Battery draining fast

Took battery and alternator to local auto parts store and battery is good next tested alternator and it was bad . I also found out the extra green wire was later added and the original was cut off and screwwdown to the nut on the regulator . It was removed and terminated . I purchased new alternator and regulator . cleaned up all the splices correctly along with he after market radio that the wires were twisted with black tape connections .
The battery held its charge for four hours .installed new alternator and regulator with ground cable off and she started right up put tester on alternator and 11.64 volts directly at the terminal .
drove it around for ten to fifteen minutes and battery now tested just over 9 volts . questions could this be a ground issue ? I found another harness as I was cleaning up coming up next to the battery was a harness with what looked like a#8 wire cutoff and there are 3 to 4 wires that are taped to it that branch off in to the compartment.
it has a after market gound to the block . i checked the block for ground with light tester and it lit up . Does the regultor need to be grounded with screws thru the firewall ? I touched the ground cable to the negitive post on the battery with everything back in and no arch tonight so i may have fixed the short , but now its not charging.