The rating you want to look for is "reserve," or the Ampere-hours (Ah) rating. The higher, the better (CCA is "Cold Cranking Amps," and is a rating for high current draws for short durations in cold temperatures. By the time you're winching, your battery ain't cold anymore...)
As far as not using the side posts, I have two groups of sources on that...
1) Exide, Interstate, and Optima have all told me that side posts are not to be used for sustained drains over (number reduced slightly by me) 75-80A. You run into problems with heat, and you could end up melting the screws loose or melting the pads right out of the case. They're fine for accessory draws, but not for sustained high-current loads. Winches are right out. (Lighting and such is OK - keeping under the limit.) Connect winches to the top posts, per battery manufacturers.
2) Warn & Ramsey engineering departments (I've spent some time on the phone with them) have told me that winches shouldn't be connected to the side posts - for the same reason. Since your average winch has an instantaneous draw under load of anywhere from 250-600A, heat can become a
huge issue!
Yes, I've spent some time on the phone with these people (it was the only real way to get hold of the individual I needed to talk to, in each case. Fortunately, I speak engineering fairly well...)
This is direct from the manufacturers!
Why are there side posts? In the mid-1980's, GM had a brainstorm to use posts on the side of the battery to lower the hoodlines of some passenger cars (for aerodynamics and for styling cues.) I don't think they use it anymore - if your starter motor is getting old or weak, it draws more current than it's nominally rated for - which heats up the battery posts, and can cause trouble. The typical starter motor for a gasoline engine draws 140-300A, depending on engine size and compression (four-cylinders are down around 140-175A, while a high-performance high-compression V8 has no trouble hitting the 300A mark. Diesels are another story entirely - why do you think they have two batteries?)
To recap, here's the sources:
- Exide Batteries
- Interstate Batteries
- Optima Batteries
- Warn Engineering
- Ramsey Engineering
All of them have told me - directly - that the side posts should not be used for high loads, and damned sure not for winching (especially if you winch frequently.) They weren't a good idea for starting loads when GM did it - but they did anyhow for about ten years. As I said, I don't think they do it anymore. If you've not had trouble, you probably did get lucky (short, infrequent pulls are likely.)
