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Old 07-19-2020, 02:03 AM   #1
chris1htx
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Battery drained after 2 days

What’s up guys, I have a battery draining issue that I can’t seem to figure out. Can’t get the truck to turn over after 2 days of driving it. I did a parasitic draw test and I’m getting .02-.03 during the whole test. Did alternator tests and its good. Had O’reilly look at the battery they said it was good. Grounds are good, what else can be causing the battery to drain? If anything was causing the drain it should pop up on the parasitic test right? 84 C10 with an LT swap.
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Old 07-19-2020, 02:29 PM   #2
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Re: Battery drained after 2 days

If it's happening when the truck is being driven, it's probably not a parasitic draw. Most likely the alternator is not putting out enough amperage for your battery to get recharged. Did you pull it and have it load tested?
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Old 07-19-2020, 03:37 PM   #3
chris1htx
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Re: Battery drained after 2 days

I mistyped, 2 days parked(after driving) is when I cannot turn it over. Yes I pulled it and had it tested, passed all 3 times.
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Old 07-19-2020, 04:10 PM   #4
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Re: Battery drained after 2 days

Unplug the alternator exciter wire when you park it the next time. That should confirm if it's the alternator.
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Old 07-19-2020, 04:44 PM   #5
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Re: Battery drained after 2 days

If your truck won't crank after sitting for 2 days, what voltage does the battery show at that point (key off)? With the truck running, what is that reading at the battery?
I'm pretty dim myself with electronics but if you are getting a good reading (~13-14v) at the battery with the engine running and you are sure there is no parasitic loss, then I would say you need a new battery that does not have internal loss.
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Old 07-19-2020, 05:21 PM   #6
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Re: Battery drained after 2 days

Does the alternator maintain 13.5 volts or more under full load?? If so, the alternator is probably ok. Disconnect the battery cables and, using a battery charger, charge the battery until the no load voltage is 12.5 volts.. Let the battery set disconnected for a couple days.. If the battery voltage is lower, you have a bad battery.. If it holds the voltage, your tests are either incomplete or flawed..
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Old 07-19-2020, 06:18 PM   #7
chris1htx
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Re: Battery drained after 2 days

The voltage at engine running is 13.78. With key off drops down to 12.52. I’ve taken the battery to get tested at auto store twice and both times they said the battery was good. Is there a time frame for the parasitic test. I had it tested for 6 hrs and stayed steady at .02-.03. Since typing this the battery has dropped down to 12.38.
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Old 07-19-2020, 08:04 PM   #8
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Re: Battery drained after 2 days

When you do EVERYTHING I suggested in post #6, come back and post the results.....
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Old 07-20-2020, 01:38 PM   #9
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Re: Battery drained after 2 days

Connect your mutimeter between the negative terminal and the negative cable of the battery and take a key off reading. The drain should not exceed .003=.005 which is milliamps. Look for any obvious things left on. Pull the alternator charging wire off the back of the alternator and check the meter. It should drop to the readings I posted. If it doesn't then start pulling fuses on circuits that are hot with the key off. Brakes, headlights, emergency flashers, One at a time until the reading drops. That will be the circuit that's draining the battery. Do the other suggestions as well.
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Old 07-20-2020, 08:27 PM   #10
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Re: Battery drained after 2 days

How old is the battery? They can develop internal faults that drain off power.
What is the voltage after 2 days?
Does everything else work after 2 days with engine off? Lights, radio, wipers etc?
If things do work, might be that the starter brushes are near EOL. I replaced the ~6 year old battery in my truck a few years ago after a couple of no starts on battery but would start on jump. A few weeks later, it again wouldn't start. After a little troubleshooting, replaced the starter brushes($4) and fixed the problem. Apparently the new battery had just enough higher voltage to overcome the worn brushes for a few extra weeks.
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Old 07-21-2020, 02:41 PM   #11
chris1htx
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Re: Battery drained after 2 days

RustyPile: Truck on with a load doesn’t go below 13.5 volts. Removed the battery charged up, after charging battery it was at 12.62. That was yesterday afternoon, currently the battery is at 12.21.

VetteVet: I did that and was only pulling .02-.03

Dead Parrot: I got the battery back in January. While on the truck the voltage after 2 days is around 11.5 at that voltage it would struggle to turn over or won’t turn over at all. I did not check all the accessories but the gauges and radio would turn on.
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Old 07-21-2020, 05:23 PM   #12
RustyPile
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Re: Battery drained after 2 days

Quote:
Originally Posted by chris1htx View Post
RustyPile: Truck on with a load doesn’t go below 13.5 volts. Removed the battery charged up, after charging battery it was at 12.62. That was yesterday afternoon, currently the battery is at 12.21.
OK.. Not the two days I requested, but after less than 24 hours, you've already lost 1/2 volt. That's a bit low, almost not acceptable and not a good sign for the battery. As an example... My truck has been setting for almost 2 weeks without being started.. The engine off, no load voltage is 12.57 volts.. No drop at all.

Leave the battery disconnected for another 24 - 36 hours.. Without recharging, check the voltage again.. If it has dropped any at all, I don't care what O'reillys told you, the battery is on the way out and not trustworthy. A battery that won't hold a charge cannot meet the high amperage demand of cranking over an engine, while at the same time, hold the voltage high enough to power the ignition system.. My money is on you having a bad battery..
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Old 07-22-2020, 11:32 PM   #13
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Re: Battery drained after 2 days

So this is a bit old school but about 40 years ago a battery drain was by sorted out by disconnecting the negative battery cable leaving the positive cable in place. Connect the 12 volt lead of your high tech, at the time test light to the negative battery cable and the battery terminal and pull fuses until the light went out. If it goes out you found the drain.
So having said that I did a LS swap in a 73 Camaro that all of a sudden I had a battery drain over about 2 days as you have said you have. Pulled all fuses and still a drain. Come to find out the clip on cover on the starter solenoid had rubbed thru the main battery cable making a small but bad short to ground. Could of been bad.
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Old 07-23-2020, 05:48 PM   #14
RustyPile
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Re: Battery drained after 2 days

It's great to have everybody's input.. Several have suggested checking for a drain and/or assuming there is a drain.. The OP has already tested for a drain using a DVM.. Although the OP isn't convinced, his posted test results (a draw of 20 - 30 milliamps) indicate there is no drain.. So at this point, there is no need to pull fuses or check for a drain.. He also indicates the disconnected battery looses voltage (level of charge) in just a matter of hours... THIS ALONE indicates the battery cannot hold a charge and is failing..
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