Short Draining the Battery?

First off some background. I have a 2001 auto, 4.0 XJ. I replaced the battery that was in it when I bought it back in Dec.'06. I put in an Optima Yellow Top. I had no problems with it for a good while. I hooked up a pair of hellas the day before a wheeling trip in July '07. I don't use this XJ every day since I have another to drive everyday. I try to run it every other day or at least every two days and pretty much all weekend. In August after it had been sitting most of the week, it was quite dead. I returned the battery thinking it was faulty and got an Optima Red Top. The only other electrical thing that I have installed is the wiring for my electric locker on my toyota rear end. I wired that up in Sept. I went to go start it Thurs and it had been sitting all week since sunday and it was really dead. Not even the dome lights went on when I opened the door. So I had the battery recharged all day friday and went and put it back in. Before firing it up, I disconnected the hellas because I thought that they might be the culprit. It fired right up. The voltage gauge in the jeep said it was between 11 and 12 before firing it up. I drove it around town a bit, stopped at a store shut it off, went in, came back fired right up and went home. When I got home the volatage gauge in the jeep with it not running said it was right at 12. I tried to start it today(Sat.) and it is just as dead as the first time. No dome light, nothing. I tried jumping it, it would not turn over. My question is, assuming that the hellas were the issue and they drained the battery dead, could the battery have been damaged and even though it got charged up it wouldn't hold a charge? So that maybe I fixed the battery drain problem, but since the battery was toast it just died on it's own? Tomorrow I am getting a new battery(not an Optima) and going to test the alternator and run some other tests(using a test light and pulling fuses to see if there is still a short somewhere). Anyone have any suggestions? Any help is very much appreciated. Thanks.
-Matt

I don't have any help for you, just posting because I have a very similar problem:

1998 Cherokee 4x4 4.0, no add-on lights or anything electrical for that matter. I bought the Jeep earlier this year and have gone through 3 batteries already. I noticed the dome light would flash erratically occasionally, not every time out. Also the idiot light for the door ajar was on when the doors are closed, and of when there is one open, backwards obviously. I replaced the battery, everything seemed fine for a couple months, then it slowly died. I got it replaced with a new one, and it slowly died. I got it replaced with another new battery, drove back to Autozone and they tested the alternator, found it putting out around 72 amps, which I believe is very low, not enough to charge the battery. Drove back home and haven't driven the Cherokee in two weeks. Go out today to drive it and the battery is stone dead. Just from sitting out there not being driven. Obviously something is draining the battery when the vehicle is not even on, but where do I even start to troubleshoot this?

you definitely could've drained the battery so low that it won't hold a charge long-term. try a known good battery, or have that original load tested and if it passes, put it on a trickle charger for about 24 hrs and try it again. i just read the part about charging it "all day friday". how long was that? if it's saveable, it'll need a looong, sloooow charge to bring it fully back to life.

I don't know if this pertains in either case here, but my Camaro battery used to drain out if I didn't drive the car for two weeks or so. I hooked up an amp meter between the pos battery terminal and the pos post. With no key in, I had a pretty high constant drain. I know there should be some slight current flow, as you have memory for computers, radios, clocks, etc. Anyway, I pulled some fuses one at a time to see if I could find something significant. Turns out my biggest draw was the alarm system. Even though the alarm was never armed in my garage, the system is always powered up, waiting for input from the keychain remotes. I wound up putting an inline toggle switch on the power feed to the alarm, and when the car is parked for long periods of time, I go under the hood and switch it off. Haven't had a battery problem since, and I still only use the car maybe once every two weeks, you know, when I get the need for speed........
Also, if you have a door ajar problem, I don't know how it is on the Jeep system, but on my '02 van, there are some things that are still powered up after you turn off the key, until the last door is opened/closed. So what I'm saying is somthing might still be drawing a lot of power while waiting for the last door to be closed. Could be power locks, power to the radio, headlight auto shut off, etc. I'd start out checking into the door ajar system.
Just throwing out some ideas, keep us updated.

