Lithium Titanate Prismatic Cell Cooling

Recently Lithium Titanate batteries have become a viable option for use in Hybrid Electric Vehicles (HEVs). When used in HEVs, the batteries need to accommodate high currents over many charge and discharge cycles. In order to achieve the voltage necessary to power a HEV, many cells must be connected in series and will likely be installed in a well insulated region of the vehicle. When in use, each cell will generate heat throughout its entire volume. The cells' large current capacity and proximity to one another make thermal management a high priority concern for the proper functioning and safety of the HEV. In our lab we have designed and built a test stand that simulates actual operating conditions of the batteries. We have also put in place a method to determine the surface temperature of the entire cell, using thermochromic liquid crystals applied to the cell's surface. Using this we can test active cooling systems in laboratory conditions to ensure they will reach a steady state temperature within the confines of safe operation. The graph below shows results from an experiment that consisted of five minute charge and discharge cycles at 300 amps, both with and without an active cooling system using aluminum plates between each cell, cooled by a tube carrying chilled water. Our next step will be to test methods of cooling the batteries with ambient air, in order to optimize system design for effective cooling and power consumption.

Different regions of interest identified in the cell.
Temperatures measured in the cell over multiple charge and discharge cycles, with and without active cooling.