Xoutpost.com - BMW MY08 X5 Battery Problem

Xoutpost.com (https://xoutpost.com/forums.php)

- X5 (E70) Forum (https://xoutpost.com/bmw-sav-forums/x5-e70-forum/)

- - BMW MY08 X5 Battery Problem (https://xoutpost.com/bmw-sav-forums/x5-e70-forum/100690-bmw-my08-x5-battery-problem.html)

BMW MY08 X5 Battery Problem

I replaced the original battery on my X5 back in 11/2014 and it was working fine until 2 months ago when things start to act up. I would go to start the car and it wouldn't start. So then I tried a couple of time afterward and it started. This happened 4 or 5 more times the past 2 months. So I've been doing alot of my own investigation. I've confirmed that there are no parasitic draw when in sleep mode (10mA after 30 minutes). I've confirmed the alternator is good as it's constantly putting out 13-14.5V at the battery as I'm driving or when car is started. I've taken the batttery to Advaced Auto Parts and they've told me that this battery is good based on their test.

So I attached a voltmeter on the battery last night and the reading was 12.5V. This morning, before I started the car I checked the battery and it was readying 12.3V which should still be good. Then I unlocked the car door with the key and after 30 seconds, the voltmeter would ready 9.2V. I was shocked to say the least. So I started her up and she started up and then alternator kicked in. When I turned her off this time, the voltmeter reading is back to 12.5V and it stayed that way. So I repeat the entire process of locking the door, waited, then unlocked the door and the same thing happend. Voltmeter reading went from 12.4V to 9.1V within 30 seconds to minute after unlocking the car. Is this a sympton of a bad battery? I'm clueless at this point what the issue would be and how a battery can go from 12.4V to 9.2V within a minute. Please help.

Thank you.

Kiet

I think you should also consider the alternator.

The voltage of the battery means nothing if there are no Amps doing the work.

Quote:

Originally Posted by trader4 (Post 1038141)

First, we have to assume that your meter is accurate. If so, then
12.5V the night before is already a problem. A fully charged battery
should be ~12.65, so it's slightly low. Worse, the next morning,
12.3V is not still good. That's a battery that's about 70% charged.
You put a small load on it and it dropped to 9.6V, which sounds like
a battery that's not charged very much at all. Coud be a bad battery,
but then you said it was tested, was it load tested?

I guess this is where I'm confused since once I start the car and let it run for one minute, the battery would read 12.50V after turning the car off and letting it sit again. Does it make sense after letting the car run for 1 minute that the battery will jump from 9.2V to 12.5V again. It's odd or maybe I just don't understand enough about batteries. Plus - how am I able to start the car with just 9.2V reading on the voltmeter? That is also odd in itself.

[/QUOTE] Testing it once and seeing no parasitic drain isn't conclusive. Some
of them are sporadic and you might not have caught it. You could
try measuring the battery at night, then leaving it disconnected
over night, see what it reads then.[/QUOTE]

I have done the parasitic test several times already and it shows 10mA everytime after the X5 is in sleep mode. I have also done the measuring battery overnight with it disconnected. It was from 12.75V to 12.68V the next morning with it disconnected. I've done several alternator test and all indication is that my alternator is fine. We drive this car all the time so it should be sufficiently charged at all times. I guess I could try to buy a new battery just to rule out the battery issue but I hate to waste over $200 and it not being the problem. The battery is only 6 months old.

Thank you all for all the advice so far.

Have you looked that parasitic draw overnight??? Like logging it for 12 hours?

These cars will shut down, draw seems fine...but then a module wakes up the whole system and it then draws the battery down. Can happen every hour. Pretty soon, after a year of being deeply discharged every night, the battery is toast.

Quote:

Originally Posted by trader4 (Post 1038145)

I missed the part that the battery goes back from 9.2V to 12.5V
after just running it for 1 min, then turning it off. I thought it was
while it was running. So, yes, that makes no sense. Are you
confident in that meter? Where exactly are you testing it? Right
on the battery terminals? Battery cable connectors at the battery?
Are they tight, no corrosion?

Yes - I am testing it right at the battery in the trunk. I've checked for tightness and for corrosion and both are good. I'm pretty confident my meter is correct. When I check my other cars, it read 12.7V.

Quote:

Originally Posted by trader4 (Post 1038145)

The 12.75 to 12.68 overnight with the battery cables disconnected
sounds normal. Starting at 12.5V, going to 12.3V overnight sounds
like a parasitic load or a bad battery. More likely a bad battery,
because 12.5V is already a battery discharged by about 10%.
But then you had the battery tested. Did they do a load test?
I'd take the battery someplace else, as long as you can get it
tested for free.

AAP have a machine that they used to connect to the battery and it will print out a report stating whether the battery is good or bad. According to that machine, it's good. I think they also did a load test as well.

I have also noticed that when I first start the car, the voltage reading would drop from 12V to 11.5V for about 30 seconds or so. The car would hesitate during this time until the alternator kicks on and the voltage ready goes up to 14.5V on idle. Is it normal for the alternator to take 30 seconds or so to turn on after engine is started?

Kiet