How to make an external voltage regulator for any car, truck, vehicle, or boat alternator. Output voltage depends on which zener diode you use. Use a 12 or 13 V zener for charging (1) 12v lead acid battery, and use a 25-27V zener for charging (2) 12V lead acid batteries in series, OR use a 6V -6.2V zener to charge a 6v lead acid battery. You may have to adjust the value of the 1.5K resistor in the schematic to get the 2n3904 to work properly.

Visit Gary’s website at: chemelec.com(New Schematic Shown)

http://chemelec.com/Projects/Alternator/Alternator-Reg.htm

For the schematic shown in this video:

I used a 3.7K in place of the 1.5K, 900 ohms instead of the 1K, (2) 250V – 2.2uF electrolytic caps instead, and I used (2) zeners in series to get a total of 12.7V which gives the output of 14.7V.

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22 Comments

  1. nice but what i thought was the 2n3904 switches off the tipp 122. not the case it just splits the power lowering the current going to the tip122 so the field current is cut in half.

  2. Hi I am just curious. This circuit (mosfet one) will reduce the field current to adjust the voltage to the desired level at + ve terminal? Or just cutoff complete field current?

  3. How stable was your output voltage when a load was applied and when at idle speeds? My old V-belt style Toyota has a 120A alternator that charges at barely 12V when at idle, so if I'm sitting at an intersection with fans, stereo, wipers, and turn signal going it'll drop down to 11V and sometimes even below, even with a new Denso internal voltage regulator in it. First thing I'll be doing is upgrading the rectifier, then will break out my electronics gear and experiment with an external voltage regulator that I can mount somewhere that'll stay cooler than its current location.

  4. How to rewind the alternator stator for wind turbine ist the same way of winding the original coil just by adding more turns on the coil?

  5. Hello, Nice videos
    Do you have a alternator external variable voltage regulator squematic

  6. Can you make a video how do back calculation for designing alternator if we know output voltage and current and rpm

  7. need to add an Alternator to a 22 hp engine. Using a 12-volt PTO clutch, requires at least 10 amp charging circuit. most engines only have a 2-4 amp charging rating.. Any suggestions would be great.

  8. You Mosfet version looks interesting.

    Like all other regulators it controls current to field (rotor)coil.

    I fully understand this an alternator regulator but my question is this, generators also regulate current output by regulating field coil, so why shouldn't it be able to work on a generator? One side of generator field is connected to the Armature, but if grounded like your schematic, shouldn't it work?

  9. I No Longer sell this Transistor Regulator for 12 Volt alternators.I Now have a Mosfet  version that doesn't get hot and doesn't require a Heat Sink.People here should also know that the Normal Charge for a 12 Volt Car battery is 14.8 Volts.Or 7.4 Volts for a 6 Volt Car Battery.Gary………chemelec.com

  10. Those resistors look like they are in series so the total value is 1012ohms not 920 something. To achieve that they need to be in parallel.

  11. If you simply attach a 300amp bridge rectifier, what will the ouput voltage look like??

  12. I have two 22SI 150 amp alts they are 12 volts. is it possible to convert them to 24 volt? or connect them in series? I need it to charge my 24volt bank of golf cart batteries. with a similar setup. I guess I should listen to the whole video . before asking questions. so if I can get a rebuild kit for a 24v 22 SI. I will have a 24 volt alternator. I thought the volts could be raised. since it generates in the hundreds of volts. that looks like a great setup. I have only rebuilt alternators. I never had one to tinker with. if it's that easy. I may get a few of them to overhaul. or convert. I'm thinking about putting the alternator on my riding mower. so I can charge the batt bank when I don't get enough sun. or when the lil creek is in drought. I'm planning a water wheel generator. and I haven't got my solar up yet. so I need it now. to help keep my off grid home charged. thank you soo much for the video. is there any more planned for this subject?

  13. how much do you know about alternators, im working on a custom project and would like to chat, 734-755-9532

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