My terrible magneto-battery charger

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Model T Ford Forum: Forum 2018: My terrible magneto-battery charger
Top of pagePrevious messageNext messageBottom of page Link to this message  By kep on Monday, August 06, 2018 - 03:15 am:

Folded & soldered some of the legs on a bridge diode down & soldered them together.

Screwed to the generator and magneto wires, after this I put a screw through the hole that held a layer of insulation on the firewall side & an aluminium heatsink on the other. No thermal paste, wouldn't even know where to find that.

Most of the time I see nothing on the ammeter. At flat out speed I was getting 4 amps charge.
Probably one small problem... Should the diode burn out & short internally the battery would discharge through the magneto & kill the magnets, and flatten my battery.
I might add a light bulb, but where to put it that it won't be in the way i'm not sure..


Top of pagePrevious messageNext messageBottom of page Link to this message  By Jim Davis. Tomball Texas on Monday, August 06, 2018 - 10:59 am:

Thermal Compound! Most electronic supply houses such as All Electronics carry it. some auto supply houses may also have it as well. used between regulator and alternator heat sink in older alternators.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Jay - In Northern California on Monday, August 06, 2018 - 11:22 am:

Light bulb?? We don't need no stinking light bulb!!

Put one of these on your dash and your magneto will be fine. :-) :-)


All joking aside I wouldn't risk toasting my magneto running without the light bulb in the circuit.


Top of pagePrevious messageNext messageBottom of page Link to this message  By kep on Monday, August 06, 2018 - 04:16 pm:

That heat sink gets rather warm....


Top of pagePrevious messageNext messageBottom of page Link to this message  By John F. Regan on Monday, August 06, 2018 - 06:48 pm:

Its worse than just demagnetizing your magnets when that diode shorts and that is for sure the way it will fail if/when it fails. If you are using a 12V battery and it is more than a very small storage battery, the peak current could hit a value over 50 amps and that could heat up your mag ring enough to cause the windings to fall off the frame and get into your motor. Magneto ring DC resistance is about .25 ohms TOTAL so 12.6 Volts could provide 12.6/.25= 50 amps reduced only by the resistance of the wires that you have in the connection. A single diode with no fuse is playing very very high stakes poker. Adding a fuse only allows the damage to be magnet discharge unless the fuse is too heavy in which case you probably end up with discharged magnets, open or damaged mag ring and boiled battery due to excessive discharge rate. It is not far fetched to even suggest the wires could turn red hot and fire up the T with a whole new meaning to the word fire. Not something to try let alone make jokes about. I would implore you NOT to proceed but I suspect some simply have to learn the hard way.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Neil Haywood on Monday, August 06, 2018 - 07:56 pm:

Add the bulb like I did. Use the rear light



Here is the diode in my battery box


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