So I just picked up this rzr. Built a fresh motor for it. Runs great. I knew the battery was old. I put a new battery in it. I charged the new battery it’s at 12.9 v. When I go to crank, starter just clicks like it’s dead.checked voltages while cranking. With the starter connected, I’m only getting like 5v while cranking. When I unhook it, at crank mode, I got 11.9v.But as soon as I hook up a jump box, it fires right up. During this process it stopped charging..any help with what the next thing to check would be great!