H3 Expected Amp Draw / Parasitic Battery Drain

[Graham2990]

So I've just recently picked up a beater car to use for my 65 mile round trip work commute to help save on gas vs. driving my H3.

For the first time since I've owned it (2 years) the H3 sat garaged for nine days without starting.

Yesterday when I attempted to start the truck the battery was dead enough that the keyless entry wouldn't function.

Battery is a 24 months old 34/78 Platinum Super Start (Oreilly Brand) AGM battery.

After getting it open and hitting a voltmeter to the battery it registered at 5.71 volts.

Jumped it off and let it run for 30 minutes, and then drove about thirty miles. Started right up the today with no issues, showing 12.4 volts.

My mutimeter is showing a parasitic battery drain / amp draw of 1.1 amps, with the key out of the ignition, doors closed, no lights on, ground unhooked, nada.

I haven't added any additional electronics other than changing to an aftermarket head unit (no amps, subs, etc) and a scan gauge.

Is this considered a too be expected amp draw for these trucks?

Went as far as removing the radio fuse and the draw was reduced by about .05 amps, so that isn't it either.

Thoughts?

 

[deserth3]

This is normal. I can usually only go a week without a long drive or putting on a battery tender

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[chaos254]

1.1 amps is very high. Start pulling fuses until you see it drop down to normal range. That way you know what circuit is at fault. Im not 100% sure on the exact GM spec for draw but anything more than 50 milliamps is too much.

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[Graham2990]

1.1 amps is very high. Start pulling fuses until you see it drop down to normal range. That way you know what circuit is at fault. Im not 100% sure on the exact GM spec for draw but anything more than 50 milliamps is too much.

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Any particular circuits you think I should try first?

Oreilly was able to replace the battery for me under warranty without question, so I've ruled out any issue there.

There's a lot of fuses in this thing so I didn't know if there is a better place to start as far as common circuits this issue crops up on.

 

[rascole]

My mutimeter is showing a parasitic battery drain / amp draw of 1.1 amps, with the key out of the ignition, doors closed, no lights on, ground unhooked...

If I read your statement correct, it is impossible to draw any amps with the ground unhooked. By removing the ground wire from the battery you have opened the circuit for the whole vehicle. There is no return path. Double check your multimeter is set up correct and try it on another car maybe. As stated above, try the "one fuse at a time" method but I would put your multimeter in place of the fuse to see how many amps each circuit is drawing. Could be multiple small draws causing the drain. Ghost drain from a short somewhere can easily drain a battery and make you pull your hair trying to find it.

 

[deserth3]

Try unplugging the OnStar module. I seem to remember something having problems with the module drawing excessive amperage when deactivate

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[Graham2990]

If I read your statement correct, it is impossible to draw any amps with the ground unhooked. By removing the ground wire from the battery you have opened the circuit for the whole vehicle. There is no return path. Double check your multimeter is set up correct and try it on another car maybe. As stated above, try the "one fuse at a time" method but I would put your multimeter in place of the fuse to see how many amps each circuit is drawing. Could be multiple small draws causing the drain. Ghost drain from a short somewhere can easily drain a battery and make you pull your hair trying to find it.

I couldn't think of any other way to test parasitic battery drain, probably been at least fifteen years I've been using that method to measure current on a multitude of circuits.

To clarify:

I'm unhooking the ground and connecting one lead of the meter to the negative terminal of the battery, and the other to the factory ground.

Therefore using the meter connected in series to measure the amount of current passing between Battery - and Chassis -

Meaning, it's like the ground was never disconnected from the battery because the meter is bridging the gap between the two, the truck doesn't know any difference.

Thanks for the tip on the Onstar module also.

 

[4speedfunk]

Check the wiring harness going to the trailer socket. Specifically near the license plate, where the harness is routed between the tow bar and the body. There is a rather sharp body seam here, and it is a common chafe point. I frequently find bare and/or corroded wires at this location when installing rear bumpers. Amazingly, they often melt in half, without blowing a fuse.

 

[rascole]

I couldn't think of any other way to test parasitic battery drain, probably been at least fifteen years I've been using that method to measure current on a multitude of circuits.

To clarify:

I'm unhooking the ground and connecting one lead of the meter to the negative terminal of the battery, and the other to the factory ground.

Therefore using the meter connected in series to measure the amount of current passing between Battery - and Chassis -

Meaning, it's like the ground was never disconnected from the battery because the meter is bridging the gap between the two, the truck doesn't know any difference.

Thanks for the tip on the Onstar module also.

Got it. I agree with 4Speed, check the wires, my loom was worn but I caught it in time.

 

[chaos254]

How are you making out? I forgot to mention that when doing a draw test you need to let the vehicle sit for at least 30 minutes before performing the test. There are certain modules that will stay on even after shutting off the vehicle, once they go to sleep you can perform the test. Otherwise it will show you a draw until those modules power down.