strange battery question

[skeletor]

i have a battery question that has kinda boggled my mind. yesterday my battery (6 month old carquest 1075 cranking amps) was holding aound 13 volts today i checked it and it was at 3 volts. how can a battery go from 13 to 3 volts that quick? i cant find any parasitic wires except for my sunpro voltmeter but that wouldnt kill my battery like that. should i just blame it on a bad battery?

[jpcoutts]

I'd try pulling the negative cable and set up a volt meter btween the cable end and the battery post. Maybe you've got a bad wire and it hasn't shown up yet. Good luck!

[tkiller13]

Check the water level. If it's good, put the battery on a low charge overnight. Load test the next morning, that will tell you if you have a bad battery or you have a draw from the jeep.

[duncanstives]

Pull a cable off and touch it to the battery a few times... High levels of sparking indicate load. This would only work after charging the battery obviously.

[Chevelleguy]

A stuck rear window key switch has drained more than a few batteries.

Headlights left on?

Ignition switch not turned off all the way when you pulled the key out(my key will come out with the switch in any position)?

[DAHoyle]

Have your alternator tested. One of the most common causes of a battery inexplicably draining, is the alternator. It could have a shorted diode in the rectifier, which will allow it to charge, but then discharge thru the alternator when not running. Easiest way to check it on your own is to let it charge up, and then disconnect the alternator overnight. If the voltage is good, then hook it back up. The next night, leave it hooked up. If it drains, then you have the culprit.

[Joe Guilbeau]

Have your alternator tested. One of the most common causes of a battery inexplicably draining, is the alternator. It could have a shorted diode in the rectifier, which will allow it to charge, but then discharge thru the alternator when not running. Easiest way to check it on your own is to let it charge up, and then disconnect the alternator overnight. If the voltage is good, then hook it back up. The next night, leave it hooked up. If it drains, then you have the culprit.

Or, you could just open the hood at night without any thing powered up, and disconnect the Negative Battery Cable.

If the alternator is discharging the battery a good spark will jump across the post to cable when you re-connect it.

Remove the alternator BATT cable from the rear of the alternator and re-check it.

If the spark continues (a small spark is ok, due to stuff like clocks etc...) then you have another issue such as a path to ground that is draining the charge on the battery.

If you have a ammeter, put it between the cable and the neg battery post to monitor the amount of current that is being drained out of the battery. It should be in the milli-amp range.... small amount of current being used by Digital Clocks etc...

[skeletor]

yeah i tested all that stuff, charged the battery, right after charging it was at 13.8 2 hours later 12.1. i guess bad battery. thanks for the help.

[DAHoyle]

Or, you could just open the hood at night without any thing powered up, and disconnect the Negative Battery Cable.

If the alternator is discharging the battery a good spark will jump across the post to cable when you re-connect it.

Remove the alternator BATT cable from the rear of the alternator and re-check it.

If the spark continues (a small spark is ok, due to stuff like clocks etc...) then you have another issue such as a path to ground that is draining the charge on the battery.

If you have a ammeter, put it between the cable and the neg battery post to monitor the amount of current that is being drained out of the battery. It should be in the milli-amp range.... small amount of current being used by Digital Clocks etc...

I just went with the alternator, because that rules everything else out of the equation. If you disconnect the alt, and still have a problem, then the alt isn't it. Just two ways of doing the same thing.

If it was mine, the alt would be on the bench, and the rectifier being checked out. it isn't hard to do, but not a novice job either.

[DAHoyle]

yeah i tested all that stuff, charged the battery, right after charging it was at 13.8 2 hours later 12.1. i guess bad battery. thanks for the help.

it was down to 12.1 even with everything disconnected? if so, then I would have to agree with you,

[Joe Guilbeau]

I just went with the alternator, because that rules everything else out of the equation. If you disconnect the alt, and still have a problem, then the alt isn't it. Just two ways of doing the same thing.

If it was mine, the alt would be on the bench, and the rectifier being checked out. it isn't hard to do, but not a novice job either.

That is fine, however lets make sure that the battery is discharging before trying to troubleshoot what is draining the battery, eh?

A quick disconnect of a battey cable tells you right off the bat if there is an issue... no drain, then go directly to a load test on the battery.

[El_Diablo]

Check the water level....

just as a note, i would advise against this as it voids your warrenty and is potentially hazardous, all of the newer automotive batteries are maintenance free, in other words.... dont touch them!! we've had guys kill their otherwise good batteries by poping the tops and adding water, then they get pissed because even though its label "REMOVING CAPS VOIDS WARRENTY" it should be covered.....


just a heads up FYI