I need a new battery for my 2024 F57 JCW. (It sat too long and died.)
I know about the ECU mapping.

I'd like to get a lithium battery replacement, to save a little weight and for the extra lifespan. An AI query says this is possible, yet everything I've read elaswhere says the battery MUST be an AGM for the ecu to recognize it. (Something to do with the ridiculous stop-start function, which I never use since I'm always in sport mode.)

Does anyone know if this can be done, and also maybe what specific battery I'd want to get?
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FWIW, here's a recent search result:

"For Mini Coopers, the best 12V lithium starter battery is typically an Antigravity H6/Group 48 Lithium-Ion Battery (40Ah or 60Ah models), which offers significant weight savings (16–27 kg) and high cranking power. These batteries often feature built-in RE-START technology, preventing accidental drain. Proper fitment requires matching the original size, commonly Group 48/H6 or H7/H8, and registering the battery with the car's computer.2022 models also listing Antigravity H8/Group 49 and Group 51R. "

 

I have a Lifepo4 Cell in my R60 ans R56 as the main battery for my car audio. The R60 even has the IBS system and both cars have no issues with it. Just make sure to register the battery to a similar Ah rating. I woukd also charge the lithium with a charger first before installing it.

The problem with lithium is its temperamental with tempature. I would relocate it into the trunk...I would not put it in the engine bay. I would also expect it not to do great in winter. A voltage gauge is a must, it wouldnt hurt to use 1/0 wires, make sure the ground wire is less than 16 inches.

Go Lifepo4 instead, its much safer, closer to AGM voltage and has a higher discharge rating but its just as light.
This is my 40Ah Lishen Battery, Im upgrading it to 80Ah with a 16v 1000F Maxwell Ultracap when I put in my Slap Audio 7k Amp.

 

Thanks, Ray.
That's quite an audio rig. What amp are you running?
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The Lifepo4 Cells sure are inexpensive, but that worries me. Then again, the top-end lithium batteries are around $1,000, which is an absurd amount to spend just to save 20 lbs.

It would be nice to find a less-expensive lightweight battery that still has all the cold-cranking amps and reserve you need, with maybe the trade-off being you have to replace it more often. So far I can't find any. There's the Braille 17 lbs "street" battery, but the owner of the company talked me out of getting one ! He said it would probably be more trouble than benefit. (Cold weather.)
I'll probably just get a Duralast for now, and hope the goof Lithium cells come down in price someday.
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I like the idea of remote-ing the battery. I've seen them put under the passenger seat.
- but it also seems like that would add more weight due to the heavy wiring, even though the car would be better balanced.
For racing that might be worth it, but for street use it seems rather excessive ! (Yes, I realize you did it for yet another reason completely.)

 

Lifepo4 has been around just as long as Lithium, we used to use them in RC and Ebikes, they are actually in all the power tools that you use. Lithium itself is an expensive material and producing them is expensive due to their volatile nature - this is one reason costs will stay high. The cheap 12v cells on ebay would do more than well enough for your normal street use, people use them in solar/RVs often for the reserve and lightwieght.

Im currently running a CAB2000.1D for the Sub and a Skar 200.4D for my door speakers. The sub is seriously underpowered, even thought its wired to a half ohm right now...

 

Skip the lithium, get a good AGM battery, and be done. A good AGM should last 5-7 years.