Battery Dying overnight

[ab_slack]

I am looking for some general input. This is actually for a 94 Jeep Cherokee

We've had a problem with battery getting discharged over a relatively short period. Typically days.

I was/am pretty sure it isn't the battery itself, but after the battery had been hammered flat a few times and left that way for a couple weeks I didn't trust the battery. It has a new battery, it hasn't been allowed to go completely flat but it has gotten down to where there is not enough energy to crank the engine more than a few seconds.

Sometimes it goes a couple days, sometimes (like last night) it goes from fully charged to not enough to start the engine in about 20 hours.

Disconnecting the ground and looking at the load with everything off I am seeing 0.30 Amp. To me that is a bit high, but is a rate I would expect to cause problems after a week, not overnight.

Still I hunted that down, when I pulled the fuse marked for radio light, dome light, etc the current dropped down to 0.02 Amp. Okay maybe that is it. But I noticed a second fuse labeled for essentially the same thing. So I put the first fuse in and pulled the second. The same 0.02 Amp. I put both fuses back in and expected to see 0.30A, but with both fuses in it still shows 0.02A. Leaves me scratching my head.

Anyway that doesn't seem enough either way to cause the discharge as fast as it has been happening.

I also noted that with the door open there was a 2.5A draw. That seemed to bit high to me. Am I right that seems a bit high? Also despite the other fuses being labeled for the dome light, the dome light functioned in both cases when the fuse was pulled.

Other thing is that this vehicle has an after marked automatic starter and alarm. I suspect that is doing something odd and would like to pull it out as it has been more headaches than it is worth, but have no idea where to start looking. I see a bundle with some sort of unit taped up in the harness under the dash, but not sure if it is it and not sure what the make or model of the starter is.

Any thoughts or suggestions would be appreciated. I do know electrical stuff outside vehicles, but are uncertain of the norms in the vehicle and the odd things that typically go wrong.

 

[kimcrwbr1]

Normally you only have a few things that use full time power the clock, radio memory and computer. Pull the posative cable off the battery and check for resistance between chassis ground and the pos cable connector. Pull fuses and relays and you should have no resistance or infinity. Then start putting the relays and fuses in one at a time to find the shorted circuit. Anything less than 5 ohms is considered a direct short. High resistance is normal for a clock, radio or computer memory. Look for a direct short and then trace the wires it could be a relay stuck closed on fuel pump, computer ect just keep at it you will find it. I used to have a cherokee sport and the wiring in them is almost overwelming. Find the shorted circuit and trace it from ground back to battery pos!

 

[RonD]

Say a battery at 75degF will last 4 weeks with vehicle sitting power draw.
At 32degF(freezing) same battery would last 2 weeks(50%).
At 0degF it would last 1 week(25%)
Just an example, good battery will last a few months of sitting

So cold effects batteries, and it can be quite drastic when battery gets older

First check vehicle's system, it shouldn't need battery power after starting.

With engine running voltage at the battery terminals needs to be higher than 13.4volts and lower than 15volts.
Out of that range will cause battery problems, if it is VERY cold out then you may see 15.5volts but no higher.
A few minutes after starting engine voltage should start to drop under 14volts but stay above 13.5volts

Once you have confirmed vehicle system is not draining power when engine is running then you can test the battery.

Unhook battery over night, but test battery voltage after unhooking it and then in the morning after it sat over night.
12volt battery should be 12.4volts to 13.2 volts depending on age and state of charge.
Write down voltage then test it in the morning, should be the same.
If it has gone down then there is a short in one of the 6 cells in the battery, battery is self draining, replace it.

If voltage is the same then you start to look at what circuit in the vehicle is draining battery.
.03-.07 draw is usual for newer vehicles, yes, radio, clock and keyless entry/remote start are always "awake" and drawing power.

.3 would be too much, BUT........many newer vehicles have a higher drain for up to 30 minutes after key is removed and/or doors are locked, Ford has the "battery saver relay" that cuts extra power after 20-30 minutes, other manufacturers have similar systems and modules that take 20-30 minutes to go into "sleep" mode.

