Electric Bobby Car Hoverboard Upgrade

This project puts four 350W hoverboard motors in a Big Bobby Car toy vehicle, to give it independent four wheel drive and a top speed of 29km/h with turbo activated. All controlled by two potentiometer triggers on the steering wheel.

• Electric Hoverboard Monorover R2 Teardown

Specifications

• Project start: January 2019
• Main controller: STM32F103 72MHz ARM Cortex-M3 core
  • Flasher: ST-Link V2 Programming Unit clone
• Motors: 4x direct drive 3-phase brushless electric wheel hub motors with hall effect sensors, 350W ea
  • Continuous Current(A): 1 to 25A
• Tire type: non-pneumatic rubber tire, road pattern
• Tire size: 7-inch / 170 mm
• Battery: Lithium-ion rechargeable 18650-cells, 10S2P 36V 4400mAh 158.4Wh pack with XT60 connector
  • Upgrade: Controller can handle 13S (48V), 12S battery upgrade easiest
• Charger: Lithium-ion charger 42V 2A 3-pin connector with built-in fan
  • Upgrade: External charger for anything else
• Internal connectors:
  • PCB headers: JST B4B-XH-A 2.54mm pitch
  • Cable connectors: JST SM 4-pin and 5-pin 2.54mm pitch
• Vehicle base type: BIG New Bobby Car Red - important it's the BIG for leg carryability
• Dimensions assembled: L57 x W30 x H39 cm
• Original load-bearing: 50 kg max.

Control inputs

The hacked firmware supports a quite a few different types of control types, either partially or fully emplemented:

1. ADC Analog voltage input via potentiometer
2. I2C Nintendo Nunchuck official remote
3. UART Serial control via another MCU or directly via terminal
4. PPM Remote control via R/C radio

Overview

A rough overview of the components in the system.

Schematics

• File:Hoverboard schematic full reverse.pdf - Full reverse engineered schematic of the classic hoverboard circuit board
• File:Hoverboard schematic simple reverse.pdf - Simple schematic the circuit board

Pin-out

Pin-out of the hoverboard connections, by NiklasFauth:

Illustration courtesy NiklasFauth.

STM32F103 MCU pin-out:

Throttle filter and connection board

This is a PCB I designed to break out the ADC/UART/PPM/I2C signals to make it easier to finish the build. It has master and slave throttle splitting, where one driver board can be turned off without interfereing with the other - allows for 2x2 front/rear or 4x4 drive! It also adds filtering to the analog signals for voltage/potentiometer based throttle and pull-ups to the I2C-lanes for Nunchuck-throttle. All configurable via solder-jumpers for quick setup/change.

Inspired by the Jan Henrik break-out boards.

• bobbycar_throttle_rev6 - Gerber-files

• File:Bobbycar hoverboard throttle breakout schematic.pdf - Schematic of the throttle filter and connection breakout board

Inspiration

• Larsm Allrad e-Bobby Car - great write up and custom firmware fork
• Niklas Fauth Hoverboard firmware hack - original firmware
  • GPN18 HowTo: Moving Objects - great talk
  • Build Instruction: TranspOtter - Another build, lots of helpful pictures
• Fisch's detailed build guide - great documentation of the assembly
  • Fisch's trailer build - trailer for the Bobby Car
• Jan Henrik breakout boards - PCBs for easy connection to serial and Nunchuck