Thermal Characteristics of Selected EV and HEV Batteries

Battery management is essential for achieving desired performance and life cycle from a particular battery pack in Electric and Hybrid Vehicles (EV and HEV). The batteries must be thermally managed in addition to the electrical control. In order to design battery pack management systems, the designers need to know the thermal characteristics of modules and batteries. Thermal characteristics that are needed include heat capacity of modules, temperature distribution and heat generation from modules under various charge/discharge profiles. In the last few years, we have been investigating thermal management of batteries and conducting tests to obtain thermal characteristics of various EV and HEV batteries. We used a calorimeter to measure heat capacity and heat generation from batteries and infrared equipment to obtain thermal images of battery modules under load. In this paper, we will present our approach for thermal characterization of batteries (heat generation, heat capacity, and thermal images) by providing selected data on valve regulated lead acid, lithium ion, and nickel zinc battery modules/cells. For each battery type, the heat generation rate depends on the initial state of charge, initial temperature, and charge/discharge profile. Thermal imaging indicated that the temperature distribution in modules/cells depends on their design.