The energy density of Lithium-ion (Li-ion) batteries is two to ten times more than other battery technologies. But, Lithium-ion uses a flammable substance as an electrolyte. If overcharged or overheated, Li-ion cells are a fire risk.
Cell balancing equalizes the voltages and state-of-charge (SOC) among the cells, when they are at full charge. Balancing can be either voltage-based or SOC-based. It’s a non-trivial task that – ideally — aims both to increase the life of a battery pack and to enhance battery safety. A classic whitepaper examines the tradeoffs between various approaches.