What are the methods for achieving balanced charging of lithium-ion batteries?

What are the methods for achieving balanced charging of lithium-ion batteries? There are currently several important methods for achieving uniform charging of individual cells in a series connected battery pack.

1. Attach a parallel balancing circuit to each individual cell of the battery pack to achieve the purpose of current diversion. In this mode, when a battery reaches full charge first, the balancing device can prevent it from overcharging and convert excess energy into heat energy to continue charging the battery that is not fully charged. This method is simple, but it may cause energy loss and is not suitable for fast charging systems.

2. Before charging, discharge each individual cell one by one through the same load to the same level, and then perform constant current charging to ensure a more accurate balance between each cell. However, for battery packs, due to physical differences between individuals, it is difficult to achieve completely consistent ideal results after deep discharge of each individual cell. Even if the same effect is achieved after discharge, new imbalances may still occur during the charging process.

3. Test and uniformly charge the individual batteries in the battery pack on time, in sequence, and separately. When charging the battery pack, it is ensured that each battery in the battery pack will not experience overcharging or overdischarging, thus ensuring that each battery in the battery pack is in normal working condition.

4. Using the time-sharing principle, additional current is controlled and switched through switch components to flow into batteries with relatively low voltage, in order to achieve balanced charging. This method is relatively efficient, but the control is complex.

5. Use the voltage parameters of each battery as the balancing object to restore consistent voltage across all batteries. During balanced charging, the capacitor is alternately connected to two adjacent batteries through a control switch, receiving charging from the high-voltage battery and discharging from the low-voltage battery until the voltages of the two batteries converge.