Battery life uncertainty prompts concern over used EVs

Meanwhile, 2014 examples of the Nissan Leaf show 23% degradation after almost six years. After four and a half years, the batteries in 2015 Tesla Model S cars that Geotab sampled had degraded by 10%. 

Autocar compared Geotab’s results with the same models being advertised by private sellers. A 2012-reg Nissan Leaf with 102,000 miles had, said its owner, only eight bars of the 12 showing on its range display, meaning its battery had degraded by around 30%. As a consequence, he said, the car had a real-world driving range of 50 miles. 

A 2015-reg BMW i3 with 33,000 miles had degraded by 19%. Its owner claimed that on a full charge and in Eco Pro mode, the car had a driving range in summer of 85 miles. A 2014-reg Tesla Model S with 70,000 miles displayed a range of 270 miles when fully charged, compared with 280 miles when it was new. 

In contrast to these private sellers, Autocar found that dealers were less forthcoming about their cars’ battery capacities and ranges. However, one specialist EV dealer has recently begun displaying the battery health of its cars in its advertising. Drive Green, based near Bristol, uses a plug-in battery monitor to generate a battery certificate that it displays with the car. For a 2014-reg Renault Zoe with 54,000 miles, the company quotes a battery state of health figure of 96%. A salesman said the garage is the only one in the UK offering the service. 

Some dealers are sceptical about the reliability of battery readings taken this way, however. One EV specialist told Autocar that it’s important to know what condition the battery was in before it was analysed by a third-party, plug-in system. “A warm battery will give a good figure, so sellers run the car first then check it,” he said. “I’ve seen it happen when dealers are selling to the public as well as to each other. This way, they get a better price for the vehicle. The best thing is to go by the car’s range display. We’ve sold hundreds of EVs, and on this basis, we see 1-2% battery degradation each year.” 

One organisation that might be expected to have a clear picture of the scale of battery degradation is Recovas. The partnership – which includes EMR, a vehicle recycler; car makers including BMW; the University of Warwick; and the UK Battery Industrialisation Centre – is developing an end-of-life supply chain for the electric vehicle industry. As part of this work, EMR salvages end-of-life EV batteries. But EMR managing director Roger Morton said it’s early days as far as supply is concerned. 

“EV batteries are lasting far longer than anyone expected,” he said. “Although batteries degrade over time, for third owners and beyond, driving range is less of an issue. The car is probably a second or third vehicle for short trips, and in any case the car is much cheaper than a new one, so they make allowances.