EV battery health check: what dealers must test before buying
How to run an EV battery health check on a used electric car: state of health, test methods, acceptable values and the effect on trade price.
· 8 min read
An EV battery health check measures the battery's state of health (SoH): the usable capacity today as a percentage of what it had when new. Dealers get it from a diagnostic read-out of the battery management system, an independent battery test or certificate, or, as a rough check, a controlled range test. Compare the result with the manufacturer's warranty threshold and with cars of the same age before you set your bid.
What an EV battery health check measures
State of health is the share of the original usable capacity the battery still has. A 60 kWh battery that now stores 54 kWh has an SoH of 90%. It is the single most important number on a used electric car, because it decides range, and range decides the price a buyer will pay.
A good EV battery health check gives you more than one number:
- SoH, ideally measured, not just estimated by the car;
- cell balance, the spread between the strongest and weakest cells or modules, which can reveal a single weak module;
- fault codes stored by the battery management system (BMS);
- charging history where available, such as the share of DC fast charging;
- warranty status: remaining years and kilometres, and the threshold the manufacturer guarantees.
Remember that SoH is not the same as the state of charge (SoC). A car showing 80% on the dashboard tells you how full the battery is, not how healthy it is.
How to measure battery state of health
There are four practical ways to test an EV battery, from quick and rough to precise and slower.
| Method | What you get | Accuracy | Best for |
|---|---|---|---|
| Car's own display or app | Range estimate, sometimes an SoH figure | Low to medium; depends on driving history and software | First screening |
| OBD read-out with a diagnostic tool or app | BMS-reported capacity, cell voltages, fault codes | Medium to high, depending on the model and tool | Your own workshop check |
| Independent battery test or certificate | Measured SoH with a report, often recognised by buyers | High | Retail cars, higher-value stock |
| Brand workshop diagnosis | Manufacturer's own battery data and warranty status | High | Warranty questions, suspected faults |
| Full-charge range test | Real range in known conditions | Low; weather and driving style distort it | Rough plausibility check only |
For cars bought at auction or abroad, ask whether a battery report exists. Many remarketing platforms and leasing companies now include an SoH figure in the condition report. Treat a missing report as a cost: you will have to test the car yourself before you can sell it with confidence. Our article on EV auctions explains how to read these reports at trade sales.
For car dealers
Know your margin before you buy
MyCarDealer compares any car from an auction or listing with the market in your country and shows the net margin after VAT, transport and costs – and the maximum bid.
Request accessWhich battery health is acceptable for a used EV?
There is no single legal pass mark for used cars, but two benchmarks help you judge a result.
The warranty threshold. Most manufacturers guarantee a minimum capacity for 8 years and a mileage limit, commonly 70% within 8 years or 160,000 km; some versions have a higher mileage limit. Check the exact terms for the model and the remaining time from first registration. A car close to the warranty threshold but still within the period may qualify for a battery repair at the manufacturer's cost; one that has left the warranty carries the full risk.
The EU durability benchmark. The Euro 7 Regulation (EU) 2024/1257 sets minimum battery durability for new passenger cars of 80% after 5 years or 100,000 km and 72% after 8 years or 160,000 km. It applies to new types from 29 November 2026 and to all new cars from 29 November 2027, so it does not cover cars already on the road, but it is a useful yardstick. A five-year-old car below 80% is weaker than what new cars must now be designed to achieve.
As a working rule for stock decisions:
- Clearly above the benchmark for its age: price the car normally.
- Around the benchmark: price it a step below comparable cars and disclose the figure.
- Close to the warranty threshold, or with a weak module: buy only at a price that covers repair or a long holding time, or not at all.
How much poor battery health reduces a used EV's value
A weak battery reduces the price by more than the lost range alone, because buyers fear further loss. The clearest way to put a number on it is to compare with the market.
According to listings tracked by MyCarDealer across Germany, the Netherlands, Belgium, Poland, Italy, France, Austria, Spain and Sweden in October 2026, a 2019 Tesla Model 3 had a median asking price of €20,900 (347 listings, median 132,600 km), while a 2021 Model 3 was at €25,990 (351 listings, median 93,600 km). Two model years and about 40,000 km made a difference of around €5,100.
That gives you an anchor. A 2021 car whose battery is as tired as a typical 2019 car is, in the buyer's eyes, closer to a 2019 car. So:
- start from the market price of the same model, year and mileage in your country;
- if the SoH is clearly below the norm for its age, price it towards the older model year's level;
- deduct the cost of a battery test and certificate if you need one to sell;
- add a margin for holding time, because a car with a weak battery sells more slowly.
MyCarDealer shows current market prices for the same EV in your country, so you can judge the battery discount against real numbers instead of guessing. You can check one car with the free valuation.
What battery certificates and warranties cover
A battery certificate documents the SoH at the time of the test. It does not guarantee the future, but it gives the next buyer a figure they trust, which shortens selling time. When you buy a car with a certificate, check the test date, the method used, and whether the VIN on the certificate matches the car.
Manufacturer battery warranties usually cover capacity falling below the stated threshold within the stated years and kilometres, plus defects. They do not usually cover normal gradual loss above the threshold, damage, or misuse. Read the conditions for the specific model, including whether the warranty transfers automatically to the next owner and whether servicing must be done in the brand network.
In future, the EU battery passport will help. Under the Battery Regulation (EU) 2023/1542, every EV battery placed on the market from 18 February 2027 must have an electronic battery passport that includes its state of health. Cars in today's used stock will not have one, so for the next few years the dealer's own test remains the main source of information.
Red flags in an EV battery health check
Some findings should stop a purchase or change the price sharply:
- an SoH figure the seller will not show, or a report without a VIN;
- a large spread between cells or modules, or stored BMS faults;
- a battery replaced under warranty with no paperwork;
- a car that has stood for months with a flat battery;
- signs of flood or accident damage under the car near the battery pack;
- a reduced charging power warning or a limited maximum charge set by the manufacturer.
For a broader view of which electric cars are worth stocking, see our guide to used electric cars for dealers, and for pricing principles, used car valuation for dealers.
Frequently asked questions
How much does an EV battery health check cost?
It depends on the method. A reading with your own diagnostic tool costs only time, while independent battery tests and certificates and brand workshop diagnoses are charged by the provider. For retail stock, a recognised certificate usually pays for itself through a faster sale.
What happens to an EV after 8 years?
The battery usually still works, but typical manufacturer capacity warranties end at around 8 years or a mileage limit. After that, any further capacity loss or battery fault is at the owner's cost, so the SoH figure becomes even more important for the price.
Is 70% battery health bad?
For most used EVs, yes. 70% is the threshold many manufacturers guarantee within 8 years, and the Euro 7 benchmark for new cars is 72% after 8 years. A car at 70% has noticeably less range and needs a clear price discount.
Is there an app that can check the health of an EV battery?
Several apps work with an OBD dongle and read the battery data reported by the car. Their accuracy depends on the model and on how much data the manufacturer makes available, so use them for screening and an independent test for cars you retail.
What is EV battery state of health and how is it measured?
State of health is the usable capacity today as a percentage of the capacity when new. It is measured by reading the battery management system with a diagnostic tool, by an independent battery test, or by the manufacturer's workshop.