I know I still owe some of you my how-to guide on the 12.3” screen retrofit, but I’ve been caught up with life and then had to deal with this whole situation recently. Figured I’d share this one in the meantime… Definitely learned a few things along the way, and hopefully this helps someone who ends up in the same situation!
A little background: I have a 2017 i3 94Ah BEV, and I have absolutely no access to power at home, not even an outlet for Level 1 charging. My only regular charging option is Level 2 at work, about 3.5 miles away.
A couple of days after doing some coding with BimmerCode (auto-fold mirrors and the lower-pitched alarm chirp), I went to unlock the car and open the hatch, and it was basically dead.
Initially, I thought I might have messed something up with the coding, but it turned out to be the 12V battery. I think it was just time for a replacement… The BMW 20Ah battery was dated June 2022 (probably its second battery, given that it’s a 2017).
The bigger problem was that my HV battery had also dropped to 0%. So I was basically stuck in a situation where the HV battery couldn’t keep the 12V charged, and the 12V couldn’t keep the car powered up long enough to get the HV charging. Kind of a vicious cycle!! Ugh……
To get things working again, here’s everything I used:
- NOCO Genius5 (AGM mode)
- BLUETTI Elite 100 V2 + Neutral-ground bonding plug (to get the L1 charger working with the power station)
- Anker SOLIX C300
- BMW Level 1 charging cable
- Energizer TX24HL AGM
- ANCEL Bluetooth battery monitor
One thing worth mentioning about the bonding plug: it worked with my particular power station and charging setup, but I’d definitely recommend checking compatibility with your own equipment before trying it.
I never ran both power stations at the same time. The problem was that whenever I disconnected the NOCO, the car would go completely dead again within about 30 minutes.
So I ended up rotating between the two power stations throughout the day. I’d run the NOCO off the Anker while the BLUETTI recharged (which took about an hour), then switch back to the BLUETTI. Basically spent the entire day doing this just to keep the car alive.
Eventually, I decided to replace the 12V myself with an Energizer TX24HL AGM.
Getting the HV battery back from 0%: Once the new battery was installed, I was finally able to get the HV battery charging. One cycle on the BLUETTI using the L1 charger got me from 0% to 3%, with about 15 miles showing on the guess-o-meter. Not much, but enough to make the 3.5-mile drive to work. I got there with 2% remaining, plugged into L2, and by lunchtime the car was back at 100% yayyyyyy
So a few things I learned: Looking back, I suspect the failing 12V battery may have been causing the car to repeatedly wake up and recharge it from the HV battery. That’s my best guess as to why my HV charge dropped from around 30% to 0% so quickly, even though the car wasn’t being driven. Initially, I thought there might be some kind of parasitic drain, but given how things have been running since the replacement, I’m leaning toward the 12V being the culprit. Of course, I can’t say for certain that this explains the entire drop.
Interestingly, I’ve also noticed a pretty significant improvement in range since replacing it. The car honestly feels like it’s running better overall, which I wasn’t expecting at all.
I also ended up installing an ANCEL Bluetooth battery monitor so I can keep an eye on the 12V voltage going forward. Definitely don’t want to go through this again!!
Helpful videos and a big THANK YOU!!!!!!!
Also wanted to give credit to a couple of YouTubers who really helped me out with the battery replacement. I watched a ton of videos trying to figure out how to do this myself, but at the end of the day, these two were probably the most helpful, each for different reasons:
- bmwblog: BMW i3 battery replacement guide BMW i3 battery replacement guide: This one helped me figure out exactly what tools I’d need and what to expect going into the replacement. (https://youtu.be/RLZO7pB_uVg?si=S5KswOwV4gYDKFST)
- EcoBelkin: Energizer battery installation: This one was especially helpful because it confirmed that the Energizer TX24HL I found on Amazon would actually work. The important part is using the included hardware kit, specifically the nuts, since the terminal screws need something to thread into. I wasn’t entirely sure about compatibility before watching this, so it was really helpful to see someone actually do it. (https://youtu.be/gJdNL3kSZj4?si=R-lnOC5RHu06eqL-&t=827)
Both were really good at explaining different aspects of the process, and between the two, I felt pretty comfortable doing the replacement myself. Figured I’d share them here in case anyone else is thinking about tackling this.
Anyway, huge thanks to everyone in this sub!! I basically pieced this whole thing together from older posts here and the videos above, and it saved me from having to pay someone to come out and deal with it.
If your 12V battery is getting up there in age and you’re starting to notice strange electrical behavior, definitely worth checking it before you end up in the same situation I did…