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I have a 4 hp, 90 VDC, 12A @ 5200 RPM treadmill motor and a 80 V, 6 Ah lithium battery.

The project is to use this motor to convert a lawn riding mower to electric using a tractor transmission and pulley to reduce the RPM and increase torque.

Curious as I am, I decided to briefly connect the motor to the battery to see if it would turn (yeah... dumb idea). 

Result: It works - with a huge welding like spark and the motor wire terminal partially melted at the point of connection.    Conclusion: a LOT of amperes were pulled from the battery due to stall current.  

I'm planning to build a PWM controller with a 555 IC using a single 100 V, 80 A IRF3710PbF MOSFET.

I learned electronics on my own but this is my first experience using a MOSFET and I am seeking help/advise from the community.

Questions: 

  1. Will the PWM power the motor properly without overheating the MOSFET?
  2. Will the PWM control the inrush current or do I need an additional current limiter?
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  • \$\begingroup\$ I think all your questions are answered here: electronics.stackexchange.com/questions/42051/… and here: electronics.stackexchange.com/questions/172385/… \$\endgroup\$
    – Dejvid_no1
    Commented Sep 20, 2022 at 21:18
  • \$\begingroup\$ This would be a very difficult design even for an experienced power electronics engineer. I would suggest looking to buy a suitable controller. You can't just switch it on with a FET (SCRs may be better choice for this btw). Careful attention needs to be placed on managing the inrush current and handling the load dump back EMF. Current sensing and feedback control required. Multiple parallel FETs or SCRs and a lot of thermal design. Google "DC motor controller 3kw". (BTW I assume it is not a brushless motor). You will still struggle to find one that can handle 90V for sensible money. \$\endgroup\$
    – Jay M
    Commented Sep 22, 2022 at 1:15
  • \$\begingroup\$ @JayM - Thanks for your feedback. It is indeed a brushed motor. I was under the impression using multiple FETs might not share the load properly. Thus my decision to go with a possible overkill one so it can handle the inrush. I'll look into SCR though. Thanks gagin for the pointers. \$\endgroup\$
    – gzmo
    Commented Sep 28, 2022 at 22:02

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