Battery
Battery State of Health and Dynamic Data
How dynamic data works in a battery passport — SoH measurement, BMS integration, update frequency, privacy design and second-life scenarios.
What separates the battery passport from every other DPP is that its data is not static. Annex XIII requires unit-level dynamic data to be made available to legitimate interest holders: state of health (SoH), battery status and usage-derived performance.
What is SoH?
State of health expresses current capacity relative to initial capacity. Measurement methods vary by manufacturer, which is why the passport must declare the method alongside the value.
Data flow architecture
- The BMS collects cell and pack data.
- The vehicle or industrial system gathers it via telemetry.
- An aggregation service normalises and validates it.
- It is written to the passport service periodically, creating a new version.
- Authorised roles read it from the restricted tier.
See passport lifecycle management and EN 18222 passport APIs.
Update frequency
Updating too often makes version history unusable and raises cost. A practical cadence:
| Data | Suggested frequency |
|---|---|
| SoH | Monthly or quarterly |
| Cumulative cycle count | Quarterly |
| Event records (fault, service) | On event |
| Ownership or status change | On event |
Privacy
Usage data can be linked to a vehicle and therefore to driver behaviour, which can bring it into GDPR scope. Design rules:
- Do not write personal data into the passport; use aggregated or anonymised metrics.
- Do not carry location data.
- Restrict access by role and keep an audit trail.
See GDPR and DPP data and access rights and roles.
The second-life scenario
When an EV battery falls below a given SoH threshold for automotive use, it can serve in stationary storage. The data needed to make that decision is exactly what the passport holds: SoH history, cycle count, temperature exposure and fault records.
Here the passport stops being a compliance document and becomes second-hand market infrastructure. See DPP in resale and second-hand.
Frequently asked questions
Who writes the dynamic data?
Responsibility sits with the economic operator, but the data comes from the vehicle maker or fleet operator. Secure the data flow contractually.
What happens when the battery is removed from the vehicle?
The passport is tied to the battery's identity, not the vehicle. Removal and redeployment are recorded as a status change.
Should SoH be shown in the public tier?
Annex XIII places it in the legitimate interest tier. Publishing it is not required and is commercially sensitive for resale pricing.
