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Is it my Batteries or my Truck's electronics?

1K views 19 replies 6 participants last post by  symbols 
#1 · (Edited)
My 2002 PSD is losing battery charge really fast and its getting worse. Where it used to take 3 to 4 days for the charge to fade, today it was less than 24 hours for both batteries to get below 12V. I'm positive that there's nothing ON in the truck. Extra ground wires were attached to each battery, and the original two batteries were swapped out for some from another truck. no change for any of these.

I've removed batches of fuses several times and nothing seems to have any affect on the system. Today my neighbor suggested that it might be the batteries and I'd like to know for sure.

After running the truck awhile I disconnected the batteries from the truck and from each other. They measured 12.64 and 12.59V right after running.

An hour later they were at 12.59 and 12.53, so there's a drop.

My question is that IF the batteries are normal, what kind of voltage drop should be normal for an overnight time period?
 
#2 ·
Take them to get them tested. If you are absolutely positive there is no parasitic draw (which there could be even though nothing is "on"). You could get an ammeter and see how many amps are being pulled when everything is off and see if something is draining the batts. Otherwise take them to Advance Auto Parts and they'll remove them and test them for free. Unless you have a load tester laying around...
 
#3 ·
That's what I'll do if I can get to it this coming week. What I'm hoping for is to learn something tonight about current drop overnight.

If they drain by morning, we're going to the big city for Thanksgiving and I'd be able to buy some batteries up there if we think that's the culprit.

Has anybody ever checked how much current drain is normal for un connected batteries?
 
#4 ·
Yes but I can't for the life of me remember what it is.
 
#6 ·
That was one of the tests I had to do in school here, it's in my lab manual, somewhere... I could probably find it.
 
#7 ·
Nevermind, I just looked up your rig on AllData and it said no more than 0.05 Amps, or 500milliamps. And that sounds right to me. I remember for sure it was less than one, so go off that. Have fun. :D
 
#9 ·
Is there a way to convert the Amps to Volts on my voltmeter? or....is my testing the batteries with a volt meter just a waste of time because I'm not reading the Amps?
 
#8 ·
Don't bother yourself tonight, it's going to be me posting what they read in the AM that you can compare your notes with. I'm guessing that they shouldn't drop much more than .05 or so overnight.

What bothers me is that I first suspected the batteries and switched them out with the ones from my other Ex. No change.

Anyhow, if I get them tested at Advanced (thanks for the suggestion) and they test good, then I'd like to know what the pros would do to isolate where the current is going.

This danged thing has about 50 fuses and relays, so what's the drill to not make this an all-winter-long project?

:dunno:
 
#10 ·
Well the easiest way to find parasitic load is hook up the meter and if it's reading over 0.05Amps then start pulling fuses one by one (one at a time) until it changes and you'll isolate whatever is drawing current. Once you isolate it you can see if something is shorted out. Since it is easy, I would do my own thing and take off the alternator power wire to make sure something in there isn't shorting out. I HOPE it's not your ECM or something.
 
#12 ·
1/2 amp is ideal but you will normally will be fine with less than 1 amp parasitic draw. Once you go over that your batteries won't last.

First you need to make sure your charging system and batteries are in good working order. Your batteries need to be load tested individually and your charging system tested under load.

Once you know for sure that your batteries and charging system are good you can move on to the phantom draw testing. It's easy to do it just takes a little time to find the culprit.
 
#13 ·
The overnight battery drain wasn't bad at all the batteries dropped about .06 during a 40 degree night, which is different from them dropping .25 or so when connected to each other and to the truck.

I'm going to take them for testing, but it's looking like something in the truck is sucking juice out of them big time.

I have a voltmeter but have never used the mA function. If that's how I'm going to find the current drain, what would be the process? Where would each lead connect to if I'm going to remove a fuse for testing? Do I insert the leads into the slot where the fuse went?

If so, how will I know whether something changed?
 
#14 ·
The testing at the auto parts store is about useless for our trucks. I had two batteries that would probably start a Toyota for another three years, but they lacked the juice to kick the beast over. The kid at AZ said he had to test them before he could replace them. Of course they tested fine. I showed him how slow the truck cranked, and I told him to put two new batteries in the truck, if it didn't fire up right away I would pay for the batteries and his time!! Of course it kicked right over and the kid learned something that day and I got two Free batteries that have been going strong ever since.

NCH
 
#15 ·
Make sure they adjust the battery tester for the CCA for your ruck batteries. They usually have it set on car batteries and all of our batteries will test OK. I went through this at AutoZone.
 
#16 ·
Ok, I've never done this on a system with 2 batteries so somebody correct me if I am wrong and feel free to add anything I may have left out.

I want to start by saying that 99% of the time these issues are aftermarket related. I am not saying you didn't wire your stereo or whatever correctly, it's just a fact. So if you have something that was installed aftermarket then I would start there.

Go to whichever battery is easier to use and loosen the negative cable and get ready to take it off. Put one lead of the meter on the battery post itself and one lead one the battery terminal. Now slowly and carefully take the terminal off the post without losing your connections to the meter. This is easier to do with helping hands or a special tool but you can do it if you take your time. The reason you don't want to lose the connections is that you could "wake something up" and that will give you a false reading. Now your going to need to clamp the meter leads onto the post and terminal somehow if you plan on doing this yourself otherwise you can get your buddy to do the rest. See what your meter reading is and remember that. If it's less than 1 amp you probably have another issue. If it's over 1 amp then you need to start pulling fuses one at a time. Once it drops you need to stop there and mark it and also remember what the drop is (probably best to write all of this down). Continue until you've pulled all of the fuses. If you have more than one which I am sure you will, I would start with the largest amp drop and go from there.

Now that you know what circuit you need to look at you need to know what all is on that circuit. Once you know that, start unplugging things on this circuit and continue until you find the problem.

I hope this helps.
 
#17 ·
I swore up and down my truck didnt have a draw, it ended up being my relay for my hella aftermarket lights. I did the test as above but only the one battery version. I went through several batteries, learned my lesson and no longer have the lights hooked up.
 
#18 ·
My trip to the parts store (local, not a chain) was a learning experience. One of the batteries was tested at 525CCA and the other one was at 127CCA. Now I have a new battery and will install them both after we get home from the holiday.

I'm hoping that this is a fix, but if not, we still have a battery that's a whole lot better than the 127 one.

There's a bunch of aftermarket stuff in the truck from the PO, so next week I'll start to know whether the testing is going to be needed.

Have a good Thanksgiving, guys!
 
#19 ·
Yeah that might do it lol. They must not be holding a charge, they do that sometimes, where they will read good voltage but once a load is on 'em they just DROP. Hope that's your problem though.

symbols...wow, that there is why I'm not a teacher :hehe:
 
#20 ·
Thats from many years of greasy, broken, and cut up hands:icon_ford:
 
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