A new worldwide study of electric cars has revealed the EVs whose batteries last longest and highlighted the impact of charging on battery health.

Battery degradation remains a hot topic around EVs but the massive study by Aviloo shows that it is nowhere near as big an issue as it was once expected to be. In fact, the Austrian battery diagnostics firm found that after 50,000km (31,000 miles) none of the models tested had, on average, lost more than 10% usable battery capacity.

The global study looked at 20 of the most popular EVs worldwide and drew data from 500,000 individual vehicles across North and South America, Europe, Australia and Asia. It used this to establish state of health (SoH) figures, which reflects how much of a battery’s original capacity remains usable throughout a car’s life.

It found that at 50,000km, the median (SoH) across all 20 models was 95%. However, it also revealed clear differences between different models and even between individual examples of the same model.

Marcus Berger, CEO of Aviloo said: “The truth in this data is that averages hide a lot. Yes, EV batteries are ageing better than the ‘they wear out fast’ myth suggests – but that’s not the most useful thing this report tells you.

“What matters is that battery health varies significantly between models, and even more between individual cars of the same model.”

Longest-lasting EV batteries

At 50,000km and 100,000km the Hyundai Ioniq 5 showed the highest state of health. At 50,000km its median SoH was still 97.13%, with the best-performing examples retaining 99.15% of their original capacity. By 100,000km, that had dropped to a median of 93.79% and peak of 98.42%

However, at 150,000km, the Mercedes-Benz EQA snuck ahead of the Hyundai, with a median SoH of 93.97% compared to the Ioniq 5’s 93.79%.

At the opposite end of the table, the Mk1 Nissan Leaf and Renault Zoe performed worst. After 50,000km, the Leaf had dropped to a median SoH of 91.23% and by 150,000km to 86.67%.

The first-generation Mini Cooper EV showed similarly poor results, highlighting the impact that frequent charging can have.

According to Aviloo, smaller-battery EVs, which need more frequent charging cycles to cover the same distance, tend to show faster degradation than larger-battery models.

The Leaf also demonstrated the largest gap between individual models – highlighting the impact that different use can have on a battery’s longevity. At 150,000km there was a 13.5% spread between the best- and worst-performing examples, equivalent to a difference of around 18 miles.

Most EVs, including best-sellers such as the Tesla Model Y and Volkswagen ID.4 showed variation of around 10-12%.

Berger noted: “A gap of 10 or 15% in state of health is a real difference in range, in what a car is worth, and in what you can rely on it for.”

Mandatory testing

The new report comes amid increasing calls for all used car dealers to provide a standardised SoH report with every secondhand EV.

In August, three leading bodies in the EV sphere called for the Government to introduce mandatory battery health checks for any used EV sold via a dealer.

Electrifying, New AutoMotive and BatteryIQ said that even as demand for used EVs soars, buyers deserve more transparency to give them confidence in the longevity of any car they are considering.

Nick Bailey, founder of BatteryIQ, added: “Battery health is probably the single biggest unanswered question for used EV buyers, yet it’s also one of the easiest things to measure accurately.

“We already have the technology. We already know how to assess battery condition consistently. The missing piece is making that information available as standard. A battery State of Health certificate should become as routine as an MOT certificate.”