2000 WJ. Owned it less than a year but haven't driven in much since it was stored in a different state than I lived in. I am back in the state it is in now and I have been driving it for about a week. I popped the hood for the third time this week and noticed that there was white residue on the top of the battery. I took off the caps and the water was low surmising the battery had boiled over. I added distilled water.

I did a quick net search on the topic and it said the most likely cause was over charging. I have only been driving it for a week and have glanced at the volt gauge enough to know that the needle sits just to the left of 14 volts. I didn't notice it jumping around or moving higher. Battery is new. Cables look clean and tight.
My questions:
1. are these vehicles prone to have voltage regulators that fail over charging?
2. can over charging be intermittent? Or once the regulator fails it stays over charging.
3. What other than a failed regulator can cause over charging?

I am 65 and I have driven a slew of vehicles in my time. I have had generators fail, external voltage regulators fail, alternators fail, all stopped charging . I have never experienced over charging in all my years.
Thanks!

 

How many cold cranking amps is the battery?

 

675 cold, 845 cranking

The battery came with the vehicle. I didn't put it in.

Thanks

 

The reason I asked is because people always buy the battery with the most CCA they can find, in most cases this is not a good idea. The proper way to size a battery is to take the cubic inches of the engine and double it plus about half. So if you have the I6 it's 242 times two then add half. It's not an exact science, just a rule of thumb. So the proper size battery for the 4.0 would be around 575-600 CCA. Batteries with a high rated CCA have less water in them because of the larger plates inside. That water/acid acts as a cooling system for the battery. If the cooling system is smaller the charge rate for the battery has to be lower in order to keep the water from boiling out. So having a 1100CCA battery may be doing more harm than good.

 

This has got the 4.7 in it. I bought it from a repair shop that bought it from a customer. They put a battery, full brakes on the front, rotors back, a position sensor of some kind , upper radiator hose and battery cables. It only has 138,000 miles on it. It runs great . Only real issue is the heater. I have read here about the heater's in these blowing cold. Mine just blows lukewarm. Not enough to be effective. Based on the comments in YELP this is a good reputable shop. The battery fits the tray. I assume they know how to pick a battery. Up to now, I didn't know anything about battery sizing. I just bought what had been in there previously, or relied on the info at the place of purchase to tell me what to buy. I haven't heard from anybody else from the forum. I have to bring it back for them to look at the heater. I;ll ask them what they know about this.

 

Okay, here's the thing. On this system the PCM controls the voltage and charge rate from the alternator. Underneath the battery, there is a temperature sensor that tells the PCM when the battery is getting hot so it can cut back on the charge rate. This sensor is probably bad or disconnected. Most mechanics aren't aware it's even there. It looks like a small round button in the center of the battery tray. When this system works, it doesn't matter what size battery you have, the PCM protects it.

The build sheet on my '00 WJ 4.0 calls for a 625 amp battery, but it's a base model Laredo. I'm 70 and have owned this jeep for 3 years. I also owned a '97 ZJ for 2 years prior to this one.

 

Interesting. So there isn't any voltage regulator in the alternator? In my opinion. Bad design. Some vehicles get that white corrosion on the cables and in and around the battery compartment. I had it on an Isuzu once and it ate through the battery tray and part of the inside fender. I couldn't keep up with it and I couldn't get rid of it. I have read various theories about what causes it. Once it starts its almost impossible to get rid of. That stuff could eat that sensor or the wires and stop charging all together.I will lift the battery up and take a look.

 

I have just read up on the battery temperature sensor you spoke of. Before i go pull the battery. If I had had even a moment of over charging for any reason. Wouldn't I likely get a check engine light? I am looking at the evidence and made the decision that I had a boil over. I could be wrong about that.

 

White corrosion around the battery terminals is evidence of acid vapors leaking around the seal where the terminals come thru the case. In recent years, this has been all but eliminated by better seal design, BUT if you go twisting or banging on the terminals they could start to leak anyway. If you've got white deposits over the whole battery, I'd say you are right, boilover has occurred and more than once.

To stop the corrosion, use a paste of baking soda (bicarbonate) and paint it all over the battery tray and other stuff. When it stops foaming, rinse it off and do it again until it doesn't foam. Then use a good rust-stop paint like Rustoleum on the bare metal. I've seen battery acid eat right thru aluminum boat hulls because people didn't use a plastic battery box.

 

I did that already. My experience is this condition is vehicle related and not battery related. That Isuzu I spoke about. Had that problem regardless of what battery we had in it. And this is a new battery. I think it was put in and nobody has messed with the terminals since.

What made me think it was over heated was the white stains on the battery top and the low water level. What about my question with the check engine light? Would that over charge condition spark a engine light?

 

I don't think so. I just went through my list and didn't see one specifically for overcharging.