System and method for cell balancing and charging

An apparatus for charging and balancing a plurality of series-coupled battery cells, the apparatus comprising:

• first and second input terminals configured to provide a charging voltage to the plurality of series-coupled battery cells;
• a transformer including a primary side associated with the charging voltage and a secondary side including a plurality of portions each coupled across a respective at least two of the plurality of series-coupled battery cells;
• a plurality of first diodes, each coupled between a respective single portion of the secondary side and a corresponding first battery cell of the at least two of the plurality of series-coupled battery cells and configured to provide a charging current to the first battery cell during a first half of a cycle of a current in the primary side of the transformer;
• a plurality of second diodes, each coupled between the respective single portion of the secondary side and a corresponding second battery cell of the at least two of the plurality of series-coupled battery cells and configured to provide a charging current to the second battery cell during a second half of a cycle of a current in the primary side of the transformer;
• and
• wherein each of the plurality of portions of the secondary side is configured to have a first polarity during the first half of the cycle of the current and a second polarity opposite the first polarity during the second half of the cycle of the current.

A method for charging and balancing a plurality of series-coupled battery cells, the method comprising the steps of:

• receiving a charging voltage for the plurality of series-coupled battery cells;
• transferring the charging voltage from a primary side of a transformer to a plurality of portions of a secondary side of the transformer;
• providing the charging voltage from each of the plurality portions of the secondary side at a first polarity to a first portion of the plurality of series-coupled battery cells during a first half of a cycle of a current in the primary side of the transformer;
• switching the polarity of the voltage for the plurality of secondary sides of the transformer from the first polarity to a second polarity opposite the first polarity;
• and
• providing the charging voltage from each of the plurality portions of the secondary side at the second polarity opposite the first polarity to a second portion of the plurality of series-coupled battery cells during a second half of the cycle of the current in the primary side of the transformer.