Will the Fun Projects magneto battery charger keep a battery charged sufficiently enough to sustain the use of a 6 volt spotlight on a non-generator Model T?
Probably so. Presumably a spotlight isn't on very long, like headlights are. But I would use an LED bulb. That draws a lot less current than an incandescent does. It's what I did with the HF trailer lights I adapted for tail lights. I don't do much driving after sundown, but what little I have done with them hasn't depleted the battery.
Steve I have the same arrangement except I used 6 volt bulbs in the lights.