The battery is half the car. Prove its worth.
The car's papers prove who owns it — the Akkubrief proves what its battery is worth. Connect your Tesla account, get a degradation history instead of a snapshot, cryptographically signed: verifiable by any buyer in the browser.
Or start the free quick check right away →
Most batteries are healthier than owners think — and even an honest number sells better than none.
Login happens at Tesla · read-only access · revocable anytime
How it works
Three steps, entirely on your phone — no workshop, no dongle (USB stick), no waiting.
Connect your Tesla account
Login happens at Tesla, not with us. We only receive read access to vehicle data — no password, no control.
Your history builds itself
Usable capacity is estimated from charging data — over weeks and months, robust against outliers.
Share the certificate
Signed certificate with QR code for your listing. Buyers verify authenticity and VIN binding right in the browser.
An Akkubrief beats any snapshot
How this differs from classic battery tests with a measurement box:
Hardware test
✓Our certificate
And honestly: a workshop test has its place — when you suspect a defect. For proof at the point of sale, the history is what counts.
For both sides of the handshake
A healthy battery is your strongest selling point — prove it instead of claiming it. The certificate defends your price and shortens the negotiation.
Don't rely on the range display. Scan the QR code, verify signature and VIN binding in your browser — and decide with data.
Tamper-proof, verifiable, private
Every certificate is cryptographically signed. Verification runs entirely in the buyer's browser; the VIN is stored only as a checksum. Any manipulation is immediately visible — including reusing someone else's certificate.
Even a weaker battery has its value
Afraid of the result? That's exactly when the Akkubrief works for you.
Honest beats unknown
Without proof, every buyer assumes the worst. A documented number — even below Grade A — defends a fair price instead of letting it get talked down.
Warranty check included
Many EVs carry an 8-year battery warranty, often from around 70% capacity. If your value falls below that, it may trigger a free battery replacement — the Akkubrief shows you whether a claim is worth it.
Disclose with legal safety
Documenting the condition openly protects you from disputes and reversals after the sale. Honesty is also your safeguard.
Frequently asked questions
Do you need my Tesla password?＋
No. Login happens exclusively on tesla.com. We only receive a read permission that you can revoke in your Tesla account at any time.
Can you control my car?＋
No. We request read-only permissions — no unlocking, no charging control, no waking the vehicle.
Which vehicles are supported?＋
Tesla at launch (Model 3, Y, S, X). More brands will follow via official vehicle APIs.
What does it cost?＋
The quick check is free. The signed certificate will be a one-time purchase at the moment of sale — far less than a hardware test. Early-access users get special conditions.
What happens to my data?＋
Vehicle data is stored encrypted and never sold. The certificate shows the VIN only masked and as a checksum. Deletion anytime on request.
Who is behind this?＋
An independent project from Germany — not affiliated with Tesla. Our methodology and verification process are public.
Do I still pay if the result is poor?＋
The free quick check shows you the value up front. The signed certificate is an independent assessment — you pay for the honest, verified evaluation, not for a particular result. That's exactly what makes it credible to buyers, and it's worth it at any value: for an honest sale, the warranty check, and legally safe disclosure.
How do you calculate battery health?＋
From the charging history: every charging session reveals capacity, and many sessions combined with robust statistics yield a reliable range instead of a snapshot. The full methodology — including limits and a changelog — is publicly documented.
Get early access
We're starting the beta with a small group of Tesla drivers. Sign up — you'll get the free quick check first, plus special conditions for the certificate.
Beta invitation only. No newsletter, no sharing. Confirmed via double opt-in.