Circuit and Method for Cell Balancing

A controller for balancing a plurality of cells connected in series, the controller comprising:

• a timer for measuring balancing time for each cell;
• and
• a control unit for controlling pre-balancing and balancing of each cell according to the cell voltage of each cell and the balancing time measured by the timer,
• wherein the controller pre-balances a first cell by enabling a first shunt path connected in parallel to the first cell for a first pre-balance time and balances the first cell by enabling the first shunt path for a first balance time if an unbalance condition of the first cell is detected by the controller.

A method for balancing a plurality of cells of a battery connected in series, comprising:

• determining a first pre-balance time for a first cell based on the actual operation of the first cell which is evaluated through previous balancing cycles;
• pre-balancing the first cell by enabling a first shunt path connected in parallel to the first cell for the first pre-balance time;
• monitoring an unbalanced condition of the first cell;
• and
• balancing the first cell by enabling the first shunt path for a first balance time if the first cell is unbalanced.