Slowly sorting through the parts now! The eBay kit came with a whole range of fun toys to play with:

• Throttle potentiometer
• Headlight/horn unit
• Two brakes with electrical switch output (for brake lights and motor braking)
• 24V DC motor
• 24V DC-DC motor controller (with many other functions specific to electric bicycles)
• Motor mount
• Key start switch
• Ratcheted mounting “thing”
• Bike chain to couple the motor
• Various mounting screws and accessories

For my case I am interested in only the motor, DC-DC converter, throttle control and anything that helps connect these devices to the bicycle.

The motor is a 3000rpm 24V DC machine with an inbuilt step down gearbox with a 9.78:1 ratio. I have seen this exact motor in many auctions online, each claiming different power ratings (200W – 350W). It’s going to be fun seeing just how much current it will try to draw under load.

Similarly, the matching motor controller is a 24V DC-DC step down converter with a continuous current rating of 21A. It claims to be 250W, but it sounds more like 500W (peak at least). Interestingly if the voltage drops below 20V it reduces the output current instantly, but once the voltage rises back above 20V it will immediately try to run the motor again. Other motor controllers will sometimes shut off for ‘x’ seconds – an annoying feature when playing with “soft” voltage sources. The “1-4V” is for the throttle potentiometer voltage levels.

The throttle potentiometer up close:

It seems to be nothing more than a potentiometer, though I am yet to actually measure its output with any instruments.

Next up is the key start switch. I have no idea how I’d mount this and it seems useless for the most part.

So instead I made it a switch to turn on my 3D printer: