Quote Originally Posted by Yendor View Post
Without a battery positive connected to the B+ terminal of the alternator and the negative connected to the housing of the alternator it's very unlikely to start charging.

It is possible with the battery connect as above and the warning light circuit (or trigger/field as per the diagram you posted) not connected for the alternator to start charging. But you would need to find the sweet spot in the RPM.
Yes, if I learnt it correctly from your posts, the wiring of my proposed home made generator has to be almost like the wiring in the wiring diagram to make it useful, including having a battery.

So, "self excitation" of modern alternators is NOT possible without the initial "flash" of electricity into the trigger/field/exciter wire.
After that, self excitation can continue, provided I get the correct RPM right for that.