Off-topic battery stuff.

[FotoPlasma]

I'm sorry for being so off topic, but I figured this would be the most appropriate place to ask my question.

Recently, my area (San José, California) has been getting more than its fair share of power outages, and I've been wondering about investing in a UPS for my computer, and a few other things. I recently had the chance to open up an older (but not ancient) UPS, and was slightly disappointed when I found a 12V 2.2Ah battery.

Now, FIRST has given us 18Ah Exide motorcycle batteries in the past, so I've been thinking about replacing said 2.2Ah battery with a cell which has more capacity. After the thought of pilfering a battery from my team crossed my mind, I began wondering about the plausability of using a typical car battery as the cell of a UPS.

When researching car batteries (mainly on a trip to the local Costco's automotive and handtool section) I saw many references to a "Cold Crank Amperage," being the amperage said battery could output at 32degF with no amount of time appended (so as to calculate Ah), but I could never find a description of any of their batteries in Ah, so I couldn't really tell what I was looking at.

If anyone could enlighten me on any of the technical aspects of lead-acid cells, or even general battery theory, it would be much appreciated, along with the specific feasability of replacing the standard cell of a UPS with that of a higher capacity.

Thanks in advance.