Very simple series regulator for motorbike

Discussion in 'The Projects Forum' started by repmovsd, Sep 21, 2013.

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  1. repmovsd

    Thread Starter New Member

    Sep 19, 2013

    I have an old school Royal Enfield motorbike which uses a blackbox rectifier regulator unit driven by a 4 wire alternator (permanent magnet rotor, two separate pairs of coils). By default one set of coils drives the headlights via a shunt regulator and the other set charges the battery via the rec-reg unit.

    The consensus among enthusiasts is to switch to a DC headlight circuit, by connecting the alternator coils in parallel and using them only to charge the battery. Many people successfully do this, this avoids running separate AC wires to the front of the bike and lets the headlight work brightly even at low RPMs in the city.

    However I don't like the fact that they use a shunt regulator : The alternator produces about 180 watts and maximum of about 50 volts - at full RPM, the shunt will be dumping all that wattage and it will dissipate as heat in the alternator coils, inside the primary case which is already burning hot from the clutch and primary drive friction.

    I wan't to make a simple series regulator with minimal component count, and also have the ability to run without battery if need be (this is a points based bike). Perfect regulation is not critical, it's more of an overcharge protection.

    This is the circuit I have in mind :


    Note that the alternator will produce upto 6200 Hertz, peak voltage is about 50V, maximum current output is about 15 AMPS - peak intermittent load from the bike (horn, lights, ignition) may be upto 20 amps.

    I wonder if maybe the 10K is too high or whether a 2n3055 can take that voltage and current. The output should be 13.6 volts as far as I know.

    How would one build a similar circuit around an IRF540 instead?
    Does it make sense to put the capacitor as shown? My intention is that if the battery goes kaput (it happens often!) , i can simply disconnect it and the capacitor should be able to handle the ignition load at least.
  2. ErnieM

    AAC Fanatic!

    Apr 24, 2011
    Well... you used the wrong forum for this question, you are asking for an automotive modification on a board that expressly forbids such, youd you are asking to do the impossible (well, not impossible but still "not a good idea").

    Besides that... welcome to the forums.

    Your thread will be closed shortly. Better luck next time.
    Last edited: Sep 21, 2013
  3. bertus


    Apr 5, 2008

    I am closing this thread as it violates AAC policy and/or safety issues.

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