Batteries & chargers 38 The 12V battery is still killing hybrids and EVs and the aftermarket needs to be ready Data from Which?’s car reliability survey confirms something many in the trade will already recognise: the humble 12V starter battery is proving to be one of the weakest links in modern hybrid and electric vehicles. Battery supply company Veloris looks at what is behind the problem and how independent workshops can help their customers deal with the issue. The survey, covering more than 63,000 owners between April and June 2025, found full hybrid owners four times more likely to suffer a flat or failed 12V battery within four years than petrol drivers, and EV owners more than twice as likely. Petrol and diesel sit at a comparatively benign 1.4% and 1.8%. By brand: Hyundai’s EVs top the table at 16.1%, Kia’s EVs at 7.5%, Toyota/Lexus full hybrids at 10.3% and 9.4%. At model level it gets starker; Lexus LBX (29.2%), Hyundai Ioniq 5 (27.3%), Kia EV6 and Soul EV (both 18.8%) fail at 10-20 times the rate of an equivalent petrol car. Why these batteries are struggling The 12V units fitted as standard across this parc are conventional flooded lead-acid — excellent at cranking, poorly suited to what hybrids and EVs now ask of them. Keeping infotainment, telematics and DC-DC converter cycling alive while parked puts these batteries through repeated slow, shallow discharge-recharge cycles rather than the brief high-current burst they were designed for. That cycling pattern drives acid stratification and early sulphation, and life expectancy drops accordingly. A Kia spokesperson told Which?: “In 2024, Kia issued an ICCU software update to improve charging of the 12volt battery and manage its voltage/ thermal behaviour.” Hyundai cited similar updates for the Kona and Ioniq 5 models. Toyota and Lexus, by contrast, point to a hardware issue (undersized Model Fault rate Direct replacement AGM upgrade Lexus LBX (2024-) 29.2% LP202 LF202 / A10 Hyundai Ioniq 5 (2021-) 27.3% LP027 LF027 Toyota Yaris Cross (2021-) 19.1% LP202 LF202 / A10 Kia EV6 (2021-) 18.8% LP027 LF027 Kia Soul EV (2019-24) 18.8% LP079 LF012 Hyundai Kona Electric (2018-24) 16.7% LP079 LF012 Toyota Yaris (2020-) 12.2% LP202 LF202 / A10 Ford Kuga PHEV (2020-) 11% LP079 LF012 Toyota Corolla Hatchback (2019-) 8.9% LP079 LF012 Toyota C-HR Hybrid (2017-23) 8.3% LP027 / LP079 LF027 / LF012 On Hyundai and Kia models, check for an outstanding software campaign before replacing the battery as without it, the fix may only last a few months. On Toyota and Lexus models, confirm charging system compatibility and battery location before offering the AGM upgrade; where either rules it out, an OEspec replacement plus a CTEK charger is the safer recommendation For the models named in the survey, here’s the direct replacement and, where the vehicle’s charging system supports it, the AGM upgrade:
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