Used PHEVs You Should Avoid: Results of a Large Battery Study

How do plug-in hybrid batteries behave after long-term use? ADAC (the German automobile club), together with analysts from Aviloo, examined data from around 28,500 plug-in hybrids (PHEVs) from six major car manufacturers.

According to the analysts, a “healthy” battery should retain more than 92% of its original capacity after 50,000 km (31,000 miles). After 100,000 km, it should remain above 88%, after 150,000 km above 84%, and after 200,000 km it should still hold at least 80%.

Mercedes-Benz ranked as the strongest performer. The batteries in its PHEVs maintained around 90% capacity, even with frequent EV-mode use.

BMW showed highly variable results depending on driving style. Vehicles driven mostly on the petrol engine retained more than 90% capacity at 200,000 km. Frequent EV-mode use resulted in capacity dropping to 77%, and a mixed driving style left batteries at around 85%.

Volkswagen and Volvo demonstrated stable and predictable degradation. When EV mode was used regularly, their batteries kept more than 85% capacity even at the 200,000 km mark.

The worst results were recorded for Mitsubishi and Ford. Mitsubishi PHEVs lost more than 20% capacity by 100,000 km, even with minimal EV-mode use, and fell below 75% at 200,000 km. Frequent EV-mode driving resulted in capacity dropping below 70%.

Ford performed particularly poorly under active EV-mode use – capacity dropped to 90% after just 25,000 km.

Researchers therefore recommend considering the brand-specific characteristics and the driving conditions in which a used PHEV was operated. The main risk factors include extreme temperatures, long periods of inactivity, and incorrect charging habits.