Battery and charging system experts please chime in

[GenXer]

Thanks for the update! I'm in a holding pattern also, seems with a fresh battery things are fine for awhile, then after a few weeks or after its been sitting, the light becomes more active. Maybe I'll try hooking it to my Battery Minder for awhile and see what happens. Never had a problem until my original alternator went out in June, since then been dealing with issues...probably should have just taken it to BMW, instead of an Indy.

[generx]

Definitely update this thread if you find anything new. You may also just have a battery drain somewhere, FSR issue, who knows. If you are getting a lot of voltage drain over the course of a week or 2 then it's definitely something else and the constant low battery charge will eventually deteriorate your new battery causing the warning light. The tender may be a good temporary fix until you can pinpoint it.

[GenXer]

Thanks, will do. The X is going to sleep like it should, already ruled that out. As a side note, I unlocked the test routines on the dash display and the voltage it was putting out max was 13.7 at 2000 rpm. If I turned on all power hogs (seats, fan, lights, radio, etc) it would bounce around between 12.9 & 13 then go back to about 13.4. Not sure if this is normal or not.

[toddjoh]

The Amp rating of 120 and 140 indicate the maximum output that the alternator is capable of. It can only put out that maximum for very short periods. It's better to have excess capacity than to operate in near max. That said the 120 will likely have no problem as long as your not running a lot of aftermarket lights, stereos, etc. that might further tax the electrical system.

[X5 Meister]

There is an SIB discussing a a faulty diode in the alternator regulator on E53 X5's with the M54 engine. Basically you need to replace the voltage regulator and not the alternator.

SIB 122205

[GenXer]

Thanks for the info, but I have an 01 with the 4.4 and 150 amp alternator.

[bmwbmwfan]

HELLO!

Two days ago I noticed the battery light would come on upon starting the car an then go away within 10mins of driving. Then yesterday, noticed again the blasted thing....drive all morning no problems.

Getting back from work, I see the battery charge light come on again, but with many friends (all of the warning indicators came on), and car stalled 30secs after.


I was able to use the momentum of the wheels to fortunately roll it near a Mr. Lube shop. The guys there tested the battery for me an obviously it was very low. They were convinced it was the battery...I was not.


In my case, does this not sound more like the alternator?? Please help.

[ika]

its alternator problem. before replacing whole alternator, check Alt Regulator Module which is located on Alt.

[X5girl]

Yes, almost certainly the alternator. They just want to sell you a battery.

[GenXer]

Could be alternator or battery, both should be checked out, if found to be fine, I would look to ignition switch, as it will cause a multitude of weird problems.

I've been through two alternators, two batteries and a belt tensioner, realized Indy was guessing also as to what was causing the flashing battery light. I've got an 01 4.4 X5 with 130k, so it probably needed those parts anyway, but the problem persisted. New wrinkle, last week X didn't want to start, no crank, nothing, even though battery was fine with alt delivering proper volts, finally started after a few min of trying, ran fine, but battery light has not stayed on or flashed since while driving, so I'ved decided to replace ign switch this week, can't hurt, it is a cheap easy fix, about $70 for part, will update once completed.

Bottom line, I don't think anybody has a clear cut fix to BMW electrical issues, basically it's just hit or miss.
Alex