A removed traction battery sits on a pallet, the buyer asks about its condition, and a number goes into the listing: SoH 87 per cent. It comes from a diagnostic tool that derives it from control unit data. Another tool reports 91 per cent the same day. Neither is wrong — they measure different things. Selling a battery therefore means selling a traceable record, not a number.
What the law already requires
Article 14 of Regulation (EU) 2023/1542 is headed “Information on the state of health and expected lifetime of batteries”. Since 18 August 2024, the battery management systems of stationary storage systems, light means of transport batteries and electric vehicle batteries must hold up-to-date data on ageing parameters — accessible to the end user and to third parties acting on their behalf. From 18 February 2027 the battery passport under Article 77 follows, reachable through a QR code. For the secondary market that means the data exists; the question is whether your record contains it.
Why two tools report two numbers
- Different reference quantities. Capacity against rated capacity, internal resistance, energy throughput — every definition yields a different percentage.
- Different states. Temperature, state of charge and rest time before measurement shift the result, sometimes considerably.
- Manufacturer logic. Many values come from the control unit and follow its internal calculation, not a standard.
- Cell level against pack level. An average across the pack hides a weak cell group that determines behaviour in use.
- No history. A snapshot without a trace says nothing about fast-charging share, deep discharges or thermal events.
The battery record that carries a sale
| Field | Content | Why it matters |
|---|---|---|
| Identity | Manufacturer marking, type, pack serial number | Without an item identifier no history can be attached |
| Origin | VIN of the donor vehicle, mileage, removal date | Separates everyday use from an accident vehicle |
| Measured value | SoH with method, tool, software level | Makes the value comparable and repeatable |
| Conditions | Date, temperature, state of charge, rest time | Explains deviations from a later measurement |
| Safety finding | Housing, connectors, tightness, anomalies | Decides transportability and usability |
| Events | Accident, water ingress, thermal event, recall | Rules out uses that the measured value alone would allow |
| Intended use | Repair, second life, recycling | Requirements differ markedly by purpose |
Where tapinomahub fits into that record
The platform does not measure batteries and does not read control units — diagnostic equipment does that. It carries the record's surroundings: GET /vin/{vin}/vehicle evidences origin and vehicle type, GET /recalls/vehicles/{vin} matches recalls for the donor vehicle, GET /parts/oe/{oeNumber} confirms the pack's part identity, and POST /vision/identifiers/redact keeps serial numbers out of listing images while they do not belong there. The measured value stays what it is: a statement from your test equipment, which you own.
Limits
- Visual inspection is not diagnosis. Image analysis can show housing damage, not the state of the cells.
- A snapshot is not a forecast. Remaining life depends on the future duty cycle, not only on today's condition.
- Transport and storage follow their own rules. Damaged or critically defective batteries are subject to special requirements — see Storing, handing over and transporting damaged high-voltage batteries safely.
- Second life is a question of status. Repurposing a battery can make you an economic operator with your own obligations; see Second life or recycling? Deciding the right route for traction batteries and Battery law for parts traders: take-back, supply chain and evidence.
- Occupational safety comes first. Work on the high-voltage system requires qualification and isolation — Dismantling electric vehicles: high voltage, battery, competence.
The sentence that carries a listing is therefore not “SoH 87 per cent” but: “Ageing value read out at 87 per cent, method and tool named, measured on 12 September 2026 at 21 °C and 60 per cent state of charge, origin evidenced, no safety-relevant findings.” It is longer — and it is what a commercial buyer can actually check.
Sources and legal references
Frequently asked
Does the manufacturer have to release SoH data?
Article 14 of the Battery Regulation has required since 18 August 2024 that the named battery management systems hold ageing data and make it accessible to the end user and authorised third parties.
When does the battery passport arrive?
From 18 February 2027, reachable via QR code, for light means of transport batteries, industrial batteries above 2 kWh and electric vehicle batteries.
May I sell a value read from the vehicle without measuring myself?
Yes, if you label it as a manufacturer value read out and state the conditions under which it arose. You may not present it as your own measurement.
What is the most common mistake in listings?
A percentage without method and date. It invites complaints, because the buyer's own measurement almost always produces a different number.