wug

I am in same situation probably and also looking forward for Adie84 reply. For the past 7 days or so i have had the yellow indicator "window anti trap on" and yesterday suddenly red light with battery no charging. Obviously today battery went dead. Haven't had time yet for a computer diagnose. I have a 520d 2009 177hp steptronic.

Adie84

Hi guys, sorry for the delay in replying. After trying to diagnose whigh component was causing the high drain message and discovering that the drain was only 210mA at its highest (in my opinion not enough to cause an issue) I disconnected the IBS as earlier described. I have not had any problems starting the car and have checked the voltage on the battery a few mornings and it never drops below 12V. It is worth noting that I probably do still have an issue but as it is a relatively low drain and the fact the car is never left standing more than 36 hours without being driven it has not suffered any ill effects.
I do plan to get a decent metre that'll allow me to check some of the higher current components such as the heated seats at some point and will post the results if I find the cause of the drain then.
Cheers.

Adie84

My apologies, I forgot about Redtwin's suggestion that the sleep time may have been longer than I first thought but have not had chance to measure the current again since my metre broke. Again, when I get a new one I'll test to see if this is the case and it is indeed the IBS causing the issue in the first place once the car is fully asleep.

wug

Quick update! My problems were from generator. Battery voltage was 11.8V with engine off and generator was charging 8-9V with engine on. Replaced generator with new one and battery was put on charger overnight and all back to normal now. Cheers!

tonyb635

I might have missed this, but did you mention how old your battery is? A weak battery can cause this issue and even more frequently if one is moving around the car, getting in and out etc. If the battery is more than a few years old, maybe consider changing it out. I would assume the batter is dated and you should be able to tell how old it is. Anytime you are around the car and it awakes you are drawing power...

wug

Battery seems original from 2009. I couldn't locate the DOT. Due to the generator issues obviously the battery had a little hard time to handle without any help. Now all seems fine and no errors anymore. The "window anti trap on" error was because of a disconnected wire. Thanks!

leggomysakyo

Thanks for this info, guys.. I'm having a similar problem with my 04 530i (204k miles). I already replaced the alternator and the battery is less than a year old. Both are OEM. But still having a battery drain issue. I also noticed that sometimes the alternator is charging and sometimes its not.. Hopefully this IBS is the culprit. I'll let you know what I find.

BimmerFan52

You said you replaced the alternator but sometimes it is not working. What voltage are you measuring when drawing the conclusion that it is not working? The alternator not charging is a more serious issue than a parasitic drain.

I assume you have disconnected the BSD line from the IBS to prevent waking the ECU (ECU will fix alternator output at 14.2V absent the IBS). The IBS cannot interfere with alternator charging.

leggomysakyo

I haven't done anything yet... I'm planning on disconnecting the BSD line from the IBS tonight and see what happens. Thanks..

twh

I'm pretty sure I read somewhere that the BMW alternator doesn't always charge. That is, there is some computer that decides when it needs to charge.