Lithium battery pack equalization charging -Lithium - Ion Battery Equipment

Lithium battery pack equalization charging -Lithium - Ion Battery Equipment

Lithium-ion battery pack equalization charging method

In order to reduce the influence of unbalance on the lithium-ion battery pack, an equalization circuit is used during the charging process.

At present, there are two main methods for balanced management of lithium-ion battery packs, energy consumption type and feedback type. The energy consumption type refers to supplying a parallel branch to each single cell, and transferring the electric energy of the single cell with excessive voltage to achieve the purpose of balance. The regenerative type refers to the energy converter that feeds the deviation energy between the cells back to the battery pack or some cells in the battery pack.

Theoretically, when the conversion efficiency is ignored, the feedback does not consume energy and can achieve dynamic balance. However, due to the complex control method and high manufacturing cost of the feedback type design, the charger adopts an energy consumption type design.(Lithium - Ion Battery Equipment)

Since the DC internal resistance, polarization voltage, and maximum usable capacity are specific parameters of the battery, they basically do not change during one or several continuous charging and discharging processes, so the balance of the lithium-ion battery pack is important by adjusting the SOC of each single cell. to fulfill. After research, the SOC is taken as the reference object of the balance, the balance object is relatively fixed, the balance time is fully utilized, and the balance utilization rate is improved to reduce the balance current capacity.

Taking the SOC of the battery as the control object, the SOC difference between the batteries is narrowed by charging and discharging the single battery. The first step is to determine the balance target. Usually, in order to improve the efficiency of balance and give full play to the advantages of charge-discharge balance, the target is set as the average state of charge (SOC) of the lithium-ion battery pack. The equalization control band (dSOC) is also set to prevent the fluctuation of the equalization, and the discharge equalization is performed for the cells with high SOC, and the charge equalization is performed on the contrary.

Commonly used lithium-ion battery pack equalization charging technologies include constant shunt resistance equalization charging, on-off shunt resistance equalizing charging, average battery voltage equalizing charging, switched capacitor equalizing charging, step-down converter equalizing charging, inductor equalizing charging, etc.



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