We happened by a Sam's Club today, and I had a quick gander at their battery department.
Previously I'd been to WalMart and found a 125AH 12v deep cycle battery for $74.95. It was the only battery that had this high of an AH rating. Most, even with several hundred CCA's, only had maybe 35AH ratings. That goes along with what the experts on here say - "starting" batteries are for short bursts of high current, not deep discharges. But I digress.
Sam's had some "commercial" batteries that were about twice the width of your run-of-the-mill car battery. Surely these would be good candidates, some with upwards of 1000 cold cranking amps. No AH ratings on these, so I moved along.
Then I saw them. "Energizer GC-2" Golf Cart Batteries. Holy Cow. I have never seen a battery that big. It was about 50% taller than a regular car battery and over twice as wide. It had obviously-removable caps over all the cells, and it weighed a TON. Then I looked closer - $67 for 225AH! Holy Cow again!
Then I saw what REALLY made me appreciate the difference between Golf Cart and every other battery in the whole place - This humongous beast was a SIX VOLT BATTERY! So to get your 12 volts, you're talking about a battery footprint that is literally FOUR TIMES LARGER than a regular car battery.
I've seen Ghurd on here mention the weight to people. Yes Sir. He's absolutely right. You cannot mistake these things for anything else.
So if you're like me, looking through a shelf of ordinary-sized car batteries, comparing all the labels, ratings, deep cycle, marine, whatever... STOP. You're not even close. Look for something that makes your back hurt just looking at it. Look for the "I need an associate to carry this for me" kind of battery.
No matter how much you guys who are "in the know" describe the right kind of battery, I never got an appreciation until today!
By the way, they also had an 8v version. Don't see how we could use that. But you 24v or 48v guys might be able to get away with fewer batts that way.