Introduction: As early electric cars age, standard NMC modules are quietly becoming the building blocks of a fast-growing repair and retrofit market.
Ten years ago, a worn-out EV battery meant an expensive dealer conversation or a car heading for the scrapyard. Today, a growing number of workshops open the same pack, test what is left, and rebuild it with fresh modules. That shift has created a real aftermarket around NMC battery modules, and it has also created confusion about who actually does what. Battery manufacturers, module assemblers, and suppliers all look similar in a search bar, yet they sit in very different parts of the value chain. Knowing which layer does which job makes the whole retrofit trend easier to read.
Early mass-market EVs are now old enough to show their age. Nissan Leaf packs from the 2010s have spent years in daily use, and capacity fade shows up as shorter range, longer charging stops, and weaker output in cold weather. For most owners, the decision is not about buying another car. It is about whether the existing pack can be repaired or upgraded at a sensible cost. Battery demand across passenger EVs has scaled up quickly, and high-nickel NMC chemistries have carried a large share of that growth. That installed base is exactly what feeds the retrofit market. NMC matters here for a simple reason: energy per kilogram. Retrofit work usually reuses the original battery box, so the available volume is fixed. A chemistry that stores more energy in the same space lets a workshop raise pack capacity without cutting into the chassis. That is why NMC modules, rather than heavier alternatives, tend to appear in upgrade conversations for compact cars that were never designed for a bigger pack. Retrofits also need building blocks, not mystery boxes. A pack sealed with welded connections and matched cells is difficult to repair one cell at a time, so the practical unit of work becomes the module. A module with a known voltage, footprint, and energy rating lets a workshop replace a weak section or multiply modules into a larger system. The arithmetic stays simple: 24 modules rated at 2.6kWh each add up to a 62kWh system. That is why modules, not loose cells, drive the aftermarket conversation.
The words supplier and manufacturer get used interchangeably in search results, and that blurs how the aftermarket really works. In practice, four distinct jobs show up in almost every EV retrofit project.
Why does the split matter? Because the useful question changes depending on which layer you are talking to. Cell and module makers can speak to construction and consistency. Suppliers can speak to what is on hand, how it is packed, and where it ships. Workshops can speak to fit and real-world behavior. Someone searching for an ev battery manufacturer or a nissan leaf battery module supplier is usually standing at two different points in that chain, even when the search terms look identical.
VDA 355 is a mechanical standard for EV battery modules, and its most visible feature is a shared footprint. Modules built to it occupy the same basic space, which is what makes comparisons across suppliers possible in the first place. A published example is the CATL 4S1P 177Ah NMC module, listed at 14.8V, 177Ah, and 2.6kWh, and referenced in Nissan Leaf battery replacement and EV retrofit work. NOGI POWER's listing of that module is a useful factual reference for what a standard VDA 355 NMC part looks like on paper. For the aftermarket, that standardization does three things. It makes modules comparable, because voltage, capacity, and physical size can be lined up side by side instead of guessed at. It makes them replaceable, because a module that fails can be swapped for one built to the same shape and rating. And it makes them tradable, since standardized lithium-ion battery modules cross borders under a shared international nomenclature. What a standard module is not is a finished pack: a retrofit still needs correct series wiring, structural mounting, and BMS matching before a car drives safely. This is the quiet engine behind the retrofit market. When a part has a known size, known electrical values, and a documented build standard, repair work becomes a planning exercise instead of a one-off engineering project. That is why modules, rather than complete packs, have become the working currency of the aftermarket, and it is also why the same handful of module formats keeps appearing across very different rebuild projects.
The EV retrofit market is not a niche curiosity anymore. It is the natural result of an aging fleet, repairable packs, and modules standardized enough to be compared, replaced, and traded. Reading that market becomes much easier once the layers are separated: manufacturers make the cells and modules, suppliers move them into the world, and workshops turn them back into working vehicles. Anyone curious about how a real standard module is specified can look at the published data for a VDA 355 NMC part and see the same numbers a retrofit planner works with every day.
A：They solve a practical problem. A pack sealed with welded connections is hard to repair cell by cell, so the module becomes the working unit. Standard NMC modules carry known voltage, capacity, and dimensions, which lets a workshop replace a weak section or stack modules into a larger system. NMC chemistry also stores more energy per kilogram, which matters when the space inside the original battery box cannot change.
A：A manufacturer makes the product, controlling chemistry, construction, and production consistency at the cell or module level. A supplier moves that product into the market by aggregating stock, holding inventory, preparing export paperwork, and shipping to workshops and distributors in smaller, more varied quantities. Some companies do both, but the two functions answer different questions for a workshop planning a build.
A：VDA 355 gives a module a shared mechanical footprint, so a replacement can occupy the same space as the part it replaces. It also standardizes how electrical values are read, which keeps comparisons straightforward. In aftermarket work the module is the swap-in unit, while the installer still handles series wiring, structural mounting, and battery management system matching.
Trends in batteries - Global EV Outlook 2023 - IEA
CATL 4S1P 177Ah NMC Module Replacement Solution for Nissan Leaf EV Batteries
