Updated "Aug 29, 2011
As a Request from a guy wanting a Voltage Regulator to give: Much Higher Voltage Outputs from a Car Alternator, So I designed up these Circuits below.
The Upper Circuit on the Schematic below is for a typical 14.5 Volt output to charge a 12 volt car battery.
The Lower Circuit can be set to Higher Regulated Output Voltage Levels. But it still Requires a 12 Volt Battery to drive the Field Coil.
Most car Alternators draw about 2 Amps on the field coil and the TIP121 Darlington Transistor is rated at 5 Amps.
From my Tests, it should be quite satisfactory without overheating. For added Safety, I Do RECOMMEND using a Small "Heatsink on this transistor".
Also be aware: The Alternator requires a Higher RPM, if it is to generate a High Voltage. EXAMPLE: For 100 Volts Output, you will require a Engine RPM of around 2000 to 2500 RPM.
CAUTION
The Diodes in Alternators can Vary in Voltage Ratings. Some may be as low as 30 Volts, while others may be 50 or 100 Volt Ratings.
If you DON'T Know which Diodes you have in your Alternator, I Suggest you REPLACE Them with Appropriately Rated Diodes.
Also, Definately Fuse the Output appropriately.
For BEST PROTECTION, Put your new Diodes External to the Alternator and add a Seperate Inline Fuse going into Each Diode.
And Remember: DIODES Require Suitable HEAT SINKS, if expected to operate at their Rated CURRENT!
Also make sure these Diodes have a Good Air Flow for Cooling.
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