At present, there are mainly the following methods to realize the equal charging of each single battery of the battery pack in series:
1. Add a parallel equalization circuit to each single battery of the battery pack to achieve the function of shunting. In this mode, when a battery is fully charged first, the equalizer can prevent it from being overcharged and convert the excess energy into heat to continue charging the battery that is not fully charged. This method is simple, but it will cause energy loss and is not suitable for fast charging systems.
2. Before charging, each cell is discharged to the same level through the same load one by one, and then charged with a constant current, so as to ensure a more accurate balanced state between each cell. But for the battery pack, due to the physical differences among individuals, it is difficult to achieve completely consistent ideal results after deep discharge of each monomer. Even if the same effect is achieved after discharging, new imbalances will appear during charging.
3. Timing, sequencing, and independent detection and uniform charging of the single batteries in the battery pack. When charging the storage battery pack, it can ensure that each storage battery in the storage battery pack will not be overcharged or over-discharged, thus ensuring that each storage battery in the storage battery pack is in a normal working state.
4. Using the time-sharing principle, through the control and switching of the switch components, additional current flows into the battery with relatively low voltage to achieve the purpose of balanced charging. This method is more efficient, but the control is more complicated.
5. Take the voltage parameters of each battery as the equalization object to restore the voltage of each battery to be consistent. As shown in Figure 2, during balanced charging, the capacitor is alternately connected to two adjacent batteries through the control switch, receives the charge from the high-voltage battery, and then discharges to the low-voltage battery until the voltage of the two batteries tends to be the same. This equalization method better solves the problem of unbalanced battery pack voltage, but this method is mainly used in occasions with a small number of batteries.
6. The whole system is controlled by a single-chip microcomputer, and the single battery has an independent set of modules. According to the set program, the module manages the charging of each single battery separately, and automatically disconnects after charging is completed. This method is relatively simple, but it will greatly increase the cost when the number of single cells is large, and it is also not conducive to the reduction of the system volume.
