Is this yet another mod for the Razor’s Crazy Cart, a kids’ toy with one front wheel and two caster wheels in the back? Yep, but it is not similar to anything I’ve seen on the internet. I offer a solution which leverages the availability of scooter and hoverboard components. The vehicle you get at the end reaches at least 30kph, making it way more fun and dangerous!

1. ABOUT HOVERBOARDS

Hoverboards contain two inclination sensors, two motor controllers, two wheels and a lithium-ion battery (usually 10S-2P, 42V). Those features make them the perfect platform to cheaply build electric vehicles. LucysRausch has done extensive research on how the hoverboards can be reflashed with custom firmware and repurposed. Emanuel Feru has added Field-Oriented Control to the firmware, which increases the output power and efficiency of the powertrain.

2. MOUNTING THE WHEEL

The modification implies completely replacing the original chain-driven wheel and the 24V brushed electric motor with a brushless DC motor from an electric kickscooter. I started by removing everything from the fork and test fitting. I had to drill out the hole in one side to make it square so that the motor can fit. The new wheel had two sides – one with the wires and one without. I tapped an M10 thread on the side with no wires. Afterwards, I used a bolt to hold the wheel in place from one side, while the other side fit nicely into the enlarged hole in the fork.

3. WIRING EVERYTHING UP

Then I had to deal with the wiring. The motor part should be obvious, but always test with a current-limiting power source. The hoverboard’s 42V charger works really well for that (it has a 2A limit).

The cart’s original pedal has 5 wires. 2 wires go to a push button that gets shorted when the pedal is pressed, and the other 3 go to a hall effect sensor. The button had likely been added as a protective measure in case the hall sensor would give a false reading. I omitted the button and only connected the hall sensor to the analog inputs of the hoverboard ESC.

The firmware was configured as VARIANT_ADC, with a command to disable the unused motor output on the board.

4. WILL IT HANDLE 12S and 48V?

Although the hoverboard ESC is rated at 42V max, I was tempted to try it with my 50V 12S battery pack. All the capacitors and FETs are rated for at least 63V, so I plugged the battery in without much hesitation. As expected, the magic smoke didn’t come out and the cart started driving with a noticeable increase in power. The speed record of 31kph was set in this configuration.

Here is a video where I test the max speed with the modifications.

5. A XMAS EXTRA

As Christmas was coming up, I decided to decorate the cart as a sleigh. The front wheel survived the mechanical stress of around 50 different people testing it, many of whom didn’t particularly care about careful driving. We must have gone through two or three completely charged batteries. It was an absolute blast and I am now completely confident that this modification was successful.