Battery SoH Gets a Global Standard: What UN GTR 22 and Euro 7 Mean
Anyone who deals with the battery condition of used EVs knows the basic problem: two measurements, two numbers, both called "SoH" — and yet several percentage points apart. This was never a matter of sloppiness, but of the fact that "State of Health" was not a standardised term. Every provider was free to decide what it measured and what it compared against.
That is now changing fundamentally. For the first time there is a worldwide standard for how the ageing of a traction battery is to be measured — and we align our methodology precisely with it.
The Standard: UN GTR 22
In 2022 the United Nations Economic Commission for Europe (UNECE) adopted Global Technical Regulation No. 22 — a globally agreed rule on the durability of vehicle batteries. It introduces two cleanly defined metrics:
- State of Certified Energy (SoCE) — the battery energy still usable today relative to the energy certified at type approval, in percent.
- State of Certified Range (SoCR) — the same principle for the certified range.
The decisive advance: SoCE is energy-based (kilowatt-hours), not charge-based (ampere-hours), and it is determined under specified conditions. This finally defines what the number means — and two correctly determined values are comparable. The EU sets binding minimum thresholds in Euro 7: new passenger cars are required to retain at least 80 percent of their certified energy after 100,000 km or 5 years, and at least 72 percent after 160,000 km or 8 years.
Why Energy Is the Right Reference Quantity
That the standard relies on energy rather than charge is not a detail. An aged cell not only loses capacity, it also shows a steeper voltage drop under load. The extractable energy captures both effects together — and it is exactly that which determines real-world range. A charge-based value can therefore make a battery look better than it feels in everyday use.
That this approach can be applied in practice is not an industry claim but is documented: the Joint Research Centre of the EU Commission ran the GTR 22 methodology experimentally on an aged electric vehicle and published the results — including the individual test steps for SoCE (see sources). That is the scientific foundation on which our approach also stands.
How Akkubrief Aligns With It
Our calculation determines exactly the quantity the standard standardises: the usable energy of the battery. We do not read it from a single test cycle, but estimate it from hundreds of real charging events over time — with robust statistics that average out outliers, temperature effects and BMS drift. The result is deliberately a range with honest uncertainty, not a falsely precise single value. How this works in detail is laid out openly in our methodology.
That this telematic, history-based route is viable is also shown by research beyond the standard: large-fleet analyses across thousands of vehicles (such as Geotab's) and open, physics-based ageing models (NREL BLAST) rest on the same principle — many real data points beat the single measurement.
The honest distinction matters to us: a SoCE under GTR 22 arises through a certified on-board monitor in a new vehicle plus a test procedure at the manufacturer. Akkubrief is not a certified on-board monitor — it is an independent, traceable estimate of the same physical quantity for vehicles that have no such monitor. We align with the concept of the standard; we do not pretend to be the standardised test procedure.
Will Euro 7 Soon Make Akkubrief Redundant?
The obvious question: if every new vehicle will display its own SoCE in future — why still a certificate? The EU adopts the GTR 22 requirements into Euro 7 (Regulation (EU) 2024/1257); future cars must make SoCE and SoCR accessible via the on-board electronics. Even so, the answer is a clear no — for three reasons.
First, the timeline. Euro 7 applies to new vehicle types from 29 November 2026, and to all newly registered passenger cars from 29 November 2027. This concerns new cars exclusively. The entire fleet on the road today — every EV that changes hands used over the coming years — will never get a SoCE on-board monitor. That is our market for well over a decade.
Second: an on-board display is not the same as a record. A value the vehicle displays about itself is, in a sale, something different from an independent, tamper-proof record. The odometer reading, too, sits in every car's display — and yet there are roadworthiness tests, service histories and expert reports, because in a purchase no one relies on the seller's self-declaration alone. That is precisely the role Akkubrief takes on: the independent, signed record that can be verified in the browser.
Third: snapshot versus history. An on-board display states a value for today. But what counts for the buying decision is how a battery ages — steadily or with a conspicuous kink. That trajectory over months is not delivered by a single displayed value, but only by a continuous history.
The bottom line: Euro 7 makes battery condition more important and more comparable for every buyer — it lifts the whole category. What the standard does not deliver is the independent record for the millions of vehicles without an on-board monitor, and for the trajectory over time. That is exactly where we come in: when cars start outputting a standardised SoCE in future, that is for us a further, better input value — not a replacement for the certificate, but a building block within it.