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Starter Motor H-bridge

Discussion in 'Motor actuators and drivers' started by rafael_design, Sep 27, 2013.

  1. rafael_design

    rafael_design Member

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    Hi,
    I just bought this old big second-hand starter motor (from a Fiat Tempra I think) and want to try driving it with mosfets. I thought about doing this with my Thanos H-bridge but I am afraid its insane. :)

    I am not sure how much current it (the starter motor) draws but I am afraid it is close to 50A as a guess.
    The IRF3205 has a Continuous Drain Current of 80A.
    And the IRF4905 Continuous Drain Current, 52A.

    If I reinforce the h-bridge with MORE solder could I give it a try? :thumbs

    Any idea or information about driving as big motors please advise me, ok!

    My regards!
    Rafael.
  2. Ads Master

    Ads Master

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  3. rafael_design

    rafael_design Member

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    I built this motor controller to see how this toys behave.
    Here is where I am so far:


    Next step: To built the Big H-bridge!

    My regards,
    Rafael.
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  4. BlazinH

    BlazinH Well-Known Member

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    Hi. I wish you luck but I'm very doubtful. Car starters were designed to, well, start cars. They are made to put out an extreme amount of torque, but only for a few seconds at a time. And I think you have way underestimated at 50 amps (that's less than 1hp at 12v). I don't think I have ever bought a car battery that was less than 500 cold cranking amps. In fact usually more like 700-800. They don't make them that high amperage and call them cranking amps for nothing! So if you can manage to put out the current to run your starter motor, you better have a great way of keeping everything cool, otherwise you motor and h-bridge will be overheated in no time. If you can make it work for an extended period of time, please let us know how you did it!
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  5. danalog

    danalog Motion Sim Wannabee

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    Car starters are pretty strong indeed. 50cc or 80cc mopet starters are a bit lighter, easily available everywhere and matching gears as well. Hmm... you got me thinking here!
  6. bsft

    bsft

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    Car starter? Thats a big motor really, what are you planning to move? if you are looking at 12v wiper alternatives, look at the 12v 200w worm gear or 12v 900kg rated winch motor.
    If you need more power, look at 24v, there are some interesting plans in the works for those motors.
    Remember , as BlazinH says, car starters are designed to suck MASSIVE current for a few seconds, so on a sim, its doing that all the time and the h-bridge is changing voltage and current direction constantly at stall current, so its very high. I think you will be nuking h-bridges in no time going that way.
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  7. rafael_design

    rafael_design Member

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    Well, as you can see in the video linked, I put my fingers on the mosfets and diodes and everything are just warm. Including the motor that is even colder. I made other tests where I accelerate it to full speed for longer times and the motor never got hot. I think it have to do with the LOAD you put on it. Maybe a well balanced simulator will never demand the load as a could stopped 2.0 litre motor.
    My regards!
  8. rafael_design

    rafael_design Member

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    I know you might be right. But the only way to find out is trying :D

    I was looking for winch motors but I could not find it yet. I am looking for a second hand one...
    Last edited: Oct 31, 2013
  9. BlazinH

    BlazinH Well-Known Member

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    The mosfets will dissipate heat much faster than your motor can. However, once you have used your starter motor under load for a period of time, it will overheat! A starter motor is an intermittent duty motor. One thing that means that it is not designed to dissipate heat fast enough to allow for continuous duty. It needs off time to cool down! However, you may be able to add a cooling element to your motor that will keep it cool!

    One trick I use to keep my motors cool is to get a piece of 1/2 inch (13mm) soft copper tubing, and coil it around my motor(s). I then connect some plastic tubing on the ends of the copper coil and run the ends of the plastic tubing to a bucket full of water where one end of the plastic tubing is connected to a fountain pump. It works quite well for me!

    I found some information on the web that states a starter motor for a 4 cylinder motor usually pulls around 130 to 150 amps. Have you considered having your starter motor tested to see how much current it pulls? Here, you can just take your starter motor to most auto parts stores and they can check it to see how much current it draws. They don't need to know that your not there to buy a replacement if its out of spec.

    I guess what I'm trying to say is that you may save yourself some time and money if you make sure the math works first. Using math must work well, it got men to the moon and back!
  10. bsft

    bsft

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  11. speedy

    speedy Well-Known Member

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    OH no ... you're a killer :thumbs... Love it :cheers ... this H-bridge should be exploded by now :eek:..." knocks on solid oak " :grin

    But P-MOSFET's for high side are an old way for h-bridge my friend ... Try for sure all N-MOSFET's of N-MOSFET's H-Bridge project and allow me to put a link for your good project there .
    Last edited: Jan 4, 2014
  12. speedy

    speedy Well-Known Member

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    Hi @rafael_design ...
    Great job my friend ...
    As you say you built that motor controller ... But It doesn't seem like Thanos h-bridge ...
    what is it please ?
    can you please describe the connection to the motor ?
    did you modify any thing in the motor itself ?

    pictures for less writing is preferred ...:thumbs
    thanks buddy
    Last edited: Jan 10, 2014
  13. Vassago

    Vassago New Member

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    Wow a car starter that is a new one to me. There is a company called Werner Electric that sells all sorts of linear actuators. Just thought I would put that out there. :)
  14. bsft

    bsft

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    Got a link?
  15. Vassago

    Vassago New Member

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