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Control alternator voltage back to 6vlt battery?

Discussion in 'Power Electronics' started by Firdog, Jun 11, 2019.

  1. Firdog

    Firdog

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    Jun 6, 2019
    Can someone on here help make a suggestion to regulate the voltage on this diagram included?

    I am Thinking I can add a inline diode or resisters to control voltage back to my battery on this diagram below for my 1981 Suzuki GN400 motorcycle. It is a 6 volt system and the only battery that fits is a wet style battery. After riding it for a couple hundred miles the acid seems to be expelled from the battery and if you don’t catch it and refill with distilled water in time it cooks it and you have to replace it. The bike only uses the battery for lighting head lamp, turn signals, controls lighting, brake, and tail light. It is not needed to start the bike because it only has a kick start. Bike will run without battery but lighting goes from bright to dim with out the battery. It seems they did not do a very good job regulating the return voltage from the alternator. So I am looking for help to put something in place to keep from overcharging it. Thinking I need to control to 6.9-7.2 volts.
    For reference The 4 AH battery model is a
    Yuasa® 6N4B-2A - Conventional Battery


    upload_2019-6-11_12-2-6.jpeg
     
  2. duke37

    duke37

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    704
    Jan 9, 2011
    I am not familiar with small motorcycle generators but have a vague memory that they have a constant current output, It should be possible to restrict the voltage to 7V by adding a load such as the headlights when the current is too high.

    I do not see how to maintain 7V when the generator is not up to the job.

    Diluting the acid to replace spurted out acid by adding water is not a good thing.
     
    Last edited: Jun 12, 2019
  3. Firdog

    Firdog

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    Jun 6, 2019
    Thanks for the response. I actually want to limit the voltage to 6volts as it is cooking the battery which is also 6 VDC. I never have to charge it unless it needs refilled after it’s has all boiled out.
     
  4. Bluejets

    Bluejets

    3,374
    678
    Oct 5, 2014
    One cannot charge a 6v battery with only 6v.
    The daytime (lights off) regulation as can be seen in the diagram supplied is the "running light" called parking or city light and the resistor.
    What we see in the diagram I would imagine be a lot different from what is actually there in the bike given it's age.
    I sure it would have been hacked many times by now and not much would be original, hence the problems.
     
  5. duke37

    duke37

    5,190
    704
    Jan 9, 2011
    12V cars are usually charged between 13.8V and 14.4V. It is necessary to use as high a voltage as possible without gassing. A 6V system should be charged at 7V.

    You should never have to charge the battery if you use the motorbike once a week or so. I have just changed my 12 year old car battery which has never been topped up or externally charged.
     
  6. Alec_t

    Alec_t

    2,607
    686
    Jul 7, 2015
    I'm not a bike guy, but it's my understanding that voltage stabilisation on older bikes with magnetos is usually achieved very crudely with simple shunt regulators. Such a regulator may be no more than a beefy zener diode or two to clamp the voltage to around 7V (for a 6V system).
     
  7. Firdog

    Firdog

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    Jun 6, 2019
    Thanks for the reply.
    Zener Diode to control the voltage. OK. So what Diode would I use and can I put it in the battery connection? Would this limit voltage back but not voltage out? Looking to control to 7 VDC. Please recommend what is needed and where.
     
  8. Firdog

    Firdog

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    Jun 6, 2019
     
  9. Firdog

    Firdog

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    Jun 6, 2019
    I am sorry Bluejets. If you read the first post I wish to control the charging voltage back to the 6vlt battery. Please make a recommendation to control to a voltage needed to charge it. I am thinking 6.9 to 7VDC should do the trick. Currently the system seems to fluctuate and over charge the battery and kills it.

    Also they show a switch in the circuit to control the headlight but the headlight is not switchable and is ON all the time when motor is running.
    Thanks for the response.
     
  10. duke37

    duke37

    5,190
    704
    Jan 9, 2011
    If the headlight is on all the time the engine is running, then perhaps the bulb is not powerful enough to limit the voltage.

    If you use a Zener diode across the battery, then it will need to be powerful and have a sharp knee so that it does not discharge the battery when the bike is not being used. You may have difficulty in finding a 7V Zener, they often have quite a large variation from the nominal voltage.

    More complicated circuitry could be used for more accuracy.

    A lead/acid battery can easily produce sufficient current to start a fire so be very careful. An explosion is also possible if the oxygen/hydrogen gas is ignited as my nephew found. He leapt into a cattle drinking trough to dilute the acid and was not harmed.
     
  11. Firdog

    Firdog

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    0
    Jun 6, 2019
    Good to know and thanks Duke37
     
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