Swapsafari
Posts: 17
Joined: Thu Dec 24, 2020 2:20 pm

Charging after changing the 12V battery

Tue Jul 27, 2021 7:08 pm

Hello,

I just changed the battery on my 2017 BMW i3 since it was dead this morning and would not start. After reading online figured it must be the aux 12V battery and sure enough it was the issue. After charging the battery, the car started fine however, the range isn’t showing correctly. Currently it shows low when I turn off the car. When I plug the charger in, it shows all green as if it is fully charged and the charging bar on the dashboard shows full but orange in color. No display of total miles available? I am not sure what to make out of it. I can drive around a bit to see if goes to normal but don’t want to get stuck if it really is low. The last I remember before the battery went dead yesterday was that the car has around 60% charge so don’t think it is fully charged or drained either so defiantly not showing correct information. I haven’t had a cha car to register the nee battery yet since don’t have the OBd scanner. May have to order it but do you think this may cause the issue of showing charging?

BL5
Posts: 55
Joined: Sun May 03, 2020 10:23 am

Re: Charging after changing the 12V battery

Tue Jul 27, 2021 11:32 pm

When you replaced the 12V was it FULLY charged? That seems to be the biggest issue.

I’d let the car sit overnight on a L2 charge, see if the issues sort out. Next step is to pull that 12V out and put an overnight charge on it. You should also be prepared with BimmerLink and and OBD II scanner. That way you can clear codes.

Once the car sits on a dead or dying 12V is seems to go into a projection mode. The i3 is very sensitive to that 12V’s voltage for some strange reason. I had a 36 hr battle replacing my dead 12V in my 2015 a year ago.
2015 White REx, loaded Tera, ACC
2017 White REx, every option
2018 Tesla P3

Swapsafari
Posts: 17
Joined: Thu Dec 24, 2020 2:20 pm

Re: Charging after changing the 12V battery

Wed Jul 28, 2021 5:57 am

Thanks for getting back! The 12V battery is brand new and I checked the charge before installing to be sure. It was over 12V so I think we are good there. At this point the car is also been plugged in for whole night and is showing the charging point as fully green. The next step probably is to have the OBD scanner and bummerlink to clear out any code? I might take it out for a spin and see if it does anything. I doubt the main battery is drained fully like it is showing on the dashboard.

alohart
Posts: 2430
Joined: Sat Nov 01, 2014 7:36 pm
Location: Honolulu, HI

Re: Charging after changing the 12V battery

Wed Jul 28, 2021 11:54 am

Swapsafari wrote:
Wed Jul 28, 2021 5:57 am
The 12V battery is brand new and I checked the charge before installing to be sure. It was over 12V so I think we are good there.
12.0 V is a very low charge level for an AGM battery. The voltage at full charge is ~12.8 V. Many "new" batteries have been sitting on a warehouse shelf for several months and aren't at full charge.
Swapsafari wrote:
Wed Jul 28, 2021 5:57 am
next step probably is to have the OBD scanner and bummerlink to clear out any code?
When the old battery went dead, the low 12 V system voltage almost certainly resulted in the storing of several DTC's that need to be cleared to restore normal operation. However, if the new battery's voltage is low, DTC's could be stored again. I'd disconnect the negative cable of the battery (after opening the high-voltage disconnect) and measure the 12 V battery's voltage. If it's less than 12.5 V, I'd charge it with a battery charger before reconnecting the negative cable.
Aloha,
Art

2014 BMW i3 Arravani Grey, Giga World, Tech + Driving Assist, Parking Assist, DC Fast Charging, JuiceBox EVSE

Swapsafari
Posts: 17
Joined: Thu Dec 24, 2020 2:20 pm

Re: Charging after changing the 12V battery

Wed Jul 28, 2021 1:46 pm

Just to update - the car showed a proper range few hours later. May have been some sort of a glitch earlier but is driving fine now with no issues. Even the charging has resumed its normal operation. Thank you for your help!

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