Module, pack or container: what counts as one battery for the passport

For the battery passport, what counts is the finished, safely working battery you place on the market. That can be a single module, a sealed battery pack or an entire container. If several packs depend on a common battery management system (BMS) or other common components and together form one working battery, the whole system needs one passport. Independently functioning units are considered one by one. That is how the European Commission reads Regulation (EU) 2023/1542 in its battery passport FAQ, and it stresses that the decision is made case by case.

This guide shows how to make that decision for your products and how to record it. For the bigger picture, see our battery passport guide. Which industrial batteries need a passport at all, and how to read the 2 kWh threshold, is covered in Industrial batteries over 2 kWh.

How does the Regulation distinguish cell, module, pack and battery?

Article 3(1) defines four levels:

The definition of a battery is deliberately open. A battery can consist of a single cell, of one module or of several packs. The definitions alone therefore do not tell you which level is “the battery” for the passport.

Two rules help. Under Article 1(4), cells and modules made available for end use without further incorporation or assembly into larger packs or batteries count as batteries placed on the market, and the requirements of the most similar category apply. And under recital 14, do-it-yourself kits that the end-user makes ready for use with commonly available tools are batteries too.

What does the Commission mean by “the finished battery”?

The Commission has published its reading in the EU Digital Product Passport FAQ for Batteries. The FAQ is not legally binding, but it shows how the Commission interprets the Regulation.

• The finished battery counts (FAQ 3.1). The passport applies to a finished and (safely) working product that can deliver electrical energy. It may contain several cells, modules or packs. For a traction battery it would normally include the BMS and any other components necessary for safe operation.
• A common BMS means one system (FAQ 3.2). If packs depend on a common BMS or other common components and together form one working battery, the whole system is the battery and needs one passport. If they are complete, independently functioning batteries, each is considered separately.
• The threshold follows the classification (FAQ 3.3). For independent units, each unit's capacity counts; for one integrated system, the combined capacity.

Four test questions follow from this. They are our working aid, not a rule of the Regulation:

1. Does the unit work on its own? Can it deliver energy safely without other parts?
2. What monitors it? Does it have its own BMS, or does it rely on a BMS that belongs to another part?
3. How is it sold? On its own, with its own rating plate and declaration of conformity, or as part of a system?
4. May the end-user split it up? A battery pack is a unit not meant to be split up or opened by the end-user (Art. 3(1), point 2).

Which designs are typical, and how are they classified?

The overview below applies the FAQ to common designs. It does not replace a case-by-case assessment; it reflects our check on 25 October 2026.

One case remains open: the extension module a customer buys years later for a stackable system. If it runs on the existing system's BMS, it is not a finished battery on its own, and Article 1(4) only covers modules without further incorporation. How the existing system's passport reflects the extension is addressed neither by the Regulation nor by the FAQ. It is different if the module works on its own and has its own BMS: then it is a battery with its own passport, provided it falls under the passport obligation itself. Record which case applies to you.

What applies to grid-scale storage with racks and containers?

Many grid-scale systems are built in tiers: cells in modules, modules in racks or strings, racks in a container, often with a BMS on several levels. Under FAQ 3.2, what matters is whether the units depend on a common BMS or other common components and only form a working battery together.

• One battery per container is the natural reading when a system BMS monitors and shuts down the racks together, when the container is delivered, tested and covered by one declaration of conformity as one system, and when the racks only work safely with the container's HVAC and fire protection.
• One battery per string is the natural reading when each string has its own BMS and its own power electronics, can be operated alone and is sold or put into service separately.

A plant-level energy management system that only sends set-points to several containers does not, in our reading, turn them into one battery; it monitors neither cells nor temperatures. What else a stationary system needs in its passport is covered in Battery passport for stationary storage.

Who becomes the manufacturer when you assemble in the EU?

