stohje
Posts: 4
Joined: Wed Jul 22, 2020 6:54 pm

12 volt battery depleted

Wed Jul 22, 2020 7:11 pm

So I'm an idiot. I used our 2015 i3 REX with 14k miles to power an air compressor to blow up some pool floats over the weekend. I did not start the car completely, I left it in accessory mode (or whatever). I noticed the "Excessive Battery Discharging While Parked" error close to the end of using the compressor so I did start the car all the way. I then locked the car and went about my business. Monday morning on the way to work I noticed the auto open lock didn't work when I grabbed the handle, the unlock button on the key worked fine. I of course then got the same error when starting the car. I googled the issue and couldn't find much about recharging the battery, lots about replacing it. Oh and I HAD NO IDEA the i3 had a 12volt battery!!! Seems odd to me hat an electric car would need one. I did find a BMW service bulletin that appeared to say the fast charger would recharge the 12volt. So I've been plugging the car in every night when I get home (use about 12-15 miles electric range daily) and am still getting the error. No issues yet with starting or driving the car but I'm concerned about long term problems.

Questions:
Does the 12v battery need replacement? Or Will it eventually recharge?
Is there a way to tell if the 12v is being charged by the main battery (which i understand is the process)?
Is there a way to see the charge level of the 12v?
I used Bimmercode to enable the full gas tank and a few minor tweaks (decrease lock beep volume etc.) a few months ago, so not sure if that's a problem?

Any advice would be much appreciated!
Jeremy S.
2015 i3 Rex, Solar Orange Metallic, Tera World, Technology & Driving Assistant, Parking Assistant, 19 inch 428 wheels

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MKH
Gold Member
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Joined: Fri Nov 02, 2018 5:48 am
Location: Dallas

Re: 12 volt battery depleted

Thu Jul 23, 2020 3:31 am

Yes, when the car is 'active' the DC/DC converter charges the 12v battery from the HV battery pack. When the battery gets to the point that it won't hold that charge, with a low voltage you get the warning. You may have triggered the warning with the battery low because you depleted the charge filling the pool toys. The DC/DC converter will charge it back up. Is the car still giving you the warning? If the warning repeats, it means the battery will no longer hold a full charge because it is is failing due to age, and needs to be replaced. Average life of the i3 12v battery is around four to five years. Only way to see the charge and health of the battery is with a battery tester. This is the one I use: https://www.amazon.com/gp/product/B07ZT ... UTF8&psc=1
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
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Joined: Sat Nov 01, 2014 7:36 pm
Location: Honolulu, HI

Re: 12 volt battery depleted

Thu Jul 23, 2020 3:54 pm

stohje wrote:
Wed Jul 22, 2020 7:11 pm
Does the 12v battery need replacement? Or Will it eventually recharge?
I'm pretty certain that the DC-DC converter should have turned on to recharge your 12 V battery. This occurs on our 2014 BEV when the 12 V system is on even when the car is off. I suspect that your 12 V battery is failing and needs replacing. A replacement can be purchased from an East Penn Manufacturing retailer for considerably less than the typical BMW dealer cost. Installing it is pretty easy as well. BMW dealers charge several hundred dollars to replace the 12 V battery.
stohje wrote:
Wed Jul 22, 2020 7:11 pm
Is there a way to tell if the 12v is being charged by the main battery (which i understand is the process)?
Not without measuring the 12 V system voltage which would be ~14.3 V when the 12 V battery is being charged. I have an inexpensive 12 V voltmeter plugged into the auxiliary power port below the center of the dashboard for this purpose.
stohje wrote:
Wed Jul 22, 2020 7:11 pm
Is there a way to see the charge level of the 12v?
Unfortunately not. The DC-DC converter in our i3 is very aggressive charging the 12 V battery so that even with a voltmeter, it's very difficult to measure the resting voltage of the 12 V battery.
Aloha,
Art

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

stohje
Posts: 4
Joined: Wed Jul 22, 2020 6:54 pm

Re: 12 volt battery depleted

Thu Jul 23, 2020 5:39 pm

Thank you both so much for the quick responses!
You pretty much confirmed my suspicion the battery needs replacement, darn! I've been plugging it in nightly and the auto unlock works in the morning but not when I leave work so that seems pretty definitive also. (my '05 M3 did some truly bizarre things that didn't seem obvious that its battery was almost done).

I was watching videos on youtube that show how to replace, didn't look too hard. I've never replaced a battery myself, so wondering if it's easy to do without getting shocked (assuming I don't get super clumsy and grab both poles at the same time). The fiddly drain pipe bit looks like a pain though.

