Common EV Faults to Watch For (Used Buyer's Guide)

The common and cheap

12V battery failure. By some distance the most frequent EV fault, and the reason most EVs that "won't start" won't start. The main pack can be nearly full while the little 12V battery that wakes the car is dead. Symptoms include an unresponsive car, flickering displays, slow wake-up, and warning lights that come and go. Replacement is inexpensive and they last three to five years, same as any car. Not a reason to walk away. See can you jump-start an electric car.

Software and infotainment glitches. Frozen screens, connectivity dropouts, phantom warnings. Often fixed by an update, sometimes over the air without a garage visit. Annoying rather than serious, though worth checking whether the car is up to date and whether the manufacturer still supports it.

Charging port faults. Latches that stick, flaps that don't release, locking pins that fail. Usually a modest repair, but test both AC and DC ports before buying if you can.

Seized or corroded brakes. Because regenerative braking means the friction brakes are used so little, discs can develop surface corrosion and calipers can seize, particularly on urban cars in the UK climate. Listen for grinding and check the discs visually.

The moderate

Uneven tyre wear. Very common, and a useful tell about how the car's been driven and whether it's been rotated. See EV tyre wear.

Coolant system issues. Most EVs use liquid cooling for the battery and power electronics. Leaks and pump failures happen and matter more than they would on an engine, because thermal management protects the most expensive component in the car.

Onboard charger faults. If a car will rapid charge but not AC charge, or the other way round, that points at the onboard charger or associated wiring rather than the battery itself. Worth diagnosing properly, because the two have very different costs.

Heat pump or heating faults. Not catastrophic, but a failed heat pump hits winter range noticeably.

Reduced power warnings. Sometimes a genuine fault, sometimes the car protecting itself in extreme temperature. Worth investigating rather than assuming either.

The serious

Battery degradation beyond what's normal for the age. Not a fault as such, but the single most consequential thing to check. A pack well below the typical range for that model and age means reduced range now and reduced value later, often with no warranty claim available because it hasn't crossed the threshold.

Individual cell or module imbalance. A dashboard reading won't show this, but a proper diagnostic will. Can be the precursor to a fault, and can sometimes be repaired at module level rather than requiring a whole new pack.

High-voltage system fault codes. Anything relating to the traction battery, BMS or inverter needs a specialist assessment before you commit. Don't accept "it's just a sensor" without evidence.

Battery management system faults. The BMS protects and balances the pack. Faults here are uncommon but serious, and any sign of third-party tampering with it is a warranty-voiding red flag.

Model-specific things worth knowing

Early Nissan Leaf (2011 to 2015). Passive air cooling rather than liquid, so more exposed to heat-related degradation. The 12-bar gauge is coarse, so get a precise reading. Also check whether it's CHAdeMO, since that rapid-charging standard is being phased out.

Renault Zoe. Confirm whether the battery is owned or leased. Some early cars were sold on a battery lease that carries an ongoing monthly cost.

Any ex-fleet or ex-rental car. Likely to have lived on rapid chargers, which tends to show in the battery health figure.

Any car with a write-off marker. On an EV this matters more than on a petrol car, because it can invalidate the battery warranty entirely.

How to check for faults before buying

1. Run a battery health check. The one thing a test drive can't tell you.
2. Check MOT history. Advisories build a picture, and timestamped mileage catches odometer discrepancies.
3. Test both charging types. AC and DC use different hardware.
4. Look at the tyres. Uneven wear across an axle says a lot.
5. Check the brake discs. Surface rust and scoring on a low-mileage car suggests it's barely been driven or has sat unused.
6. Sit with the car powered up for a few minutes. Intermittent electrical faults often show themselves.
7. Check for outstanding recalls using the VIN.
8. Ask about software updates and whether the model is still supported.

Putting it in perspective

Most of this list is minor. EVs consistently suffer fewer breakdowns than petrol equivalents because there's simply less to fail, and the serious category is short and mostly rare.

The point isn't that EVs are unreliable. It's that the risk is concentrated rather than spread out, and that the concentrated bit happens to be invisible. Everything else on this page you can spot with a careful look round the car.