Abstract: This disclosure describes a battery management system that can balance a string of battery cells rapidly, at high power, and without the use of a large auxiliary battery or excessive switches/transistors. A single switched tap is provided at each intermediate node of the battery string, allowing charging and discharging of subsets of the battery string (e.g., cell 1, cells 1 and 2, cells 1-3, etc.). A common charge/discharge (CCD) node can be connected to any one of the intermediate nodes, resulting in a parallel connection with the battery string for each cell at or below the connected intermediate node in the string. A sink is provided which can be used to discharge groups of cells using the connected intermediate node. Additionally, a source can be provided, such as a buck-boost chopper acting as a current supply, to charge the group of cells using the connected intermediate node.