A new Swedish-Chinese research study has found that a small number of ageing battery cells can significantly reduce the performance and lifespan of electric vehicle (EV) battery packs.
The study was led by researchers from the Chinese Academy of Sciences’ Dalian Institute of Chemical Physics and Chalmers University of Technology in Sweden, together with researchers from Beijing Institute of Technology and Zeekr Technology Europe.
The researchers analysed more than three years of real-world operating data from electric passenger cars and buses using different types of batteries. Some of the vehicles had travelled up to 300,000 kilometres.
They found that differences between individual cells can become increasingly important as batteries age. In a battery pack, the fastest-ageing cell can effectively become the limiting factor for the entire pack.
According to the study, this reduced usable battery health by 6.2 per cent in passenger cars and 7.5 per cent in buses. Battery-pack lifetimes were shortened by 17.7 per cent and 22.8 per cent respectively, compared with the average lifetime of the individual cells.
The researchers say that better battery manufacturing, cell grouping, balancing systems and thermal management could help reduce these differences and make better use of battery resources.
The study was published in Nature Energy.
