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Weird defective battery

R

Rocketman

NAXJA Forum User
Location
Bolingbrook, IL
A first for me. Anyone ever have a battery that besides being unable to hold any charge it seems to be shorted to a point that keeps the vehicle from continuing to run, makes panel lights flicker and dim? A jump will start the vehicle but it wouldn't stay running? It is the battery because swapping it solved the issue. Put in a nice Optima Yellow.

BTW I'm talking about my wife's KJ V6. Thought it was the alternator, yanked it, tested it... OK. I have to say, I like the idler tension pulley on those. No bolts to loosen to remove the serpentine belt. Easy easy swap for alternators too. EXPENSIVE though. GLAD it was OK.

Oh well, anyone have any weird battery stories??
 
hey as far as im concerned if the battery fixed it, its all good.
a couple things to keep in mind:
1. batteries are recycled remaned. ect. so it wouldent suprise me to see a weird problem like that.
2. the way batteries are constructed: there are metal plates inside them and they do shed metal shavings so it is possible that the shavings filled up all of the bottom of the battery and reached the metal plates and shorted them out. when this happens, if you shake the battery you can hear some metal sloshing around in the bottom of the battery.

as long as it is on the road and it doesent do it again, its all good
 
The OEM batteries on the KJ aren't known for going any spectacular distance. I got about 3.5 years out of ours, which is a little low in my books. Just replaced it in December as we were in the middle of moving, and it lost a garage to be parked in over night....the cold weather started killing it pretty quick.

When I got my XJ, it still had the OEM battery in it. I'm the 3rd owner, and replaced it in April of 05. Do the math....a 99 model year vehicle, orig. registered in NYC, spent 4 years in the NYC NY state area (harsh winters, short distance driving), and was on 6, pushing 7 years when I replaced it. Didn't give me a bit of trouble and was showing no signs of failing. I only replace it because it was WAY over due, and as a preventative maint. thing.
 
I had one like that once. No, not a Diehard, but some parts store brand. Took it back and got a new one. Sometimes they're just defective.

I did also short the innards of a battery once, using too small a battery to start a diesel. It behaved much the same way.
 
This sounds similar to a problem I had. I can shed some light.

All modern computer controled vehicles have to have a battery to run. strange but true. The system voltage supplied by the alternator will not keep the truck running. Try it. start your jeep, and disconnect pos. or neg. terminal. Jeep will die.
Try the same stunt with a CJ. You can start it, pull the battery, and drive home. (Do not ask how I found this out.)
Last year, my battery started to go dead, and the truck started running progressivly worse, up to the point where it would not idle. Engine would crank fine, and start up. Idle at about 250rpm and quit. 'buddy of mine(a dodge mec.) said to change the batt. Problem solved. I have no idea how the computer isolates the battery voltage, but it can tell.

If you have a shorted out battery, it wouldn't suprise me if you can jump-start, crank, do everything, and have the truck die as soon as you let off the starter.
 
Last edited:
tbburg said:
This sounds similar to a problem I had. I can shed some light.

All modern computer controled vehicles have to have a battery to run. strange but true. The system voltage supplied by the alternator will not keep the truck running. Try it. start your jeep, and disconnect pos. or neg. terminal. Jeep will die.
Try the same stunt with a CJ. You can start it, pull the battery, and drive home. (Do not ask how I found this out.)
Last year, my battery started to go dead, and the truck started running progressivly worse, up to the point where it would not idle. Engine would crank fine, and start up. Idle at about 250rpm and quit. 'buddy of mine(a dodge mec.) said to change the batt. Problem solved. I have no idea how the computer isolates the battery voltage, but it can tell.

If you have a shorted out battery, it wouldn't suprise me if you can jump-start, crank, do everything, and have the truck die as soon as you let off the starter.
Click to expand...

My understanding here is that a battery that doesn't take a charge properly will result in overvoltage to the system. Add to that that the output of an alternator is native AC, chopped into DC by diodes, which makes for a very dirty signal, for which the battery acts as a filter. Chrysler systems seem particularly susceptible to this.
 
Yes, new late models require a charged battery to run the alternator and electronics. The electronics require a good 12V signal to run- a bad diode will even effect the injectors on a Renix ( I found out the hard way.)

Disconnecting the battery on late models to check alt output may cause an overheat or short out, so it's no longer the way to do it. Everybody, please use a voltmeter!

Added, a undercharged battery will also overheat - short the newer alternators, as there isn't enough to excite the windings fully, and the systems goes to full output trying to charge the battery. It's the #1 cause of "failed" new alternators, according to the suppliers. Apparently that 135 amp rating isn't continuous like the old 40 amp, its peak, like speaker ratings, and the alt is simply not built to do it for hours.

It's a new kind of world out there.
 
Ditto, don't pull the battery on a running fuel injected engine. The battery stabilizes the voltage and the electronics really don't like the raw, nasty voltage from the alternator. I've personally blown a Ford EEC by doing this. The guy who wired it didn't realize that the alternator charge wire goes on the battery side of the kill switch. He tried the switch with it running and the computer fried pretty quick due to the 40-volt dc spikes coming from the alternator. (Really, I blame a crappy Ford design on the computer).
 
The part about disconnecting the battery on a running engine wasn't suposed to be advice or a challenge to anyone out there. Kind of irresponsible on my part. 'Said it more to make a point then anything else.

Sorry about the mis-understanding. I'll go down with everyone else: don't disconnect the battery while the engine is running.

Matthew Currie: Interesting, never thought about over-voltage causing the problem. The Dodge guy I know never explained it, and I never asked.
 
Rev Den said:
Yes.

Die-Hard by any chance?

Rev
Click to expand...

Ya I know everyone hates Die-Hards and everything, but I must be one of the lucky ones. I have run down my battery many times listening to music in my driveway while working on it and it has never had any problems recharging or holding a charge. I'll definitely be going to Optima next though when it does die hard.
 
lawsoncl said:
Ditto, don't pull the battery on a running fuel injected engine. The battery stabilizes the voltage and the electronics really don't like the raw, nasty voltage from the alternator. I've personally blown a Ford EEC by doing this. The guy who wired it didn't realize that the alternator charge wire goes on the battery side of the kill switch. He tried the switch with it running and the computer fried pretty quick due to the 40-volt dc spikes coming from the alternator. (Really, I blame a crappy Ford design on the computer).
Click to expand...

So, was it TFI-IV, or the old DuraSpark?

Man, I hated DuraSpark the first time I worked on it. The ignition module was blown, but nothing electrical would work. Don't know who in the Hell came up with that idea, but it was probably the only electrical job I had on a domestic that was more irritating than early electronic-ignition Chrysler...

As far as DieHards, I've not had any trouble with them - I used to use them exclusively. My grandfather managed to get 22 years out of one (yes, he had the truck that long!) and I figured if it was good enough for that, it would work for me as well.

I'd probably still be using DieHards if I hadn't switched to Optima (greater power density AND a lighter battery.)
 
EEC-IV.

Looking inside the dead unit, the voltage regulation consisted of a single big 12-volt zener diode so any excess voltage was dissipated as heat. Once the zener cooked itself trying to clamp the voltage spikes, it failed open and let the voltage through to the rest of the board. Even fixing the zener didn't help since the controller chip and half the transistors were fried. Another 50-cents in parts would have given much better protection.
 
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