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Battery Overheating?

Weasel

NAXJA Forum User
NAXJA Member
Had this issue 3 times where the voltage gauge drops, check engine light comes on and engine dies. 2000 XJ, 4.0, AGM battery.

One was last fall winching through some snow. We sat for awhile, popped the hood and started checking various things. After 15 minutes tried the key and noticed the gauge was reading around 10 volts, it had come up. Sit a bit longer and came up to 14 volts. Started up and turned around and drove home 45 minutes, no issues.

Same thing happened this weekend. After about 45 minutes of slower speed trail running Jeep died. Let it sit and took a hike around, after about 15 minutes started back up and drove another hour at moderate to highway speed with no issues. Noticed the battery was warm/hot this time around.

Happened once more that afternoon under similar slower speed conditions. Noticed the battery was hot to the touch and realized the upper coolant hose is resting on the forward edge of the battery. Found a stick to put between the hose and battery.

Dumped a bottle of water over the battery, cooled it down and started right up and drove home, about 1 hour no issues.


So anyone had this issue? Is the battery temp sensor going wonky or s the coolant hose transferring to much heat into the battery?
 
The only reason a battery gets hot is from charging or in most cases, overcharging.

Start the vehicle and put a voltmeter across the battery. If the battery is fully charged and everything is working fine, it should read around 13.4 volts.

Overcharging can boil the electrolyte in the battery. Pull the caps and make sure the levels are good in the battery. Use only distilled water to refill the battery.

The most common problem with overcharging is a bad voltage regulator or control wiring. On a Renix era vehicle, the voltage regulator is in the alternator. In later years, the charging is controlled by the ECU. Very rarely you will find an alternator overcharging on its own if it is ECU controlled.

Beware, overcharging can lead to the battery exploding and cause a fire, so get it fixed ASAP.
 
The 2000 XJ should have a battery temperature sensor. The code for it is 1492. The XJ should still run with it disconnected and the battery charged. Actual charging rate with it disconnected I do not know. When the sensor is reconnected, the error will go away on its own. I did not see anything abnormal on the dash voltage gage driving with it disconnected for several days but I did not check the voltage at the battery.

As old_man said, overcharging could be caused by bad wiring, a bad battery and in the case of the 2000 XJ, a bad PCM.

My XJ have been fitted with AGM battery. Those batteries like to be charged at 14.3 volts. I check regularly to verify charging do not fall below 13.8 volts with the AC on in the hot FL summers.
 
The engine bay can get extremely hot, specially when truck is stationary, as when winching. It is logical that battery in the engine bay will get hot. at least it is as far as a way as possible in there from the exhaust manifold, but it still can get very hot. Heck it is inches from the outlet side of the radiator.

Get the battery tested, test charging system, and assure clean tight connections on both positive and negative sides.

Good luck

ps there is some xj specific general electric issues and fix info here...

http://cruiser54.com/

XJs should have things listed addressed, general info on XJ grounding locations and such is found on the above link, and might be an issue you have
 
battery isn't overcharging and it's in good condition. No issues with the wires. Gauge on the dash doesn't dip below the 13.8/14. Runs 13.8 idling.

As I said I can drive it down the road and around town and have zero issues, run on slower forest trails not a speed and the engine will just shutoff around 30 minutes. Gauge shows 9 volts and won't restart. Let it cool down, voltage comes back up and starts up and off ya go.
 
Not sure how a bad battery temp sensor can cause low battery voltage (you measured 9V at one point).

Maybe the battery isn't good after all and has an intermittent open/short across the plates? Plates have soldered connections and cracked solder joints are affected by temp swings, thermal expansion/contraction. Can you temporarily swap in another known good battery?
 
Plus just because your seeing voltage doesn't mean your putting out any amps.
 
how old is the battery? I'd have it tested.
 
how old is the battery? I'd have it tested.

2nd that!

And at low RPMs the alternator may not be putting out sufficient to charge the battery.
 
Not sure how a bad battery temp sensor can cause low battery voltage (you measured 9V at one point).

