Battery degradation driving up repair bills
New research suggests that nearly nine million cars on UK roads could be vulnerable to unexpected repair bills due to battery degradation.
Automotive diagnostics specialist Carly analysed more than 550,000 vehicles across most brands between January 2025 and January 2026 and found that about 25% could have 12-volt batteries in poor condition.
With more than 34 million cars in the UK, that means that about 8.6 million cars could be operating on low power and liable to suffer non-starts and security glitches.
Unlike most failures, 12-volt batteries decline slowly and with little warning; often the first time drivers realise there is a problem is when their car doesn’t start.
However, a weakened 12-volt battery could cause additional issues in modern cars, with low battery voltage impacting vehicle reliability and security systems such as central locking, alarms and keyless entry.
Battery degradation
Emma Brown, Carly UK growth manager, said: “Because battery degradation develops gradually, it’s easy for drivers to miss the warning signs until the vehicle suddenly fails to start.
“In modern cars, a weak 12-volt battery can affect far more than just starting the engine, which is why early diagnostics and better visibility of battery health are so important. Identifying issues sooner can help drivers avoid more disruptive failures, breakdowns and the knock-on repair costs that often follow.”
