New Battery Meter

Here’s a preview of our update to our BCM-524 battery meter. The old analogue model has been extremely popular and features in many designs. However battery technology marches on and we wanted something that would give more accurate results with lithium batteries and other types with flat discharge curves. We’ve used an ATtiny micro to produce a programmable replacement that can work with the small voltage changes these batteries give. Other features include temperature compensation, and a switchable output that can be used for a low voltage cut-off. Oh, and it still has the same hole spacings so it’s a direct physical replacement in most applications.

The first model will be suitable for 12V – 24V, we’ll produce some standard voltage curves for the common battery technologies, but if you want something custom please let us know.

Pronch’s PDQ Power Trike

Pronch Mulholland brought his PDQ power trike in for some TLC. We’ve now found a way to fit our Porter 5 into the existing control box making for a neat installation that retains most of the existing wiring. We’ll write it up when time permits and put instructions in our knowledgebase.

pdq power trike

The supersize battery box is made from steel and houses 3 x 15AHr sealed lead acid batteries. It gives much better traction for hill starts as well as extending the range.


Our New Baby

Drum roll………. 4QD are pleased to introduce to the world our new baby – the SST-31.

It’s a small but perfectly formed, very clever, single direction controller for 12-35V and up to 30A.

It’s built around a Picaxe microcontroller, so as well as providing basic motor speed control, it can accept multiple control inputs and also has spare outputs for controlling ancillary equipment.

It’s ideal for the smaller motor control project, particularly those that need some element of customisation. We’ve made the software open source, and the Picaxe development system makes writing your own programs easy.

Pro-160 boards

An exciting day for us – we’ve just received the first PCBs for our new Pro-160 controller.

This is a modular, relay free progression from the Pro-150, headline features are

  • Up to 250A and 84V depending on mosfets, capacitors, and heatsink fitted.
  • 2 x 16 digit display.
  • Multiple control modes e.g. open loop, RPM, and current control.
  • Radio control input.
  • Separate communications board.
  • Loads of other features and control inputs.

Where’s my soldering iron? – lets get building!


Electric Monster Truck

Is this a mini monster truck, or a monster mini truck?

Either way it’s a great piece of engineering and a totally new take on what to do when the kids say “Dad, can you build us a car please?”

A water cooled 4QD-300L is fitted to deal with the high currents that this beast needs.

Electric monster truck
Electric monster truck using a 4QD-300L


Here’s a sneak preview of our soon to be launched Softstart. This is a small motor controller stripped down to the basics that gives a progressive start-up ramp to eliminate the large torque spikes that occur if a motor is switched on instantly via a relay or switch. We’ve designed this using a small microprocessor which means that the ramp time is configurable, and also given it a couple of other inputs so that it can be used for a variety of other simple switching tasks. We’ll be making the code available to allow [encourage?] experimentation.

Renault Voiturette

Here’s a lovely rendition of an early Renault Voiturette that a customer has built. It’s using one of our Pro-150s driving a pair of electric scooter motors.

Renault Voiturette
Renault Voiturette with a Pro-150 driving 2 electric scooter motors

Electric Trials Bike

Here’s a prototype electric trials bike that a customer brought in today. Really powerful and very light, it’s using a Lynch motor and one of our 4QD-300s which we are modifying to give the required throttle response.

electric trials bike

Humvee Turret Drive

Here’s one of our Pro-150s driving the turret ring gear on a pretty serious looking Humvee. It’s a challenging application as it has to change direction rapidly, and the EMI and physical environments are hostile.

humvee turret

Water Cooled Dummy Load

Seeing as how we’d melted our air cooled test load, we knew that we needed something that could handle some really high currents. Here’s a quick video showing how we built a water cooled dummy load.

Steeple Cab Electric

This mighty machine has been built by Doug Wilkinson. It weighs in at 1200 lb and is using a 4QD-200.

Doug Wilkinson's Steeple Cab Electric. Using a 4QD-200, and weighing 1200lbs

Scarletts Ferrari

I’ve just got to share this clip of Scarletts Ferrari, it’s using one of our DNO-10s and looks absolutely stunning. I guess that’s what happens when your Dad restores cars for a living – not that I’m jealous – oh no!

