Positive grounding of a PV solar system?

Who ever told you to use positive grounding is dead wrong. In these modern times, the negative terminal is grounded. Since the 1960's, even cars have used negative grounding. Either that person is thinking of current flow, which one theory is that current flow is from the negative side of the power supply, they might have been seeing if you would fall for a dumb joke, or are terrible confused. In any case, ground the Negative side, NOT the positive. Your panel, batteries and load should all be grounded together at the same place. Get a copy, or search the magazine on the web, of Home Power. If you believe no one else, believe the people who make a living installing PV systems. They'll tell you, ground the negative side of the system.