Any Electronics Geniuses Out There?

I need help with the last phase of adding turn signals to my bike. As on the factory models, I want to run them off a battery (6V) which is charged by the 10W brake light coil. However, I would also like to use the battery to power my headlight when I am at slow speed or stopped at a light, since the 22W coil puts out zilch at that time.


a four coil magneto - ignition, 5W tail light, 10W brake light, 22W headlight

a set of turn signals that I am going to convert to 6V bulbs, hopefully LED to reduce power drain from battery

An electronic flasher unit designed for 6 or 12 volts

a 6V sealed rechargable battery (UB 645), rated 4.5 amp/hours

a handlebar switch for the turn signals, lights, etc


When the bike is up to speed and the magneto is putting out sufficient power, I want the brake light circuit to charge the battery. During this time I want the battery completely OUT of the headlight circuit, so the headlight gets full power and voltage from the 22W coil.

When the bike is stopped, the headlight gets power from the battery.

The turn signals operate off the battery at all times.

I'm not sure what I want to do with the tail light. Suggestions appreciated.

This guy:

does something similar, but switches modes manually. I'd like a system that switches automatically.

You can see a wiring diagram for my bike on that link as well as how he added a battery into the circuit.

If anyone wants to figure this out for me, I'd be eternally grateful. It might help a lot of others out there as well.


Re: Any Electronics Geniuses Out There?

Does the magneto output DC? (I guess that would technically make it a generator.) If not, you're going to need to rectify its output before you can use it to charge a battery.

Re: Any Electronics Geniuses Out There?

Yes, the magneto output is AC. I know I'm going to need stuff like zener diodes, rectifiers, and such. I just don't which ones, their specs, or where they go. Electric theory and application is NOT my area of expertise, but I know enough about it to know that I DON'T know enough about it to design or build this circuit correctly. That's why I'm asking for help. If I can get a design, I can try to find someone locally to build it small enough to use in the limited space of my moped.

Re: Any Electronics Geniuses Out There?

Ben Van Zoest /

From past experiences the problem lies in selecting and procuring the components, one can't buy oncies and twoies mostly multiples of ten. The simples way is the use one of the brake light switches to turn on the 6VDC batt. via a 6V relay tapped in the 24W output, switching the batt. parallel to the existing light circuits and charge the batt. with a wall charger.

For directional flashers, I bought 2" flasher units at the TrueValue hardware store, however they have sealed in batteries. Too much monkeying with the little buttons, came in handy tho for tracking my dogs whereabouts on his nightly outing, clip um on his collar been working for a year or so.

Good luck, hope you find a solution to ur liking.

Re: Any Electronics Geniuses Out There?

Just a thought, but I know on cars, everything electonic runs off of the battery and the alternater consantly recharges it. An option would be to do something like that. Another thing is if im thinking right, if you hook your headlight wire up to the battery, then it should run off of the battery until the coil starts to put off more power than the battery, at which tiime the headlight starts to pull power from the coil. I'm not an electroncial engineer, but i know quite a bit about wireing mopeds.

Mountain Kid

Re: Any Electronics Geniuses Out There?

🇮🇹💦 Of the Loin /

I dont think you could do what you want to without using switches

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