Re: Generator ?
If the generator puts out AC, then the diode is necessary. If the generator puts out DC, then no diode is necessary.
In reality, Generators all put out DC, and Alternators put out AC. AC stands for "Alternating Current". Sometimes people refer to Alternators as "Generators", and that's where the confusion is.
Some alternators have built in diodes, and put out DC; cars are like that.
I have a bicycle generator and lights, but I haven't checked it out yet. Lights will work on AC, but batteries will not charge with AC.