Bypassing weak cells: how electric vehicle batteries could last longer
Researchers at Chalmers have calculated the benefits of reconfigurable battery packs. In the best case, batteries in electric trucks and long-range electric cars last more than 20 per cent longer.
Archive image · Photo: Zhangzhe0101 at Chinese Wikipedia / Wikimedia Commons, Public domain (cropped and resized)
In a conventional battery pack, the cells are permanently wired together. "Since they are bound to each other, everyone has to keep the same pace as the slowest cell and stop when that cell stops," explains PhD student Albert Škegro of Chalmers University of Technology in Gothenburg. The team led by Professor Changfu Zou has examined the benefits of so-called reconfigurable battery packs, in which switches and control electronics change the connections so that weak cells are bypassed and the capacity of the others is used better.
According to the modelling study in the journal Nature Communications, battery life in high-voltage vehicles such as electric trucks and long-range electric cars can increase by more than 20 per cent in the best case. This figure assumes that each cell is controlled individually and is considered a theoretical upper limit. As an example, the researchers cite an 80 kWh battery driven 12,000 kilometres a year: instead of after about ten years, it would reach the same point of wear after about eleven – roughly 14 months later.
The extra electronics initially make the batteries more expensive; according to the authors, longer use and a higher residual value can offset this under many realistic conditions. The technology is not yet used in series-production vehicles and has so far been tested in research and industrial prototypes. Supplier PHINIA and truck maker Scania were also involved in the study.