EV batteries tend to hold up pretty well over time, at least according to what we know so far. A recent Arval study of 8,300 battery state-of-health (SoH) certificates for used EVs from 30 different brands and across eight countries, including the UK, reported average capacity of 93%-100%. Generational, which specialises in SoH tests, says typical battery degradation is 1.82% a year (it stresses that is a broad average and varies by individual vehicle).
If those sorts of numbers prevail, then worries about longevity could eventually die down. For now, it is an understandable concern, albeit one fanned by the flames of misinformation. Beyond just wanting something with decent range, used buyers less educated and incentivised than company car drivers could well be worried about a five-figure bill if the battery goes bang – and potentially completely unaware of the industry-standard eight-year/100,000-mile battery warranties.
That is where SoH certificates come in, with a time- and date-stamped record of how much original capacity remains. They typically comprise a pdf or a jpeg, often with a QR code that leads to a download and more information. There are various ways of pulling the data (the most scientific – and labour-intensive – can involve fully decharging or even extracting the battery) but the combination of a dongle plugged into the vehicle’s OBD port and an app to run the test/generate the certificate is among the quickest, even if it relies on OEM data stored in the vehicle.
A European study by SoH specialist Aviloo claimed buyers were willing to pay €550 to €1,100 more for a used EV with a certificate from an independent provider than one without, and analysis of UK vehicle buyers by Generational last year again suggested it added value to the car.
So far, there is no independent metric to prove a certificate’s impact on residual values. Both Cap HPI and Glass’s told us it was not yet possible to put a figure on their effect, but the former’s head of current car valuations, Chris Plumb, says they are “helping to dispel the myth that batteries won’t last”.
In demand
Crucially, consumers are asking for them. Arval sells and re-leases a portion of its used vehicles through its Autoselect direct-to-retail platform and claims to be the first leasing company to issue SoH certificates – generated by Aviloo and Moba – when reselling EVs. It says such enquiries are increasingly common.
“[Buyers] will ring up, then probably the second or third question will be ‘do you test the battery?’” reports head of B2B and remarketing partnerships, Stuart Chamberlain. “Two years ago, one person might’ve asked, and if you said no, they’d probably go ‘don’t worry about it’. But now, there’ve been a few who say ‘please can I see the battery certificate?’ and if they can’t, they might consider not buying the car. It’s becoming more prevalent.”
It chimes with results from a Cox Automotive survey of used EV buyers’ considerations, published in April. When asked ‘What performance information would be most important when looking into a used EV?’, 73% of the 2,776 respondents said, ‘battery health and remaining capacity’, and ranked it above five other metrics. Also in April, Polestar said used Polestar 2s sold through its dealer network would include an SoH certificate.
“Since they went live, one of our customers had a 300% increase in ad views on their EV listings,” says Oliver Phillpott, Generational’s co-founder, of dealers using the service. “Another says having the battery health reading is instrumental in about 50% of the cars they sell.”
There are questions about where and when the tests take place and who in the remarketing chain is responsible for them, as Philip Nothard, Cox’s insight director, explains.
“One of the things that seems to be in a lot of conversations at the minute is the timing of it, and who takes the cost.”
He likens it to industry efforts to catch illegal mileage blockers – again by plugging a device into the OBD port. The time and expense were allegedly such that some suppliers said it was not worth it and offered to take the vehicles back if a problem were later discovered.
Usage-based pricing is common – Generational does it, as does vehicle data app Carly, which also supplies SoH tests. Phillpott says his firm’s testing kits cost less than £100 and the tests themselves are “broadly mid/low tens of pounds per test as an entry point, and that number can come down with volume”. Carly launched its B2B service in the UK in April, and the European prices published on its website in May spanned €8.50 to €11.90 per test, depending on the plan.
Scheduling question
As for timing, there is a strong case for ‘the later, the better’, which speaks more to the certificate’s current chief purpose of instilling confidence than illustrating minute battery degradation, if any, over a few weeks. However, logistics could dictate that it is easier to do the check earlier.
“A rental company raised this with me and said they’d do the test at end of use,” says Nothard. “Say it’s 88% on 1 May. That car will then go into the wholesale environment, and it might take a month to sell, so you’re into June. Then it goes into the retail environment. How relevant is the test from 1 May by the time you get to the end of June?”
SoH specialists point out the speed and ease of the tests. Generational’s YouTube demonstration video shows it takes about a minute, and Phillpott adds that most businesses in the sector already use mobile devices for vehicle inspections.
“As long as it’s done within 30 days of the car being sold, from a consumer perspective, that’s reliable, and it gives them [buyers] peace of mind,” adds Daniel Meeghan, Carly’s country manager. He believes certificates could be generated both when vehicles are defleeted as part of the remarketing proposition, and again by dealers, especially if the car is sold as part of a used approved programme a la Polestar (we asked Polestar to confirm when and by whom its SoH tests were conducted, but it did not supply answers before our deadline).
Industry focus
In April, the Association of Fleet Professionals called for “an industry backed battery health check” as part of efforts to assuage used car buyers’ fears around EVs and produce consistent results. Europe already has one, in the form of the Car Remarketing Association Europe’s (CARA) approved battery health check, to which specialist providers (there were three at the time of writing: Aviloo, Moba and Laika Lab) must apply for accreditation. Phillpott said Generational was applying for CARA accreditation when we spoke in May and Meeghan said Carly planned to.
It may also become possible to access battery SoH through vehicles’ infotainment systems, as you can with smartphones, and the EU and UK governments have expressed interest in mandating accessibility, which could challenge the business model of testing specialists.
Speaking at a Vehicle Remarketing Association meeting in July last year, Abdul Chowdhury, head of vehicle policy at the Office for Zero Emissions Vehicles, said the principles had been outlined in Labour’s Automotive Sector Plan, published in October 2023, and highlighted the government’s work on the United Nations Global Technical Regulation (GTR) Number 22 on EV batteries.
“GTR 22 provides the requirement for a battery state of health monitor which is in an easily accessible manner, such as through the vehicle’s dashboard,” said Chowdhury at the time.
SoH certificates have already made a splash in remarketing and, if momentum continues, the percentages they convey could end up in the same league as age, mileage, spec and other key used car metrics. The logical next steps would be a CARA-style scheme for the UK, to ensure consistency across mushrooming SoH testers, and industry-standard inclusion in online used car adverts as filterable criteria (they can already be found in the image carousels of some classified ads).
Questions about costs and logistics remain valid, but the signs so far suggest used car buyers respond well to the certificates, and ‘demand’ has always been a watchword for the used car market. Give them time to mature, and they could start to have more than an anecdotal impact on residual values.
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