When the BMW i3 first arrived on the market in 2014, it was hailed as one of the most innovative electric vehicles of its time. With its carbon-fiber chassis, futuristic design, and sustainable materials, it showcased BMW’s new vision for urban mobility. But while the i3’s engineering was ahead of the curve, its battery was not. Early models launched with just 18.2 kWh of usable capacity—good for about 80 miles of range when new, or below 60 miles in the winter. We had one so we lived through those times.
Today, many first-generation i3s struggle to manage even 60 miles on a full charge considering the battery degradation over time. Now, more than a decade later, a Chinese company may have just solved the i3’s biggest limitation.
Martigi Manufacturing (MTG), a battery retrofit specialist, has unveiled a high-capacity replacement battery pack for the BMW i3 that allegedly offers a significant increase in range—up to three times the original—without requiring major vehicle modifications. Using next-generation battery cells from Chinese industry giant CATL, MTG’s upgrade transforms the i3 from a short-range commuter into a long-distance electric hatchback.
A Drop-In Upgrade with Modern Chemistry
The upgraded battery uses Nickel Cobalt Manganese (NCM) chemistry and maintains the same external form factor, voltage, and configuration as BMW’s original pack. The kit includes 96 CATL cells arranged in eight modules, with a total capacity of 154 amp-hours and 54 kilowatt-hours—compared to just 60 Ah and 18.2 kWh in the original i3. That’s a 156% increase in capacity over the earliest models, and still a 28% boost compared to BMW’s final 42.2 kWh pack introduced in 2019.
Importantly, MTG’s solution is compatible with all versions of the i3, including the earlier 60 Ah and 94 Ah models, which make up the bulk of used inventory on the market. The battery pack interfaces with the car’s existing systems using a modified battery management system (BMS) provided in collaboration with Chinese firm Echi Tech. All required wiring, connectors, and hardware are included in the kit.
While MTG markets the upgrade as a DIY-friendly product, it strongly recommends professional installation due to the high-voltage systems involved.
Triple the Range—At Half the Cost
Range gains are substantial. MTG claims that the 54 kWh battery can deliver up to 248 miles of driving on a full charge under ideal conditions. In real-world testing documented by the company, an i3 fitted with the upgraded pack traveled 186 miles on the highway at a consistent 62 mph—nearly tripling the usable range of many older models.
Even more impressive is the pricing. The 154 Ah pack is listed at $5,800 on Alibaba, not including shipping or installation. A 120 Ah version, comparable in size to BMW’s final i3 battery, is available for $4,800. Both options come with a three-year warranty and are rated for 2,000 charge-discharge cycles.
By contrast, a new factory battery from BMW costs approximately $15,000 before labor—pricing that has effectively rendered many early i3s uneconomical to repair. The MTG solution changes that equation dramatically. A well-maintained used i3 can now be purchased for under $8,000. With the upgraded battery installed, owners could have a 250-mile EV on the road for less than $16,000—less than the cost of a base-model Nissan Leaf.
Here is a video showing the new battery pack: