A cost optimized battery management system with active cell balancing for lithium ion battery stacks

A method for active cell balancing of lithium ion battery stacks is presented. Balancing the charge of cells in a multi-cell lithium ion battery stack is often employed to guard against damage and improve the lifetime of the battery. Battery stacks which are in production today largely use a passive cell balancing method, which dissipates charge through a resistor, as heat. The method described uses a flyback converter to pass charge from cell to cell with low losses and only a small cost increase from a typical passive system.