South Wales has seen a significant rise in used EV listings over the past two years — on AutoTrader, Facebook Marketplace, and local dealerships alike. Prices have come down, range anxiety has eased for most daily drivers, and more people are making the switch. But buying a used EV carries a risk that petrol car buyers don't face: the battery.

This guide covers what to check, what questions to ask, and how to protect yourself before handing over money on a used electric car in Pontypridd, Cardiff, RCT, or anywhere else in South Wales.

Why the battery is the only thing that matters

A used EV with a worn battery isn't just a car with slightly less range. It's a car whose main asset — the expensive part — is already degraded. Replacing an EV battery costs between £3,000 and £15,000 depending on the vehicle. That's not a repair you budget for the way you budget for a clutch replacement.

The problem is that EV batteries degrade silently. A Nissan Leaf showing 11 bars on the dashboard could have 89% State of Health or 76% — the bars are the car's own estimate, not an independent measurement. Sellers don't always know the real number. Dealers often don't either.

The only reliable answer

An independent Aviloo certified battery health test measures the battery directly using professional equipment — not the car's own BMS estimate. It gives you a precise State of Health percentage, timestamped, in a certificate any buyer, dealer, or insurer will accept.

What to check before you buy

1. Get an independent battery health test

Not the dealer's own health check — their own. An independent Aviloo FLASH Test takes about 20 minutes, can be done at the seller's address before you commit, and costs £79 through PAD. It tells you the exact State of Health, State of Charge, WLTP range estimate, and cell-level balance. If the battery is healthy, you have proof. If it isn't, you walk away — or negotiate hard.

2. Check the MOT history

EVs still have MOTs. The history reveals odometer readings at each test (useful for spotting mileage discrepancies), any advisories that have been quietly accumulating, and whether warning lights have been cleared before previous tests. PAD's free DVLA reg check pulls MOT history directly.

3. Run an OBD diagnostic scan

EVs store fault codes across all modules — battery management, charging system, motor controller, 12V system. A seller can clear warning lights from the dashboard. They cannot clear the stored code history from the BMS. A professional OBD scan reads both active and stored codes, including ones that were cleared before the viewing.

4. Check the 12V battery

Every EV has a conventional 12V battery that runs the low-voltage systems — lights, locks, infotainment, and critically, the high-voltage system wake-up. 12V batteries in EVs fail more often than in petrol cars because they're rarely charged by an alternator. A dead 12V can leave an EV stranded even with a full main battery. A load test takes 5 minutes.

5. Run an HPI check

Outstanding finance, insurance write-off category, stolen markers, mileage discrepancy. PAD runs full HPI checks for £6 — standard practice before buying any used car.

Red flags from sellers

  • Refusing to allow an independent inspection before purchase — no legitimate seller has a reason to refuse
  • Saying the battery is "fine" without any documentation — fine isn't a number
  • Dashboard showing "90%" health — that's the car's own estimate, not independently verified
  • Unusually low asking price for the age and mileage — usually means the seller knows something
  • Charging cable included but seller says they "never really used the EV mode" — on a PHEV, this often means the EV battery was never charged and may have degraded

What a good used EV looks like

State of Health above 80% is generally considered acceptable for a vehicle more than 4 years old. Above 85% is good. Above 90% is excellent. For newer vehicles, you should expect higher — a 2021 EV at 78% SOH has degraded unusually fast and is worth investigating.

Cell balance matters too. Tight cell voltage variance (under 20mV delta) suggests a well-maintained pack. Wide variance can indicate individual cell failure or an ageing pack that will degrade faster.

PAD covers South Wales

PAD is a mobile Aviloo certified EV battery testing service based in Pontypridd. We come to the seller's address — whether that's Cardiff, Merthyr, Bridgend, Aberdare, or anywhere across Rhondda Cynon Taf. A pre-purchase EV check (Aviloo SOH + OBD scan + 12V test) costs £79 and takes about 30 minutes on site. You get the results before you transfer any money.