CB, I have just looked over your reply. Please note right now after me being a light weight and having just found I can get Shlitz Beer with the retro Classic 1960's Formula, I can just reply in overview.
The diode would be in series between the generator and the battery so that when you’re at a stop and there is no current from the generator flowing, the battery does not charge the generator. Funny I said that, but I suspect you know that a generator would not like to get a charge.
A few more things are that the diode will probably have a forward voltage that will drop about 0.6 volts so that the generator has to put out enough to overcome both the 0.6 volts plus about 1 volt above the battery to allow for charging. If it were a 6 volt battery and 6 volt generator that would not do, it would have to be 6 + 0.6 + 1 = 7.6 volts output from the generator or higher.
Thinking of what could work is I’m remembering that they were 6 volt generators, so that two just using three of the high amperage hour AA rechargeable nickel metal hydride cells (like the Enercell 2500 mA) in series for nominal 1.2 times 3 = 3.6 volts could work in a scenario.
The diode also must have enough current capability for the job or it will burn out. This is where a current limiting resistor can be added also in series with diode so that just allows for a trickle charge of the battery and the diode is saved as well from over current as it does get the same current through it.
I’d have to look at the specs of the parts first before getting any of the parts to know it would all work out. I just thought that Nuts & Volts Magazine I have subscribed to or ARRL probably have a circuit worked out. I’ll check on that. But since I was going here is the rest in a pinch.
6 volts minus at most 1.25 top off volts times 3 = [6-(1.25*3)] = 6-3.75 = 2.25 volts 2.25 volts > 1.6 volts by 0.65 volts to spare.
With particulars not yet figured but can be done later for the components for the trickle charge circuit to the battery, using a handful of the real bright white leds would mean most likely the generator charging the battery would be enough never to have to take the batteries out and charge them with a home charger.
Though the huge bulbs if you could get them in a lower voltage so that they could work with the 6 volt tire rub gen in the above scenario would be fun to see operating full retro. Those dotted bulb surfaces for the light diffraction are such a charm, unlike the leds.
There is actually a way to overcome the problem if you really want the retro bulbs and the 6 volt gen and 6 volt or whatever came with the gen light set uses for bulb voltage that are too high to work.
This is a very small DC to DC converter that is about 15 or 20 dollars and is adjustable. If I remember right it took as small as like 3 volts and had a step up to as much as 20 volts with a little loss in current, but still efficient. It was rated at about 1 amp. No one could be the wiser why you had light output while idling!
Measure Twice
PS …. I’ll look to see what is already been done and get back to you
