Battery Draw Test Procedure

[ninety15.0]

Hey guys...i've had this problem lately with my battery going dead after just one week of the car sitting. I just went out there to start the car now and it was completely dead. The car has a 130A 3G alternator on there with all the appropriate wiring...and the car charges fine when running with no accesories on. When in turn the lights on however, i can see a noticeable draw in the bat voltage.

I was wondering if anyone has a good parasitic draw test procedure for identifying circuits that may have problems. I was thinking to just use a DMM to test the voltage at the battery posts. I'm expecting to see something less than 12V obviously. Then i was thinking to start pulling fuses until voltage draw stops. Does anyone have any other ideas or procedures for tracking down problems? Thanks in advance!

 

[jake2582]

what you want to do is test it on amperage
make sure nothing is on and disconnect the neg bat cable.
connect one lead of the meter to the bat. cable and one lead to the bat. post
meter should be set to measure amperage and it should not pull more then like .2 amps. (clock, radio and pcm memory) should be all in use.
if it is more than that pull fuses till you find it.
BTW: if it pulls more than 10 amps it will blow the fuse in your meter.

BTW: battary voltage should be 12.65V when the car is just sitting and 9.86V with the starter engaged for 10 seconds.

 

[ninety15.0]

Jake...thank you for the information. That was very helpful. So instead of testing the voltage across the bat, i should be testing the amp draw through the circuit. Do you know if the headlight and taillight circuits are on the same fuse? or if they are even fused at all? Thanks again for the help!

 

[jake2582]

Jake...thank you for the information. That was very helpful. So instead of testing the voltage across the bat, i should be testing the amp draw through the circuit. Do you know if the headlight and taillight circuits are on the same fuse? or if they are even fused at all? Thanks again for the help!

i dont know that.
but be sure not to turn anything on or else you will blow the fuse in your meter. like i said it is usually only 10A fuse.

 

[HISSIN50]

Yes, the headlights and taillights are fused. You will be looking for an item staying on, so chances are that the headlights and tails are not the issue.
Be very sure all glovebox lights, vanity mirror lights, trunk lights, etc are all turning off. Those guys will wipe your battery's butt if left on for a couple nights.

I do the same method of testing (current draw with an ammeter in series with the disconnected negative battery cable and terminal). Remember to re-peg your DMM (most require moving the Positive lead to the third port).

You can check specific gravity with a hydrometer. Or each battery cell should have just over 2.1 volts.

Good luck.

 

[ninety15.0]

no its not anything simple like a light staying on...i have checked all those possibilities many times. I think this is probably an exposed/grounded wire that isnt supposed to be. I have been doing some reading about how to test for parasitic draw...i will try it tomorrow and see what i come up with. thanks again for the help guys...