I'm late to the dance here but for what its worth I disconnect either battery terminal fairly frequently on my 84 GMC and my 77 Ramcharger and then start turning on all the accessorys til it dies to check its charging/output under load. Never had a problem. Had somebody cross the + and - on my old ladys car giving it a boast and that took out some diodes or something. Never a problem with disconnecting the battery, other than sometime I need to reprogram the radio. Im in my 40's and I just copied my dad. If I have a meter though I will use that instead, but more often than not I have a 1/2 wrench handy.