Originally Posted by Nihon_Ni
I was taught years ago that Cessna used the Bendix switch for the master, so you cannot have the alternator on without the battery on first, as a safety measure.
Cessna has used a split master switch since at least the 70's, that mechanically prevents disconnecting the battery while leaving the master still on.
I am aware of over voltage events that have occurred and caused failure of a lot of equipment mounted in the panel, while experimenting with disconnecting the battery with the engine running and the alternator on line.
This was with older vintage externally regulated alternators. Point is, that depending on what your airplane has for an alternator, regulator and over voltage protection, disconnecting the battery on an operating system could be very expensive.