passive balancing" cannot solve the balance of each small battery during the discharge process, which requires a new solution - active balancing - to solve it.

Active balancing abandons the passive balancing method of consuming current and changes it to a method of transmitting current. The device responsible for charge transmission is a power converter, which enables the small batteries in the battery pack to transmit charge whether they are charging, discharging or idle, so that the small batteries can often maintain dynamic balance.

Because the charge transmission efficiency of the active balancing method is extremely high, it can provide a higher balancing current, which means that this method has a stronger balancing ability when the lithium battery is charging, discharging and idle.

1. Strong fast charging capability: The active balancing function can make the small batteries in the battery pack reach balance faster, so the fast charging is safer and suitable for high-rate charging with larger current.

2. When idle: Even if each small battery has reached the balanced state during charging, due to different temperature gradients, some small batteries have higher internal temperatures and some have lower internal temperatures, which will also make the internal leakage rate of each small battery different. Test data shows that the leakage rate doubles for every 10°C increase in battery temperature. The active balancing function can ensure that the small batteries in the idle lithium battery pack "continuously" regain balance, which is conducive to the full utilization of the power stored in the battery pack, so that when the working capacity of the battery pack ends, the residual power of a single small lithium battery is minimized.

3. When discharging: There is no lithium battery pack with a discharge capacity of 100%. This is because the end of the working capacity of a group of lithium batteries is determined by a small lithium battery that is discharged first, and it cannot be guaranteed that all small lithium batteries can reach full discharge at the same time. On the contrary, some small lithium batteries will retain unused residual power. Through the active balancing method, when the lithium battery pack is discharged, the large-capacity lithium battery inside will distribute the electric energy to the small-capacity lithium battery. Therefore, the small-capacity lithium battery can also be fully discharged, and there will be no residual electric energy left in the battery pack. The battery pack with active balancing function has a larger actual storage capacity (that is, it can release electric energy closer to the nominal capacity).

Finally, it should be noted that the system performance adopted by the active balancing method depends on the ratio between the balancing current and the battery charge/discharge efficiency. The higher the imbalance rate of a group of lithium batteries, or the greater 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 obtained due to internal balancing. Moreover, this active balancing is also conducive to the extension of the life of the lithium battery pack.

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