I love your approach. Funny story. I was in a hit and run with my 2014 i3 in 2021 and used the payout to purchase a can't-pass-up certified pre owned 2018 i3s. The BMW financial loan was so favorable, I added extended warranty through 2026 - which I've never done, AND added tire replacement and key fob replacement coverage. I've had 7 tires replaced in 3 1/2 years for free and two fobs, easily paying for the warranty. I also had this odd drivetrain error fixed under warranty. The warranty has also paid for several flatbed tows and several Ubers back and forth from the dealer... And really hilarious but crazy said warranty win... I came back from a short trip to LAX late at night a few months ago and when got back to my car in long term parking to drive home NO KEY FOB. Locked out of my car in a sketchy parking lot. BMW paid for the 45 min Uber back home to pick up my backup FOB roundtrip back to the airport. I mean, I have made sure to get my money's worth. If I could only find a way for them to cover by mortgage and the 12v battery replacement - yes a bit scammy, but all legit.It shouldn't because its fully charged open circuit resting voltage, ~13.3V, is less than the DC-DC converter output voltage, so no 12V component experiences higher voltages than it was designed for.
When I took our former 2019 i3 to our dealer for a warranty integration level increase to enable voice over LTE so that emergency voice calls would work (this was overlooked during the 3G to 4G LTE migration), I swapped out the LFP battery for the OEM battery that it had replaced to avoid any dealer complaint.
I no longer have an OEM battery. The warranty on our 2021 i3 will effectively be expiring in about 2 months. I hope that our dealer won't deny warranty coverage should I need it. I wish that the original 12V battery had lasted until the car's warranty expired, but 3.5 years was the best it could do. I wouldn't replace a functional OEM battery with a LFP battery before the car's warranty expires, but I already had 2 LFP batteries and didn't want to buy another OEM battery. Keeping my fingers crossed…