New member - Battery drain / Not holding charge/ Not charging

[thejonross]

G'morning all,

I'm a member over at E46fanatics. I have my 325xi as well as an E53 X5 we picked up back in December. I've decided that it's finally time to join the Xoutpost party! I'm not really a fan of "help me out" first posts, but I'm having some issues and the wife is getting irritated.

I'm having a starting issue with our 2005 X5. (M54B30, 160,000 Miles, Automatic w/step)

The car is having starting issues, directly caused by a low battery charge. Lets say I jumped it this morning (which I did) and my wife and son take it to the gym, it will restart and get them home as well as restart throughout the day just fine. Additionally, the car will start perfectly the morning after a day of in-town driving, but only once. I started the car before I left, but then it wouldn't start when my wife went to leave 30 minutes later.

The starter doesn't struggle when it does start and no issues arise when driving. I have only seen the battery light during the pre-start dash test, and never once while driving.

I took the car to O'riely's to have them test the battery / alternator (as I couldnt find my multimeter), their tester was on the fritz, but the salesman said the battery reported good but needed a charge. We cranked the car and he tested alternator voltage (which I confirmed via the OBC self-test). The alternator voltage was slightly low at around 13.0V rather than the nominal 13.5-14.2...ish. However, this should still be enough to charge up a 12V battery, albeit more slowly than with the alternator at nominal output.

My three hypotheses are thus:
Bad battery - although it tests good, and is about 3 to 4 years old, might not be holding a propper charge.
Bad alternator - possible because I have a power steering system leak and there is ATF sludge on the alternator, but output seems ok with no issues while driving.
Current draw/drain - something may be staying on/ coming on and pulling the power/grounding out.

The car does enter sleep mode fine and the FSR/FSU is not making any alarming noises while running, nor turning back on after shutdown as it did when it when out in the 325. I have considered the BMW Assist/TCU module, glovebox light, sludge on alternator grounding out the generator.

I'm sorry for the long post, but I wanted to be as thorough as possible. Any ideas or confirmations about what is most likely happening?

Thanks again everybody.