Battery light came on.

DJBassman · **Posted:** Mon Oct 09, 2006 9:43 am

Sunday, it was raining and cold here in the springs. I had my head & fog lights on. The fog lights are the mopar standard lights for the 06. The heater, rear defogger, radio and front and back wipers on. I was sitting at a light, with a long line of cars, so I was there for about 10/15 minutes, when the battery light came on.

I turned off all the stuff and it is now my turn to drive and the battery light turned off. I slowly started things again, and when I had all of it all turn back on, I was at another light that was about 3/5 minutes and the battiery light came back on. So I turn off the rear defogger and the fog lights and the light went out.

When I got home, I checked the battery and it was slightly low, so I charged it and it was fully charged in about 15 minutes. My idle is 600 RPM's. I know that the alternater does not charge the battery at idle. But I don't think running all the stuff I had should have been running off the battery, that the alternator, even at idle should have handled this stuff.

Any thoughs?

2006KJSPORT4x4 · **Posted:** Mon Oct 09, 2006 10:00 am

Same thing happened to me a while back, but I was sitting in a parking lot while mom ran an errand inside....not sure what the deal is except that maybe there is a large draw on the battery and the alternator then recharges it after we start to drive again...kinda worrisome though. It never happened on my old KJ and I left the key in the "ON" position so it would play music for about an hour while I watched and flagged a Porsche Club Race this past Spring...the battery light never came on...not sure what the deal is...maybe just need a better battery...Optima???

Jeepjeepster · **Posted:** Mon Oct 09, 2006 11:08 am

Ive got an optima in mine and Ive never seen the light come on. I got the 65watt fogs, stock silver star headlights(not stock but the same watts), two 55watt hellas and Ive never seen the light with all of those on and my sub. Some time Ill turn all of those on with the windshield wipers on high front and rear, both heated seats on high, and crank the heat up! That should pull some amps. :lol:

You could get your alternator checked for free at an advance auto or autozone. Alternators do no put out there full amps until the rpms go up.

Next time it does it, put the tranny into N and rev the engine up to around 1.5k-2k rpms and see if the light goes off.

If its cranking good then the battery should be fine.

spoonplugger1 · **Posted:** Mon Oct 09, 2006 4:06 pm

Have your alternator checked, the light comes on when it is not making enough power the run the equipment and charge the battery. It should be able to do that easily. You may have a bad connection, lost a diode in the diode trio, any number of things.

DJBassman · **Posted:** Wed Oct 11, 2006 9:10 am

Took the libby into the dealer to have them check out the charging system, everything was ok. The tech said that at idle, the altinator will not be able to keep up with all the things I had on for a long time, and would not change the battery at idle (even if I did not have all that stuff on).

so I guess it needs a bigger battery if I had to do the same thing again, in winter.

sleeve84028 · **Posted:** Wed Oct 11, 2006 9:15 am

What is the stock CCA on the Liberty battery? Isn't it only like 530CCA's? A battery like Optima or even a traditional Diehard /Interstate battery could provide more reserve power for situations like this. I just haven't gotten around to buying one yet but two winters ago we had a real good snow storm and when I went out to play in the Liberty; I saw the battery light come on so it's not like this is an uncommon problem.

DJBassman · **Posted:** Wed Oct 11, 2006 9:23 am

The tech said my battery was rated at 600 CCA. But, that is just to start the libby, after it is running the CCA doen't means anything, right? when I get the money, I will get a larger battery.

sleeve84028 · **Posted:** Wed Oct 11, 2006 9:26 am

CCA is for starting but it also gives you an idea of how big the battery reserve will be.

Say if you went from 600CCA to 700, you would have that additional power in reserve for situations when all of the wipers, seat heaters, HVAC, Radio, Full-Time 4wd, All lights are on.... Now we are talking about some serious drain on the little battery. Let me go find the stock CCA and some specs on it's reserve.

Edit: here is a link to the optima battery that fits the Liberty - http://www.jeep4x4center.com/liberty/Op ... iberty.htm

The Optima battery model number 34/78 (800) with top and side posts or the 34/800R with top only posts has the following

V=12
CA=1000
CCA=800
RC=110
L=10"
W=6.9"
H=7.8"
Wgt = 39bs

Much, much better than our stockers.

Jeger · **Posted:** Wed Oct 11, 2006 9:41 am

Cranking amps and reserve capacity are not directly related, although generally a battery with a higher CCA or CA rating will have a larger reserve capacity it is not guaranteed. Just make sure you check the specs on any batteries you are considering.

I like the optima batteries very well, they can really take a beating compared to traditional batteries, red tops are good, but I think the yellow tops are designed to run a load longer.

spoonplugger1 · **Posted:** Wed Oct 11, 2006 11:16 am

I wouldn't change batteries, I'd go to the next size larger alternator or maybe see if there is one size smaller pulley you can use to increase the rpm on the alternator you have. The pulley would be the cheap route.

DJBassman · **Posted:** Wed Oct 11, 2006 12:46 pm

according to the build sheet, I have a 136 amp alternator. If I get a bigger one (what would that be for the liberty? 160?), would that still not generate power at idle? that is where the problem was. According to the tech, the alternator does not generate power to charge a battery at idle, so it will not run extras either. I though that was ture for every car, idle does not charge a battery.

sleeve84028 · **Posted:** Wed Oct 11, 2006 1:41 pm

The Renny's come with a 160A alternator for the factory. You could try to find one or pay for a new one from the dealer and have it installed. But you are correct that an alternator doesn't generate full power at idle. Lets assume that an alternator puts out about 10% of it's total output at idle for the sake of math:

136 *0.10 = 13.6A

160 *0.10 = 16.0A

So you would see a increase of 15% for charging. This would be a nice gain and might cure the problem entirely, but the cost of a new MOPAR alternator will greatly outweight the cost of a new battery. That is why I mentioned switching out the batteries.

Thus far, I have not seen a company that produces an overdriven pulley for the stock 136A alternator. An overdriven pulley would be smaller than stock, making the alternator put out more juice at idle. This too could solve the battery light problem, but you would also need to switch to a smaller belt to compensate for the pulley change but this is still the cheapest option. If you have a lathe in your garage and enough billet aluminum on hand well... it's time to start selling a product.

DJBassman · **Posted:** Wed Oct 11, 2006 2:09 pm

ok, that is what I was thinking. It gets pretty cold here, so a more powerfull battery would be an all around solution. Besides, not sure if I will be on a two way highway, with a church letting out, a stop light, 150 cars lined up, frezing rain, oh wait... that just happened :roll:

sleeve84028 · **Posted:** Wed Oct 11, 2006 2:23 pm

Yeah you guys out in the midwest / rockies area are really getting some ugly weather. Over here in Michigan it's just going to turn cold and rainy tomorrow. No freezing rain / accumulating snowfall in the forecast.

Battery light came on.

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