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Conaway2 · 09-21-2019, 04:36 PM

I built a full-wave rectifier circuit with an RC filter section consisting of 2 220uF capacitors with a 10 watt 10 ohm resister between the positive leads on the capacitors. At the output of the RC filter section, I have a 5-watt 14-volt zener diode to limit output to 14 volts to charge the 12 volt battery. We confirmed that the circuit works when connected to the Model T magneto - we measure 14 V DC.

However, when we connect the output of my converter circuit to the battery, output drops to 12 V - probably because the battery (motorcycle battery) has such a hugh reservoir of current. We probably need to connect an ammeter in series with the battery to see if any current is actually flowing to the battery to charge it.

Today, we ran another experiment - connected a Fun Projects 12 V regulator to the car and made the following observations.....with no charger connected, the car runs very smoothly on the battery. When it is switched to magneto, the engine rpm immediately drop and the engine does not run as smoothly. With the Fun Projects regulator connected, the engine continues to run smoothly when switched to magneto. However, we cannot tell if the battery is charging. An ammeter connected in series with the regulator and battery showed no current flow. I’m very puzzled....

Can anyone offer any insights ? From my point of view as someone who has worked with electronics for over 40 years, rectifying an AC signal into useable DC should be a very simple thing to do.

09-21-2019, 04:36 PM	#10
Conaway2 Senior Member Join Date: Apr 2019 Location: Mt. Pleasant, SC Posts: 601	Re: Magneto battery charger I built a full-wave rectifier circuit with an RC filter section consisting of 2 220uF capacitors with a 10 watt 10 ohm resister between the positive leads on the capacitors. At the output of the RC filter section, I have a 5-watt 14-volt zener diode to limit output to 14 volts to charge the 12 volt battery. We confirmed that the circuit works when connected to the Model T magneto - we measure 14 V DC. However, when we connect the output of my converter circuit to the battery, output drops to 12 V - probably because the battery (motorcycle battery) has such a hugh reservoir of current. We probably need to connect an ammeter in series with the battery to see if any current is actually flowing to the battery to charge it. Today, we ran another experiment - connected a Fun Projects 12 V regulator to the car and made the following observations.....with no charger connected, the car runs very smoothly on the battery. When it is switched to magneto, the engine rpm immediately drop and the engine does not run as smoothly. With the Fun Projects regulator connected, the engine continues to run smoothly when switched to magneto. However, we cannot tell if the battery is charging. An ammeter connected in series with the regulator and battery showed no current flow. I’m very puzzled.... Can anyone offer any insights ? From my point of view as someone who has worked with electronics for over 40 years, rectifying an AC signal into useable DC should be a very simple thing to do.