2006 Yamaha Rhino 660, Explorer, new Progressive 429 Shocks
Nice rig, expensive reservoir shocks. Stock they don't use an alternator and running the aftermarket light bar and stereo will likely drain the battery and that's probably why it has a car battery installed. Does it still a starter battery under the cover? You'll likely have to recharge that car battery with a plug in charger often, don't let it drop below 50% charge.