To maintain battery performance throughout a long service life in a large-format battery system, a charge-balancing strategy is usually necessary to account for variances in cell performance. An effective cell balancing system maintains the intended amount of battery output with an appropriate safety margin throughout the battery's life without adding excessive expense, weight, or complexity.
Balancing is the process of equalizing the charge level in lithium-ion batteries cell by cell. Cell balancing may be accomplished in two ways: active cell balancing and passive cell balancing.