How do you recharge an ATV battery?

The best way to charge any dead battery is to charge with low amps over an extended period of time. The best device for this is what is called a "trickle charger". You can find them at any automotive store. Make sure that while charging the battery you disconnect it from your vehicle. It is also best to sit it on a table, preferably on wood, so as to not act as a ground that will drain the battery even more. Also, once you're battery has drained completely, it won't have the same strength as a new battery, so make sure you turn off any additional electronics when the vehicle is not running so the battery doesn't die completely.