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Increasing numbers of motorists are buying used electric cars. They offer good value for money and have very few powertrain components to go wrong compared to petrol and diesel cars (and of course the running costs of EVs are much cheaper for most drivers). But many people have concerns about the condition of the batteries in used EVs. The good news is that the health of an EV’s battery can easily be tested, and even better news is that testing has shown that batteries in the vast majority of used EVs are still performing very well.
So you want to buy a used EV, how do you test the battery?
If you’ve found a used EV online and want to understand the battery condition of that specific car, the first thing to do is ask whether the retailer has already carried out an independent battery assessment and can show you the result.
ClearWatt, an EV battery testing company, now works with a significant and growing proportion of major EV retailers in the UK, so in many cases that information may already be available with the vehicle.
If the retailer hasn’t already assessed the battery, consumers can also test the vehicle themselves using the ClearWatt app. This can be done during a sufficiently long test drive, provided the necessary driving requirements can be met.
Before travelling to see the car, it is also useful to understand what that particular model and specification should be capable of. ClearWatt’s consumer products can provide vehicle-specific information including expected real-world range, charging performance, battery warranty information and other things worth checking when you see the vehicle. That gives the buyer a useful benchmark before they arrive.
So in simple terms: understand what the car should be capable of, ask the retailer for independent evidence on the actual vehicle, and if that isn’t available, test it yourself.
ClearWatt has also looked at its data to see how batteries in Used EVs are performing, specifically older vehicles approaching the end of their manufacturer battery warranty. For this analysis, this is defined as vehicles within two years or 20,000 miles of the end of the applicable battery warranty.
Across that group, more than 9 in 10 (92.4% to be precise) received an ‘Excellent’ ClearWatt battery assessment (from the last 1,000 EVs analysed that are within two years/20,000 miles of their warranty expiring).
Importantly, “Excellent” does not mean that a manufacturer-reported State of Health percentage has been read and a threshold has been applied. ClearWatt’s Battery Scorecard is designed to assess battery condition using the broadest relevant evidence available for the individual vehicle. Depending on the vehicle and test method, that can include manufacturer-derived battery information, battery diagnostics such as cell balance and voltage behaviour, age, mileage and usage, vehicle-specific expectations based on battery chemistry and pack architecture, benchmarking against comparable vehicles, software status, recalls and manufacturer campaigns, and warranty context.
Fault detection is also an important part of the assessment. A battery can return an apparently reassuring headline State of Health figure while other diagnostic signals indicate something that warrants investigation. That is one of the reasons that ClearWatt deliberately avoids treating a single OEM-reported percentage as synonymous with battery condition.
In summary, it’s not simply that ‘EV batteries last’; even among vehicles already relatively close to the end of their battery warranty, the overwhelming majority that ClearWatt assesses are still receiving an Excellent overall battery assessment.
So just because a battery warranty is due to expire, this doesn’t mean that the battery life is due to expire.