Follow the links to see some of the other fantastic cars he’s made.



Steve W sent us this picture of his Robot Wars contestant Gyrobot. It’s using one of our Porter 10XXs to control what must surely be one of the most powerful rotating energy weapons we’ve seen so far. We’ve made some mods for him to allow the current limit to be adjusted, and he’s also trying out a prototype heatsink arrangement to cope with the rather unusual power profile.

gyrobot in robot wars

Panto magic

Mr B sent us this picture of a highly classified Xmas panto prop built out of a commercial scissor table with one of our Porter 10s driving a hydraulic pump.

panto magic

Oh not it’s not……

Cooling results

…and here they are…. the first results for our new range of cooling options for the 4QD-300.

cooling results

The finned air cooled heatsink gives approx 50% increase in performance and this can be increased further if a fan is fitted.

It’s the water cooling that we like the most though, it turns the 4QD-300 into a real powerhouse. More detailed results at higher currents to follow once we have uprated our test rig!

We’re still working out the pricing for these but please get in touch if you are interested.

Water Cooling

Here’s a picture of our embryonic test set up for the soon to be launched water cooled 4QD-300. On the left is our current air cooled load cell, ammeter, and data logger. Front right is the 4QD-300 fitted with the water cooled heatsink. Right rear is the control and pump for the water. We’ve left space for a second pump which will be needed when our water cooled load cell is ready. Can’t wait to run this lot and see what results we get.

water cooled
test rig for water cooled 4qd-300

Tow truck

Jeff Ivers sent us this picture of his tow truck that he uses to haul a gravity racer to the start line.

Fitted with one of our Pro-150s

Uprated 4QD-300

Here’s a sneak peak at our uprated 4QD-300X. We’ve had a custom heatsink made which really improves it’s ability to handle high currents for extended times. During testing it melted our test rig and was still only warm to the touch! Full details will be announced once we’ve built a new test rig.

The heatsink itself will also be available as an aftermarket upgrade.



We’ve also got a water cooled version coming soon that will take things even further, and be particularly suitable for electric boats.


PDQ Powertrike

Patsy brought a couple of PDQ Powertrikes to us with broken control boxes. We fitted one with a Porter 5, and one with a DNO-05 to see if we could get reverse, however we discovered that the motor has a one way clutch that prevents reverse from driving. The standard twist grips were swapped for our Magura throttles, and we fitted one of our key switches to the DNO for security.

WP_20160802_002DNO with key

















Two weeks later Patsy sent us this picture of the neat bag she made to tidy it all up

Patsys powertrike cover

And the verdict:….

"The power box is working briliantly, so speedy that I tend to do wheelies
unless I am careful. The battery is lasting longer too........
Thanks again for doing a great job on the trike."

Enduro bike

Chris Sharpe sent us these pictures of his enduro bike. It’s running a 4QD-300 controller, Lifepo4 batteries, and an Agni 95 motor.

Chris Sharpe 1 Chris Sharpe 2

Product testing

Here’s Charlie having his first go at driving a loco. Thanks to Pete Ottley of Riverside Models for letting him try out his Class 37 at ndsme

Running a Pro-120 with switchable radio control / hand throttle.


A grand day out

A big thank you to the Electric Boat Association for inviting us along on their trip around St Ives / Earith.

Electric boats 1

In the foreground is Cedric Lynch’s remarkable electric canoe. It has no batteries [apart from a very small one to “get under bridges”], uses a small Lynch motor, a model aircraft propellor, and one of our old 1QD controllers. Goes jolly fast it does too!

Welcome to our new website!

We hope you like the new look. We’ve tried to make it easier to find the controller and accessories that you need, whilst still keeping all the interesting information and technical support articles in a new knowledge base that makes it easier to find what you’re looking for.

All of our controllers are now on the range page.

In our new knowledge base we’ve sorted all of our old articles into some clear categories. All of the information about our old controllers is there, and a lot of background information about motor speed controllers. Our sister site still has all the reference and circuit information.

We’ve also added some application areas that show just a few of the areas that 4QD controllers are being used in.

We’d like to say a big thank you to Adam from Cambridge web solutions for his excellent work in creating the new site.