Charge Management Systems for Electric and Hybrid Electric Vehicle Battery Packs – Lab Testing to Evaluate Cycle Life Improvement

Electric and hybrid electric vehicles reaching the market today utilize battery packs for on-board energy storage. Due to manufacturing, operational and environmental variations, the behavior of individual battery modules in a high voltage series-string will diverge significantly after a number of cycles. It has been proposed that the use of a battery charge management system to maintain charge balance across the modules will limit this divergence and extend the pack life.

To evaluate the benefits of battery charge management, a project was undertaken to acquire candidate charge management systems, test these systems on a high voltage series-string of battery modules, and compare the resulting cycle life of charge managed packs to a non-managed (control) pack. This paper summarizes the project results, including a description of the charge management systems tested, the test methodology used, and the results achieved.