Thanks again!
Jeremy S.
2015 i3 Rex, Solar Orange Metallic, Tera World, Technology & Driving Assistant, Parking Assistant, 19 inch 428 wheels

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

Re: 12 volt battery depleted

Thu Jul 23, 2020 8:56 pm

stohje wrote:
Thu Jul 23, 2020 5:39 pm
I've never replaced a battery myself, so wondering if it's easy to do without getting shocked (assuming I don't get super clumsy and grab both poles at the same time). The fiddly drain pipe bit looks like a pain though.
12 volts is insufficient to push electrical current through one's body, so you could grab both terminals with no risk of electrocution. Also, there is no high-voltage risk, either.

Although doing so is apparently unnecessary, I will disconnect the high-voltage disconnect before I replace the original 12 V battery in our 2014 BEV (I have a replacement waiting on a shelf). I'll be following these instructions.
Aloha,
Art

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

Timjohn
Posts: 50
Joined: Mon Nov 11, 2019 9:37 am

Re: 12 volt battery depleted

Thu Jul 23, 2020 9:28 pm

The link to the instruction is OK but the actual instructions are not very good. The writers of this document did a lousy job. Not very concise, clear or easy to follow or maybe its me....

alohart
Posts: 2074
Joined: Sat Nov 01, 2014 7:36 pm
Location: Honolulu, HI

Re: 12 volt battery depleted

Fri Jul 24, 2020 12:24 am

Timjohn wrote:
Thu Jul 23, 2020 9:28 pm
The link to the instruction is OK but the actual instructions are not very good. The writers of this document did a lousy job. Not very concise, clear or easy to follow or maybe its me....
The NewTIS site might be identical or very similar to BMW's TIS site and is the only source of BMW repair information that I've found. I think these are typical of hyperlinked instructions. The same steps occur in multiple tasks, so rather than repeating these same steps in each task, hyperlinks refer to the steps. I've gotten accustomed to this style and am happy to have it since workshops manuals on CD's, DVD's, or paper are not available for the i3.
Aloha,
Art

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

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MKH
Gold Member
Posts: 605
Joined: Fri Nov 02, 2018 5:48 am
Location: Dallas

Re: 12 volt battery depleted

Fri Jul 24, 2020 6:11 am

You can check in your area for an East Penn Manufacturing distribution warehouse - they are the OEM supplier (Transportation Division) of the BMW i3 AUX 18L battery. They will sell over-the-counter. https://www.eastpennmanufacturing.com/c ... re-to-buy/

Remy sells the East Penn brand i3 battery on line under their Remy name as well - though their online price seems to have jumped from around $120 to $220 recently.

You might even check with local BMW dealers. Some owners have reported actually getting both reasonable battery price and replacement price quotes.
Mark H.
2015 i3 Rex, Capparis White, Tera World, Technology & Driving Assistant, Parking Assistant, Harman Kardon Audio System, 19 inch 427 wheels, EVoInnovate EVSE

flyboy320
Posts: 32
Joined: Sat Jun 02, 2018 5:38 pm

Re: 12 volt battery depleted

Fri Jul 24, 2020 6:12 am

I replaced mine proactively a couple of months ago, it's not that hard to do. Some people have had issues after replacing it like the car throwing error codes and it seems this is because if you don't charge the battery before replacing, if it's discharged when you install it, it could be a problem. The work around is to fully charge it before replacing it. Here is a good YT video on how it's done.

https://www.youtube.com/watch?v=Ee36vWXMHBg

stohje
Posts: 4
Joined: Wed Jul 22, 2020 6:54 pm

Re: 12 volt battery depleted

Sat Jul 25, 2020 9:49 am

Thanks for all the great info!
I couldn't find a local retailer for the OEM battery so ordered it from REMY. Should be here on Thursday. I absolutely LOATHE my local BMW dealer. Gotten much worse in the time since we leased the i3. They treat you like a loser if you try to haggle at all (and we've bought 3 cars there). Tried to get me for ~$1,000 in "safety inspections" etc. at lease end when we purchased car. BMW corporate sent me a notice that the residual on the lease would be reduced by ~$10k. So I used that as a test for the dealership. They were going to charge full residual until I showed them the letter from corporate. The finance person then did the "let me talk to my manager" thing and came back 15 minutes later with the great news that they would honor that price. Then talked about the safety inspections etc costs. We just use the car for in town commuting and only had ~12k on the odo at the time and had been serviced recently. So I kept the dealer on the hook (texting back and forth a bit) for a couple days then texted them we were going with corporate. Zero communication after that, no "okay thanks for your business", "let us know how we can help in the future" etc. Crap customer service. <END RANT>
Has anyone found non-dealer mechanic/service options for the i3 in their area? We have several BMW/European specialist mechanics locally but none do i3. Guessing local shops don't want to invest time/money in equipment and training for a fairly low volume vehicle...

Thanks again, I'll let you know how the battery install goes.
Jeremy S.
2015 i3 Rex, Solar Orange Metallic, Tera World, Technology & Driving Assistant, Parking Assistant, 19 inch 428 wheels

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