What decides if a module can be swapped
A battery pack is the sealed case holding the cells that store charge in an electric car. One repair option is a module, a smaller unit built from several cells in its own housing, swapped in for a failing one instead of the whole pack. A peer reviewed paper from Hamburg University of Applied Sciences compared 3 real packs holding about the same energy, measured in kilowatt hours, how much electricity a battery holds. A Volkswagen ID.Buzz pack, 82 kilowatt hours, is built from 288 pouch cells in their own housings, a design the paper states can still be repaired by swapping a single module. A Tesla Model 3 Performance pack, 78 kilowatt hours, is built instead from 4,416 small cylindrical cells bonded tightly together, a design the paper states can leave a shop with no option but to scrap the whole pack after a severe failure. The paper states the tightly bonded design is lighter and more efficient, trading away the option to repair a single module.
The BYD M6 figure uses the top of the range stated in the paper, 120 to 160 cells. All 3 packs hold between 72 and 82 kilowatt hours.
Show the numbers
| Tesla Model 3 Performance, 2022 to 2023 | 4,416 |
| Volkswagen ID.Buzz | 288 |
| BYD M6 | 160 |
The price gap when a swap is possible
Where a car is built to allow it, the saving is large. Recurrent Auto, a company that gathers real world data from electric cars, reports a single BMW i3 module costs around 3,500 dollars, while dealers have quoted 33,000 dollars or more for a full pack, with one customer quoted 71,000 dollars. That full pack quote runs more than 9 times the module cost, a comparison of those 2 figures. Volkswagen designed the ID.4 for modular repair and sells a single module for around 2,000 dollars.
Figures are as reported to or billed by the manufacturer or a dealer, not a standard test, and the BMW i3 figure is the low end of a reported range that reached 71,000 dollars for one customer.
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| Ford Mustang Mach E | 34,000 |
| BMW i3 | 33,000 |
| Volkswagen e Golf | 23,443 |
An independent Massachusetts shop, Leo and Sons Auto Shop, posts its own prices for a full Nissan LEAF pack, rising with battery size, from 4,000 to 6,500 dollars for the smallest pack up to 12,000 to 15,000 dollars for the largest.
Prices are posted by Leo and Sons Auto Shop, an independent Massachusetts repair shop, for a full pack replacement, not a single module.
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| 24 kilowatt hours | 4,000 to 6,500 dollars |
| 30 kilowatt hours | 5,000 to 8,000 dollars |
| 40 kilowatt hours | 8,000 to 12,500 dollars |
| 62 kilowatt hours | 12,000 to 15,000 dollars |
Why a swap is hard even when the car allows it
A working pack needs its cells to hold close to the same charge, states Battery University, a technical education resource sponsored by Cadex Electronics, a battery test equipment maker. Mixing a new cell or module into an old, worn pack causes a mismatch that shortens the repair life. A reputable manufacturer also sells cells only to approved pack builders, so a shop cannot buy one on the open market. Different lithium ion chemistries cannot be swapped for each other either. A standard cell charges to 4.20 volts, a lithium iron phosphate cell to only 3.65 volts, and a lithium titanate cell to just 2.85 volts, so a shop must match the chemistry already inside the pack.
Why even skilled shops still do not offer it
The Electrified Garage, in Seabrook, New Hampshire, was founded in 2019 by 2 former Tesla employees, among the first independent Tesla repair shops anywhere. Its website lists the high voltage work it offers, battery diagnostics and replacement, drive unit repair, charging systems, contactors and thermal management. Module level pack repair is not on that list. The company later built a separate training school for other technicians, evidence the skill is scarce. A technician at Leo and Sons Auto Shop reports lithium ion modules usually degrade evenly across a pack, so the shop mostly replaces whole packs instead, except on the Toyota Prius, where cell level work matters more. Material, not labour, makes up around 95% of the cost of a battery replacement there.