The 'battery health' percentage on your EV's dashboard is basically a lie and usually misses how much the battery is actually dying.
March 24, 2026
Original Paper
Battery health reporting fails independent validation across manufacturers
arXiv · 2603.21592
The Takeaway
A study of over 1,000 EVs from five manufacturers found that internal software often misses massive 25% differences in real battery capacity. This means your car could report a healthy battery even when it has significantly degraded, hiding vital information from owners and used-car buyers.
From the abstract
Battery state-of-health (SOH) reported by on-board battery management systems (BMS) is the primary metric available to electric vehicle (EV) owners and regulators, yet no study has validated its reliability across manufacturers against independent measurements. Here we show, through an epidemiological study of 1,114 EVs spanning five manufacturers and 375 days, that battery health reporting is fundamentally unreliable: real capacity differences of 12-25% exist within every model, but BMS SOH fai