Ya know, Bustedback always starts his replies to electrical problems with "Have your battery charged and load tested." Well I thought it's a good way to start, but it didn't always seem necessary. Well, I've changed my mind.

I have a 4 year old Interstate battery in my WJ that never failed to fire it up even at -15*F. Yesterday, my first start of the day was a slow crank. I was on the way to my mechanic to fix an coolant leak so I had him check it while I was there. Sure enough, it tested bad on the load test. The test needle started in the red zone and steadily dropped in seconds. I had had no problems even the day before so he checked the alternator output. It was varying from 13.75 to 14.25. An hour later I bought a new Interstate 650 CCA ($71 installed) and with the new head and plugs, the starter just barely engages and it's running. I bought it locally at a place called "Battery World". They will supply batteries for ANYTHING! They've been here forever.

So trust Bustedback when he tells you to load test your battery!

 

I'm glad to see you didn't go for the highest available CCA battery you could find. Those high CCA rated batteries tend to overheat and gas out after only a short time. High CCA means bigger plates. The battery itself is not any bigger so those bigger plates displace the acid/water inside the battery. The acid/water acts as a cooling system for the battery. Less cooling requires a lower charge rate. A 550CCA battery can take 40 amps of charging without an issue. A 1100CCA battery can only take about 15amps of charging before the heat becomes a problem. Bigger is not always better.

 

The one I took out was a 575 CCA and the smallest he had in that case size was a 650 CCA. It still has the vent caps where you can check the electrolyte level which I like. I haven't looked at this one yet, but the old one had about 2" from the top before the plates started. I pointed out to him the temp sensor underneath and he'd never heard about it. He did say it was a good idea. BTW, mine is a 1" diameter spring loaded button and was clean and not corroded.