MTFCA Forum

Looking at the hot shot charger pictured, I was wondering how it worked.
As currant comes from the mag does it go thru a diode to keep power from the battery from flowing back thru and demagnetizing the magnets? Also it looks like it has an 1151 single element bulb. Does that help change the ac currant to DC and reduce the voltage so as to not send a high voltage to the battery? There has to be something to do the magic.

This earlier post gives a bit of info, but the charger diode converts the AC to DC and the magneto current is limited by the type of light bulb .

https://search.app/sdsLFZAQyhAM7j2w8

FWIW - pulsating DC is noisy. It may be unnecessary, but in my car (12 volt) I installed a voltage "smoother" between the car wiring and Garmin power plug for my GPS. This is after I had a GPS fail with no explanation. Such "smoothers" are often sold to remove noise from the lines feeding add-on rearview cameras and the like. Cheap insurance in my opinion. I've provided a link to an example.

<https://www.amazon.com/Rectifier-Americ ... 34&sr=8-30>

I never noticed any noise from mine with just a diode and a bulb. If there was any, it was lost in the general noise from the rest of the car.

It simply converts the mag AC TO DC and the bulb limits the current going into the battery to try and prevent overcharging of the battery. I don't have direct experience with one so I can't tell you if it doesn't overcharge the battery or not. It's a very simple but effective design if you don't have a generator on your car. Automotive Battery charging does not need clean DC to charge. In fact the old FP voltage regulator used a bunch of power pulses in quick succession to charge the battery.

The word "noise" in this context comes from car stereos that would whirr with changing engine revs creating "engine noise" through the speakers. I use to install car stereos as a kid and was the in-house expert at removing that noise. Capacitors, inductors and other devices were used to help mitigate it down to a manageable level.

If you don't have electronics like a GPS in your car it makes zero difference if the charging voltage is "clean" or "dirty".

Jeff

Dennis
The primary reason the Fun Projects Hot Shot battery charger circuit design includes the 1151 lamp is to, should the diode fail shorted, prevent sufficient current flow from the battery into the Magneto field winding to discharge the magnets.
Ron Patterson

For some Club members I made chargers . Toon

I would like to know, since I have no idea, what diode is needed to make this charger? Thanks

...what diode is needed to make this charger?

https://dauntlessgeezer.com/DG102.htm

When clicking the link it says "Not Found" So the link is broken

Steve Jelf wrote: ↑

Sat Nov 09, 2024 2:06 pm

...what diode is needed to make this charger?

https://dauntlessgeezer.com/DG102.htm

Mark, try this:

https://dauntlessgeezer.com/DG102.html

Hello,
I have always wondered why I could not use a rectifier/regulator from a riding lawn mower in my 1914 Model T. My riding mower engine puts out 30 volts AC and it goes into this little box and comes out 12V DC and it keeps the battery charged. My riding lawn mower has a lot more vibration and is a lot dustier than my car also. Why wouldn't this work?

Thank you...