jshac
Posts: 9
Joined: Fri Sep 28, 2018 9:28 pm

HELP: just replaced the 12v battery but can't start my i3

Fri May 29, 2020 11:01 pm

Hi,

The old 12v battery died a few days ago and I wasn't able to turn on my i3 at all. Luckily it happened at my garage.

Today I replaced the 12v battery in my i3 with East Penn Deka AUX18L, which seems to be the same as the OEM battery. I followed this youtube:
https://www.youtube.com/watch?v=lKRj8gLcsfI

It was ok. I don't think there was any issue. But my i3 shows "Unable to Charge" error when I turn it on. What could go wrong? The high voltage battery was fully charged before the battery was replaced.

I'm worried about my new 12v getting drained while I figure this out.

Thanks!
Last edited by jshac on Fri May 29, 2020 11:57 pm, edited 1 time in total.

jshac
Posts: 9
Joined: Fri Sep 28, 2018 9:28 pm

Re: just replaced the 12v battery but can't start my i3

Fri May 29, 2020 11:22 pm

By the way, mine is 2015 i3 with Range Extender.

Again I just disconnected the high volt battery and then the 12v battery, waited a bit, and then connected the 12v battery back and then the high volt battery.

When I turn it on, it says "Unable to Charge". The high voltage battery range on the dash doesn't seem to be working, although it was almost fully charged before I changed the 12v battery. The gas range seems to be shown properly.

Now I left both batteries disconnected. I don't want to get my 12v battery drained.

Please help me out! Thanks!

SwissDI3
Posts: 12
Joined: Sun Dec 17, 2017 2:34 am

Re: HELP: just replaced the 12v battery but can't start my i3

Sat May 30, 2020 12:09 am

Make sure your new 12V battery is charged.

Connect both batteries, plug charger into car, lock car if you can and let it sit overnight.

If that doesn't help, then try to clear any error codes with an app like bimmercode or carly.

If nothing works, then it might not have been only the 12V battery that gave you the problem in the first place.

Let us know what helped in the end!

jshac
Posts: 9
Joined: Fri Sep 28, 2018 9:28 pm

Re: HELP: just replaced the 12v battery but can't start my i3

Sat May 30, 2020 8:00 am

SwissDI3 wrote:
Sat May 30, 2020 12:09 am
Make sure your new 12V battery is charged.

Connect both batteries, plug charger into car, lock car if you can and let it sit overnight.

If that doesn't help, then try to clear any error codes with an app like bimmercode or carly.

If nothing works, then it might not have been only the 12V battery that gave you the problem in the first place.

Let us know what helped in the end!
I've measured the 12v battery and it was about 13.5v. I have purchased Bimmerlink for battery registration. I tried to register it, but I wonder it was successful or not. When I first plugged in, I could see the battery was 99% on Bimmerlink, but I open BimmerLink after i3 produces all the beeping and errors, the battery status on BimmerLink was very low, starting only about 20% and now to 3%.

Maybe the 12v battery is defective? I should try to replace it. But I am not sure.

Before the battery replacement, I have not had any issue with my i3 so far.

User avatar
MKH
Gold Member
Posts: 585
Joined: Fri Nov 02, 2018 5:48 am
Location: Dallas

Re: HELP: just replaced the 12v battery but can't start my i3

Sat May 30, 2020 10:39 am

If, after plugging the car in to charge and leaving it overnight, the car is still dead, I'd take the battery out, and take it to an auto-parts store or local service garage to be tested, just to make sure your battery isn't bad.
Mark H.
2015 i3 Rex, Capparis White, Tera World, Technology & Driving Assistant, Parking Assistant, Harman Kardon Audio System, 19 inch 427 wheels, EVoInnovate EVSE

alohart
Posts: 2046
Joined: Sat Nov 01, 2014 7:36 pm
Location: Honolulu, HI

Re: HELP: just replaced the 12v battery but can't start my i3

Sat May 30, 2020 10:46 am

jshac wrote:
Sat May 30, 2020 8:00 am
I've measured the 12v battery and it was about 13.5v.
The resting voltage of a fully-charged AGM battery at 77º F is ~12.7 V.

If you measured the battery's voltage while it was installed in the car, you were likely measuring the output voltage of the DC-DC converter that charges the 12 V battery unless the high-voltage disconnect was disconnected. The DC-DC converter turns on when a door, the frunk, or the hatch is unlocked or opened.

If you had recently charged the 12 V battery with a battery charger before you installed the battery, you might have measured its voltage before the resting voltage was reached (several hours after charging).

If you're still having problems, disconnect the negative 12 V battery cable and measure the battery's voltage at its terminals the following morning.
Aloha,
Art

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

jshac
Posts: 9
Joined: Fri Sep 28, 2018 9:28 pm

Re: HELP: just replaced the 12v battery but can't start my i3

Sat May 30, 2020 1:36 pm

alohart wrote:
Sat May 30, 2020 10:46 am
jshac wrote:
Sat May 30, 2020 8:00 am
I've measured the 12v battery and it was about 13.5v.
The resting voltage of a fully-charged AGM battery at 77º F is ~12.7 V.

If you measured the battery's voltage while it was installed in the car, you were likely measuring the output voltage of the DC-DC converter that charges the 12 V battery unless the high-voltage disconnect was disconnected. The DC-DC converter turns on when a door, the frunk, or the hatch is unlocked or opened.

If you had recently charged the 12 V battery with a battery charger before you installed the battery, you might have measured its voltage before the resting voltage was reached (several hours after charging).

If you're still having problems, disconnect the negative 12 V battery cable and measure the battery's voltage at its terminals the following morning.
Thanks for the advice! The 12v battery seems to be drained now.

I got the battery from a wholesale East Penn distributor nearby. The new battery isn’t supposed to come charged properly? I'd better buy a charger?

alohart
Posts: 2046
Joined: Sat Nov 01, 2014 7:36 pm
Location: Honolulu, HI

Re: HELP: just replaced the 12v battery but can't start my i3

Sat May 30, 2020 7:47 pm

jshac wrote:
Sat May 30, 2020 1:36 pm
I got the battery from a wholesale East Penn distributor nearby. The new battery isn’t supposed to come charged properly? I'd better buy a charger?
The East Penn battery that I bought had about a 50% charge. I doubt that many sellers fully charge 12 V batteries before selling them. An AGM battery like the AUX18L has a low self-discharge rate but needs to be recharged at least annually. My battery had been manufactured over a year before I bought it, so I'm guessing that it had never been recharged before I bought it.

I'm guessing that the problem you've been having is due to your new 12 V battery having too little charge to boot the i3's many electronic modules including those required for battery pack charging. Time to buy a 12 V battery charger. I've had the compact high-quality Swedish CTEK US 0.8 charger for several trouble-free years.
Aloha,
Art

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

jshac
Posts: 9
Joined: Fri Sep 28, 2018 9:28 pm

Re: HELP: just replaced the 12v battery but can't start my i3

Fri Jun 05, 2020 8:22 pm

Hi all,

The problem got fixed after charging the 12v battery and installing it back. Initially, I had some error messages but they disappeared in a day. So, when you replace the 12v battery, make sure it is charged! Thanks!

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