MTFCA Forum

I am buying my first Model T this week. It is a touring car that was made in October of 1913 so it has a 1914 body style. The car was restored to be the way it came from the factory without a battery or electrical lights. I want to add a battery, turn signals and brake lights for safety.
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I have two questions about about the simple light bulb and diode setup that is commonly used to charge a battery from the magneto.
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Question 1
Can 2 LED bulbs be substituted for the single dual filament bulb most people are using? I was thinking I could mount the two LED lights in a hidden location on the front of the car to help people see me coming....if the lights are going to be on anyway, why not use them to enhance safety.
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Question 2
Just wondering if I should go with a 6V or 12V system. They have brake lights and turn signals for both 6 and 12v, but I was wondering which voltage the magneto system and the car's ignition system would work better with.
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Thank you.....Bryan

Bryan,
If you are running the car on magneto, and only use the battery to startvthe car, and use LED lights, you can probably run your car all season long on one battery charge. LED lights draw a fraction of the amperage if incandescent or halogen bulbs.
I'd go with 12v and squirrel the battery away under the back seat.
Keith

Bryan. Question #1 is NO. You can replace the bulb with a resistor of the proper size and wattage but not a led. The purpose of the bulb is two fold one is to act as a poor boy voltage regulator to limit current flow to the battery and reduce the possibility of over charging.. the other function is a charge indicator to let You know it is charging without the need for a amp meter. the brightness of the lamp is a indicator of charging current. Question #2. I would say 12 volts. since 12 volt leds and solid state flashers are more readily available. 12 volts will provide more power to the buzzer coils for starting on battery before switching over to mag. There is a vendor here on the forum that sell a 12 volt led replacement for gas headlights that looks good.

My 2 cents worth maybe less.

Thank You Jim....I was thinking the light bulb was used as a regulator and indicator, but was not sure. I have looked at several of these magneto charging devices and there are different bulbs and configurations used, but they all seem to be around 1.75 amps. I guess that also defines the amount of charge the battery will receive. I was leaning towards using a 12V battery, but your comment about the 12V LED light that could be used in an acetylene lamp is interesting to me. I was thinking about sticking with acetylene because the current draw, but a 12v LED replacement bulb might work better than anything else.

Thank you....Bryan

The bulb used by the Fun Projects "hot Shot" circuit is a single filament 1156. You absolutely don't want to replace it with a LED. The charger will work with both 6 and 12 volts - Like others have said, it's easier to find 12 volt stuff these days.

Be careful not to get too small a battery. To quote John Regan, the designer of the "Hot Shot" charger, "You don't want to charge a 10 amp hour battery with 2 amps since that exceeds the typical allowed charging current. If your battery has an AMP-HOUR rating stated on it then you usually try not to exceed C/10 where C is the capacity of the battery in amp-hours. Thus 2 amps (the charger's output) would be safe with a 20 amp-hour battery or larger. I'd look for a sealed AGL battery with a 20 Amp Hour capacity. They're small and affordable.

I modified the oil lamps on my 1917 with LED bulbs, headlights too. I have a brake switch that came with my disc brakes and the single rear LED serves as a service and brake light as well as illuminates the license plate. The Tail light is 1157-R19W6 (two brightness red & white side-Dual Function 25 LED.) Sidelights are 67-A15 (amber) while the headlight LEDs were given me by a friend and there is no number on them that I can share with you. My friend soldered brass washers around the single terminal on the bulbs so they would contact both terminals on the bulb socket.

Did 2 such conversions. Noticed a single filiment bulb was extremely bright at speed. Used a double contact (lighting both) bulb. The 2nd one i worked on had a 6v single contact. It wasnt in service long. was burned out. Replace with a double contact 12v. 1157?