Whoever completes the finished battery. Under FAQ 2.5, the economic operator that completes the finished, safely working battery and places it on the market, or puts it into service where there is no placing on the market, is responsible for the passport. If you assemble imported packs and a BMS into a battery in the EU, that is you. Imported cells and modules that are merely components are not the finished battery; whoever turns them into the finished battery in the EU becomes its manufacturer (FAQ 3.4). Unfinished packs, modules and components may therefore be imported without a passport. If customs authorities are unsure whether they face a component or a finished battery, they should consult market surveillance (FAQ 4.3).

As the manufacturer, you carry the Article 38 obligations: technical documentation and conformity assessment, the EU declaration of conformity and CE marking, a model identifier and a batch, serial or product number on the battery (para. 6), and your contact details (para. 7). You keep the technical documentation and the declaration of conformity available for ten years (para. 4). On the data side you have leverage: suppliers of cells and modules must provide the information and documentation you need to comply with the Regulation, free of charge (Art. 39). How to collect it is shown in Supplier data without supplier accounts.

Importers and distributors can become manufacturers too: when they place a battery on the market under their own name, modify a battery already on the market in a way that could affect compliance, or change its intended purpose (Art. 44). Anyone swapping modules to change a system's capacity should check this.

What goes to the battery model, and what to the individual battery?

Article 77(1) requires a passport for each battery placed on the market, not for each model. The passport holds information on the battery model and information on the individual battery (para. 2). A battery model is a version whose units share the same technical characteristics relevant to the Regulation and the same model identifier (Art. 3(1), point 19).

For classification this means:

• One identifier per battery. The QR code under Article 13(6) leads to the passport and links to a unique identifier that the economic operator placing the battery on the market assigns to it (Art. 77(3)). If the container is the battery, the identifier belongs to the container, not to its modules.
• The code sits on the battery. It is printed or engraved visibly, legibly and indelibly on the battery; only where the nature and size of the battery do not allow or justify that, on the packaging and accompanying documents (Art. 13(7)).
• Keep configurations apart. If you sell the same system with three or six modules, capacity and other values differ. In our reading, that argues for treating each configuration as a model of its own, or at least giving it its own model data.

BatteryPass separates model, model version and unit: you maintain model data once per version, each unit gets a serial number, an identifier and a QR code as a GS1 Digital Link built from GTIN and serial number, and repairs or a module swap are recorded as events in the unit's history in testing. Responsibility for the data stays with you. How serial numbers come in from spreadsheets and ERP exports is described in From Excel and ERP exports to a reviewed battery passport.

What applies to spare modules and module swaps in the field?

A module fitted into an existing battery as a spare part is not a battery for end use within the meaning of Article 1(4), because it is incorporated further. On its own it is usually not a finished, safely working battery either (FAQ 3.1). On that reading it needs no passport of its own. The battery's passport still covers spare parts: Annex XIII, point 2(b), requires part numbers for components and contact details of sources for replacement spares, accessible to persons with a legitimate interest.

Whether a swap calls for a new passport depends on what happens to the battery:

A simple repair is therefore not remanufacturing (FAQ 9.2). Whoever remanufactures or repurposes a battery and places it on the market again counts as its manufacturer (Art. 38(11)), applies new labels showing the change of status (Art. 13(9)) and sets the status in the passport to “remanufactured” or “repurposed” (Annex XIII, point 4(c)). Article 77(7) anticipates that one battery may be built from several old ones: its new passport is linked to the passports of all the original batteries.

After a repair, the Article 77(4) duty to keep the information up to date remains. That includes negative events such as accidents (Annex XIII, point 4(d)).

How do you record the decision?

The Regulation prescribes no form. But the economic operator placing the battery on the market is responsible for accurate, complete and up-to-date passport information (Art. 77(4)), and market surveillance may ask. A short note per product is enough if it gives the reasons and the evidence:

Three practical tips:

• File it with the technical documentation. Then the reasoning sits where an authority will look anyway.
• Check again when the design changes. A new BMS architecture or new wiring can change the answer; it is often a new model version, too.
• Have a second person review it. The classification decides passports, identifiers and labels; a second look before the first delivery costs less than a correction afterwards.

The fields required per category are listed on Data fields; more answers are collected in our battery passport FAQ.