Abstract
Due to increasing sales figures, the energy consumption of battery-electric vehicles is moving further into focus. In addition to efficient driving, it is also important that the energy losses during AC charging are as low as possible for a sustainable operation. In many situations it is not possible or necessary to charge the vehicle with the maximum charging power e.g., in apartment buildings. The influence of the charging mode (number of phases used, in-cable-control-box or used wallbox, charging current) on the charging efficiency is often unknown. In this work, the energy consumption of two electric vehicles in the Worldwide Harmonized Light-Duty Vehicles Test Cycle is presented. In-house developed measurement technology and vehicle CAN data are used. A detailed breakdown of charging losses, drivetrain efficiency, and overall energy consumption for one of the vehicles is provided. Finally, the results are discussed with reference to avoidable CO2 emissions. The charging losses of the tested vehicles range from 12.79 to 20.42%. Maximum charging power with three phases and 16 A charging current delivers the best efficiencies. Single-phase charging was considered down to 10 A, where the losses are greatest. The drivetrain efficiency while driving is 63.88% on average for the WLTC, 77.12% in the “extra high” section and 23.12% in the “low” section. The resulting energy consumption for both vehicles is higher than the OEM data given (21.6 to 44.9%). Possible origins for the surplus on energy consumption are detailed. Over 100,000 km, unfavorable charging results in additional CO2 emissions of 1.24 t. The emissions for an assumed annual mileage of 20,000 km are three times larger than for a class A+ refrigerator. A classification of charging modes and chargers thus appears to make sense. In the following work, efficiency improvements in the charger as well as DC charging will be proposed.
Highlights
Battery-electric vehicle (BEV) sales have climbed due to continued high pressure on OEMs (Original Equipment Manufacturer) from legislators over severe penalties for excessive CO2 fleet emissions
Further for the Kia e-Niro a detailed insight in the energy consumption and drive efficiency is given in the separate sections of the WLTC
The measurements of the WLTC average energy consumption in this study with the resistance coefficients determined from UNECE-R83 table A4a/3 lead to a significant additional consumption of 21.6% for the Kia e-Niro and 44.9% for the VW e-up!
Summary
Battery-electric vehicle (BEV) sales have climbed due to continued high pressure on OEMs (Original Equipment Manufacturer) from legislators over severe penalties for excessive CO2 fleet emissions. Further incentives have been created in many countries by subsidizing the purchase of BEVs. If it can be ensured that BEVs are charged with renewable energies, these vehicles can contribute to CO2 reduction in the transport sector. Recent calculations using dynamic modeling show that BEVs will deliver CO2 savings in 2029 after less than 20,000 km compared to hybrid internal combustion engine-powered vehicles. Necessary mileage varies depending on the country’s electricity mix—but a clear trend toward low mileage is emerging [1]. The charging power may be linked to the photovoltaic (PV) system and to the energy consumption of other consumers in the household (e.g., heating)
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