Greenpower

Welcome to the 4QD Greenpower beginners page! 4QD have been involved with Greenpower for many years. Our controllers have been used in hundreds of cars, and many of the winning teams have used our more advanced products. This page is to answer some of the basic questions that we get asked by both students and teachers.

Why do I need a speed controller?

• Although some cars just use a relay to switch power to the motor on and off, this is a crude method of starting off. The motor instantly goes to full power, and this surge can be strong enough to rip motors off their mountings, or damage gears. Installing a speed controller between the battery and the motor allows a soft start up to be achieved, it also allows the driver to adjust the speed just like a normal car.

Which speed controller is best for a new team?

• The Porter 5 is the basic controller which we supply to Greenpower, and is fine for a new team. The Porter 10 gives a bit more “headroom” in terms of current capacity, and tolerance of overloading. Both these models have reverse polarity protection – meaning they won’t blow up if the battery wires are connected back to front. (The more advanced models do not have this protection, and do not offer significant benefits for a new team, there are other factors that will be more important).
• It is worth considering the water-resistant coating too, races in the UK can be wet and electrical systems and moisture do not mix well!

How should the speed controller be mounted?

• Any controller will generate some heat, and it is very important to mount the controller so that this heat can be dissipated efficiently. If there is insufficient cooling it will overheat and stop or be damaged. It is best to mount the controller on an aluminium plate that can be exposed to an airflow – but be sure to protect it from rain or spray.
• We have this page which talks more about improving heat dissipation.

Is there anything else needed to protect the controller?

• It is really important to fit motor noise suppression components. The Greenpower motors have brushes and it is common for these to cause sparks, these sparks can create electrical interference which can make transistors inside the controller turn on when they should be off, with potentially destructive consequences. We have two pages that talk about noise suppression in more detail, the short version or the long one.
• Get the gearing right. A common mistake is for teams to gear the motor too highly i.e. to aim for a high top speed that the motor is not powerful enough to achieve. A motor that cannot reach its maximum RPM can pull high currents that can damage a controller. See this page for a more detailed explanation.

What other parts do I need for the electrical system

We’ve got this page that describes what we think a basic installation looks like. The parts are…

Throttle

• You can use a thumb throttle, a twist grip, or a simple potentiometer and push-button switch. The choice really comes down to how you want the driver to operate the car.
• Either a hall throttle or a 10k resistance potentiometer / throttle is fine.
• The throttle is connected to the speed controller with 3 wires – these can be in the throttle cable or you can use multicore cable. The 3 connections are pot top (5V), ground (0V) and pot wiper (variable voltage, indicating the speed required).
• We have a number of suitable throttles here.

Battery

• The 12V batteries are supplied by Greenpower. However batteries do vary individually so you may want to test them to make sure you have the best ones for the race.

Motor

• These are supplied by Greenpower. It is important to pay attention to keeping the motor cool, and to make sure that it spins close to its peak efficiency RPM. We’ve got this page that talks about this in more detail.

Ignition switch

• A key switch or a simple toggle switch is ok.

Battery isolator

• Needed to be able to disconnect the battery. We recommend having the battery isolator within reach of the driver.

Fuse

• This is needed to protect the wiring in case of a short circuit. A 40A fuse is sufficient.

Motor & Battery wires

• These need to be large enough to carry the current without getting hot or causing voltage drop. Use at least 4mm² CSA cable. We have some pre-crimped power lead sets  here.

We have a video below that shows how to wire up a Porter controller.

What else might we need?

• We have a test board that can be really useful for checking the controller is working – it takes the place of the control wiring so can be used when troubleshooting.
• A voltmeter. This is a crucial piece of equipment for testing the wiring, and someone in the team should be handy with this. (See this video if unsure how to use).

What’s next?

We’ve got this page of hints and tips on how to get the best out of a Greenpower car.

Good luck! and we hope to see you at the Grand Final.