Mysterious battery drain

If I get the time this week, I’ll be putting one in. At this point, I can’t think of anything else it would be but it’s quite frustrating.

 

A little update:

The aftermarket fuse box that houses the fuses for my front light bar, rear light pods and invertor is drawing .014a. Removing the fuses for the lights show that they are each drawing .007a of power. Doesn’t quite make as they have an inline fuse and an additional fuse inside the fuse box. I have that disconnected for right now since I don’t plan on using any of them till this is figured out.

I also disconnected the alternator and retested the draw with no changes. Still drawing .05mA unless I disconnect the aftermarket fuse box which drops it to .03mA.

 

@SouthPaw Did you mean 0.014A & 0.07A? 0.014mA (milliamps)= 14 uA (microamps)

 

Only 1 picogram of sugar!

 

Sorry, yes you are correct. Prior measurement was .049a after removing the fuse box, it dropped to .035a.

 

I had a similar issue and literally lucked into the solution. It was the stock factory radio, which we learned when it was replaced with a new one and that corrected the problem! So, if you have the stock radio it might be the culprit.

The longer version: When I purchased my 2002 last summer, the seller warned me of a short if I applied the parking brake, which would short out the radio and interior lights. I thought that was odd, but filed it on the to-do list. Fast forward, and I kept having my new 2020 battery die rather quickly. So I began to just disconnect it overnight. That's a hassle...

I purchased a new radio from Best Buy, simply to upgrade the technology. I told the Best Buy installer the electrical issues and to watch for any abnormal wiring issues. They said they had to apply the parking brake to correctly install the DVD stereo unit. I was expecting the worst, and it doesn't happen this way too often but when that radio was pulled out, all the electrical issues have been fixed. The parasitic draw is gone, the truck doesn't drain the battery, the parking brake is not a problem, etc...

I really lucked into the solution and a $200 stereo and free install, fixed the problem. The next day I had a appointment to take my truck in and pay a mechanic labor rates to track down the issue, so the radio probably saved me many times the cost of the radio...

 

Long shot alert: my truck's PO (a reasonable person) says it has a drain that would kill the battery when the headlight switch is left in the auto-on position. He says a shop diagnosed it. I've never tested it but I intend to at some point.

FWIW, YMMV. (I did say long shot.)

Good luck.

 

Appreciate everyone’s advice and I will continue to track it down. As weird as it sounds, it almost like the more I test it, the weirder it gets. I have been messing with this for two weeks now and at one point, I got the draw as low as .03a. I did not change anything other than disconnecting the illuminated switches for my aux lights. This was two weeks ago:


This is tonight’s current draw reading with the aux fuse box that controls the lights and invertor disconnected:


This is the fuse box reconnected. Again, I’m not sure why the aux lights are drawing power when they are off, bad relays?


This is everything hooked up normally with the Viper remote start armed which activates a tiny flashing blue LED off the antenna.



What I can’t figure out is how one day it tested as low as .03a with EVERYTHING connected?! I didn’t change a thing and now I’m getting higher readings with more stuff disconnected? I did some googling and they said to get the estimated hours from your battery, take the CCA’s and multiply by 7.25 (710x7.25=98aH). Not sure how I can apply my amp draws to figure out how many hours that gives me before my battery is dead.

 

Also, is this OEM or aftermarket? Remove the fuse does not change any of the readings and the wiring leads to a two pin grey plug next to the drivers side headlight? The plug looks OEM but the fusible link doesn’t, at least to me.

 

Aftermarket.

 

Thank you. I’ll trace it tomorrow to see where it leads. It’s a really nicely done aftermarket wire though, not just a typical crimped on connector.

 

I just happen to be neck deep in testing the capacity of one of my 100ah RV batteries so I think I can help...or not...

710 CCA equaling 98ah is a reasonable approximation. What follows are also reasonable approximations but the scientists will soon want to know ambient temps, rest periods, (is it exactly 77 degrees, has the battery been free of loads for 12 hours, etc.) but we'll ignore them for now.

A 98amp hour battery can power a 1 amp device for 98 hours. Since you never want to discharge a lead acid battery more than 50%, you wouldn't want to run that 1 amp device more than 48 hours. But hell, you're dealing with a parasitic draw that you don't want to run at all.

An example: an 1156 taillight or turn signal bulb draws about 27 watts. Ohms law says 27 watts divided by 12 volts = 2.25 amps. 98ah divided by 2.25 ah = that single taillight bulb will suck every amp out of the battery (permanently damaging the battery as you've learned) in 44 hours or just under two days. That single burning taillight bulb will keep the truck from starting in 24-36 hours...ASSUMING the battery was tip-top to start.

Getting back to your original question, the amp draws of less than .1 are tiny and shouldn't drain a healthy battery for a few weeks. Which brings me to...

This log has me concerned. 12.35 - 12.45 volts is terribly low. The SOC of 55% is on the borderline of 50% which is what you don't want to drop below. I'm not clear on the SOH #s of 100% - they seem dubious to me.

