Battery management system with cell equalizer for multi-cell battery packs

This paper describes a novel battery management system to accomplish all of the necessary functions to ensure the safe, reliable operation of lithium ion batteries. An interface circuit monitors each battery voltage and temperature. It includes a trickle charger that achieves cell balancing by active instead of passive means. A series loaded resonant converter with isolation, also known as an LLC converter, is connected to each one of the battery cells so that they can be balanced, thus increasing the lifetime and utilization of the battery stack. In this paper the battery equalizer control system is presented as well as experimental measurements on a six cell string.