Patent ID: 8294421

Claim:
A cell balancing circuit for energy efficient and increased energy storage balancing of a plurality of battery cells of a rechargeable multi-cell battery pack, said cell balancing circuit comprising: a transformer having a primary winding and a secondary winding; a switch coupled in series with said primary winding; a switching controller operable for selecting a first cell coupled to said primary winding and selecting a second cell coupled to said secondary winding, wherein said first cell and said second cell are coupled in series and wherein said first cell has a cell voltage that is greater than said second cell; and a controller coupled to said primary winding and operable for controlling energy from said first cell to said primary winding to transfer said energy from said first cell to said second cell to balance said battery cells, said controller operable for sensing a voltage across said primary winding and for comparing said voltage across said primary winding to an over-voltage protection threshold, wherein if said voltage across said primary winding exceeds said over-voltage threshold then said controller turns off said switch.