Plug-in hybrids are increasingly among the cars with high-voltage battery problems. Specialists from the Australian company Test EV, which diagnoses batteries, believe that one of the reasons is related to the design features of PHEVs.
Most such cars have batteries with a capacity of approximately 15–25 kWh — significantly less than many cars with a fully electric powertrain. At the same time, the PHEV battery regularly powers the traction electric motor, and then recharges from the grid and the recuperation system.
As a result, a relatively small battery can go through more cycles and experience a higher load per unit of capacity. Test EV recommends owners to regularly charge PHEVs: according to the company's specialists, this helps to use the battery more efficiently and reduce fuel consumption.
The problem is not limited to individual battery malfunctions. According to Consumer Reports, PHEVs and fully electric vehicles on average report about 80% more problems than ICE cars. The study is based on approximately 380 thousand vehicles.
At the same time, the PHEV design itself is more complex than a conventional hybrid: the car simultaneously contains an internal combustion engine, a fuel system, a high-voltage battery, an electric motor, and a charging system.