Buying a Used Electric Car: How to Check Battery Health (SoH)

What battery health (SoH) means

State of Health compares the energy the battery can store today with what it could store when new. A battery with 100% SoH is as good as new; one with 85% stores 15% less energy, and range falls by roughly the same proportion.

SoH is not the same as the charge level on the dashboard. A car can show 100% charge with a battery at 82% SoH: the display shows how full the battery is, not how big it still is. Dashboard range estimates are not reliable either, because they are based on recent driving and temperature.

Here is what different SoH values mean in kilometres, using battery sizes and WLTP ranges from our electric car catalog:

Real-world range is lower than WLTP, especially in winter, so apply the same percentage to the range you actually need. You can read how battery capacity and electric range are defined in our glossary.

How long do EV batteries last?

Battery ageing is usually fastest in the first year or two and then slows down. The main factors are time, mileage, heat, frequent DC fast charging and long periods at very high or very low charge.

Regulators now set minimum standards. Under the Euro 7 regulation agreed in 2023, batteries in electric and hybrid cars must keep at least 80% of their capacity for 5 years or 100,000 km, and 72% for 8 years or 160,000 km. The rule applies to newly approved car models from late 2026 and to all new cars a year later, so it covers future used cars rather than today's stock. It still shows what the industry considers normal ageing.

The battery warranty

Almost every manufacturer gives the traction battery a separate, longer warranty than the rest of the car, typically 8 years with a mileage limit and a minimum capacity, usually 70%. Tesla's European warranty is a good example:

Tesla states that the original battery warranty also applies to used cars, and the warranty ends at whichever limit comes first. Other brands use similar terms, but conditions differ: some require dealer servicing or software updates to keep the warranty valid, and a few set the threshold differently. Before you buy:

• Get the first registration date and check how many years and kilometres of warranty remain.
• Read the battery warranty conditions in the service book or on the manufacturer's site.
• Check the car's service history; some brands require regular battery checks.

A battery with 85% SoH and four years of warranty left is a safer buy than one with 92% SoH and the warranty about to expire.

How to get the battery health checked

There are three ways, from least to most reliable.

1. The car's own reading. Some models show SoH in a service menu, and dealers can read it with the manufacturer's diagnostic tool. A dealer printout is useful, but it comes from the seller's side.

2. OBD apps and adapters. For many popular models, a Bluetooth adapter on the diagnostic port and a dedicated app can read the battery management system's SoH estimate. It is quick and cheap, but the quality of the reading varies by car and app.

3. An independent battery certificate. Several companies offer manufacturer-independent tests that end in a certificate stating the SoH:

• Aviloo, also offered through ADAC test centres in Germany. In the full test, a data box on the OBD port records the battery while you drive from a full charge down to below 10%, within up to seven days; the certificate arrives by email within two days. The ADAC charged €99 for it from June 2022.
• TÜV Rheinland and DEKRA offer their own battery certificates.
• Marketplaces increasingly show certificates in listings. On mobile.de, dealers can add a certificate and buyers can filter for cars that have one, with a colour scale ranging from "very good" to "reduced".

A certificate is a snapshot of the battery on the day of the test, so check the date. A test from two years and 40,000 km ago does not describe the car you are buying today.

Used EV battery checklist

Before you sign, work through this list:

• SoH certificate, recent and independent, with the test date and method stated.
• Warranty: remaining years and kilometres, conditions, and confirmation that it transfers to you.
• Fast charging test: plug into a DC charger at 20–50% charge and check that the car reaches a power close to its specification for that temperature. A healthy battery should not stall at a few kilowatts.
• AC charging: confirm the on-board charger works with a public Type 2 point or your wallbox.
• Charging port and cables: no burn marks, damage or missing cables.
• Underbody: look for impact damage to the battery casing, scraped protective covers or signs of repair.
• Warning lights and messages on a cold start and during the test drive.
• Range check: charge to 100% if possible and compare the predicted range with what the car's history and the weather suggest.
• Software and recalls: ask whether the battery management software is up to date and whether any battery-related recalls were completed.
• 12-volt battery: EVs often break down because of a weak 12-volt battery rather than the traction battery, as the ADAC's breakdown statistics show.

What a weaker battery is worth

A lower SoH does not make an EV a bad buy; it makes it a cheaper one. Work out whether the remaining real-world range covers your daily driving with a winter margin of 30–40%. If it does, a car with 85% SoH at a lower price can be the smarter choice. If the SoH is unknown, price that uncertainty in or walk away.

From February 2027, new EV batteries placed on the EU market must carry a digital battery passport under the EU Batteries Regulation (EU) 2023/1542, which will make battery information easier to access in future. For the cars on sale today, the certificate and warranty remain your best protection. Compare plug-in options in our catalog of hybrid cars if a full EV with an uncertain battery does not fit your budget, and see what a plug-in hybrid is.