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1997 GMC Suburban K1500, 5.7L gas

TL;DR - 18 moth old battery dies in 4 days. 0.02 amp on parasitic drain test

I've been dealing with this issue for a while now. Battery is about 18 months old. If I let the truck sit for about 4 days, it does not have enough power to start. This has been going on for months now. I've done a parasitic drain test at least 3 times. Each time it spikes to around .8 amp for about 10 seconds then drops to .02 amps and stays there. If I test the battery after driving or charging, it still puts out 800-1000 CCA.

A couple of other thoughts / notes...
I did have issues with water leaking in through the windshield. I believe I fixed the issue, but the leak has broken the compass on the mirror and the buttons on the right side of the radio do not work. I consider the radio suspect.

I have a key fob with remote lock, but I do not keep the keys close enough to activate the locks.

When the doors are open, the lights draw about 3 amps. They are on a timer to shut off about 30 seconds after all the doors are closed.

I've been working on a device that will email me if the voltage drops (since last reading or below a threshold), but I haven't had much success as the lighter socket will put out 11.5v, while the battery is at 12+. I might try hooking this directly to the battery next. I know I still have some bugs in my code that I need to work out.

My method for parasitic drain - Disconnect the negative side of the battery and connect a multimeter set to 10 amp between the battery and the negative cable. Open/close the doors. I've turned the ignition on and off, thinking there may be some draw after the truck has shut down.

The voltmeter on the dash says the alternator is putting out 14v. A little higher after I have to jump it.

There is nothing aftermarket on the electrical system. No winch, lights, etc., currently nothing plugged into the lighter

If I can determine the battery is the issue, I will see about getting a replacement under warranty. I'm sure discharging multiple times has put quite a hurt on it. I'm not trying to just throw another battery at it if there is still an unresolved issue.

Thank you in advance!

UPDATE: A year and a half later. The issue stopped after a couple months. I did not change anything. I still have the same battery in the truck.

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  • What is your battery voltage after you've driven it around awhile and let it sit for an hour? Has the battery been discharged since you put it in, an has it been in extremes of heat or cold?
    – GdD
    Commented Dec 14, 2017 at 13:15
  • Can't remember the voltage exactly. I want to say around 12.4. I can check it at lunch. The battery has been discharged down to ~10v a handful of times. Don't know that it's gotten worse than that. Summer gets around 90-100*F. The paint is black, so the exterior gets up around 170*-180* F. Last few days it has been around 20* F at night.
    – rpmerf
    Commented Dec 14, 2017 at 13:28
  • It could be your battery has had it, maybe it got over discharged or something. However, before you go further you need to get a reading of milliamps on your meter.
    – GdD
    Commented Dec 14, 2017 at 14:05
  • Draw was 0.02a or 20ma from what I saw using the 10a scale. Don't know if there was some condition I wasn't seeing that was increasing draw.
    – rpmerf
    Commented Dec 14, 2017 at 16:34
  • I forgot to test it before I left. When I got back, I shut the engine off and turned on the headlights for about a minute or so. Voltage with the headlights on dropped 12.08. Voltage with the headlights (and interior lights) off was 12.44.
    – rpmerf
    Commented Dec 14, 2017 at 17:52

2 Answers 2

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You are almost there with the multimeter. If you suspect the charge system isn't faulty you can preform an amp drain or voltage drop test to identify which system is the parasite.

https://axleaddict.com/auto-repair/car-batterydrain

Follow the guide here to isolate exactly which system is draining the battery. This is going to involve configuring your meter in one of two ways similar to what you were doing before, but pulling fuses to watch for a change in the system. From there you can inspect that system to find the fault.

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  • The problem is that when I am watching it, I am only seeing a 20ma draw. The site you linked (and other resources I have seen) suggests 50ma is an acceptable limit. If the draw I saw was above that limit, then I could narrow down what circuit it was. I am not sure if something is activating while I am not watching, or in some condition other than what I am testing and drawing more current than what I am seeing. Unfortunately, my test involves disconnecting the battery and not starting. Though this reminds me I have a quick disconnect to use for measuring current without losing power.
    – rpmerf
    Commented Dec 14, 2017 at 16:39
  • Try the voltage drop method if you haven't. Are you saying you aren't connecting the meter to the negative battery terminal in series to the cable and turning the key to acc or on?
    – Sam Basso
    Commented Dec 14, 2017 at 16:52
  • The vehicle should be new enough for that to work. Also make sure the battery is fully charged to start and follow all the isolation pretest steps. It could be the alternator diode or battery after all.
    – Sam Basso
    Commented Dec 14, 2017 at 16:59
  • I am connecting in series between the battery and ground cable. I am doing the test with the key off, as that is the position the key is in when the battery is dying. I have turned it to on or acc, then back to off to see if the draw continued to stay high after shutdown, but it dropped back down to 0.020a. I can try the voltage drop and diode tests tonight.
    – rpmerf
    Commented Dec 14, 2017 at 17:42
  • I'm trying to understand the voltage drop test. It sounds as if this will just show me the circuits that are active? I have determined the active circuits with a test light. I didn't find anything out of the ordinary.
    – rpmerf
    Commented Dec 14, 2017 at 18:24
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As you are probably aware 0.02A is well within spec as 0.03A is the usual limit how ever in most cases 0.1A is acceptable.

Something could be activating at random times without your knowledge after you have done your measurement. Most decent digital multi-meters have a hold high function where the display 'sticks' on the highest value, carry out a current draw test as usual and when the value drops to 0.02A put the meter in hold mode. Keep monitoring the screen say every 12hours for 4 or 5 days. If the value has risen you can then start eliminating things by removing a fuse and carrying out the test again. When the screen fails to go above 0.02A you know you have found the faulty circuit.

It may also be a faulty battery, give it a slow 'trickle' charge for a few days or use a smart charger. Then leave the battery disconnected for a few days and then carry out your battery test, if the value is now lower you know the battery is at fault.

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  • Unfortunately, I don't have a meter with this feature. I may see if I can build something that uses an arduino to monitor the current. Good idea on the self discharge rate.
    – rpmerf
    Commented Dec 14, 2017 at 18:15

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