Starter relay would like to replace it with N-MOS

Discussion in 'The Projects Forum' started by lowmail, May 28, 2014.

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  1. lowmail

    Thread Starter New Member

    May 28, 2014
    We would like to replace automotive starter relay with N-MOS.
    And the power source for automotive starter is from battery.
    So the startup voltage would be 6~16V.(typical)
    the relay steady current is 15A, the inrush current would up to 80A

    Does any body have this experience to replace starter relay with N-MOS?

    And for N-MOS gate driver is also a problem because Vin voltage varies.
  2. alfacliff

    Well-Known Member

    Dec 13, 2013
    starters for cars typicly run much more current than just 80 amps when starting. I have seen 250 amps as not too unusual. this combined with the inductive load of the starter motor might make this dificult. high compression cars draw much more current when starting.
  3. mcgyvr

    AAC Fanatic!

    Oct 15, 2009
    "ibtl" :) .......
  4. crutschow


    Mar 14, 2008
    To use an N-MOSFET as a high-side switch you will need to use a bootstrap gate driver circuit since the gate must be at least 10V above the source voltage to be fully turned on. You will also need a large diode from the switch output to ground (anode-gnd) to absorb the high transient inductive current when the switch turns off.
  5. Experimentonomen


    Feb 16, 2011
    I sense a TOS violation heading this threds way.
  6. #12


    Nov 30, 2010
    I don't think the mods will have to stop this. The basic idea is so impractical that it will die of its own.
  7. wayneh


    Sep 9, 2010
    He said the relay, not the starter solenoid or the starter itself. In other words it could be done and therefore this thread needs to be closed.
  8. Wendy


    Mar 24, 2008
    The owners of All About Circuits has elected not to host discussions of automotive electrical system modifications/enhancements due to safety concerns, the potential of legal ramifications and the possible circumvention of vehicle regulations at the state and federal level.

    This thread is against the AAC forum rules, Chapter 6, as seen here:

    This can be found in our Terms of Service (ToS)

    Automotive modifications of any kind are strictly forbidden. Therefore, this thread will be closed.

    Please try to understand the reasons behind this action, and feel free to browse and use the forums.

    You might find answers to your questions in one of these forums:

    Another good forum that shares many of the same membership is . Good luck.
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