After some pretty harsh sub zero temps fo over a week here in CO bout 3 weeks ago. My batt seems to be on it's last leg, But trying to pin it down.
If I do not run the XJ for a day or two she barely starts, crankin slowly.
My dash alt gauge then shows 14v> so I think it's charging. On occasion I have seen it read <13v then after driving go up to 14 dead center which is where it normally sits.
Put a voltmeter on batt and it read 12.71
Started engine at idle reads 13.62v give it alittle gas and only goes up to 13.73v and back to prev reading at idle again.
Odd though also is that after driving for 2 hrs she'll sometimes doesn't crank full at starting.
Alt gauge does not move dramatically when engine is revved high though it does move slightly.
?

Anybody have any advice ?
am feeling left out .....

Givvus some time...

As batteries age, they become less resistant to cold. Bear in mind that electricity is produced in a battery by a chemical reaction, and that the speed of a chemical reaction is highly dependent on temperature.

A common test, when I was growing up, was to take the battery and put it in the freezer for a couple of hours or so (sometime before the first frost of the season.) Take it out, and try to start your car with it - if it's slow, replace it.

Your battery is probably on its way out, and wants replacing as a result. The cold merely pointed this up to you before the effects of time would leave you stranded somewhere.

sounds like batt to me, just replace it, should fix all your problems. The voltage isent reading that high when it it is running cause the battery is shot.

Any parts store will LOAD TEST your battery for you for free. I would take advantage of this service. This test may very well tell the story.

not to hijack but what kind of cranking/ cca's are you guys using?

OP check the water level in your battery, could be low causing your problem. Only use distilled water to fill it.

From reading the complaint, 13.6volts charging isn't alot but it is enough for a simple XJ. Batteries go bad, they will take a charge then they won't, they will crank then they won't. Ussualy the older the battery the more crap floats to the bottom of the battery in which can short out a cell. 12.7volts is a fully charged battery but voltage doesn't equal amperage. Test the battery verfy that it is good before condeming anything else in the system. Because a Bad/Dead/Last Leg battery can pull alot of Amperage from your Alt to try and charge itself becoming a leach on the system. You can't daig anything correctly if your Battery isn't good.

The charging system looks fine, the battery is about to bite the dust though.

thanks for all the info
It is a stock XJ no xtra electrical fluff.
will do a load test at the local store first.
Cause if its the Alt replacing is not like the old days of muscle cars, right there on top, a 5 min job.
And that old battery debate:
Interstate ?
Die Hard ?
Ever Start ?
I don't think Optima is what they used to be .

Optima got crappy.

Any of the three you mentioned are good.

Cold can really take a toll on your battery, and it probably needs replacing, but if you do lots of short drives the multiple starts can take a toll on the charge itself,we have one that gets used for short running around, it never gets to run long enough to fully recharge the battery before it is shut off again, about every two weeks we have to give it sme help from a trickle charger or go drive it around for awhile to replace the juice used in starting it all the time.

did you check the water levels?

I've had good luck with Interstate, but I have a Wal-Mart battery now just because they were the only store open at the time. The only good things about Wal-Mart: Almost every crappy town has one, and you can enjoy the freak show of people while you're there.

water levels were good
replaced terminal connectors as well
then it didn't even crank so I think it bit the dust !
Will be getting new Batt
and update here later.
thanks