EV battery history: what it gives you when you sell
When you sell your EV, one question is almost certain to come up: how healthy is the battery? A current SoH figure gives an answer for today. A buyer still cannot tell whether the battery has been at that level for some time or only recently.
Akkubrief adds the history behind today's figure. For supported vehicles, you connect the car once with read-only access. The battery history then builds while you drive and charge as usual, with no extra device or garage appointment. Building it is free.
Akkubrief also shows the current battery condition: with normal driving and charging, a first figure is usually available after around three days. That is quick enough for most owners. Leave the car connected and it builds the history for a later sale. The previous months cannot be caught up on later.
A figure shows today. The history explains more.
State of Health, or SoH, describes the usable capacity today relative to the battery when new. If it originally held 75 kWh, a figure of 92% means about 69 kWh of usable energy. That helps with questions about today's range or the battery warranty. It is still a measurement at one point in time.
Take two cars that are both at 92% today. Car A reached that figure slowly over more than three years. Car B sat higher for a long time and declined noticeably only in recent months.
A test today returns the same figure for both. Only the history shows that they arrived there by different routes. It does not follow that Car B has a fault. A decline may relate to BMS calibration, the season, a change in use or a software update. Nor does it follow that Car A is the better car. This is about information content, not diagnosis.
What Akkubrief does for you
Akkubrief builds the battery history in everyday use. You do not need to copy figures regularly or book an appointment for each measurement. It repeatedly determines the same quantity from real charging sessions: usable energy relative to the reference energy when new.
You get:
- a current battery figure with a range,
- the history from which that figure comes,
- a visible data basis instead of a number without context.
Today's figure remains the main point. The history helps you explain it later. For a sale, the plan is to turn this into an Akkubrief bound to the VIN, digitally signed and verifiable by prospective buyers in their browser.
Connecting and building the history cost nothing. While the validation study is under way, the signed document is not yet available to buy. The history you build in the meantime remains in place.
Which tool suits which situation?
| Your situation | The appropriate route |
|---|---|
| You want the current battery condition and still drive the car | Connect it to Akkubrief; the first figure is usually available after around three days |
| You may sell your EV later | Leave it connected and build the history in everyday use |
| The car remains at a dealer and is no longer driven or charged | One-off battery test on site |
| You suspect damage | Controlled-discharge battery test or a garage |
A separate battery test makes sense if you need a result sooner or the car remains at a dealer and is no longer driven or charged. Akkubrief then receives no new driving or charging data. If you suspect a fault, a controlled-discharge test or a garage is the right route. A history does not replace that examination. The options are covered in our comparison of ways to check a Tesla battery and our overview of battery certificates.
When buying a used EV, ask two questions: what is the current figure, and how long has it been in this range? A single test answers the first question. A battery history helps with the second.
What your Akkubrief could look like
The sample Akkubrief shows an 18-month observation period, 72 charging sessions analysed, a current figure with its range and the history before it.
The sample uses simulated measurement data and does not describe a real vehicle. Its signature check is genuine. The 18 months and 72 charging sessions are example figures, not fixed minimum requirements. The number of measurements in your history and the width of its range depend on use and the data available.
For the technically mindedTechnical background (optional)
Why measurements vary, what SoH means and what fleet averages say about your car. You do not need this section to act.
The technical limits, and why Akkubrief shows a range.
Measurements vary. Temperature, state of charge, measuring method and BMS calibration can affect the result. Volkswagen says its own SoH data product may differ from the actual remaining capacity by up to ±10 percentage points. A 2026 study of 1,114 vehicles compared the reported BMS SoH with an independent capacity measure. The agreement varied strongly by vehicle platform.
SoH is not defined in the same way everywhere. UN GTR 22 therefore introduces a separate, standardised energy-based metric, the State of Certified Energy (SOCE). Tesla, for example, ties its battery warranty to at least 70% capacity over eight years.
Fleet averages are not a rule for your car. Analyses across many vehicles often show a larger capacity decline over the first year or two, followed by a flatter curve. Cell chemistry, use and climate affect each car's history.
A useful history measures the same quantity over a longer period, records the measuring conditions and states the uncertainty. More data points add context but do not guarantee a narrower range. Our methodology explains how Akkubrief calculates that range. Whether a history is more accurate than a good single measurement in a particular case can only be answered with an independent reference measurement. We are testing this in the pre-registered field study.
What you can do now
If your vehicle is supported, you can connect it to Akkubrief for free. You then drive and charge as usual. You will usually see a first current figure after around three days. If you leave the car connected, this becomes the history of your own car for a later sale.
A battery history does not promise a particular battery condition or predict the future. It gives you and a buyer more context for the figure that would otherwise stand alone in the listing.