The passport changes after the audit
Months pass between the audit and a market inspection. A recycled-content figure that was right at sign-off may have been quietly corrected since - and the record does not show it.
Provable integrity
Anyone can check whether your passport data was altered after the fact
A battery passport is a claim until someone can check it. Here every stored version gets a fingerprint containing the fingerprint of the previous version - and once a day we publish a root hash over all of them. Your market surveillance authority, your auditor and your customer can recompute it themselves. No account, no asking us.
SHA-256fingerprint per version
Dailypublished root hash
No accountverification in a browser, for anyone
PDFverification report for the file
The problem
Why a green tick on its own is worth nothing
Annex XIII requires data. Art. 78 additionally requires that it is authentic and unaltered. That is exactly where verifiability stops in most solutions.
“Trust the vendor” is not an answer
Whoever runs the database can write to it. A compliance tick set and checked by the same vendor proves only that they set it.
The liability stays with you
Under Art. 77(4) the economic operator is responsible for the passport. If you cannot show in a dispute what the data looked like at a given date, your vendor's software does not help you.
The mechanism
Three steps, all recomputable
No blockchain, no wallet, no token. A published hash chain does the same job here and can be verified with ordinary tools.
- 1
Every version is sealed
On save, the database computes a SHA-256 value over the complete record plus the previous version's value. It happens in a database trigger - below the application, below the API, below every import path. There is no write path that gets around it.
- 2
The chain breaks visibly
If someone alters an old version afterwards, not one following link still fits. The public check recomputes the whole chain and reports exactly where it tears.
- 3
The day is anchored
Once a day we form a root hash over all new links, chained to the previous day's root, and publish it. A published value cannot be made to fit afterwards - not by us either.
Every anchor is openly retrievable, including the ordered list of that day's chain links. Anyone who wants to can recompute the root hash in three lines of code.
Try it
Verify a passport
A passport address from a QR code, a ten-character short code, or a passport identifier. The check runs on the public passport site and needs no account.
For your own site
Embed the verification badge
An image that shows the real status. If the chain becomes invalid, the badge says so - which is what makes it evidence rather than a sticker.
The badge links to that passport's verification page. Whoever clicks it sees the result in plain words and can download the report as a PDF.
Preview
Enter an identifier to see the live preview.
Embed code
…Limits
What the proof does - and does not - show
It proves
- The stored data has not been altered since it was recorded.
- No version is missing from the history.
- The chain already looked exactly like this on the published anchor day.
- The company audit log was not tidied up after the fact.
It does not prove
- That the recorded information is factually correct - that is the responsibility of the economic operator placing the battery on the market.
- That a supplier told you the truth. Where a value came from is shown by the per-field provenance instead.
- That a certification body checked anything.
Frequently asked questions
Frequently asked questions
No, deliberately not. A blockchain solves the problem of several parties agreeing on an ordering without a shared authority. We do not have that problem. What is needed here is immutability plus a publicly checkable point in time - which a chained hash sequence with a daily published root hash delivers, without a wallet, without fees, and with a verification procedure any programming language expresses in three lines.
Not for the period before the last published anchor. A day's root hash depends on every link of that day and on the previous day's root. An altered record would miss every anchor published since. That is why publishing the anchors is the actual core, not the chain on its own.
Nothing, and it requires no account. Market surveillance, auditors, your customers and your procurement department verify in a browser. The PDF report is freely available too. We think putting evidence behind a login is the wrong call.
Only what the regulation designates for the general public anyway - and that sits on the passport page, not in the check. The check itself returns only the result, the number of versions, timestamps and hashes. Content cannot be recovered from a hash.
Then either a record was altered outside the regular write path or a version is missing. That is an incident, not a blemish: we tell you, log it on the status page and name the cause. A verification procedure that can never say “invalid” verifies nothing.
Yes. The chain has been created for every version of models and passports since July 2026 and was applied across the existing stock when it was introduced. The daily anchor has run since September 2026 - everything before that has the chain check, everything after it additionally has the published anchor.
Want this for your batteries?
The proof is included in every plan, the free pilot included. There is nothing to book and nothing to configure - it is created when you save.