[rotorwrench]

Alternators also have residual magnetism in the rotor & stator. This is similar to the residual magnetism in the generator field pole shoes. This is generally what excites the field to start with. This is why a lot of self excited alternators have to have higher rpm to come on line when they are set up as a single wire connect. They self excite much faster when the voltage sense wire and the warning light system are connected as was originally intended. The diode bridge serves to limit full AC output to a DC equivalent during operation and prevent return flow from the battery after shut down with key off. Another diode in the output line certainly will not hurt anything but it is redundant.

A battery has a tendency to sulfate if not used for longer periods than 14-days. If a person lets it set unused for a month or longer without a start or a deep cycle to knock the sulfates off the plates then it won't last very long before the build up is so thick that it won't come off.