I have the stock battery as it came. It starts the bike and runs the winch. I bought this 20ah sealed Battery off Amazon. It powers my 2 amps for stereo currently. That way if the tunes go dead, the 800 wont be. This thing has been great. I listen to it while I'm working in the garage on the bike or other projects and get some a lot of hours. Also just installed one in a speaker cooler a guy had me build for him. When its in the garage, it is hooked to a battery tinder so its ready to go whenever I am. I did not want to spend the money on an isolator because of some other mods I am saving for. A friend of mine took a look at mine and did the same. Only he is running a stereo, 22'' Led light bar, and 2 4'' spots on the back of his rzr. He has been fine so far because we do not do a lot of night riding. But when I add my led, I'll probably test my battery's life before I spend it on an isolator.
But I again, its 1/8'' too big for under the seat. I want the storage up front back plus with it under the seat, I can get the roof to fit just a tad better with power wires running out the back instead of the front