Ranger 700xp charging

Ok so I have an 08 ranger 700xp... It has a new battery in it but when running it doesn't always charge. Sometimes you have to put a charger on it to get the battery to charge.. It will sometimes run at around 10 volts and run like crap. Other times it wil run with 14 volts and run great... Anyone have any ideas what to look for? I have checked all connections and all look good and are tight... Thanks for any help guys

Voltage Regulator? ... bad part is, I don't think there is any way to test them, sry, but that is the first thing that comes to mind.

It seems like if you have to running it won't be charging and you hit the regulator with a wrench a few times and it will start charging by it be a coincidence that it starts charging but I don't know