Maybe the battery isn't good after all and has an intermittent open/short across the plates? Plates have soldered connections and cracked solder joints are affected by temp swings, thermal expansion/contraction. Can you temporarily swap in another known good battery?

Don't really know either. Drove it into town last night and back home, zero issues.

Thought was is the coolant hose is transferring heat to the battery. Battery heats up and the sensor tells the computer that it is hot and most be overcharging so it cuts the alternator voltage to nothing and kills the jeep.

But in that case the sensor wouldn't really be bad either.

Battery isn't super old, AGM. Not that they can't fail. But I can do a load test on it and see what it says.

I've had alternators fail and batteries fail but not like this before. Hard to explain why when it shuts off the battery is hot and after it cools down it will restart and run perfect for extended times?
 
Plus just because your seeing voltage doesn't mean your putting out any amps.

true as well, if it was putting out low amps and the battery was being de-charged I'm not seeing why I'd have any chance of restarting after letting it sit. Cranking over doesn't act like a partial charged battery. I can check the amp output as work as well.

Same with the voltage, the gauge seems to be reading correctly per checking with the multi-meter as best I can and doesn't ever show low voltage readings.
 
So updates, battery tested out fine. Load tested no issue. Went out and ran a real similar run, warmer temps and extended low speed trail riding.

Had no issues as the last 2 times. Looks like the stick worked or helped. I might trim the end of the hose to move it away from the battery a bit more.
 
Bump back, issues keeps coming up.

I changed out the temp sensor for the battery awhile back along with battery tray as it was broke. Rerouted the coolant hoses so they have an air gap between the battery as well. Also verified wiring and everything appears to be good and solid. Connections are clean and tight.

Thought it was all good but nope. It's happened again 3 times. 1 during snow wheeling on our Xmas tree run in early December and then again yesterday during our Easter Snow run but it did it twice on me.

Same as before, it's at low rpm (in 4 low) the engine will just cut out. Cycle the key and the voltage on the dash drops to around the 10v mark, let it sit and cycle the key and it will come back up to right under the 14v mark and then will fire right up and run until it randomly dies again.

Battery will spin the starter over really nice after it dies but doesn't seem to be providing any spark.

Fuel at the rail and pump kicks on as normal.

Now before I hadn't been driving the Jeep alot but since December it's been pulling DD duties so driven alot. Zero issues with any electrical systems in typical crappy winter weather including several weeks under zero. No starting battery or any other issues. Several time using the winch for snow removal at idle with decent loads and zero issues from the electrical side of things.

I did notice this last weekend that the battery was not hot as in times past, it was warm but nothing extreme.

Tempted to replace the alternator but really had throwing more parts without knowing if it's bad.
 
I would suspect the alternator. Low rpm's results in low charging. The typical alternator does not reach full output until about 1500-200 rpm's. Low output from the alternator depletes the battery and the PCM shuts down. The PCM requires proper voltage to operate.

I would have the alternator rebuilt locally with German or Japanese parts. Auto Parts store refurbished alternators are not rebuilt, and they have a substantial percentage of defective workmanship, and they often suffer from early failure. Cheap parts are cheap for reason.

The only charging issues I have had from several high mileage 1997-2000 XJ's I have owned is faulty alternators, and crappy batteries that only last a few years. In the olden days, batteries lasted longer.
 
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Thanks, I forgot about this again until it finally did it to me in town at O-Rileys parking lot.

I do have a couple places that do rebuilds locally but not sure what parts they use. I do see a couple places online that seem to have "upgrades".

DB Alternator
JS Alternator
Mech Man
Power Bastards
Pure Power

any recommendations?
 
Mech Man and Mean Green have been in business for along time. I would check Premier Power Welder and see if their alternators are sold separately.

My local alternator shop will rewind an alternator for higher output.
 
Is this problem solved?

Maybe I don't know what I'm talking about, but I don't think a normal good battery magically recovers from 9v back to 12v just by sitting. After all you have been through at this point, I would just try a new battery.
 
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