48V Battery Pack Thermal Design Concept with Temperature Measurement on a Single Cell

Mild hybrid topology with 48V battery packs offers a cost-effective solution with considerable improvement in fuel economy and performance over the conventional vehicles. Thermal management of the battery pack is of utmost importance to ensure a safe, reliable, and optimal operation over the target lifetime and under varying operating conditions. The battery management system needs to take into consideration the temperature of all the cells in the pack for estimating the maximum allowed current for charge/discharge. For example, at lower temperature the coldest cell in the pack would be more probable to lithium plating and hence will be the limiting case while at higher temperature the allowed current should be such that the hottest cell in the pack is taken care. Pack design with temperature sensor for each cell in the pack will increase the cost, hardware, and software complexity. An optimized pack design is necessary to keep the overall cost of the battery pack lower while meeting the design requirements. This paper discusses pack thermal design approach for 48V battery pack with 12S1P configuration considering a single cell temperature measurement instead of all the cells for a cost-effective solution. The various factors that could introduce temperature spread among the cells will be discussed in detail. A pack thermal model and simulation-based approach will be presented to derive the temperature margins relative to the monitored cell and how the margins can be considered for BMS calibration to ensure safe operation for all the pack components will be explained.