Some Geniuses Are Swapping 200-Mile Battery Packs Into BMW i3s, Creating A Potential ‘Forever Car’

BMW sold over 250,000 i3s between 2013 and 2022, and with those cars having carbon fiber bodies and aluminum frames that don’t rust; plastic and carbon fiber panels that don’t dent; and interiors that hold up to abuse, there are naturally many i3s still on the road, looking good. The issue is that many of these cars (especially pre-2017s) have battery packs that have degraded to the point where they offer only 50 or fewer miles of EV range; on top of that, even i3s with perfect battery packs don’t really go that far on a charge. For years, i3 owners have dreamed of a replacement battery pack that could give their otherwise-in-excellent-shape i3s a new lease on life, and rumors seem to be swirling now of a potential new option out of China. I just spoke with a man who’s swapping new batteries into i3s in Los Angeles, and he tells me: This is a gamechanger.

The BMW i3 began life for the 2014 model-year with a 22kWh battery pack, then it received an upgrade to 33.2 kWh in 2017, and then things jumped to 42.2 kWh in 2019. Per CNET, BMW’s CEO said the company was planning another battery upgrade before the company ultimately decided to pull the plug on the science experiment-car in 2021 (or 2022 in non-U.S. markets). So if you want the highest-range i3, 42.2 kWh and about 150 miles of range has been your only choice.

Recently, though, there has been some whispering that the aftermarket might offer a battery upgrade for the i3. That whispering comes out of China, with numerous sales representatives posting photos and videos of BMW i3s ostensibly receiving battery upgrades. Here’s a video from “CVC” showing a full pack swap:

Here are some photos from that same sales rep showing the alleged 49 kWh pack:

Clicking on “Jinchua New Energy” shows that this Alibaba listing is from the same company, CVC, which has sold Leaf battery packs for a while.

I’ve also seen replacement i3 battery packs advertised by a different company. Much of the information online comes from someone by the name of “Echi”:

MTG’s website shows 54 kWh battery packs made up of prismatic CATL cells:

Some folks on Reddit say they were quoted $6500 for the pack, which is about the same as the CVC price. But are these companies legit? Has anyone in the U.S. done a swap? Well, the answer appears to be: Yes.

I recently stumbled upon the thread above on Reddit; the OP states that they bought a pack from China (presumably from CVC since they’re Samsung cells), and they say the work was done by a company called Maxxpower, out of LA. Here’s Maxxpower’s rather basic website:

I called up Michael Boomer, who runs Maxxpower, and he told me that he actually got started with i3s after reading my articles about my beloved i3! He also says he actually saw me a few months ago in LA driving my Galvanic Gold 2021. Small world!

“The day I opened this shop you were next door at earl’s place getting hoses made,” he told me, hilariously. “The reason why this is partially your fault is I wasn’t even considering an i3 until you [wrote your story]….it snowballed. Several months later I’m at a shop where I’m installing batteries. Mainly focusing on that and taking the old batteries to be used in different capacities.”

So that’s how this is going to work. Boomer will take folks’ old batteries, replace them with new Samsung batteries from China, and charge folks $7,200. That’s an absolute steal given the alleged performance improvements.

After telling me that the weight increase of the upgraded batteries seems largely insignificant and that his own personal 2015 i3 rides fine after the swap, Boomer said:  “It’s so cool to just be able to turn on the AC and not even look and worry and plan…it’s a totally different car now. You approach it completely different with that kind of range.”

“I can tell you what I’ve seen — real world Los Angeles driving — AC just kinda running in the background on Eco Pro, I’m getting, depending on how I drive, that can be anywhere from high 160s to 200 miles.”

For reference, my 42.2 kWh battery pack in my 2019 i3S yields about 140-160 miles of EV range.

“It’s pretty drop in,” Boom told me of the installation process, “although I wouldn’t recommend the average Joe try to do this in their driveway. The AC is tricky,” he said, referring to the oil in the refrigerant and the recovery/fill process. Installing a 650 pound battery isn’t something you can do with floor jacks, though Boomer tells me he just uses a QuickJack.

To get an idea of what’s actually being replaced, you can look at the video above to see the original BMW i3’s battery pack. It’s basically a bunch of VHS-sized prismatic cells. These boxes go into eight modules that make up the battery pack.

Here you can see the 12 cells that make up each module:

And here’s what the module looks like once it’s been fully assembled with a plastic cover:

The cells are precisely glued together and configured in such a way that allows for both optimal cooling as well as room to expand and contract. Needless to say, Boomer isn’t swapping each and every one and gluing them all into place. No, instead, he’s getting entire modules from his supplier in China. “They drop right in over the same bolts,” he told me over the phone.

The “VHS”-looking cells are the same size, but they’re more dense that the original ones from BMW, hence the 49 kWh. As I mentioned before, BMW itself went from 22 kwH to 33.2 in 2017 to 42.2 in 2019, all in the same battery pack, with another upgrade in the plans before the car was killed off. It’s great to see the aftermarket deliver the power density upgrade that BMW promised.

Of course, the swap isn’t going 100% perfectly. Boomer told me that “the one thing that has been the hangup for us is the programming of the SME,” referring to the battery management controller. “We have to manipulate it a little bit to make it think that [the battery] can hold more,” he said. The result, right now, is that the guess-o-meter range-estimator is struggling to deal with the new, bigger pack. “That’s one of the things that i think people will absolutely screw up if they try to do this in their driveway,” Boomer told me, though he noted that at least one of the Chinese battery suppliers offers an SME (he doesn’t know how well it works).

Michael Boomer said he has friends in China who are able to look at products to give him an idea of their quality. “I’ve been doing business in China for years; I used to own a synthesizer shop; I used to build custom parts for vintage synthesizers,” he told me, saying he’s owned over 40 cars, though this is his first foray into automobile modification (though apparently his electronics known-how in music translates quite well).  One of his goals, he told me, is to “make EVs more accessible to people,” going on to say “and what everyone needs from it is range.” Boomer says he’s starting by offering Samsung cells instead of CATL or Panasonic, since Samsung’s brand in the U.S. is strongest.

There have been some concerns on forums about the replacement modules missing a cross-brace. “There’s a teeny cross-brace between the two rows of batteries… I think that’s way overblown,” Boomer told me.  “I’ve actually measured the deflection from one side to the other; there’s nothing,” he said, though he is 3-D printing some parts to give people peace of mind:  “It’s easy enough to fix,” he told me over the phone. As for other concerns about the quality of the packs, Boomer says he’s offering a one year parts-and-labor warranty.

[Update (03/13/2025 10:15 PM ET): I was recently emailed the link to discussions about that cross-brace. The German forum goingelectric.de includes lots of concern about the safety of these Chinese batteries, not just because of lack of bracing but because of alleged lack of thermal sensors. See the full thread here. -DT]

[Update (03/14/2025 11:30 PM ET): I received an email from a gentleman from Hungary who says he works on BMW i3s regularly and does battery swaps on them. He says he knows somebody who bought one of the Chinese batteries mentioned in this story, and that it did not function properly. So, again, it’s worth reiterating that there are lots of questions that remain unanswered, and that car batteries can be dangerous, so it’s worth approaching such products with caution. -DT]

Obviously, there are still many questions that need to be asked, and given how expensive and dangerous batteries can be, it’s going to be a while before people are comfortable forking over thousands of dollars for more range. But I’m excited to see where this goes. Because the BMW i3, with its carbon fiber body, aluminum frame, plastic body panels, and durable interior, makes for a fantastic, modular “forever car” that you could just keep until the end of time, upgrading it along the way. At least, that’s what I hope to do with my Goldie you see above.