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 Bobby Car Build - my version of the E-Bobby Car convesion
Electric Hoverboard Monorover R2 Teardown - overview of a Hoverboard

Specifications

Project start: January 2019
Controller: 2x Hoverboard main boards - 2015 date
- MCU: STM32F103 72MHz ARM Cortex-M3 core
- Flasher: ST-Link V2 Programming Unit clone
Motors: 4x direct drive 3-phase brushless electric wheel hub motors (BLDC) with hall effect sensors, 350W nom., 800W peak
- 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 - note that it's the BIG version, easier to put your legs over the front wheel
- Vehicle upgrade: Small cussion to improve seating comfort
Dimensions assembled: L57 x W30 x H39 cm
Original load-bearing: 50 kg max. - exceeded 150% 🤭

Control inputs

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

ADC Analog voltage input via potentiometer - safety pull-down resistors on ADC1 and ADC2 recommended, high frequency filter to smoothen out the voltage
I2C Nintendo Nunchuck official remote - I2C pull-ups required on SDA and SCL
UART Serial control via another MCU or directly via terminal
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 - Simplified schematic the circuit board

Pin-out

Schematic and pin-out of the hoverboard connections, by NiklasFauth. Pulled from the full schematic.

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.