Massive parasitic current leak (4 amps!)

[Multibeemer]

Not to quibble, but I don't believe the battery's 12 volts enters into the equation, because I'm placing the resistor between the battery's negative terminal and ground, and the voltage dropped across this resistor is a little over 4 volts (about 4.25V, actually) So, I believe the power is actually V^2/R, and R = 1 ohm, so it's just 4^2, or 16 watts. Or looked at another way, the current dropped flowing through the 1 ohm resistor is about 4 amps, and P = I^2*R, which also gives 16 watts. If it were actually 50 watts, I think I would fry the 10 watt resistor in no time, when in fact I'm able to keep it connected for a little while without any problems, other than a pretty hot resistor.

Junkycosmos - Good question, and I have confirmed that when I disconnect fuse 27, the car goes to sleep in a few minutes (I haven't timed it). It starts out at about 400 mV, then drops down. Interestingly, the first time I measured the current after the car goes to sleep, it went down to 38 mA, when I checked it again a day or so later, it wouldn't get below about 75 mA, and yesterday, it wouldn't go below about 105 mA. Maybe it is struggling to go completely to sleep - maybe that's a clue.

trader4 - Good question about whether 4 amps is actually going through fuse 27. I'll try measuring across the fuse's terminals. Although, I'm not sure how that will help me get closer to finding the source of the problem. The possibilities seem endless...

[Multibeemer]

OK, so 16 watts is being carried through the resistor, but when the battery cable is actually connected to the negative terminal, I'm actually getting 50 watts somewhere? That's huge - I'm surprised I don't hear or feel something, and that the car hasn't caught on fire. Come to think of it, I'm at the point where I'm thinking that could be the best thing that could happen to this vehicle, lol.

As far as the aux radiator fan, I think we're just differing on semantics. I located the connector to the radiator fan in the area you described way back in post #7 of this thread, disconnected it, and got the same 4 amp draw as when it's connected. I don't know why I called it a "switch" - it's actually a connector.

I'll check to see if I'm getting 4 amps through the fuse tonight. It's been raining, and the car lives outside, which has limited my test time lately.

[Multibeemer]

So I may be getting something less than a 4 amp draw when the battery is connected to its ground cable, without the resistor in between. But whatever the draw actually is, it must be pretty high, because it kills the battery within a couple of days or so. Not sure it's worth investing in a high-end VOM that reads up to 10 amps just to pin down the exact value of the current draw.

If I find that there isn't significant current draw across the connectors for fuse 27, does the wiring diagram you have give any indication as to possible sources of the current draw upstream of the fuse? I agree that it would be good if I could eliminate the large array of functions controlled by the GM.

[Multibeemer]

Well, I'm somewhat embarrassed to admit that this very lengthy thread has turned out to be mostly a false alarm - I was misled by the diagnostic method I was using. Following the advice of more than one person in this thread, I bought a VOM that allows current measurements of up to 10 amps, and connected its leads between the negative battery terminal and the cable that was attached to it. Initially, it read 3.6 amps - pretty close to the ~4.2 amps I was reading using the voltage-drop-across-the-1-ohm-resistor method. But after just a few seconds, I noticed it had dropped to 3.15 amps. I waited about 10 minutes (didn't get the exact time), and lo and behold, the current reading plummeted all the way down to about 35 mA, meaning everything appears to go completely to sleep, and the current draw is perfectly normal.

So, I had the battery, alternator, and starter all tested - all tested perfect. So, the question remains as to why the battery goes dead if the X5 isn't driven for a few days. The only thing I can come up with is, possibly the initial current drain of nearly 4 amps is unusually high. That, combined with the fact that the vehicle is used mostly for short trips, means that the 4 amp draw can happen many times, without the alternator (which delivers 49 amps at idle) getting the chance to adequately charge the battery. And it doesn't even have to be driven on a short trip to experience the initial 4 amp draw - I would assume that just unlocking the doors "wakes up" the systems, triggering the draw.

Anyway, I don't have any better theories. Does anyone have any idea as to what a normal initial, "pre-sleep" current draw should be? I've measured it on some of our other cars, and never saw anything close to what the X5 is producing. Thanks; sorry for wasting everybody's time, and I hope my experience provides something others can learn from - I've definitely learned a lot.

[Multibeemer]

Originally Posted by trader4

Well, there you go. It's like I said, your test method supplied the car with only 8 volts instead of 12 and who knows what that does to the normal shutdown process of the electronics.

How old is that battery? I know it tested good, but if it's 4+ years old, I'd just get a new one. I doubt your problem is the car being driven around town most of the time. Plenty of cars are driven that way, without the battery being unable to start the car in a couple of days. I'd suspect either the battery or that you have some parasitic current drain that happens sometimes, but not all the time. Does the car always have a drained battery after a couple days, or just some times? You may need to monitor it more to catch it.

That may be true, but the primary reason I never was able to wait long enough to see if the systems all went to sleep was that the 16 watts flowing through the resistor caused it to quickly get so hot that I was afraid it would burn out.

The battery is about 2 years old. It tested so perfectly that I really don't suspect there's anything wrong with it. I think I'll just keep a solar charger on it a few times a week to make sure the battery stays topped up, and move on to other things, like the sizable oil leak I found (but not its source...) while changing out the front control arm bushings.

[Junkycosmos]

I too had a batt that wouldn't hold up for a week of being parked but it would start the car fine if drive every other day. Swapped it with an agm and didn't look back. My Beast gets a lot of electric load in the winter and I noted the lights stopped dimming at stop lights with new batt. Now I have no issue if not driven for 2 weeks but I still usually use a a battery minder if that long between drives.

Wonder if it's your batt or maybe your X is not always going sleep. Can someone confirm if the indicator light next to P on gear selector is reliable way to confirm full sleep?