Thread: Battery Draining

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The past 2 weeks my battery has been draining out on me. Drive it during the day and by next morning it's completely dead. I put it on the charger, 2 amp trickle, next morning it starts, I drive it, no problems. Next morning, dead. The battery was new, 2 months old. Can the alternator drain it while the car is off. I have a multi-meter, but I'm a bit electrically challenged. What would be the best way to test it without taking it out? Thanks for any suggs.

You can take the car with the the alt. on and batt. it to most parts store and the can check your charging system for you. (Advanced Auto , Napa.)

take a battery cable off in total darkness and see if a spark flies ..

Like Hoss says, the spark will tell you if you have current flowing with key off, doors closed, everything off. You can also put a 12V test light (mine's a 1057 bulb with a couple of wires soldered on) between the negative post and the negative cable, and if it lights bright you've got a short - a dim glow may be your radio, clock or ECM drawing a very slight current which is normal. With the light glowing bright you can start pulling fuses one at a time, watching the light to see when it goes off. That fuse will ID the circuit that has your short, and you can start troubleshooting only that power group. Be sure you shut your door or tape your dome light switch while you're pulling fuses....how do I know this to be a problem???

Take it back to where you bought it and have it load tested if every thing else checks good. There are a number of things that can drain a battery including voltage regulator, bad starter, bad ignition switch and dimmer switch for the lights. If everything checks good the battery has at least one weak cell.

Cool, that sounds easy enough. I'll let you guys know what I find. Thanks again.

Also get the alternator tested, it might have a bad diode, or even more than one. With a bad diode, the battery can "drain" back through the rectifier bridge to ground/negative.

Here is a rather comprehensive article on finding a "parasitic" electrical drain:

How-to for January - Chasing a parasitic draw the easy way. - The Garage Journal Board

I finaly got around to testing a few things. First the battery, good, then the alternator, good, then the starter, good. Now when i tested the starter, I pulled the starter cable from the battery side of the starter relay and checked the amps periodically. In a matter of 15 mins it had dropped from 12.70 down to 12.53. Thus to me, it's not the starter draining power. I then reconnected the starter cable and took off the cable for the lights and horn, from same location. I then traced the individual wires to there respective landings and found that the glove box recepticle/switch was dangling inside. The amps jumped up to 12.60 and slowly started to climb. I checked it again 10 mins later and it was up to 12.74. I pulled the bulb and reconnected the cable to the starter relay. I left it like that since Sunday afternoon. I'll try it today when I get home from work. Question #1 - Is this a legitament testing procedure or am I chasing my tail? #2 - Why would the amps go up with the car off? Yes, all this testing is with the car off. I figure I learned either what to do or what NOT to do!! Thanks again.

Your not talking about amps-----------your talking volts-----------

your battery if full should read around 13.2 to 14.3 I believe

Originally Posted by cffisher

your battery if full should read around 13.2 to 14.3 I believe

With the engine running, and the battery "full"... then I'd agree with Charlie.

Yeah, volts. Ha ha! When it's running it goes down. That means something is wrong with the charging system, no? Engine off-12.7 volts. Running 11.85 volts. WTF? I felt like I was getting closer but now I'm as far as ever. AAARRGGHH!!!

The regulator in the altenator may be bad ou the diodes...Just take it off and have it tested.

A cheap test before pulling off the alt . is take a metal blade screwdriver with the motor running and touch it on the bearing cap on the back of the alt. It should act like a magnet and stick ,if not the alt. is bad .