EV batteries: repair, module replacement and the passport that arrives in 2027

A pack is not one component

A traction battery is an assembly: cells grouped into modules, modules mounted in a housing with a management system, contactors, fuses, wiring, cooling plates and seals. When a pack "fails", the failure usually sits in a specific place rather than across the whole thing.

The most common real-world fault is a small number of cells or a single module drifting out of balance with the rest, which the management system reports as a capacity or isolation fault. A contactor, a current sensor, a coolant leak or a damaged connector can produce a pack-level warning while every cell remains healthy.

That matters commercially because the pack is usually the most expensive part on the vehicle. Diagnosing to module level rather than pack level is the difference between a repair and a total loss, and increasingly it is the difference between keeping the customer and losing the car to an insurer.

What the catalog actually shows

Whether a pack can be repaired at component level depends first on whether the manufacturer publishes its parts that way. Some do: modules, management boards, contactors, seals and fasteners appear as orderable items with their own numbers. Others publish the pack as a single assembly, which effectively decides the repair strategy for you.

This varies by manufacturer and by model generation, and it is worth checking before promising a customer anything. The parts catalog is the honest answer to "can this be repaired", because it shows what the factory considers a replaceable unit.

Where modules are listed, note that they are matched tightly. Capacity, chemistry and sometimes cell supplier vary within one model, and a module from a different specification is not a substitute even when it fits the housing. The build record behind the VIN is what resolves which one belongs.

• Check whether modules and management components are listed separately at all
• Modules are matched to capacity, chemistry and often supplier
• Seals and single-use fasteners are part of any pack opening
• Coolant plates and connectors are frequent real faults

The battery passport, and why it changes the conversation

Under the EU battery regulation, traction batteries placed on the market from 18 February 2027 must carry a digital battery passport: a record, reachable from a QR code on the battery, describing composition, capacity, chemistry, origin of materials and state of health, along with information relevant to repair and recycling.

For a workshop the interesting part is not the compliance mechanics. It is that the state and specification of a pack become readable rather than inferred. Today a used pack of unknown history is a gamble, and a customer asking whether their battery is degrading gets an answer built from indirect evidence.

Once packs carry a passport, second-hand and remanufactured batteries become a market that can be assessed rather than trusted blindly, and a used electric car gains a documented battery history in the way a combustion car has a service book. That is a real shift in how these vehicles will be repaired and valued, and it starts eighteen months from now.

What repair actually involves

None of this makes pack work casual. Opening a traction battery means working with several hundred volts in an assembly that stores energy whether or not anything is switched off. It requires specific qualifications, insulated tools, isolation procedures and, in many jurisdictions, a documented competence for the person doing it.

It also requires the manufacturer procedure. Packs are sealed assemblies with torque sequences, single-use seals and fasteners, and defined resealing and leak-test steps. A pack closed without its correct seal will admit moisture, and moisture in a high-voltage enclosure is the beginning of a much worse fault than the one you set out to fix.

Storage and transport of a removed or damaged pack carry their own rules, since a damaged traction battery is dangerous goods. A workshop that intends to take this work on needs the space and the procedure before the first car arrives, not after.

Where this leaves an independent shop

The realistic position for most independents in the next two years is diagnostic rather than surgical: identify whether a fault is genuinely cell-level, rule out the contactors, sensors, cooling and connectors that mimic pack failure, and give the customer a straight answer about what is wrong before anyone quotes a replacement.

That alone is valuable, because the alternative the customer currently gets is a pack quote and a shrug. Being the shop that can say "it is the coolant plate seal, not the battery" is worth more than being the shop that can rebuild a module, and it requires accurate parts identification rather than a workshop full of new equipment.