Lesterbmwi3
Posts: 27
Joined: Mon Sep 25, 2017 12:32 pm
Location: USA- NewYork

Re: 12V battery

Mon Dec 09, 2019 3:54 pm

My 2014 I 3 is 5 1/2 years old when my 12 volt battery will be dead? Always in heated garage in NY 17000 miles and driven daily few miles should I replaced as preventative measures now bc in every car I ever own I replaced 12 V battery s every 5 years and never have an issue Looking for advice My BMW dealer price $450 to do replacement nice ! Battery alone is about $200 Thxs

alohart
Posts: 1857
Joined: Sat Nov 01, 2014 7:36 pm
Location: Honolulu, HI

Re: 12V battery

Mon Dec 09, 2019 5:03 pm

Lesterbmwi3 wrote:
Mon Dec 09, 2019 3:54 pm
My 2014 I 3 is 5 1/2 years old when my 12 volt battery will be dead?
Impossible to predict.
Lesterbmwi3 wrote:
Mon Dec 09, 2019 3:54 pm
Always in heated garage in NY 17000 miles and driven daily few miles should I replaced as preventative measures now bc in every car I ever own I replaced 12 V battery s every 5 years and never have an issue Looking for advice My BMW dealer price $450 to do replacement nice ! Battery alone is about $200
You have several options.

You could have your BMW dealer replace your battery in advance of it failing. This would be the most expensive option.

You could have an independent BMW mechanic replace your battery in advance of it failing. This should be less expensive than a BMW dealer.

You could buy a new AUX18L battery with various brand names like East Penn or Deka for much less than $200. There is no advantage to purchasing a BMW-branded battery (all U.S. i3's have the same AUX18L battery manufactured by East Penn Manufacturing). You could store it until your battery dies. However, if your battery dies while you're not at home, you could be stranded. This is the alternative that I have chosen.
Aloha,
Art

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

Lesterbmwi3
Posts: 27
Joined: Mon Sep 25, 2017 12:32 pm
Location: USA- NewYork

Re: 12V battery

Mon Dec 09, 2019 5:24 pm

Thank you for advice just happen where I live all Bmw independent shops don’t want to deal with I 3 period the dealer is only my choice is something on dash is going to show me battery is on last leg or dyes suddenly

alohart
Posts: 1857
Joined: Sat Nov 01, 2014 7:36 pm
Location: Honolulu, HI

Re: 12V battery

Mon Dec 09, 2019 6:37 pm

Lesterbmwi3 wrote:
Mon Dec 09, 2019 5:24 pm
Thank you for advice just happen where I live all Bmw independent shops don’t want to deal with I 3 period
Changing an i3 12 V battery is no different from changing the 12 V battery in any BMW vehicle. Same with changing the brake fluid. By refusing to work on i3's at all, these independent shops are leaving money on the table.
Lesterbmwi3 wrote:
Mon Dec 09, 2019 5:24 pm
is something on dash is going to show me battery is on last leg or dyes suddenly
There can be a warning message about the battery discharging. However, it's a confusing message because it doesn't specify which battery is discharging (it's always the 12 V battery), and this message isn't displayed in all cases in which the 12 V battery is failing.
Aloha,
Art

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

jadnashuanh
Posts: 4766
Joined: Thu May 22, 2014 2:07 pm
Location: Nashua, NH USA

Re: 12V battery

Mon Dec 09, 2019 8:31 pm

It's not a big deal to swap the 12v battery. It's not hard to recode the computer to know that it is new. It's a slight bit more complex if you decided to change the type or size of the battery. It will work without recoding, but the concept is that by treating it as new rather than an old, dying one, the new one will last longer if you tell the car about it. This is possible with various programming tools. Some places, like say Pep Boys will do it for a fee, and if you have the right tools, is easily done yourself. Last resort would be the dealer, where they'll typically charge you a bunch for it.

FWIW, when I was looking for a new battery for my ICE, the BMW dealer had the cheapest price on the battery alone, but their installation costs were excessive. I bought the battery there, then installed it myself along with coding it.

My i3 was built in April 2014, but the battery seems to be fine. I'll probably not deal with it until it starts to act funny. It sits outside, so in the winter, it can be quite cold, and it might sit there for a few days in between uses, but I generally leave it plugged into the EVSE, so it can top off the batteries when it thinks it needs to.
Jim DeBruycker
2011 535i x-drive GT, 2014 i3 BEV

jfran2
Posts: 53
Joined: Tue Oct 30, 2018 4:20 am

Re: 12V battery

Mon Dec 09, 2019 10:26 pm

After reading several horror stories on other forums, I decided to be proactive and change the battery in my 2014 i3 Rex. A new battery is around $140, and the Foxwell NT510 scan tool to code it is $155. (vs $500 for the dealer to do it.) There are several Youtubes available with good instructions on the procedure.