So you often need to hook up current detection and then wait 30 minutes to see if it drops to acceptable range.

Yes, the 2.5amp draw seems excessive for entry lighting, expected would be 1amp, maybe 1.5amp.

 

[enjr44]

The draw you are getting is too high. A starting battery can't take a constant draw like that. They are made to produce a high output for a very short time.

I had similar problem with an 89 B2200 that had an after market alarm system in it. There must have been a malfunction causing the extra draw. Finally found an inline fuse that powered the system and pulling it stopped the problem (and lol, the alarm system).

 

[ab_slack]

Ron, the battery is good still...in fact the battery that had gotten flattened a few times still holds its charge on its own. Your point about drain current being higher for a time is a good one, perhaps related to why I saw it go away...although I had been disconnecting and re-connecting battery all thru that time so I would expect a timer to reset.

enjr44, that is the sort of thing I kinda hope. I was trying to track it when it went away. I don't care about the remote start or the alarm at all. I just don't know where those things typically are wired in other than the obvious like they must be able to bypass the ignition.

 

[CajunPwnStar]

Mine started doing this yesterday when I saw this thread. Went out to go to the store, no start. This morning, no start. After work, no start. Alternator is putting out right at 14v, so now it's time to try and find what's drawing so much.

 

[bronco2fan]

Have you logged into jeepForum.com and checked there? I have 97 Grand Cherokee and that site has helped me more then once. Jeeps are way more complicated with electrics then most people realize. Mine was killing the battery and setting the alarm off randomly till I searched there and found out there was a switch connected to the rear window that was going out. Hope this helps a little.

 

[swifttony]

I initially thought that you had a bad alternator.

 

[CajunPwnStar]

I have the luxury of a charging system tester at my shop. Found my battery needs replacing. Double check for gremlins taking power and found nothing above threshold while it's off.

 

[RonD]

One free test is to take off 1 battery cable for over nite stop, doesn't matter which one.
Then hook it back up when you need to start engine again.
If it starts OK then you have a drain in the vehicle's electric system.
If it doesn't start then battery is self-draining, an internal short

 

[Mark_88]

I've been dealing with something similar and it is kinda baffling. I think the battery is getting old on mine but it can hold a charge for a week or so no problem...even cold weather. But then suddenly it is not able to turn over the engine and I need to charge it.

I thought mine was internal lighting but the only light I have connected is the glove box...and I can see if that is on or not because there is no trim panel where the airbag goes (96 dash in 88 Ranger). 

Mine is still a mystery...and I completely yanked out the third party alarm system that the previous owner installed (Viper). 

I'm still thinking mine is the battery but how do you test something that works fine for a number of days and suddenly stops working?

 

[RonD]

Check hood light, some Rangers had a light that came on when hood was opened.

Load test can tell how many amps a battery can hold, new battery is usually above 500.
You need 150 amps for starter motor to work, as a battery gets old it can't hold as many amps so even nominal drain can bring it down under 200amps and then you can get the click, click, click.

The click, click, click is because battery voltage is needed to hold the starter relay closed, to pass power to starter motor.
Starter relay doesn't need much but it does need voltage, when relay closes(click) starter motor draws the big amps and voltage drops down, if it drops too much starter relay opens(click) and voltage comes back up, then if key is still turned to START, relay closes again(click), and starter pulls the big amps and click again.

 

[Mark_88]

The Jeep may have a hood light but I know the 96 didn't have one and the 88 (original wiring) never had one...I was thinking of putting one in but decided against it as just another thing to mess up.

I also pulled the radio out to test for that but I remember you mentioned that the newer systems have an automatic power off after 30 minutes so everything should, hypothetically, be powered off.

 

[det107]

This is unrelated to battery discharge but I bought a 3 owner vehicle & the lights/radio/dash/etc was troubling. I bought a can of penetrating fluid to spray the fuse holders after checking each one. I even sprayed more inside for good measure. I also applied to every ground I could locate plus the battery cables. Believe it or not......No more headaches-