Bidirectional Charging Hardly Affects the Service Life of Electric Car Batteries

(CONNECT) RWTH Aachen University and The Mobility House Energy have compared the effects of intelligent charging (V1G) and bidirectional charging (V2G) on the ageing of electric car batteries with the effects of instant charging.

Intelligent charging was able to significantly reduce battery ageing by 3.3 percent to 6.8 percent after ten years, according to a press release from The Mobility House, headquartered in Munich and located in Technopark Zurich. Compared to instant charging, this resulted in a capacity gain of 1.8 to 3.6 kilowatt hours (kWh) or a range of 10.9 to 22.5 kilometers according to WLTP (Worldwide Harmonized Light Duty Test Procedure, meaning the standard range of the electric car). Taking the current energy market into account, smart charging can save 200 to 400 euros a year.

Bidirectional charging (vehicle-to-grid or V2G), in which the electric car battery feeds surplus energy back into the power grid, resulted in additional ageing of 1.7 percent to 5.8 percent after ten years. V2G thus resulted in a capacity loss of 0.9 to 3.1 kWh or 5.8 to 19.2 kilometers of range according to WLTP. This loss of capacity amounts to costs of around 100 to 300 euros per year, but brings in around 600 euros over the same period.

The study concludes that a flat charging and discharging cycle is essential in V2G operation, while extreme charging states such as 0 or 100 percent should be avoided for the sake of the battery. According to the press release, immediate charging therefore leads to the highest ageing and grid load, as the battery is often in the 100 percent range and is not sufficiently monetized, as is the case with V2G charging.

"The joint study with the experts from The Mobility House Energy has once again proven that Intelligent charging and vehicle-to-grid are game changers for electromobility. The frequent concern that this damages the battery and causes premature ageing can thus be dispelled if intelligent management is used," comments Prof. Dr. Dirk Uwe Sauer from the Institute for Power Electronics and Electrical Drives (ISEA) at RWTH Aachen University and the Helmholtz Institute Münster on the study results. ce/yes