[Mike Peters]

I know pretty much nothing about powerhouse generators, but looked up a post from Tom Wessenberg, who knew everything about powerhouse generators, and he said that there is a set screw that needs to be loosened in order to adjust the 3rd brush on a three brush powerhouse to adjust voltage. But having said that, I would second the suggestion from ndnchf to just get a new battery and go from there. Working powerhouse generators are hard to come by, so don't risk damaging your generator.