02 350 rancher not charging blowing fuse and regulator hot h

dont know what is wrong the battery is dead and the voltage regulator is getting extremely hot and i am blowing the main fuse (30 amp)

i tried a different battery but it is doing the same thing(although this batt may be bad as well it ame out of a friends 4 wheeler).
any body know what it might be or does anybody know how to test the regulator?
i would appreciate any help

p.s. if it is started with the battery disconected the lights are very dim which is leading me to think its the regulator but not sure i dont want to spend ther money for the regulator if it somethying else.
also does anybody know what other hondas use the same regulator

thanks