Lawn mower batteries are generally all the same size and about $29 each at most Walmart and auto supply places. As far as differences, not sure but car batteries have more CCA than a lawnmower battery of the same size(if you can find one that size) and for the most part, lawnmower batteries tend to last 1-2 years max and then no longer take a charge for some reason. My Craftsman lawnmower had a Die-hard battery in it and it died after the first season. Sears replaced it free and now I keep a trickle charger on it, now going on second season and all is good (so far) My JD 332 diesel engine garden tractor / mower has a fairly large automotive type battery that is at least 4 years old and still cranks as it should. I keep a 12volt- 15 watt solar charger on it all the time, so far not a problem with overcharging or under charging.