Factors Influencing Liquid over Air Cooling of High Voltage Battery Packs in an Electrified Vehicle 2017-01-1171

Automotive vehicle manufactures are implementing electrification technologies in many vehicle line-ups to improve fuel economy and meet emission standards. As a part of electrification, High Voltage (HV) battery packs are integrated alongside internal combustion engines. Recent generation HV batteries allow extensive power usage, by allowing greater charge and discharge currents and broader State of Charge (SOC) ranges. Heat generated during the charge-discharge cycles must be managed effectively to maintain battery cell performance and life. This situation requires a cooling system with higher efficiency than earlier generation electrified powertrains. There are multiple thermal solutions for cooling HV battery packs including forced air, liquid, direct refrigerant, and passive cooling. The most common types of HV battery pack cooling, for production vehicles, are air cooled using cabin interior air and liquid cooled using powertrain cooling systems. This paper focuses on air and liquid cooling systems. Each cooling system supports HV battery pack heat rejection using different methods and components. Each method has advantages and limitations. When using the HV battery pack as an alternative power source, customer expectations regarding driving comfort with respect to cabin climate, cabin interior noise, driver and passengers’ leg room, and interior storage space plays a critical role in sizing and selecting the HV battery cooling system. This paper deliberates the factors influencing the selection of liquid cooling over air cooling for a given hybrid electric vehicle architecture.