MakeItHappenCaptain - yes that's what I was referring to. I remember when learning to fly asking what the purpose of this placard is (not in POHs I apologise, it was a while a go and I can't remember where exactly I saw it). Except for the obvious eventual depletion of the battery - my instructor said it was more to do with if you turned the alternator ON in flight - then proceeded to draw on the blackboard the waves of alternating current sprouting something about turning it on with the engine spinning at say 2200rpm would create a large spike in current that would pop your relay/regulator whathaveyou.
We all prefer an explanation of any kind rather than no explanation at all, just wondering if anyone could back this instructor up. He was a good'n