Ok I did some tests today and am still stumped. First off I got a new battery and put it in and it started right up. I got a volt meter and tested the battery to make sure and yup, 12 volts coming right out. So I leave the positive cable hooked up and unhook the negative cable. I use the volt meter on the negative cable and the post, it says that 12 volts are coming out. Is this normal? I would think that it shouldn't be putting out full juice, but I am an electrical noob. So, I tried pulling fuses with the volt meter still hooked up and could not get the voltage to go down. I also unplugged the alternator and still nothing. The only things that I have wired up recently(this year) have been the lights and the locker, which are both disconnected. I am thoroughly stumped here. Any suggestions? Thanks again.
-Matt

What kind of voltage tester do you have? You refer to 12 volts. With vehicle not running it should be around 12.8 volts or so. With vehicle running it should be around 13.8 or so. If you know how to set your voltage tester meter on amps. With the vehicle off disconnect the negative battery lead and check the amp draw between the battery cable and the battery negative post. With the computer you are going to get some milliamps. If you are reading over one amp you have something staying on that should not be. If you don't know how to read amps. Get a friend that does to help you out.

So 12.8 volts is normal to be coming off the negative battery cable when it's disconnected? My Dad has a multimeter that can read amps, but I think I will buy one since it seems like it is very handy. Thanks for the input.
-Matt

yes, a fully charged battery at rest should have about 12.65V. You are only reading the available voltage the way you're checking. Checking Amp. drain is not too difficult and quite effective, but if you would like to check even cheaper, use a 12V test light and hook into the same place. The light should be VERY dim if no shorts exist. If it's fairly bright, start pulling fuses one at a time until the light dims.

Items other than original fused circuits to check include the accesories installed (verify the relays are wired correctly) and the alternator (if one or more of the diodes are faulty they will allow current to flow back through the alt. to ground and slowly kill a battery, yet still give the illusion of a functioning alternator. )

--Shorty

Ok I got a multimeter today and tested the amp draw from the negative battery cable to the negative battery terminal. This is with the hella lights and the electric locker unhooked. I got .30 amps. So then I hooked the locker back up and tested it again. It jumped to just over 11 amps! I had no idea that it was drawing that much power. So I pulled the inline fuse to the locker and tested it again. Same .30 amps as the first test. So as a quick fix for now until I can find a way to make it not draw so much power is that I made the inline fuse holder easily accessable from the dash so I can just put the fuse in when I need to power the locker and pull it out when it's not in use. The wiring kit that I used for the e-locker was from Inchworm Gear. This is the diagram that was provided.
The only thing that I found when following this diagram was that I had to take out the resistor to make the locker function. For some reason with the resistor in place, it would get burning hot, but nothing would work. The other thing that I did differently from the diagram was instead of the power wire going to the fuse panel I have it wired to the 12v cigarette power outlet, same thing with the ground. Could this be why it is constantly pulling power? What I did was cut the cigarette outlet off and used the power and ground wires that ran to that and tied them into the locker kit. I haven't tried hooking the lights back up to see if they are drawing power too, but for now they can stay unhooked. So I think I've solved my mystery drain, but I still have a few questions. Does the ECM/radio/other accessories that need a small constant power supply pull the full 12.8 volts and there are resistors or something that reduce the power to minimal? Does anyone have an idea how that works? Thanks to all for your input, it has been a big help.
-Matt

XJ_Jeeper01 said:

Does the ECM/radio/other accessories that need a small constant power supply pull the full 12.8 volts and there are resistors or something that reduce the power to minimal? Does anyone have an idea how that works?
-Matt

Click to expand...

Yeh, the radio/ECM still need the full 12+ volts when the key is off to keep memory settings, clocks, etc. Any reduced voltages are generated within the unit as needed. The thing is, they are supposed to be low current draw (unless of course if something fried and is shorted), so with average day to day use, they won't kill your battery. Lights and motors are high current draws, and will empty a battery pretty quick.
Now, you mentioned the "12v cigarette power outlet". Is that always hot in the '01s? I know in my '88 the cigarette lighter power is dead with the key off.

I am not sure if the cigarette outlet is always hot. I want to say no, but am not entirely sure. I'm puzzled as to why the locker is drawing so much power. Thanks again to all the responses, I have definitely learned something.
-Matt

I'm not familiar with the electric locker, so I am guessing at this. But the switch that controls it, does it spring back to the center (off) position after you lock or unlock the rear? Or does it stay in one position or the other? If it's staying up or down, it's probably supplying constant power to the locker motor after it has completed it's movement. If that's the case, you would need a "double pole-double throw-center off-momentary" switch. Without seeing what goes on inside the Toyota harness (and motor assy), it's really confusing the way they have the rest of the wiring hooked up to the switch. From my experience, there's an easier way to hook up a switch to control a motor's direction. But, like I said, I really don't know what the rest of that harness is doing.