Improvements in test protocols for electric vehicles to determine range and total energy consumption

Abstract

As electric vehicles have entered the market fairly recently, test procedures have not yet been much adjusted to address their particular features. Mostly EVs are tested the same way as the ICE-driven cars with the exception that determining range is also part of the procedure. However, the current procedures address mainly primary energy consumption, i.e. energy needed to propel the vehicle, whereas the secondary energy, like energy used for cabin heating, cooling and ventilation, is not accounted properly. Main reason is probably the fact that a large proportion of this energy is catered by the waste or excess energy, but in an EV also this part of energy uses is drawn from the battery. Therefore, range of an EV may differ fairly strongly depending on ambient conditions, as in adverse conditions secondary energy use may rise considerably. Furthermore, unlike propulsion energy use that is mainly dependent on driving speed, secondary energy use is mostly dependent on ambient temperature and driving time, and energy is spend even when the vehicle is stopped. However, the challenge to determine a procedure that would more properly address the various parameters that affect range is quite substantial. Also any laboratory test procedure is always a compromise, because it is not possible in practice to replicate the real-life driving completely. Therefore, the authors call upon the engineering community to work on this subject. This chapter outlines our attempt to address this issue, and presents data from in-laboratory testing at normal and low ambient temperatures. It was found that cold driving at -20 °C ambient can shorten the range by about 20%, even without cabin heating engaged, compared to normal ambient conditions. Using the electric cabin heater will shorten the range further by about 50% in urban driving and some 20% in road-type of driving with higher average speeds. © Springer-Verlag 2013.