I don't think I've ever seen a set of 6V headlights pull more than 20 amps or so, (120 Watts, not amps) even on high beam. With a 30 amp generator, almost all the gen output will be consumed by the headlights and ignition, leaving very little capacity left over to recharge the battery. You should see the ammeter deflect very slightly to the "charge" side at highway speed with the high beam headlight on.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!