Knowledgebase Contact Us
How Can We Help?
< Knowledgebase

Eagle Speed Controller

This page is for reference only: the Eagle is no longer manufactured (manufacture ceased September 2005). Suggested replacement is the Porter.

4QD’s Eagle series is a motor speed controller for 12v, 24v, 36v battery operation. It is a MOSFET chopper driver giving fully variable fine speed control. The Eagle is a fully cased unit complete with wiring.

A close relative is the Egret – a bare board version of the controller which is more suitable for customer installation.

The controller is designed primarily for small, slow machines such as golf caddies with only one controller. It is not recommended for passenger carrying machines, for fast moving machines or for machines using multiple controllers. These restrictions are because the controller has no main capacitor, relying on being close to the battery, with very short power leads.

The Eagle is suitable for 12v, 24v or 36v operation with only one internal adjustment. The design has 4QD’s own special circuitry to reduce heat dissipation so 4QD’s 40 amp controller is similar in cost to industry standard 25 amp controllers.

The controller has a slow, linear acceleration ramp to give smooth power take-up. It also has unique power-down so that the controller itself draws no current when the speed control is at zero – the speed pot itself draws only ½ milliamp.

The ingenious design uses the three pot wires not only to control the speed, but also to operate the electronic ignition: at zero speed the controller deactivates and draws zero current. The leaded version has 4 wires, the 4th (yellow) wire being battery positive and it is only needed if a battery condition meter is to be used.


Supply voltage 12v – 36v (adjust gain preset to suit)
Supply current 20mA with no motor load
Output voltage 0 to 100% full speed
Output current (typical) 40 amp version 40 amps
35A – 1 minute rating
Voltage drop 280mV at 20 amps, typical
Switching frequency 20kHz approximately
Input 10k pot or Hand Control Box
Input voltage (gain at max) 0.6v power up
3v full speed
6.5v overvoltage cutoff
Acceleration ramp time 2.3 secs, approx (to full speed)
Size (boxed) 111mm x 60mm x 31mm (without wiring)
Weight 100g
  • High speed circuit
  • MOSFET chopper
  • Half Bridge
  • Fast current limit on drive.
  • Electronic Ignition – Pot.
  • Pot fault protection (voltage).
  • Ramped acceleration
  • Without main capacitor.
  • Unidirectional. Reversing by external switching.
  • Input is suitable for a standard 10K potentiometer. Various speed controls can be supplied as extras, including a spring-return-to-zero speed pot arrangement suitable for hand operation.
  • Power connection Torberry 30 amp type, motor connections are by tails.
  • Stand-off timer is available for golf caddies, quantity orders only.
  • 4QD can also supply suitable LED battery indicators.

View above is of cased controller EAL-40, as preferred version supplied.

Hand Control Box

Optional hand control control box, available for 12v operation only. The hand control has a 3 pin connector strip and we supply a 3 pin IDC separately so that you can feed the wire through the framework of the caddy before fitting the connector. The box needs a 10mm hole drilling to feed out the lead to the Eagle.

The unit is current limited with 4QD’s fast monitoring circuitry so it is safe with any motor, whether stalled or even into short circuit. The current limit folds down as the controller heats up keeping the MOSFETs safe until the case is well over 100°C.

The control range of the standard controller is approximately correct for 24v operation with a 10k pot or twist grip. For other values of pot or battery voltage the internal gain control requires adjustment.

The controller in its standard form (cased with leads) is also very suitable for low volume users and the repair/replacement market.


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