What "dynamic data" really means: connecting the BMS to the passport

Most of the 90 or so data attributes in the EU battery passport are written once: chemistry, mass, carbon footprint, recycled-content shares. A smaller group describes the battery's condition, and condition changes with every charge cycle. Regulation 2023/1542 requires this state-of-health and usage data, defined by the parameters of Annex VII, to be kept up to date through the battery's entire life. From 18 February 2027 the passport is therefore not a static record but a feed, and the feed has one credible source: the battery management system.

What does the regulation mean by "dynamic data"?

Annex XIII, the list of everything a passport must contain, mixes two kinds of data. Most attributes are facts of manufacture: cell chemistry, critical raw material content, the carbon-footprint declaration, recycled-content shares. They are established once and never move. The exception is the block covering state of health and usage, where the regulation points to Annex VII and its parameters:

• State of health: remaining capacity and capacity fade, remaining power capability and power fade, remaining round-trip energy efficiency and its fade, the evolution of self-discharge rates, and internal resistance or electrochemical impedance.
• Expected lifetime: energy throughput and capacity throughput, read against the dates of manufacture and of entry into service.
• Incident history: the passport also carries information on negative events such as accidents, so damage records travel with the pack.

"Kept up to date" is the operative requirement. A passport still showing factory values five years into service, 100% capacity and zero cycles, is simply wrong. And this block sits behind the passport's access tiers: it is not public data, but it must be readable by the battery's owner and by persons with a legitimate interest, a category that explicitly includes the recyclers and second-life operators who will one day evaluate the pack.

What does the BMS already measure?

Nothing in Annex VII calls for new sensors. Article 14 of the regulation requires that EV batteries, LMT batteries and batteries in stationary storage systems fitted with a battery management system hold exactly these state-of-health and lifetime parameters in the BMS, with read-only access for whoever legally owns the battery. The regulation assumes the data already exists on board, and it does:

• Capacity fade: the BMS estimates remaining capacity continuously from charge counting and voltage behaviour; comparing it against nameplate capacity gives the fade curve.
• Cycle count and throughput: full-cycle equivalents plus total energy and ampere-hour throughput, the raw material of any lifetime estimate.
• Resistance growth: internal resistance rises as cells age, and the BMS tracks it because power and fast-charge limits depend on it.
• Temperature extremes: time spent above and below safe thresholds, one of the best predictors of accelerated ageing.
• Fault and event flags: overvoltage, deep discharge, isolation faults, crash signals from the vehicle, each one relevant to a later safety assessment.

The gap is not measurement, it is plumbing. Today these values live in proprietary formats, on a CAN bus behind an OEM gateway, or in a telematics cloud governed by a bilateral contract. The passport requirement turns them from private telemetry into structured, regulated data.

How does the data get from the BMS into the passport?

A BMS-to-passport bridge is less exotic than it sounds. It is an integration with four jobs:

• Extraction: reading the parameters wherever they surface, from the telematics backend for connected fleets, a gateway device for stationary storage, or a diagnostic read-out where no online channel exists.
• Translation: mapping proprietary signals onto the Annex VII definitions, with consistent units and estimation methods, so that "state of health" means the same thing across a mixed fleet.
• Writing: updating the per-unit passport record, keyed to the unique identifier behind the QR code, on a defined cadence.
• Integrity: timestamping every update and attributing it to its source, because a health record that cannot be audited is worth little more than no record at all.

The cadence point deserves emphasis. Dynamic does not mean streaming raw telemetry into a public database. The passport needs current values and their history, not a millisecond waveform; a snapshot per day or per week is a defensible baseline. The trajectory between snapshots is the valuable part: two packs at 85% capacity are not equal if one got there in a smooth glide and the other in a step change after a summer of fast charging.

Who owns the health record when the battery changes hands?

A first life of 10 to 15 years rarely stays with one owner. A pack can pass from OEM to leasing company to private buyer to exporter before anyone says "second life". Today each transfer is where history dies: telematics contracts bind the data to the first owner's account, and the next owner starts blind.

The regulation reorganises this around the battery rather than its keeper. The passport is attached to the unit for its whole life, Article 14 grants the current legal owner read access to the BMS data, and the access tiers define what everyone else may see, from public sustainability facts to the detailed health block for legitimate-interest parties. Three practical consequences follow:

• Continuity survives resale. The record accumulates across owners because the passport, not a customer account, is the container.
• Responsibility follows the role. The economic operator placing the battery on the market opens the record; operators along the life feed updates into it; nobody's exit closes it.
• Privacy stays manageable. Annex VII parameters are battery-level aggregates: fade, throughput, resistance. The passport does not need location traces or driving profiles, and should not carry them.

Why does the reuse-or-recycle decision need live SoH?

Everything above is infrastructure for one decision. When a pack retires, between 2027 and 2035 for the first mass EV generation, someone must decide whether it is a second-life asset or recycling feedstock. That decision needs exactly the numbers the BMS has been accumulating. Remaining capacity says what the pack can still do, the fade trajectory says for how long, and the thermal and fault history says whether it is safe to redeploy at all.

Without the record, the decision is made under uncertainty, and uncertainty prices as scrap: buyers discount every pack to the worst case, incoming testing eats the margin, insurers walk away. With a verified history, the same pack is worth around 30% more on the secondary market, and the assessment takes hours of data review instead of weeks of cycling tests. Live SoH is the difference between a market that grades packs and a market that shreds them.

Conclusion: build the feed, not the file

The dynamic-data requirement is the least bureaucratic part of the battery regulation. It simply obliges the market to maintain the one dataset that decides a battery's fate, a dataset the BMS produces anyway and Annex VII names precisely. What most organisations are missing is the bridge that carries it into the passport, continuously, verifiably, and across every change of ownership.

Passoria's BMS-to-passport bridge keeps live SoH flowing into a regulation-ready passport and feeds our End-of-Life Decision Engine, so every pack reaches retirement with its history attached. Our pilot program is open to a limited number of manufacturers, resellers and recyclers ahead of the 2027 deadline.