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Selling a used EV in the UK: how to prove battery health

Published 2026-10-27 · Last updated 2026-10-27

Buyers of used EVs worry most about the battery, and many won't buy without independent evidence of its health. This guide is for private sellers and small dealers. It covers which battery tests buyers trust and what they cost, what a certificate shows and how buyers verify it, cell balance, the battery warranty left and whether it transfers, what to put in the advert, and how to describe the battery honestly.

Why battery evidence matters when you sell

• Private buyers: besides the 57% above, 31% said they would buy without a check only if a significant part of the original battery warranty remained (Startline Motor Finance). In an Auto Trader survey, 34% of car buyers named battery health as a barrier to buying a used EV (Auto Trader UK, 2025-12-16).
• Dealers already do it, but rarely show it: 56% of UK used-car retailers said they always run a state-of-health (SoH) check, yet only 28% of those always put the result in the advert. Auto Trader says top retailers add images of the certificate to the listing photos and mention battery health in the description (Auto Trader UK).
• Trade buyers: in Dealer Auction research, 45% of trade bidders had avoided bidding on an EV because battery information was missing, and 45% were more likely to bid on a car with a battery health certificate (Motor Trader, 2025-06-18).

These are surveys, not proof that a certificate raises the price of any particular car.

Which test to get, and what it costs

Buyers give most weight to an independent test with a result they can verify online. The options open to a private seller in the UK:

Prices are taken from the providers' own pages on the dates shown and can change; they vary by area and vehicle. We list them for comparison, not as a recommendation of one provider. We are not paid by the battery-test providers mentioned on this page. See our disclosure.

Getting a clean result

• Follow the tester's conditions. DEKRA's driving test, for example, needs a state of charge of about 40–80% and a battery temperature of 10–30 °C (DEKRA).
• If the cells look unbalanced, Generational's certificate advises charging to full, waiting at least 2 hours and testing again (Northwest Vehicle Inspections).
• Software can move the car's own reading: one Kona Electric owner saw the BMS figure go from 97.4% to 100.0% straight after a battery-management software update (single car, GoingElectric forum). If the car had a recent update, mention it, and don't present a sudden jump as a real improvement in the battery.

What the certificate shows, and how buyers check it

Most certificates give the SoH, the test date and mileage, the VIN, and some range estimates. AVILOO adds a benchmark against similar cars and often prints the car's own BMS figure as well; Generational adds usable and nominal capacity, cell voltage difference and an indicative warranty block (Battery Health Check, Northwest Vehicle Inspections). Our guide on how to read an EV battery health certificate goes through every field.

• Share the verification link or QR code, not only a PDF or screenshot. AVILOO's QR code opens the original on AVILOO's site (AVILOO GmbH); Generational's online certificate is the definitive version (Generational).
• Keep the test recent. A certificate describes the battery on the test day only (AVILOO GmbH). If the car has covered many miles since, buyers may ask for a new one.
• Never edit or crop the result. Buyers can compare the VIN, date and figures online with the copy you sent.

Cell balance

Cell balance is the gap between the highest and lowest cell voltages, shown in mV on Generational certificates and on Moba's page 2 (Northwest Vehicle Inspections, Moba). In about 10,000 UK used-EV tests, roughly 1 in 85 cars had a gap above 50 mV, which Generational says needs investigating, and about 1 in 200 was above 100 mV, a possible underlying fault (Generational, 2026-08-24). If your result is wide, retest after a full charge before listing, and if it stays wide, have it looked at and tell buyers.

Battery warranty: what's left and whether it transfers

Remaining battery warranty reassures buyers: 31% of consumers in the Startline survey said a significant part of the original warranty would let them buy without a check (Startline Motor Finance). Most terms we track run for 8 years, with mileage caps and capacity thresholds that differ by maker (36 models on our battery warranty checker).

• Transfer: Kia UK says its warranty transfers to each new owner as long as it has not expired (Kia UK). Vauxhall describes its battery warranty as transferable (Vauxhall UK). Tesla's warranty transfers when ownership is transferred through Tesla (Tesla UK). For other makes, check the manufacturer's terms.
• Use matters: for example, Hyundai cuts the battery warranty to 5 years / 100,000 miles for taxi, private-hire or driving-school use (Hyundai Motor UK). Say how the car was used.
• Treat the certificate's warranty block as a guide: Generational marks it "indicative only" (Northwest Vehicle Inspections). Give buyers the first registration date and, ideally, the manufacturer's confirmation by VIN.
• Leased batteries: some older Renault Zoes were sold with a battery lease that the buyer has to take over or the seller has to buy out (The Guardian). See our Zoe battery lease guide.

What to put in the advert

• The SoH figure, who measured it (AVILOO calculation or the car's own BMS value), the test date and the mileage at the test.
• The verification link or QR code, and an image of the certificate in the photos (Auto Trader UK).
• Cell balance, if the certificate shows it.
• The battery version (kWh) and, where relevant, the chemistry (LFP or NMC), as shown on the certificate or the car's documents.
• First registration date, battery warranty end date and mileage cap, and whether it transfers.
• Recall status: buyers can check unfixed safety recalls by registration on GOV.UK (GOV.UK); say whether any battery recall work has been done.
• Anything that affects the battery or its warranty: taxi or private-hire use, a battery lease, battery repairs or replacement modules, recent software updates.
• Charging cables included.

Describe the battery honestly

A car bought from a private seller must match its description, and if it doesn't the buyer can claim compensation, for example the difference in value (Citizens Advice; Sale of Goods Act 1979, section 13: legislation.gov.uk). Sales by a business to a consumer fall under the Consumer Rights Act 2015 instead (legislation.gov.uk). In practice:

• State the figure you measured and how it was measured. Don't round up, and don't call a battery "perfect" or "like new" without evidence.
• Don't use the car's range readout as proof of battery health. Recurrent says its range data shows range retention, not battery health, and that some makers release reserve capacity so displayed range stays stable as the battery ages (Recurrent).
• Mention known faults, warning lights, recall work or repairs, even if they've been fixed.

This is general information, not legal advice. For advice on your situation, contact Citizens Advice or a solicitor.

Is your result normal?

Buyers will compare your figure with other cars, so do it first. In 2,742 AVILOO tests in Central Europe (all models combined), the median SoH was 95.9% at under 40,000 km, 93.5% at 40,000–80,000 km, 92.0% at 80,000–120,000 km, 90.3% at 120,000–160,000 km, 88.2% at 160,000–250,000 km (Zuvala R., Bucsuhazy K., Kadula L., Dedek J., via Zenodo). 1,000 Generational battery checks at Shoreham Vehicle Auctions (UK used EVs, all models): average SoH 98.7% under 4 years (656 cars), 92.6% at 4–6 years (279 cars, 83.5% above 90%), 88.8% at 6+ years (73 cars, 34.3% above 90%); overall median 95.6%, 88% above 90%, and only 0.4% below 80% (all older Nissan Leaf and NV200 Combi) (Motor Trader). ADAC's rule of thumb is at least 92% at 50,000 km, 88% at 100,000 km, 84% at 150,000 km, 80% at 200,000 km (ADAC).

For your model, see the model pages and the battery health estimator. Our guide EV battery state of health (SoH) explained covers why readings differ between tests.

Also see: how to read a battery certificate · the questions buyers will ask (printable checklist) · the buyer's checklist and test prices · battery warranty checker · all models compared.

We are not paid by the battery-test providers mentioned on this page. Links marked "paid link" in the "Useful products and services" box are affiliate links. See our disclosure.

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