4QD range: Reversing, 24V – 48V, 300A

£348.00£426.00 inc VAT

The 4QD-200 and 4QD-300 are heavy duty 4 quadrant motor speed controllers for currents up to 300A. They have now been superceded by our new fully digital and configurable Pro-160 / Pro-360 models.

SKU: N/A Category: Tag:

Please scroll down for full controller specification

Motor noise suppression

We strongly recommend fitting motor noise suppression components to each motor in your system to protect the controller. See this quick explanation of what EMC is and why it matters. We have interference suppression packs  and a page of advice on how to fit them, and other steps to take to reduce RFI.

Product Options


The 4QD-200/300 are full H-bridge heavy duty PWM controllers with serious current handling capabilities. With the optional enhanced air cooled or water cooled heatsink options these speed controllers can be operated at the upper end of the performance envelope for extended periods. The 4QD-200/300 dc motor controller has been used to drive the Robot Wars house robots, larger golf buggies and electric vehicles, and a wide range of electric boats.

These controllers have been superceded by our new fully digital and configurable Pro-160 / Pro-360 models. The 4QD-300 is available to purchase for those customers wanting to replace an existing 4QD-300 controller with the same model. For customers wishing to replace 4QD-200 controllers we have a limited stock, please email to enquire about availability.

The key features are:

    • 4 quadrant operation
    • Gain adjustment.
    • Adjustable acceleration and deceleration ramps.
    • Input by 1k ohm to 22k ohm potentiometer, direct voltage control, or PWM control by Pi or Arduino etc.
    • Regenerative braking [can be disabled].
    • Reversing.
    • Over temperature shutdown.
    • Battery discharge protection.
    • Pot fault protection.
    • High Pedal Lock-out.
    • Inhibit input for interlock with mechanical brake, deadmans handle etc.
    • Parking brake driver with current limit and anti-rollback.
    • Joystick (wig-wag) or single ended modes [selected by a movable link).
    • Forward – Off – Reverse push button operation is possible [see article in knowledge base]
    • Wide operating voltage: 48v controller can be used between 18v to 66v (subject to battery discharge protection setting).
    • Fail-safe, protected circuitry for reliable, safe operation even into a shorted output: no minimum inductance for safe operation.
    • Shut down circuitry shuts drive down safely under all likely failure modes, including internal or battery over and under voltage
    • Reversing speed threshold can be adjusted for operation on hills.
    • Brake Light Driver. Factory option, replaces parking brake (subject to minimum quantity order).
    • 3 heatsink options available, standard, finned air, or water cooled.
  • Also on board is an adjustable torque limit, which limits the continuous motor current, to avoid overloading smaller motors.Direction switching and drive / brake switching is entirely electronic so in a vehicle equipped with a 4QD it is quite permissible to change the direction switch whilst travelling at full forward speed. The 4QD will brake, stop and reverse under full control. There are on board ramp controls to separately adjust acceleration and deceleration rates. With maximum rates the controller is very lively!The standard 4QD series uses a large aluminium plate as the primary heatsink, this has a high heat capacity and is usually sufficient for the majority of applications. However for currents at the upper end of the envelope, or for extended operating times then fitting one of our water cooled heatsinks turns the 4QD-300 into one of the few water cooled motor controllers available for brushed electric motors. These can be added at the build stage or retro-fitted later if required.Please consult the factory for variations to the above specification or for more information.The manual provides full instructions on setting up and operating the controller. The manual is available in PDF  format:

    Adobe_PDF_file_icon_32x32   4QD-200 – Read manual

    Adobe_PDF_file_icon_32x32   4QD-300 – Read manual



Model 200 300
Nominal voltage range 24 – 48
Minimum / maximum voltage 18-66
Motor current A [max] 230 320
Motor current A [1 minute] 140 180
Motor current A [continuous]*  depends on cooling  depends on cooling
Reversing Y
Half speed reverse Link selectable
Regen braking Y [can be disabled]
Gain adjustment Y
Dimensions [mm] 250 x 103 x 60 280 x 103 x 60
Weight [g] 1300 1685
Power connections M6 studs M8 studs
Input 1k – 22k pot, or 0 – 3V min [adjustable via gain]
Reverse polarity protection N
Over voltage protection Y [68V]
Under voltage protection Y
Pot fault protection Y [>40k]
Thermal protection trip @95’C
Current limit – drive Y [Adjustable]
Current limit – regen Y
High pot lockout Y
Joystick/Wig-wag input Link selectable
Radio Control Via DMR-203
Selectable dual ramp reversing Y
Pre-select reversing N
Ramping Acceleration and deceleration adjustable between 0.1S and 5S
Parking brake Y [1A max]
Inhibit function Y
Powerdown state (motor) open-circuit
Tacho feedback Via tacho interface board and mod
Ignition, Electronic Y
Heatsink Integral
Double heading Y
Switching frequency 20 kHz
Quadrants 4

*The continuous current ratings depend heavily on the cooling that is provided. This chart shows the difference between the cooling options we have available for the 4QD-300


*This chart shows the effect a small PC case fan can have on the 4QD-200, in this case it was placed about 4″ away from the base plate at an angle of 45′ to it.

thermal performance




The manual provides full instructions on setting up and operating the controller. The manual is available in PDF  format:

Adobe_PDF_file_icon_32x32   4QD-200 – Read manual

Adobe_PDF_file_icon_32x32   4QD-300 – Read manual

The manual is designed to be printed double-sided in A4 booklet format. To print the booklet from the PDF on a double-sided printer, select Booklet in the Page Size & Handling section of the print window, and set Orientation to Portrait.

Inhibit ramp modification

If you want to change the function of the inhibit switch so that it follows the standard deceleration ramp then we have some instructions here.


For troubleshooting common to all controllers click here.

We have a page here that gives advice on general fault finding for the 4QD

This page describes how to test the 4QD base board and MOSFETS.

There are also a lot of useful articles on the 4QD range in our knowledge base here.


You may need some or all of the following

Some applications need extra cooling, and there are a number of ways to achieve this.




4QD-300 no cover
4QD-300 with cover removed
4QD-200 no cover
4QD-200 with cover removed










water cooled heatsink
4QD-300L with water cooled heatsink
finned heatsink
4QD-300X with finned air cooled heatsink