Adapting the EV Battery Technology to New Hybrid Vehicle Requirements

摘要

As the electric vehicle world is moving from the Zero Emission Vehicle concept (ZEV) to the Hybrid Electric Vehicle (HEV) one , the battery technology has to follow the same path. SAFT has developed. NiMH and Li Ion cells, modules and batteries for ZEV applications and is now developing their counterparts for HEV.rnFirst of all, new cells had to be developed. While typical ZEV battery modules have a 80 to 100 Ah capacity and a power to energy ratio (P/E) between 2 to 3, HEVs require lower capacities ( 6 to 30 Ah) and higher P/E ( 5 and 20 depending on the application). These cells are designed to meet the technical challenge of heat transfer which is the consequence of their high current utilizationrnThe weight, volume and cost burden of the technical solutions that were implemented for ZEV battery systems, such as liquid cooling or autonomous battery management controller, cannot be afforded by much smaller and therefore cheaper ZEV batteries; new solutions are developed based on air cooling and a closer integration of the battery control within the vehicle management unit.rnThe operation of an HEV battery consists of shallow charge/discharge cycles around a given state of charge. The battery management system needs to keep the overall battery state of charge as close as possible to the optimum battery operation point but also to compensate for cell to cell state of charge divergence due to self discharge and charge efficiency deviations