Electrical Problem - BMW Forum

FarhadBimmer · 09-29-2009, 08:20 AM

Hi all,

I have a 02/325XI.

The issue is I'm getting low power to start the car. With boosting it starts fine. Also, when I recharge the battery it starts fine but I can not restart it. Battery voltage at no load is 11.8VDC when car is off. Load test, when car is on at 2000RPM and battery is fully charged and all lights, fan and rear defroster are on is 14.1VDC. Also voltage regulates at 14.1VDC at up to 3000rpm that I tested (with load). Alternator belt is new and seems tight.

Although battery is showing 11.8VDC and I cannot start the car but battery indicator is still green. The green indicator is about an inch or so bellow the indicator glass.

When I shut down the car, with the voltmeter at the battery poles I can see the voltage drops from 13.2VDC (car is on at idle and no load) to about 11.7VDC and few seconds after when the fans stop, goes up and stays at 11.9VDC but I can not start it.

Any idea what is going on? Is my battery gone bad?

How can I check if I have any drainage?

Thanks for all the help in advance.

FCPGroton · 09-29-2009, 08:56 AM

If you have not had the battery tested, I would bring it to AutoZone or your local autoparts store and have them test the battery. It is checks out good, then check all the connections and wires running to the battery.

FarhadBimmer · 10-05-2009, 09:20 PM

Checked the battery by a load test. It marginally failed. Bought a battery from Sears Die Hard. CCA is 700A rather than 765. It's working now. I'll see how it works during winter up here in Canada.

Also I have borrowed an osciloscope from a friend to check the alternator in more detail. I'll let you guys know.

FCPGroton · 10-06-2009, 08:15 AM

Lets hope the CCA will be enough when it is -20 outside. :-)

Keep us posted.

FarhadBimmer · 10-31-2009, 08:48 PM

problem is solved. checked the battery with load test and it failed. changed the battery and it's working fine now.

witeshark · 10-31-2009, 09:22 PM

Glad you got it sorted!

camano4 · 11-01-2009, 01:39 PM

Glad you got it tested! A 12V battery that is in good condition would have a greater than 12V open circuit voltage. Of course, a lot of that is dependent on temperature as well.
May I inquire as to how old the battery was? Sometimes they will short internally across cells ~ if it wasn't that old, you might have had a warranty issue $$$

Cheers!

Greg

FarhadBimmer · 11-01-2009, 11:27 PM

Hi Greg,

It was the original batterry from '02. It had an internal issue for sure. I checked the alternator and it was fine.

Cheers, Farhad

DIYRN · 11-14-2009, 12:53 PM

Just how long do these original batteries last?? 02-09 seems like a long time. (My first BMW so not used to things lasting that long)