2015 i3 model: 12V starter battery flat

[hichammouline]

We're being told the 12V starter battery is flat. The car won't start at all. BMW tell us their recovery truck only brings cars that are < 3 years old.
The main battery is still charged at like 70%.
Any ideas what to do?

 

[Dutchi3]

Well if the 12v battery is dead, the only way is replacing it.

 

[hichammouline]

How do I know the exact item to buy? where to buy it? I live in London. Once bought, who can replace it? Are there spec documents for that 2015 i3 model?

 

[EvanstonI3]

Easiest place to buy it would be a BMW Dealer The battery is sort of specific to the car but there are others that will "fit". It is a 20ah AGM battery. Similar batteries are labeled "PowerSports" batteries but there are different sizes.

 

[eNate]

Is your question how to get your dead car to the shop to be worked on?

You can use a jump pack, just like with an ICE, to fire it up.

The 12 volt battery is accessible by removing the frunk (4 bolts), but it's crowded to get to the terminals.

Alternatively, you can remove the 8 or 10 screws holding the cover over the electric motor in the rear hatch. Underneath it, there are two easily accessible jump points to connect the leads to

 

[hichammouline]

The AA guy said he suspects something "sucks a lot" from the 12V battery and that's why it's dead. He charged it minimally to park the car correctly at home.

so with my limited understand of batteries, either this :

1. 12V 20ah AGM battery is simply dead and all's required is replacing it, in which case I found this
https://www.sytnerstevenagebmwparts...al-BMW-AGM-battery/132287830/61219321815.html

2. or there's a fundamental problem and even if I replace it with a new one, it'll go dead again and I haven't solved anything.

The BMW Dealer here in South London charging £250 for the investigation.


so probably something like £500 for this "jump pack", to rent it from some company to get my car to the dealer in south London + £250 for investigation + £100 for the actually battery?

Alternatively, I can do DIY here at home after getting the battery delivered to me here? and I can explore youtube

Thanks for your help

 

[EvanstonI3]

The AA guy knows nothing about how the 12v battery works on this car. When it fails, it self-discharges over time faster than the car can keep up with keeping it charged. "Jumping" the battery provides proper voltage to the terminals so the rest of the car can wake up and operate. As long as the car is "on" it may get you to a Service place. or it may die on you while driving.

While the car is "on" the HV battery is supplying power to the 12v battery and the system it supports.
While the car is "off" it will come on, by itself, to try to boost the 12v battery if the voltage falls too low. If the 12v battery is failing fast, it will not allow the system to come on and boost the 12v battery. At that point, the 12v battery keeps self-discharging down to single digits.

99.9% of the time that people post about this, simply changing the 12v battery solves everything. You should be able to find a Jump Pack for under £100. £500 would be for a heavy duty one used by Service Vehicle.

 

[tob1as]

How old is the 12v battery? If it’s more than 3 or 4 years old, there is a good chance it simply failed. (It did in my 2017 i3 when I first got it in 2020. If do, this is not too difficult to do yourself. There are good YouTube instructions and you can “register” the battery with the BimmerLink app, saving hundreds over what a BMW service center would charge you.

 

[hichammouline]

yeah, 2015. so very old.... the service centre said £190 for the first hour. quote for the 12V battery around £100.

thanks

 

[tob1as]

I think the £100 for the battery isn’t too bad (I saw someone posted a link above for a little less than that. The BimmerLINK app costs a little bit of money and you need a wireless OBDII adapter. I’ve used these instructions successfully (twice already):

 

[robthebold]

The AA guy said he suspects something "sucks a lot" from the 12V battery and that's why it's dead. He charged it minimally to park the car correctly at home.

so with my limited understand of batteries, either this :

1. 12V 20ah AGM battery is simply dead and all's required is replacing it, in which case I found this
https://www.sytnerstevenagebmwparts...al-BMW-AGM-battery/132287830/61219321815.html

2. or there's a fundamental problem and even if I replace it with a new one, it'll go dead again and I haven't solved anything.

The BMW Dealer here in South London charging £250 for the investigation.


so probably something like £500 for this "jump pack", to rent it from some company to get my car to the dealer in south London + £250 for investigation + £100 for the actually battery?

Alternatively, I can do DIY here at home after getting the battery delivered to me here? and I can explore youtube

Thanks for your help

Since an old, dead 12V battery can cause all kinds of seemingly unrelated problems, I wouldn't pay any of your good money to "investigate" anything unless the problem remains after battery replacement. And at any rate, even if your battery was merely pining for the fjords, at its age it would've been dying soon enough, and replacing it was the right move.

BTW the AA guy's advice is itself the thing that "sucks a lot". Woulda been reasonable for an ICE-mobile, but not for your i3.

 

[hichammouline]

Way too much




I will try to do it all myself then, I don't think it will impact MOT.

How do I make sure this is the right part?
https://www.sytnerstevenagebmwparts...al-BMW-AGM-battery/132287830/61219321815.html

 

[tob1as]

Way too much

View attachment 946


I will try to do it all myself then, I don't think it will impact MOT.

How do I make sure this is the right part?
https://www.sytnerstevenagebmwparts...al-BMW-AGM-battery/132287830/61219321815.html

All the i3s use the same 12v battery, so I see no reason why this wouldn’t be right.

 

[hichammouline]

I've got the battery and the seller pasted a note on it saying that the BMW software needs to be updated so the car is aware a new battery has been put in. The 1st youtube video 2 minutes doesn't show how to update the software. The "next" youtube video 25mns long mentions a Foxwell nt510 elite to hookup to the car for some reason.

I'm gonna try with KwikFit around the corner if they accept to place the battery for me and worry about the software later

 

[EvanstonI3]

I've got the battery and the seller pasted a note on it saying that the BMW software needs to be updated so the car is aware a new battery has been put in. The 1st youtube video 2 minutes doesn't show how to update the software. The "next" youtube video 25mns long mentions a Foxwell nt510 elite to hookup to the car for some reason.

I'm gonna try with KwikFit around the corner if they accept to place the battery for me and worry about the software later

all the "updating" does is register with the car when the battery was replaced. Many people have replaced the 12v batteries over the years without "registering" the battery and no one has mentioned anything bad about it. Also- you could buy the BimmerLINK app and a compatible OBDII wifi adapter and Register it yourself.

If you let the battery go completely dead and it was showing error messages before it died, those may still be there when you install a new battery. Has nothing to do with registering the new battery. You will either have to clear those out manually using a compatible OBDII reader, or use the BimmerLINK app or just plug the car in and let it sit for 24hrs and the car usually manages to clear them on its own over that time.

 

[tob1as]

OBDII connector and Bimmerlink App make it easy to register the battery.

 

[hichammouline]

I have replaced the battery (the old one didn't spark, so was totally empty, the new sparked a little when hooking it up so was not empty). followed the instructions in the youtube, it was the same car model.
The fob now works and the doors open the bonnet opens by the fob key. However, it still says "unable to charge".
I thought to leave it alone overnight and try tomorrow.

 

[EvanstonI3]

However, it still says "unable to charge".
I thought to leave it alone overnight and try tomorrow.

make sure you leave it plugged in overnight even though it won't charge right now.

 

[hichammouline]

make sure you leave it plugged in overnight even though it won't charge right now.

plugged in, as in how I usually charge the "main" battery? ok will do

 

[hichammouline]

plugged in , and on the Level 1 charging device, the Charging led doesn't get on. And the charging port on the car, the usual blue light doesn't appear
so we'll see tomorrow am what happens