Electric vehicles (EVs) experience a range reduction at low temperatures caused by the impact of cabin heating and a reduction in lithium ion performance. Heat pump equipped vehicles have been shown to reduce heating ventilation and air conditioning (HVAC) consumption and improve low ambient temperature range. Heating the electric battery, to improve its low temperature performance, leads to a reduction in heat availability for the cabin. In this paper, dynamic programming is used to find the optimal battery heating trajectory which can optimise the vehicle’s control for either cabin comfort or battery performance and, therefore, range. Using the strategy proposed in this research, a 6.2% increase in range compared to no battery heating and 5.5% increase in thermal comfort compared to full battery heating was achieved at an ambient temperature at −7 °C.

Abstract:Previous research has focused on the use of heat pumps in electric vehicles, with the focus on recuperating heat from, normally, ambient and one thermal source on the vehicle. Here 5 potential thermal sources on a vehicle have been identified and thorough testing on the benefit of each source has been performed. The results presented suggest the motor, a thermal storage device, and cabin exhaust extraction should be used >80% of the time according to the scenarios tested, while battery heating and transmission heat extraction should be used subject to conditions on the ambient temperature and drive cycle.

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One of the challenges concerning electric vehicles is their performance in cold climates. As the temperature drops below 10 • C battery capacity begins to reduce and heating demand starts to claim a larger proportion of total vehicle energy expenditure. Although efficient, electric vehicles waste heat through a few components, resulting in opportunity to harvest waste heat through a heat pump. With multiple options for harvesting heat and the option to heat the battery, a model and architecture has been developed to give flexibility in a wide range of thermal management scenarios. This paper explores the details of the model and presents two example cases of interest to demonstrate the model's applicability.