The LTC3300-1 is a high efficiency bidirectional multicell battery balancer for equalizing cell state of charge (SoC) in a series-connected battery stack. With the LTC3300-1, applications such as electric vehicles (EVs), plug-in hybrid EVs and large energy storage systems using cells with mismatched capacities are no longer limited by the lowest capacity cell in the stack. The LTC3300-1 goes beyond purely dissipative passive balancing solutions, enhancing battery performance by efficiently transferring charge to or from adjacent cells in order to bring mismatched cells into SoC balance within the stack.