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Project: build a 12/24v DC geny from 2 cycle engine

Discussion in 'General Electronics Discussion' started by Qualcomm_inside!, Jan 27, 2017.

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  1. Qualcomm_inside!


    Jan 27, 2017
    I am a novice electronics student and I am wanting to build a project.

    I want to build, mostly from scratch a 12V DC generator from a small engine.
    I want it to directly charge and maintain a car battery ( or 2 ) .
    I also would like it to be completely self sustaining as in I want to charge a battery and keep it above 50-60%, igniting and stoping the gas engine when necessary.
    Can this be done?

    For parts I'm thinking of using a small lawnmower engine and some kind of alternator. not sure if should use direct output of motor to drive shaft, or some kind of pulley system??
    I'm thinking more along the lines of a lawnmower engine mounted to a drive pulley and a belt to an alternator...
    Anyway, I need a circuit that can take 12v from a generator and charge my battery while detecting the batt voltage and cutting power, stoping engine when charged.
    Then, have the logic to restart engine once battery voltage drops down.

    If I use a engine with a built in starter/ generator like you'd find on a lawn tractor, I could maybe reverse the power to the motor momentarily to ' turn it over ' and then flip back to charge mode.
    Also what about fuel mixture of engine??
    Need reliable fuel system that will fire on demand without choking and priming carburetor. Fuel injection kit ?

    Any input would be appreciated,
    Last edited: Jan 27, 2017
  2. Qualcomm_inside!


    Jan 27, 2017
    Any ideas?
  3. duke37


    Jan 9, 2011
    A gas engine should not need a choke like a petrol engine. A diesel should start reliably if you can crank it fast enough.
    If the engine runs at 3000rpm, then you could perhaps couple directly. A dynamo may be satisfactory at lower speeds and may be powerful enough to start the engine but be less efficient than an alternator which cannot be used as a motor.

    One problem is that you will want to start the engine when the battery is low so a second battery may have to be used.
    It will be necessary to have a sophisicated control system so that transients do not cause trouble.
    Qualcomm_inside! likes this.
  4. Qualcomm_inside!


    Jan 27, 2017
    Hah yeah. I'd like to have this all enclosed.
    I was thinking of doing multiple batteries yes,
    Not sure how big an engine I'd need. I'm thinking like a 1 or 2 piston lawnmower engine. A larger one like a riding tractor would have a dynamo starter, I was thinking that could function as my generator and crank motor? as far as fuel and idle control I was thinking of maybe putting some stepper motors on the carb and have my controller device adjust it to its needs?

    As far as electronics, could I use a microcontroller board like Aurduino or Pi to control the logic of it, then have a power supply board to the batteries and the generator?
    How would be the best way to make the control system?
    Last edited: Jan 28, 2017
  5. Bluejets


    Oct 5, 2014
    Arduino is relatively easy to follow and there is a lot of support.
    As long as you are prepared to do the work, not expect a full blown coded project handed to you, then you will be fine.
    Break the project down into smaller sections and get each working initially before combining them.
    This as you have outlined is really a fairly involved system, even for one experienced, (many traps for the unwary)
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