MarkH
Posts: 45
Joined: Mon Jun 10, 2019 1:17 pm

Re: 12V battery

Tue Dec 10, 2019 6:48 pm

jadnashuanh wrote:
Mon Dec 09, 2019 2:31 pm
If you left it plugged into an EVSE, over that two months, it might activate the EVSE 3-4 times, if that, but enough to keep both batteries charged. Unlike a cellphone or most other consumer battery powered devices, the car is not getting a constant charge while connected...it only turns on once the levels drop enough to warrant it while preserving the batteries.
My domestic charger is not smart. I usually charge the car through a timer such that it charges from about 30% to 80%.
Any idea how many minutes a day would cover the "dark" drain from the 12V battery? Would 5 minutes a day cover it?

(Then the question is whether I'm happy to leave a 10amp (240V) rated timer going for 2 months while we're away :? ....)

jadnashuanh
Posts: 4766
Joined: Thu May 22, 2014 2:07 pm
Location: Nashua, NH USA

Re: 12V battery

Tue Dec 10, 2019 7:20 pm

It's my observation that it takes the car quite awhile before the main battery's voltage drops enough to activate the EVSE. There's a moderate amount of hysteresis in it, meaning that it waits until it will need to run the charging for a bit before it turns on rather than just a little bit, frequently. Not sure how often it would turn on, but when the time came, it would take more than a few minutes to bring things back to full.

Maybe someone has monitored it a bit more closely. I haven't tested my 12vdc battery, but it seems to be functioning okay at what will be 6-years in April. I plug the EVSE in when I get home, and remove it when I leave, and my range is about the same now as when it was new, too.

I expect I'll be selling it come next summer, but that's still up in the air somewhat. I'll replace the battery if I start to see problems, but until then, leave well enough alone. The AGM battery in my ICE lasted about 7-years. Since it sat in the garage a lot, I usually kept a smart battery tender on it, which may have helped.

SOme people don't trust the engineers. I figure that they have a lot more knowledge on their system than 'generic' knowledge. There are lots of different chemical mixes in various LiOn batteries. From what I've read, that chosen for the i3 is one of the more reliable ones. I let the car figure when it needs to charge and how much. I might regret it eventually, but so far, so good.
Jim DeBruycker
2011 535i x-drive GT, 2014 i3 BEV

MarkH
Posts: 45
Joined: Mon Jun 10, 2019 1:17 pm

Re: 12V battery

Tue Dec 10, 2019 11:50 pm

OK, if I'm going to be storing the car for 2 months then my best course of action is
1 - disconnect the high-voltage system from the 12V system.
2 - disconnect the 12V battery negative terminal.

Is that it?

Does everything work again on reconnection without doing anything special?

Also, if I'm needing to do this (disconnect the 12V battery) a couple of times a year, it seems it would be easier if I wired in a disconnect switch in an easily accessible place adjacent to the battery. Is there some reason that I should NOT do this?

alohart
Posts: 1857
Joined: Sat Nov 01, 2014 7:36 pm
Location: Honolulu, HI

Re: 12V battery

Wed Dec 11, 2019 11:46 am

MarkH wrote:
Tue Dec 10, 2019 11:50 pm
OK, if I'm going to be storing the car for 2 months then my best course of action is
1 - disconnect the high-voltage system from the 12V system.
2 - disconnect the 12V battery negative terminal.

Is that it?
If you want to park your car with its doors locked, you need to be aware that if the doors are locked when you disconnect the 12 V battery, the burglar alarm will sound. This is particularly exciting while your head is inside the frunk disconnecting the 12 V battery :D So don't lock the doors until the battery has been disconnected. Then lock the passenger door from inside the car and use the physical key in your fob to lock the driver's door.

Also, it's more convenient to not close the frunk completely. If you do, you'll need to use the emergency cable to unlock it when you return because the frunk unlock button on the fob or in the driver's door jam requires 12 V.
MarkH wrote:
Tue Dec 10, 2019 11:50 pm
Does everything work again on reconnection without doing anything special?
You'd probably lose your driver profiles when the battery is disconnected. Therefore, back them up to a USB thumb drive before you disconnect the 12 V battery, an iDrive command. Then after reconnecting the 12 V battery, restore your driver profiles from the thumb drive.
MarkH wrote:
Tue Dec 10, 2019 11:50 pm
Also, if I'm needing to do this (disconnect the 12V battery) a couple of times a year, it seems it would be easier if I wired in a disconnect switch in an easily accessible place adjacent to the battery. Is there some reason that I should NOT do this?
I can't think of any reason not to do this. I haven't done this because I don't find disconnecting the negative cable to be very difficult, and I don't disconnect the 12 V battery more than once per year while traveling. Maybe I should look into 12 V battery disconnect options.
Aloha,
Art

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

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