EV Battery Certificates: Cost, Rules, What They Prove (2026)
With a combustion car, a stamped service book reassures buyers. With a used EV, the value hangs on a single question: how healthy is the traction battery? That is what a battery certificate answers — a document that proves the battery's state independently of the seller, and one that buyers increasingly ask for.
What is a battery certificate?
A battery certificate (also called an SoH certificate) documents the health of the traction battery, usually as the State of Health (SoH): the share of the original capacity that is still usable today. A good certificate also names the measurement's data basis, ties the result to the specific vehicle (VIN) and lets the buyer verify it themselves.
The difference from the dashboard reading: a certificate is a transferable document. It travels into the listing, the negotiation and the buyer's records — the display in the car stays in the car.
Which types of battery certificate exist?
Three categories have established themselves:
- Quick on-site test (OBD read-out). A diagnostic device reads the on-board electronics in a few minutes — at a test centre or dealer, by appointment. Fast and affordable; the result describes a single day. How that becomes a number varies by provider: some pass on what the battery management system reports, others calculate the value from the signals they read plus a comparison database.
- Full test with a controlled discharge (loaned box). A measurement device arrives by post, records a real discharge from full to nearly empty and is shipped back. The most thorough single measurement — and, with several days of measurement driving plus return shipping, the most involved route.
- History-based certificate (from charging data). The vehicle is connected online once; the certificate is built from many real charging sessions over weeks rather than a single appointment. No device, no appointment, no shipping — and instead of a snapshot, a history that also shows where the battery is heading.
Which category fits depends on the purpose: if you suspect a defect, the full test delivers the most thorough single measurement. For proof at the point of sale and ongoing monitoring, the history plays to its strengths.
How much does a battery certificate cost?
Typical market prices as of August 2026: quick on-site tests cost around €79–99, depending on provider and region. Full tests with a loaned device sit at roughly €99–120 including shipping. History-based certificates are available from Akkubrief for a one-off €79 incl. VAT, to buy once the validation study reports; connecting, checking and building the battery history are free beforehand, and you only pay when you actually need the proof. The price comparison hides a difference that matters more: the quick and full tests measure today's condition and can be done at any time; a history has to have started earlier.
Beyond the price, count the effort: travel and an appointment for the quick test, several days of measurement driving plus return shipping for the full test — or a few minutes at a screen for the history-based route.
Is a battery certificate mandatory?
There is no legal obligation — but the rules are tightening:
- mobile.de has required since 1 November 2025 that sellers who mark a listing as having a battery certificate actually upload the document. Claiming one without proof no longer works there.
- From late November 2026, battery durability gets legal minimums for newly type-approved vehicles via UN GTR 22 and Euro 7 (80% after 5 years or 100,000 km, 72% after 8 years or 160,000 km).
For sellers this means: a documented battery state is moving from bonus to expected standard — bringing one puts you in the stronger negotiating position.
How to spot a battery certificate worth trusting
Five criteria separate a robust document from a pretty PDF:
- Independence: the issuer neither sells the car nor belongs to the manufacturer.
- Vehicle binding: the result is tied to the VIN; a certificate without a vehicle reference proves nothing.
- Verifiability: the buyer can check its authenticity themselves, ideally right in the browser, without having to phone the issuer.
- Open methodology: how it measures and calculates is published, including the method's limits.
- A named data basis: one measurement on one day, or many data points over months? Both can be sound — the certificate must say which it is.
Can you create a battery certificate yourself?
Yes, with the history-based category it works from home: connect the vehicle online once, and the battery history builds itself while you drive and charge as usual. With Akkubrief, connecting and the history are free; you create the signed, VIN-bound certificate on demand when a sale or purchase comes up — and any interested buyer can verify it in the browser.