Deep cycle batteries are used on battery back up sump pumps too. The guy at the battery store said they are able to handle the wide swings of being charged and run down, maybe the don't develop a memory, he didn't say. But with battery backup sump pumps, they are hooked up to a battery tender to keep them topped off. If I understood him correctly, they are just a little tougher. That being said, I buy the cheap lawnmower batteries for my fence charger and run them down and charge them back up, even though the same guy said I shouldn't because they would last very long. Dollar for dollar, the cheap batteries serve me better in the fence chargers than the more expensive deep cycles. Go figure!