Energy storage battery charging balance

As the index of stored energy level of a battery, balancing the State-of-Charge (SoC) can effectively restrain the circulating current between battery cells. Compared with passive balance, active balance, as the most popular SoC balance method, maximizes the capacity of the battery cells and reduces heat generation.

Charging Balance: This actively regulates cell voltages during the charging process to prevent overcharging and maintains a consistent SOC across all cells. This process ensures that each cell charges evenly, enhancing the overall efficiency and safety of the battery pack.

Here's why battery balancing is so important: Variations among battery cells in series and parallel setups reduce the system's usable capacity. For example, in a 500 kWh system with 50 series cells, each storing 10 kWh, if one cell reaches only 85% state of charge (SoC) while others are at 100%, the pack's stored energy drops to 495 kWh.

Battery energy storage systems (BESSs) are widely utilized in various applications, e.g. electric vehicles, microgrids, and data centres. However, the structure of multiple cell/module/pack BESSs causes a battery imbalance problem that severely affects BESS reliability, capacity utilization, and battery lifespan.

The proposed system includes two balancing strategies: a charging balance that redistributes excess charge from high-SOC cells to maximize capacity, and a discharging balance that addresses low-SOC cells to extend discharge duration.

Balanced cells contribute to better SOH across the battery pack, thus improving RUL predictions. ML algorithms that use balanced SOC data can more reliably estimate battery pack RUL, thus supporting longer EV battery lifespans and reliability.