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Electric vehicle

Discussion in 'Electronic Repair' started by Lenny, May 19, 2004.

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  1. Lenny

    Lenny Guest

    I would like to use a 12V automotive type starter motor to propel a
    very small electric vehicle. This motor is unique in that there is no
    Bendix drive on it, (its an old Ford starter), with just a shaft. I
    realise that a series wound motor is probably not the best choice for
    this application but I have the motor and would like to make use of
    it. Initial torgue capability and of course control are both
    concerns. The toal loaded weight of the conveyance will never exceed
    300lbs. I don't know what kind of operating current to expect as I
    can't really set this up without a controller of some sort for fear of
    having the motor take off. I can only guess at perhaps 50 amps? I'm
    sure some type of PWM controller is what I need but I'm not sure how
    to implement this. Can anyone offer any suggestions or even better a
    schematic? Thanks very much,
    Lenny Stein, Barlen Electronics
     
  2. Venom¥8

    Venom¥8 Guest

    1.) Starter motors are extremely inefficient
    2.) To utilize would require industrial strength controls (A.K.A. BIG BUCKS)
    3.) Most starter motors are one direction only
    4.) Current in most starter motors are in excess off 100 amps draw

    How about a wheel chair motor? Gear driven , cheaper to control, and more
    effecient.


    :I would like to use a 12V automotive type starter motor to propel a
    : very small electric vehicle. This motor is unique in that there is no
    : Bendix drive on it, (its an old Ford starter), with just a shaft. I
    : realise that a series wound motor is probably not the best choice for
    : this application but I have the motor and would like to make use of
    : it. Initial torgue capability and of course control are both
    : concerns. The toal loaded weight of the conveyance will never exceed
    : 300lbs. I don't know what kind of operating current to expect as I
    : can't really set this up without a controller of some sort for fear of
    : having the motor take off. I can only guess at perhaps 50 amps? I'm
    : sure some type of PWM controller is what I need but I'm not sure how
    : to implement this. Can anyone offer any suggestions or even better a
    : schematic? Thanks very much,
    : Lenny Stein, Barlen Electronics
     
  3. Don Young

    Don Young Guest

    I do not recall all of the details but once at my kid's summer camp they had
    a fleet of starter powered go-carts. There was no speed control, just a
    solenoid. Drive was by a single reduction chain, starter to axle. So it is
    possible.
    Don Young
     
  4. John Hudak

    John Hudak Guest

    Hi Lenny:
    I'd suggest you pick up a book on control of DC motors - there is just
    too much info to convey here. Series motors will draw a lot of current
    until the back emf builds up. The only current limiting device in a
    series DC motor is the armature winding. Across the line starting will
    produce a current surge well over 100 amps (average) over 3-5 seconds.
    The cheapest way to start and control a series DC motor is to have a
    stepped resistor bank that gradually reduces the series resistance as
    the motor speed builds up. There are both manual and automatic changing
    techniques.
    Another way to do it is with solid state devices (i.e. SCRs,
    transistors,etc.). For this size motor, they are usually 'expensive'
    industrial quality devices because they must handle a lot of current.
    Id suggest looking at Grainger and search for motor controllers, knowing
    the KW and Full load amps (FLA) of the motor.
    If you want to run the motor on a test bench to get a measurement of
    these values, you can a) use a pair of battery jumper cables and connect
    them to the battery, or, use a small relay to control a high capacity
    relay to switch in/out the voltage. Assume the relay contacts must be
    rated at 30 amps continuous.
    Series motors have high starting torque but the torque will drop off as
    load is applied. One common way to get around this is to use gearing to
    reduce the reflected load at the motor shaft.
    All in all, the control elements you need + the gearing you might want
    to use will reduce the cost effectiveness of wanting to use the starter
    motor because you have one lying around.
    Best of luck
    John
     
  5. Mike

    Mike Guest

    .... and if you have a local "mobility shop" they will probably be able to hook
    you up with an old electric wheelchair/scooter bits pile that they wouldn't
    dare re-use for spares, however ... your application is probably less critical.

    This way you can easily source an appropriate controller too. And maybe
    some batteries to test it out with -- people often swap out the batteries
    before they're dead as getting stranded on an electric wheelchair/scooter
    due to ageing batteries is not fun.

    The controller may need some tweaking for your application, as most of
    them seem to have settings for max current/temperature shutdown, acceleration
    and (sometimes) electronic braking. Your mobility shop may help out there too
    if they have access to a programmer.

    Mike.
     
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