4QD - DC Motor Control

4 Quadrant high power motor controllers



The 4QD-200 and 4QD-300 are full 4 quadrant motor speed controllers suitable for battery operated motors up to 300A and voltages between 24v and 60v. They give full control of forward and reverse acceleration and braking. They have been developed in conjunction with a top motor manufacturer and golf buggy manufacturers. Although small they are fully electronic and need no external relays. They have many failsafes built in for reliable long time use (and abuse).


2 basic models are currently available


Supply voltage 18v to 66v (abs max)  
Over-voltage operation 68v  
Supply current 100mA  
Voltage drop at 100 amps
(typical, full speed)
Output voltage on 24v0v to +24v
on 36v0v to +36v
on 48v0v to +48v
Output current max, cold210A and 320Atypical
4 minute rating150 amps4QD-200-24 without additional heatsink.
hot 160A and 240A
Current limit adjustment 20% to 100% full current
Overheat cut-out 95°C internal temperature
Acceleration 0.3s to 12 sec, linear adjustable
Deceleration 0.3s to 12 sec, linear adjustable
'Ignition On' threshold > 3v
'Reverse' threshold 3-6vwith link J2 open. Depends on issue
Switching frequency 20kHz approximately
Size (mm) 200250 x 103 x 60
300280 x 103 x 60
Weight 2001300g of which heatsink is 650gm
3001685g of which heatsink is 725gm
Input from Pot or joystick (5K to 10K) or voltage following
Single-ended mode0-2.5v (adjustable) for 0-25v outseparate forward reverse signal
Joystick mode 5.5v +/1 1.5v speed and direction
Mode switchSingle ended or Joystick
Brake output1Aovercurrent operates at about 1.2 amp


Input is suitable for a joystick (center zero) or for a single ended speed pot plus separate reversing switch (mode is selected on board by a movable link). There is an on-board adjustment to alter input sensitivity. Alternatively an external pot or switch can be added to give a user top-speed control.

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!

Output devices are kept in their safe operating area so failures are rare. However 4QD have considered the possible failure mechanisms. Worst would be an output device failing short-circuit so the drive would go to full speed. Such failures normally cause the MOSFET gate to go short-circuit. This condition is normally detected by internal circuitry and shuts the controller off completely and safely. Control circuit failures could be over-ridden by the ignition switch.

Mechanical construction is such that the controller can be mounted in thermal contact with the vehicle chassis, so this acts as additional heatsinking, although this is not normally required.

Please consult the factory for variations to the above specification or for more information.



The illustration above shows the 4QD-200. The 4QD-300 is 30mm longer.

Photographs are being added: click on the thumbnail for the full version.

4QD-300casedT/jpeg 4QD-300nocoverT/jpeg
4QD-300-48 4QD-300-48 without cover

Ordering and prices

Click on the link to the pricelist and the secure shopping cart.
ItemPrice ListAdd to cart
4QD-200-48 Add
4QD-300-48 Add


You can download the instruction manual, in PDF format, via our manuals and catalogues page.

Page Information
© 1996-2016 4QD/4QD Ltd.
Page's Author: Richard Torrens
Document URI:
Last modified: 2015