Something is killing my battery

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C2ndLTpigeon

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I just bought a 1999 ram 1500 Sport last week. Ive notices that if i leave it sitting for few hours and start it it will start but after it turns over a few times.
Recently I parked it at 2:30 AM Xmas eve and the next time i went to start it was 5:00 PM Xmas day, so it sat for 14 1/2 hrs and it would not crank, the battery was dead and i had t use my jumper. The battery is a Pro Start battery from pepboys and it has a sticker date of 7/16 so its New. I disconnected the negative and put the test light on the cable and touched the pen on the Neg. I then pulled fuses to see if any would kill the test light, nothing. The test light is pretty dim though so i figured its because of the PCM draw. Im stumped on what is killing the battery and wondered if there is anything that is common with the rams? What else can i try to see if its the truck or the battery? Any help would be appreciated.
 

avantiguy

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Have pepboys check the battery. You really need to be sure the battery is 100% before you do anything else. It wouldn't be the first battery that crapped out early.
 

charonblk07

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The easiest way to determine where the draw is from is with a multimeter; remove the negative cable and install the multimeter between the negative cable and the negative post. With the multimeter set to test amps through the internal fuse you can see what the off-key draw is and to narrow it down to a specific circuit you just pull fuses in sequence until the draw really drops off. Most off-ket draws are ~100mA or less, if you're above 150mA then you're pulling a lot from somewhere. With the age of your truck it may be hard to track some down as they could easily be thin or cracked wire insulation but you won't know where to start looking until you figure out what circuit it's bleeding from.
 

Gr8bawana

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I also had a mysterious battery drain for a while. It ended up being that I used the 12 volt power outlet, not the cig lighter, that is in the dash to run a small air compressor and melted the connectors on the back of it. It created a short that drew just enough that it would drain the battery if it sat for more than 1 day.
 

DodgeTx

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I had an issue where my ground cables and terminals had a ton of corrosion within the wires on the terminal, I used a wire brush and cleaned them up and put it all back together, with a new ground wire to the radiator core support. Haven't had a problem since.
 
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C2ndLTpigeon

C2ndLTpigeon

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So i disconnected the Negative and used a multi meter with one lead on the cable and one on the neg post. I set it to 10 AMPs. It shows its pulling .031 amps when the truck is off. It doesn't seem like its alot, is this normal?

I wouldn't doubt a new battery as ive had it happen before, but i wanted to make sure I test it before going to the next step.
 

dudeman2009

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What you're reading is 31 milliamps key off current. The problem is, by disconnecting the negative wire you completely shut down all running loads, potentially whatever may be draining the battery.

If you really want to find your key off draw, follow these steps.

Get a jumper wire of sufficient size as to handle 20A for a second or two, 14g wire should work if you use vise grips or clamps.

With one of the terminals disconnected use your jumper wire to connect the lead to the battery. If you have a top post simply clamp it to the post and lead. If you have a side screw in type, auto stores sell adapters that turn it into side post batteries for out of vehicle charging purposes, that is the easiest way to set this up.

Once you have the jumper wire in place, turn everything unnecessary off, such as lighting, fans and other accessories. Then turn the key to run until the dash lights go out to indicate that everything is properly booted. Then shut the ignition off, remove the key and get out.

Back up by the battery hook one lead of the multimeter to the lead you disconnected from the battery and the other to the corresponding post of the battery. Make sure the multimeter is turned on and in the proper 10A setting. Then remove one side of the jumper wire and read the measurement.

That is your actual key off drain.

There is another test i'd like you to do. Take your multimeter in the highest milliamp range and put one lead onto the positive terminal and scrape the other lead across the top of the battery. Note the highest value, this is parasitic drain due to the top of the battery being dirty.
 
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C2ndLTpigeon

C2ndLTpigeon

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What you're reading is 31 milliamps key off current. The problem is, by disconnecting the negative wire you completely shut down all running loads, potentially whatever may be draining the battery.

