Wife's x5 had a parasitic drain ended up being the "hedge hog" FSU blower resistor pack. Possibly the first repair I did on her car. It was intermittent. Just occasional dead battery. Figured out the problem using xoutpost of course. I think there is a fuse you can pull to eliminate the circuit to make the determination.

My DMM will record peak current over up to 24 hours see if yours will. Did you disconnect the battery neg terminal to run the current through DMM or have a DC clamp meter?


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Just saw this - thanks for replying my meter was on neg and it's only a basic one so no peak reading. No clamp either. Did your fsr drain the battery completely or gradually over a few days? Thnx

Needed to jump start the car after a day or two. I can't remember what I did to track down the culprit but I think u used the fuse plug ammeter. (you pull out a fuse, plug this in place and put the pulled fuse in the ammeter). Go one by one and find which circuit is pulling high draw.


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Hi, I have another thread but saw this one and it got me thinking. My running voltage using test 09 is varying from 12.3-12.6 on a 2005 e53 4.4i v8. Is this normal for these old cars? I thought it was supposed to be 13.8V. I will get a test done on the battery but could be a drain. My heating is not working but might not be related.

What is the problem you are having that caused you to check running voltage?

I would do some troubleshooting before replacing anything.

Depending on the age of the battery you might want to get it load tested. Most auto parts stores will do a load test for free.

If alternator is OK the running voltage should max out at about 13.6-13.8 but can be lower depending on load. I would test the running voltage at the battery charge posts under the hood or the at the battery with a multimeter. Test with engine running with nothing that draws voltage off and again with everything on.

You can also check for a parasitic drain on the battery with a multimeter. https://www.youtube.com/watch?v=zdIK...?v=zdIKNnwEjIs

Basic test and diagnostics

When your car battery goes dead overnight, usually either the battery is at the end of its life span, or you left something on, such as a light. Occasionally something is drawing power that's not of your doing. This is a parasitic draw, and it can cause the same result as leaving the headlights on: a dead battery in the morning.

1. Remove the negative side battery cable from the negative battery terminal.
2. Connect the black wire to the com input on the multimeter and the red wire to the 10A or 20A input on the multimeter. The meter needs to be able to read at least a 2 or 3 amps for this test to work. Connecting the red wire to the mA input on the multimeter won't work and could damage the meter.
3. Attach a multimeter (set the dial on the multimeter to measure Amps as per multimeter instructions) between the negative cable and the negative battery post. Wait a few seconds to several minutes for the car to go into sleep mode - i.e. when you make the contact with the ammeter, the cars computer systems "wake up". After a bit of time they will go back to "sleep".
4. If the ammeter is reading over 25-50 milliamps, something is using too much battery power.
5. Go to the fuse panel(s) and remove fuses, one at a time. Pull the main fuses (higher amp ratings) last. Perform the same steps for relays found in the fuse panel. Sometimes relay contacts can fail to release causing a drain. Be sure to observe the ammeter after pulling each fuse or relay.
6. Watch for the ammeter to drop to acceptable drain. The fuse that reduces the drain is the draw. Consult the owners' manual or service manual to find what circuits are on that fuse.
7. Check each device (circuit) on that fuse. Stop each lamp, heater, etc. to find the drain.
8. Repeat steps 1 & 2 to test your repair. The ammeter will tell you the exact numbers.

Part 2
 

Battery state of charge info

and more
https://www.bimmerfest.com/forums/sh....php?p=5747151

Great stuff, generic instructions for almost any car.

What are the best ways to do all the above on an E53 while dealing with the battery in the trunk and the sleep mode? Will the rear hatch being open prevent sleep mode? How to turn off courtesy lights, alarm?, etc.?

Alarm off, doors and hatch closed, lying on the folded down rear seats, reaching down into the battery area, ... ? Or something else?

I expect there are some clever things to make this easier than it seems.

Use hidden menu to read real time voltage when driving. I forget which sub menu. Volts should never be below 13


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Hidden BC menu #9 - and it usually reads about 0.3-0.5v lower than the actual battery voltage.