It's under the airbox, so that has to come off first...loosen the 3 clamps at the rear of the airbox with phillips screwdriver, so the airbox can pull away from the carb boots. Then unhook the rubber strap at the front of the air box. You now should be able to carefully slide the airbox off the carb boots, and to the right side of the sled, without removing the breather hoses. You should now be able to see the battery, which is enclosed in a plastic case - from there you should be good to go. When reassembling the airbox be sure that BOTH breather hoses (a larger diameter one on the side, and a small diameter one on the bottom - hard to see) stay attached. The small one is critical...if it pulls off down near the crankcase fitting, oil will seep out of your engine - not good. The clamps are kind of flimsy wire, so the hoses can and will come off easily if you're not careful. Not a bad or hard job replacing the battery, just need to be aware of the above. Good luck and let us know how it goes!