If you really want to find your key off draw, follow these steps.

Get a jumper wire of sufficient size as to handle 20A for a second or two, 14g wire should work if you use vise grips or clamps.

With one of the terminals disconnected use your jumper wire to connect the lead to the battery. If you have a top post simply clamp it to the post and lead. If you have a side screw in type, auto stores sell adapters that turn it into side post batteries for out of vehicle charging purposes, that is the easiest way to set this up.

Once you have the jumper wire in place, turn everything unnecessary off, such as lighting, fans and other accessories. Then turn the key to run until the dash lights go out to indicate that everything is properly booted. Then shut the ignition off, remove the key and get out.

Back up by the battery hook one lead of the multimeter to the lead you disconnected from the battery and the other to the corresponding post of the battery. Make sure the multimeter is turned on and in the proper 10A setting. Then remove one side of the jumper wire and read the measurement.

That is your actual key off drain.

There is another test i'd like you to do. Take your multimeter in the highest milliamp range and put one lead onto the positive terminal and scrape the other lead across the top of the battery. Note the highest value, this is parasitic drain due to the top of the battery being dirty.

I followed your instructions and i did get a different reading. I am now getting .004, alot less then before. Im starting to think this is not a problem with the truck but the battery itself. What do you think?
 

charonblk07

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I followed your instructions and i did get a different reading. I am now getting .004, alot less then before. Im starting to think this is not a problem with the truck but the battery itself. What do you think?

Battery or alternator then. Get the battery tested and if it comes back in good shape then have then test the alternator, if it's not charging properly then your battery is only getting a surface charge and you'll have a very low reserve capacity.
 

dudeman2009

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4 milliamps is about right. After 10-30 minutes that would have risen slightly, but thats ok. Any problems on this age of vehicle would've been apparent right away.

I would complete that second test I wanted you to do, or clean off the top of the battery really well.

To test the alternator, start the vehicle and let it idle for about 5 minutes. Then turn on everything, high beams, fogs, high speed blower motor, interior lights, etc. and let it idle for another minute. Then test voltage at a few places.

Across the battery terminals.
From battery positive to bare metal on the engine or the alternator casing.
From battery negative to the alternator positive stud.

The battery terminal measurement is your baseline, neither of the other two readings should vary from it by more than a volt. The battery voltage should be no lower than 12.8V during the test.

To test the battery, charge it first. To test if it is charged measure the terminal voltage with the lights off. If the reading is above 12.8V you must first remove the surface charge by running the headlights for 2 minutes. Then let the battery settle for 5-10 minutes after that. Then measure the battery voltage, it should read no lower than 12.4V. Anything less indicates a weak battery for a standard flooded lead acid battery.
 
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C2ndLTpigeon

C2ndLTpigeon

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4 milliamps is about right. After 10-30 minutes that would have risen slightly, but thats ok. Any problems on this age of vehicle would've been apparent right away.

I would complete that second test I wanted you to do, or clean off the top of the battery really well.

To test the alternator, start the vehicle and let it idle for about 5 minutes. Then turn on everything, high beams, fogs, high speed blower motor, interior lights, etc. and let it idle for another minute. Then test voltage at a few places.

Across the battery terminals.
From battery positive to bare metal on the engine or the alternator casing.
From battery negative to the alternator positive stud.

The battery terminal measurement is your baseline, neither of the other two readings should vary from it by more than a volt. The battery voltage should be no lower than 12.8V during the test.

To test the battery, charge it first. To test if it is charged measure the terminal voltage with the lights off. If the reading is above 12.8V you must first remove the surface charge by running the headlights for 2 minutes. Then let the battery settle for 5-10 minutes after that. Then measure the battery voltage, it should read no lower than 12.4V. Anything less indicates a weak battery for a standard flooded lead acid battery.

I will try the second test tomorrow. The top of the battery is pretty clean as its only 3 months old.

I will also do the other test mentioned and get back to you on the results.
 
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