battery question

my jeep has side post battery terminals i see I shoud have top post anyway what is the group number? ex group 75 and such

next question does it matter what my cca's are? I can get one side post with 1000 cca's 800amps for the same price as the one that is actually called out for my jeep which is 720cca or something. The bat. that I have is out of a olds cutlass.

The biggest battery you can fit in the tray. But you have to be careful of the height (might be the reason for the side posts). It can hit the hood latch rod on the passengers side, or worse short on something metallic on the hood.
The battery hold down can also give you some trouble, whatever you do make sure the battery is tied down.
I've never had any trouble out of the stock size and rating. But have on occasion had to settle for what I could get, XJ has an odd sized battery.

The OEM group size is, I think, BCA group 58. Optimas are BCA 34, so I know that size will work as well (even with marine-style battery clamps.)

A note on side posts - if you check, you'll find that General Motors (they came up with the idea) doesn't even use them anymore. They came up with the side post idea to allow for lower hoodlines, but there were problems with the terminals literally melting right out of the battery case! Side posts can be used for light accessory draw - about 80-100A total - but overuse of the starter motor (~160-180A draw, intermittent) can cause them to melt loose, and using them for a winch (~200-500A draw, depending on winch make, model, and weight being pulled) can melt them out with the first use!

The BCA 34 will also fit under the early OEM battery retainers - I'm not sure about late models, but it will probably work with those as well.

CCA (Cold Cranking Amps) is a measure of how much current the battery can supply, at nominal voltage (12.6VDC,) at about 0*F (IIRC.) A higher CCA rating can help your starter motor crank your engine faster.

HCA (Hot Cranking Amps) is a similar rating, but at a higher temperature (I don't recall which offhand.)

"Reserve" is a rating of a constant draw, in ampere-hours. A reserve rating of ~80-100Ah is fairly typical (80Ah means you can draw 80 amperes for one hour, or one ampere for eighty hours, or any combination that will multiply out to 80 [40x2, 10x8, 20x4, 400x12 minutes] before the battery cannot maintain current or voltage. You're using your reserve when you're winching or when your alternator heads deep south on you.)

"Deep-cycle" batteries are primarily rated in terms of ampere-hours, and usually at a much higher rating than automotive "starting" batteries. Deep cycles are also designed to sustain deep drawing for long periods of time, while starting batteries are designed for a rather sharper draw for much less time. I've seen industrial deep cycle batteries with ratings up to around 500-600Ah at 12VDC (but they were rather large - larger than even BCA Group 27. Electric forklift batteries are usually rated in kAh - kilo-Ampere-hours, or thousands of ampheres per hour...)

I had an S10 with side posts, and they corroded so bad that I went to loosen the battery cable one day and the post snapped off. I never want to see another car with side posts.

thanks for the explanation.