Regardless, if I had a battery reading 12.4 volts I'd put it on a charger immediately because it's on the edge of permanent damage and certainly struggling to start if it's drained more.

In summary, those reported voltages suggest the battery isn't adequately charged. I'd require 12.6 and above 12 hours after a test drive or a complete charging with the neg cable disconnected. With a higher State of Charge (SOC) the battery might be able to withstand small parasitic draws.

- Charge the battery completely, to 12.7 or so volts.
- If the truck is going to sit for days or a week at a time consider an on-board battery maintainer. Plug that in and have confidence your battery is being maintained even if you miss a few weeks of driving. I'm a big fan of maintainers that cost $30 but preserve the life of a $100 battery

I hope this helps. I welcome corrections. Battery University, Parts 1, 2 and 3 have been helpful in learning about these mysterious beasts.

https://batteryuniversity.com/

 

For what ever reason, a previous issue keeps popping in my head regarding this mystery and Aliens

Dome/map lights come on randomly

 

Excellent information and very informative. I noticed that as well that the voltage seems to drop rather quickly which isn’t consistent with the amp draw. Again I checked this morning about 12 hours apart from last nights drive/test which left the battery SOC at 98%. Here were the results:

06/01 - After test drive 6:44pm
12.72v
SOH: 100%
SOC: 98%
CCA: 742
R: 4.04m-ohm

06/02 - 7:10am
Amp draw - .035
12.37v
SOH: 99%
SOC: 61%
CCA: 708
R: 4.24m-ohm

 

Quite the drop overnight

 

Precisely which doesn’t compute with the .03 amp draw. At the current amp draw, I should have a lot better results than that.

I’m literally guessing at this point but the only thing left is the alternator to look at. Even though it’s testing good, maybe the quality of charge isn’t there?

 

Funny you say that, I thought about this last night. At this point, I don’t think it’s a amp draw problem anymore. After checking it yesterday evening vs this morning, the volt loss isn’t consistent with the amp draw.

 

Are there any lines coming from the battery positive terminal that are not factory? if so, unplug all but the factory batter cable from the + terminal and see what the voltmeter readings are then.

 

The battery measured 12.72v after a test drive and dropped to 12.37 overnight. As mentioned, that's a big drop. For starters, your point on the quality of charge is good. A 98ah battery starting at below 12.5v will need a good long drive (hours) or to be put on a charger for a few hours or more to bring it back to full-charge. After a test drive you may be measuring surface charge of 12.72 but that can dissipate quickly. The article below recommends a min. voltage of 2.07v per cell or 2.07x6 = 12.42

For starters, give the battery a complete charge. If you have a charger, remove the neg. cable and charge it for 12 - 24 hours. The battery has to be fully charged to complete the tests you're doing. Batteries are boxes of mysterious science and can cause all sorts of headaches. The first step is a healthy, fully charged battery.


https://batteryuniversity.com/learn/article/water_loss_acid_stratification_and_surface_charge

Keep at it.

 

Agreed. Heck, just disconnect the negative cables to isolate the battery from the truck, charge it completely and see what happens.

 

I did have it fully charged on Sunday by the parts house. I’ll get a charger and charge it again today and disconnect it from the truck.

If it is the battery, this will be the fourth one in less than a year.

 

Ain't my money but not a bad idea or at least open her up and check diodes ?

God forbid you take too long on this and receive the PHM biased, poorly planned, "greased", un-scientific poll from hell

 

Which sucks and get's back to your search of the root cause of what's killing the battery: parasitic drain, failed alternator, odd short caused by water intrusion, bad grounds, etc. At some point, someone will have to take this truck off your hands (too soon?).

 

Well I borrowed the old mans battery charger and it’s been sitting on 2a charge since 3:30pm today (three hours so far). I’ll retest it in the morning and and then let it sit to see if it’s draining. I think it would need to piss me off a whole lot more before I pass it on to someone else lol.



The positive terminal started getting weak in its grip tightness probably from all the tightening and loosening I’ve been doing the last few weeks. I could tighten it all the way and could still spin it around by hand so I opted to replace it. Comparing the two, the OEM one is kind of dinky compared to the NAPA HD version.


This is the other end of the fuse-able wire I posted about. As you can see, it ties into the factory harness so I’m not sure what it does. My truck does have the OEM security system so maybe it is a part of that?

 

I am really close to pulling the trigger. I replaced the starter on my motorcycle today and the guys on that forum all recommended DB electrical. I got it hooked up an hour ago and it spins that big Vtwin so fast and easy. I checked the price for one of their alternators and it’s only $100. That is an easier pill to swallow vs the $180+ NAPA one.

 

DIBS!
I'm already in CO and his paint scheme matches my Jeep.

 

I do have the factory alarm and my truck doesn't have that little box. I have to wonder if that's part of the remote start system? Good call on that battery terminal...

 

It actually looks like it’s for the trailer lights/harness.

 

I guess I can't say that you'll need a bigger charger...