Efficiency of LiFePO4 battery and charger with a mixed two level balancing

This paper is intended as the second part of a two paper series that evaluate the efficiency of a battery pack with charger that has an integrated cell balancing solution. In the first paper a simple passive balancing with a half bridge charger was designed and tested for energy efficiency. This paper continues the work by redesigning the half bridge charger circuit to implement a multi secondary winding transformer balancing circuit. The designed active balancing circuit splits the battery pack in four sections - each section is balanced actively. Each of the sections contains five cells which use the same passive balancing as before. The result is a mixed two level balancing circuit that is integrated in the charger topology. The battery pack with the charger/balancing circuit has been tested to obtain energy efficiency measurements which are compared with the previously obtained passive balancing measurements.