There are two main components most UTV's use for charging the battery, the Alternator (sometimes called a Stator) and a Voltage Regulator (sometimes called a Voltage Rectifier)
the alternator produces the A/C voltage... generally around 25 to 30 volts while idling and running, the Voltage regulator then converts the A/C voltage to D/C voltage through a series of Diodes and resistors and stuff i don't know much about, and converts it down to a low amperage usually .5 to 1 or 2 amps on healthy battery, but it is capable of providing anywhere from 10 to 20 or even 40 or 50 Amps, to run accessories. dependent upon the machine what the manufacturer designed for.
you will definitely need a service manual if you want to fix this your self, i did some research and it appears the HiSun Strike 250 is the same as the Massimo Gunner 250, so this should cover it for you.
It is a free download from our library here , or you can purchase a paper copy on Ebay for about $50 or one from a Hisun dealer for $100.