BEV Thermal Management

Li-Ion Battery Resistance Increases with Decreasing Temperature
• Power decreases with decrease in temperature
• Impacts power capability of motor and vehicle acceleration

Li-Ion Battery Capacity Decreases with Decreasing Temperature
• Useful energy from the battery decreases with decrease in temperature
• Impacts driving range and performance of vehicle

Battery Thermal Management is needed to regulate pack to operate in the desired temperature range (15 – 35 degC) for optimum performance/life, reduce uneven temperature distribution (Less than 3 – 4 degC) and Eliminate potential hazards related to uncontrolled temperatures – thermal runaway. For each temperature degree rise, it is estimated that the battery lifetime shortens by two months. A non-uniform temperature distribution inside a single cell leads to a variable rate of electrochemical reactions in different zones of the cell and therefore to a partial energy utilization and a reduced battery lifetime.

In Li-ion batteries there are two main heat generation sources, namely the one by Joule effect, determined by the internal resistance during the transfer of electrons, and the one caused by the electrochemical reactions or entropy change.

If heat is not dissipated at least at the same rate at which it is generated in the batteries, temperatures may increase uncontrollably, resulting in the disintegration of materials and component.