1. Passive balancing method: Passive balancing method is to connect the high voltage single battery through the circuit-a load resistance to discharge it, and compare the circuit to determine whether its voltage is the same as the voltage of other single batteries. Stop discharging if the same is the same. The disadvantage of the passive equalization method is that it consumes the energy of the single battery, generates heat, and the equalization time is long.
2. Dynamic equalization method: Active equalization method means that the energy of the higher voltage battery is not consumed through the resistance during charging and discharging, but the energy is transferred to the lower voltage battery, so as to realize the balanced charging and discharging of the lithium battery pack ; The active equalization circuit is complicated and cannot equalize all the batteries at the same time. The reliability needs to be improved.
3. Equalization method: The internal equalization method uses BMS to adjust the charging current and control the topological algorithm of the charging voltage in the process of charging the battery in series, so that the charge of each single battery in the battery pack is basically the same. The characteristics of internal equalization technology are simple algorithm, no energy loss, no additional charge and discharge process, no impact on battery life, no increase in hardware equipment, but if the battery charge varies greatly, it will take a longer time to balance. From the perspective of the battery management system, the parameters of the single cells are detected during the use of the battery pack, the voltage distribution is under dynamic and static conditions, and the inconsistency development law of the single cells in the battery pack is grasped, and the extreme parameter batteries are adjusted or replaced in time , To ensure that the inconsistency of battery pack parameters increases with the use of time. At the same time, from the perspective of energy management and strategy, a practical battery pack energy management and balance system is introduced, and a reasonable battery balance strategy is formulated to actively intervene and reduce battery inconsistency.
The inconsistency of the battery comes from the internal resistance, capacity and SOC of the battery, and the traditional consistency evaluation method and the voltage consistency other than the equalization method are used as the control target, which does not effectively increase the usable capacity of the battery pack, so it cannot improve the consistency of the battery pack. The problem has an adverse effect on the use of battery packs.
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 consecutive charging and discharging processes, so the balance of the battery pack is mainly achieved by adjusting the SOC of each single cell . After research, the SOC is used as the reference object of balance, the balance object is relatively fixed, the balance time is divided and the balance utilization is improved to reduce the balance current capacity.
Post time: Aug-25-2020
