2008 X5 4.8i Battery Drain Issue

[Paul925]

I have a 2008 BMW X5 4.8i which I have been battling battery drain issues with. I recently replaced the alternator and I've tested the battery with the car idling and it charges just fine. The first time after changing the alternator, I drove it about 5 miles and it was good. A couple days later I drive it again and 3 miles into my trip, I see dsc and transmission lights pop up so I pulled over and tried to restart the car hoping they would go away but the car wouldn't start. In fact, the battery was drained. Idk how this is possible because the car charges just fine when testing the voltage on the battery at idle. The alternator is new and the battery works and I know the battery works because I put the battery in my e46 for a couple weeks and everything was fine. I am suspecting that the positive terminal cable for the battery may have been damaged somehow. Any ideas? suggestions? Does a broken positive cable sound like the cause of my problem? I've been driving it around the block everyday just to keep it from sitting still and it does fine. I don't get any errors popping up but then again, driving around the block might not be enough driving to trigger them.

Not sure if this helps but, originally, I swapped the battery from the x5 with a battery from my e46 and used the x5 for a couple days because I thought the old battery was the problem. When the battery died again, that's when I knew the problem wasn't the battery.

[Paul925]

I have a 2008 BMW X5 4.8i which I have been battling battery drain issues with. I recently replaced the alternator and I've tested the battery with the car idling and it charges just fine. The first time after changing the alternator, I drove it about 5 miles and it was good. A couple days later I drive it again and 3 miles into my trip, I see dsc and transmission lights pop up so I pulled over and tried to restart the car hoping they would go away but the car wouldn't start. In fact, the battery was drained. Idk how this is possible because the car charges just fine when testing the voltage on the battery at idle. The alternator is new and the battery works and I know the battery works because I put the battery in my e46 for a couple weeks and everything was fine. I am suspecting that the positive terminal cable for the battery may have been damaged somehow. Any ideas? suggestions? Does a broken positive cable sound like the cause of my problem? I've been driving it around the block everyday just to keep it from sitting still and it does fine. I don't get any errors popping up but then again, driving around the block might not be enough driving to trigger them.

Not sure if this helps but, originally, I swapped the battery from the x5 with a battery from my e46 and used the x5 for a couple days because I thought the old battery was the problem. When the battery died again, that's when I knew the problem wasn't the battery.

So I just tested my alternator with a smart battery charger and it tested with bad voltage. So now my question is, could there still be a chance that a bad cable is causing alternator to not charge properly resulting in bad voltage or is it just straight up a bad alternator that I bought?

[yanivmy]

So I just tested my alternator with a smart battery charger and it tested with bad voltage. So now my question is, could there still be a chance that a bad cable is causing alternator to not charge properly resulting in bad voltage or is it just straight up a bad alternator that I bought?

Hi.
Having the same problem,
Have found the solution?

[jclausen]

Or the alternator is defective what brand alternator did you buy and from whom