Slow drain on battery... What to check?

Because my XJ got stolen my CJ is now my DD. The problem is, they battery doesn't want to stay charged. I jump it, and drive it (can't let it sit and idle forever because it doesn't have an E-brake) and I've ran it for 20-30 minutes at a time. Then, if stop when I come back the engine won't even turn over. Flagging down a stranger to jump me is getting old. Is there any normal places I might find slow short?

 

pull neg cable off bat. put test light wire on cable and pointed nd on neg tetmal on bat if it lights up you have a drain.
to find the drain keep test light hooked up and start pulling fuses when test light goes out you have found the circuit the drain is on. also pull wires to alt. it may be their.

one other thing to test AZ. is hard on battries. you may want to have it tested.

Good luck with some time and a little work you will find it.

 

What Jeepen said...

If the jumpstart does the trick then the battery could just be wore out, or in need of a session on a battery charger rather than just hoping the alt will do the trick.

Here's a little troubleshooting trick if it won't start--
Turn on the headlights--if they come on the battery at least has some juice, depending on how bright they are
Try to start--if the lights go off(or very dim), the battery is dead, if the lights don't go off, it is a switching problem, as in a bad starter relay or ignition switch. This can help narrow down a bad battery or bad relay/switch problem very quickly.

Might go without saying, but you want to make sure your battery cables are in good shape and have good connections at both ends. Excessive resistance could cause starting/charging problems.

If you do find you have a short and need to start pulling fuses to identify it, don't forget to check the battery cables. I had a chevy where the pos bat cable rubbed against the edge of the frame, and was having intermittent short problems from frayed insulation. Often on turns it would cut out and die, finally found it when I jiggled the cable while it was running and got the engine to stumble...

 

If she starts every time with a jump, I'ld change the battery. sounds like it is trying to go south for the summer, and doesn't want you to come along.R)

 

You can also use the amps scale of your DMM - the meter goes in series with the battery and battery cable, just like the test light. This will give you a number in milliamps (hopefully) and is a more informative test than the test light.

 

I was wondering how to do this same thing. But I wonder if the drain would be larger than what a DMM can handle before popping a fuse (hopefully not just toasting it) My DMM has a 10 amp setting. Think the drain could be larger than that, especially if his battery seems to drain so fast?

 

I was going to mention the DMM option, which is what I usually do. 10 amps SHOULD be enough, just make sure your meter is fuse protected, I THINK most are, my radio shack one is, however on the smaller scale sometimes they are not. You are measuring amps so I recommend getting help if you are electrically challenged.
Probably not a problem on Jeeps, but remember to pull the bulbs from any underhood lights or dome lights that may come on automatically when you raise the hood or open a door. Stereos with memory also draw power all the time (if wired up correctly)

 

Maybe when you get home for the evening disconnect the battery. If it is dead in the morning, your battery is probably bad. If not, then start your diagnosing.
You could have more than one problem, bad battery, weak charging system, continuous amp draw, all with the same end result, dead battery. Start with the easy stuff, like the battery and go from there. Let us know what you find, Good luck!

 

10 amps is a lot, even though it's only 12 volts. You'd definitely see a spark whan you touch the cable to the post - think about the spark you'd get touching the cables together on your battery charger. Still, it would take 7.5 hours to discharge a 75 amp-hour battery (new Optima) at that rate.

Good tip about disconnecting the battery - I'd bet on the battery being internally shorted and discharging itself.

Another problem may be that you aren't charging the battery for enough time. A trickle charger (a couple of amps) will take days to charge a fully discharged battery - even at 10 or 20 amps, a full charge will take overnight.

 

take the battery to an auto parts store and have it tested. I've seen that story a dozen times if not more, and it's often the battery.

 

Battery is less then a year old and all the battery cables are replaced. I'll try using a charger on it and go over the system with a volt meter. It looks like the guy before me patched together the wiring harness with electrical tape so it might be in there. I'll pull fuses with it hooked up to an amp meter (a buddy of mine has one) and we'll see if I can find it.

If we don't find anything tomorrow in the electrical system we'll pull the battery and probably the alternator and have them tested.

 

I'm betting alternator. Check your voltage regulator. Make sure it's wired correctly. Make sure some PO didn't jumper wires causing your alt to be excited with the key off.

http://www.earlycj5.com/tech/wiring/pdf/CJ_With_V6.pdf

Just not much else on an ECJ5 that would drain a batt fast (within a few hours) without you seeing/hearing what is doing the draining.

 

R) Pull the ground lead off the battery. Stick it back on after charging the battery. If you get a spark doing this with the key and all switches in the off position, then you have a short in the wiring and get to chase it down.
Any circuit that doesn't go through a switch or the ignition could be the culprit. If you are still running the original cloth covered wiring in your ECJ, then bite the bullet and replace the whole thing.
Any place the wiring comes into contact with the body or frame will be a potential short spot from rubbing. Wiring shorts will make your hair fall out, and your noodle go limp from frustration. Good luck, and have fun.

If you charge the battery up and don't get a spark hooking the ground back up, I'ld bet on the battery being bad. And you can get bad ones new from the store.

One thing to check, if you don't get the spark and the battery will supply good voltage to the head lights is the starter selenoid. After a long life these little beauties will build up carbon on their contact areas and act like the battery is dieing. Jump starts seem to put through enough extra to overcome the carbon buildup. Just replace or rebuild it. (even more rare is the windings in the starter motor going bad.)

 

X2 on the alternator/regulator route. Contacts on the regulator may be remaining in the closed position due to contaminated or corroded contacts, energized field, or weak spring. May not apply to your case, but often times this was the gremlin in the system when I diagnosed customers charging systems. Since the former owner rewired the system, (I bet also he was wiring challenged) I would thoroughly go through the wiring system using a repair manual with the wiring schematics. Also, check for loose connections at ALL points, it could be as simple as that. A loose connection will prevent the juice from flowing. Good luck.