BMW IBS - battery drain.

[Cliff J]

Hi all.

Can I just ask for clarity and opinions on an issue I’m chasing please?

Recently I have been getting in my BMW (6 series E64 645ci) and I’m greeted with a bong, then error message “High rate of battery discharge”.
This only occurs on the first turn of the key each day.
My car always starts without issue.

My battery after a long run was reading 12.08 volts. Whilst checking with the boot open it went down to 11.9v.
My car at idle is 13.7v, that’s with headlights and AC, heated seats etc all on.

I decided that as my battery was last registered 6 years ago that I would replace it and register the new battery as I couldn’t 100% determine the age.

Job done. Battery fitted and coded.

Next morning, “High rate of battery discharge” !!!

I’m being told that if I disconnect my IBS lead to the sensor then I can prove if that is the issue...

But.... won’t that just mask the fault if the battery drain is elsewhere?
Doesn’t disconnecting the IBS just stop any battery drain being reported regardless of where it comes from on the car?

Any input much appreciated.

[bearman68]

From my perspective removing the IBS will hide a drain, rather than fix it.

So options are.
1) IBS is defective, or needs resetting / coding / calibration.
2) Battery is defective.
3) You have a battery drain.

If this were in my workshop, I would run a 24 hr battery drain test, to measure consumed power over that period. This would confirm points 1 and 3.

[Cliff J]

bearman68 said:

From my perspective removing the IBS will hide a drain, rather than fix it.

So options are.
1) IBS is defective, or needs resetting / coding / calibration.
2) Battery is defective.
3) You have a battery drain.

If this were in my workshop, I would run a 24 hr battery drain test, to measure consumed power over that period. This would confirm points 1 and 3.

I’m just reading up about how to find the drain using meters.

I did accidentally clear a code in my OBD recently without fully reading it which said something about my headlight causing a battery drain, so I have pulled the headlight fuses overnight as it was 20 seconds work.

The general feeling on my BMW 6 series page was that if I get no error message after disconnecting the IBS then it shows the IBS to be at fault.... but it just didn’t make any sense to me.

[helix402]

The ibs system records current consumption which can be read via diagnosis software. Or you can do a closed circuit current drain test as mentioned. Look for around 30mA max drain.

[d_a_n1979]

Shouldn't the voltages be c12.4v when the engine is off and c14.4v when the engines running?

Wondering if you've got alternator issues (or IBS issues as already mentioned)?

[Cliff J]

helix402 said:

The ibs system records current consumption which can be read via diagnosis software. Or you can do a closed circuit current drain test as mentioned. Look for around 30mA max drain.

So with the IBS disconnected it wouldn’t register battery drain from anywhere, ie a module not going to sleep.

[Cliff J]

d_a_n1979 said:

Shouldn't the voltages be c12.4v when the engine is off and c14.4v when the engines running?

Wondering if you've got alternator issues (or IBS issues as already mentioned)?

I found somewhere on the net (rightly or wrongly) that the alternator voltage at idle should be between 13.5 and 14.5?

[helix402]

Cliff J said:

So with the IBS disconnected it wouldn’t register battery drain from anywhere, ie a module not going to sleep.

Yes, that’s my understanding of the system.

[Cliff J]

Ok, thank you for the replies. Before I’ve got too deep into it I managed to find a working spare IBS for testing, collecting this weekend.