For lifetime, safety and performance reasons, typical lithium ion batteries have to be kept within a certain temperature window of about 10-30 °C. Increased temperatures drastically reduce the calendric and cyclic lifetime of the battery cells. As the target temperature of the battery can be lower than the ambient temperature, the cooling system of the battery has to be integrated into the air conditioning system of the vehicle. At low temperatures, the battery needs to be heated up, if the performance is too low to meet the power demand of the vehicle. Both cooling and heating of the battery consume electrical energy from the battery itself and thus, reduce the electric driving range of the vehicle. In addition to that, the efficiency of the battery decreases at cold temperature and regenerative braking is limited, resulting in further energy demand. The performance of the battery is highly dependent on cell temperature, which makes a coupled thermal and electrical simulation necessary. Within this paper, the energy demand for cooling and heating the battery is analyzed for a compact class vehicle during electric driving mode. Reduced performance and battery heating increase the energy consumption for the investigated vehicle and the Artemis Road driving cycle by more than 30 % at -20 °C ambient temperature compared to 20 °C ambient temperature. Battery cooling at 40 °C ambient temperature was found to increase the energy demand by around 5 %, assuming a cell target temperature of 30 °C. If weighted with the ambient temperature distribution over the year, the temperature related additional energy consumption for the battery is only around 3 %. But even though the occurrence of extremely cold and hot temperatures during the year is very low, the thermal conditioning system has to be designed to guarantee the vehicle performance under all circumstances. A severe driving range reduction is not acceptable for customer satisfaction, so an efficient battery thermal management system is mandatory for electric and hybrid vehicles.
Thermal management for lithium-ion-batteries: Trade-off between driving range, lifetime and performance
2012
17 Seiten, 12 Bilder, 11 Quellen
Aufsatz (Konferenz)
Englisch
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