Electric Skateboards (eSk8) have an interesting duality. They are getting easier and simpler to build, but the technology that powers them can be a lot to take in for the average rider. I’m going to breakdown some of the components and terminology used in most electric skateboards. For this article I will focus on electronics, motors, and gear ratios.
Most of eSk8’s are build on top of traditional downhill longboards and components. Downhill Longboarders typically travel at speeds from 30-40 mph, but 60mph is not unheard of, the current record for a downhill longboard run is right around 90mph! In comparison the current electric longboard record just under 60mph, so its safe to there is some work to do before the electric drivetrain can compete with gravity.
For more information on mechanical components such as trucks, wheels, decks, bearings, refer to ……. downhill links here…….
There are 4 main electronic components used in every eSk8:
- Electronic Speed Controller (ESC)
- Remote Control
While some boards may include additional components, these are the only required parts.
Modern electric boards, and almost any lightweight vehicle including ebikes, RC cars, drones and electric cars use a type of motor called a Brushless Direct Current (BLDC) motor. These are great because they have a very high power to weight ratio, which means a motor about half the size of soda can is capable of handling over 2000 watts of power. While BLDC motors have been around since the 1960’s, they have only recently made it to the mainstream use. This is because BLDC motors require complicated high speed electronics to be used effectively and efficiently, these electronics are packaged into a single device referred to as an ESC, which will be cover in detail in the next section.
BLDC motors an be further broken down into several types, currently the most common in use are Out-runners named because of a ring of magnets that rotate on the outside of the motor. The power and torque of a motor is directly related to the size of the motor, increasing the diameter or length of the motor will result in more wire windings, bigger magnets, and hence more torque. Common sizes used in production boards are 50mm diameter, and range from 50 – 65mm in length. While DIY/Custom boards use motors 63mm diameter and 54, 64, or 74 mm long. Motor names typically use the size to describe them where a 6354 will be 63mm diameter, and 54mm long, while this can vary by manufacture these dimension often represent the outer can of the motor. Some brands such Emax and Tacon state dimensions of the stator.
The Electronic Speed Controller or ESC for short, can be thought of as the electric heart of a board, it contains a microprocessor (tiny computer chip), sensors, and transistors (MosFET). The microprocessor follows various algorithms to regulate the voltage, current and temperature of the motor. While there is some success using ESC’s designed for large scale RC Cars and Boats, the ESC I will focus on is the an open source project created by Benjamin Vedder, appropriately named Vedder’s Electronic Speed Controller (VESC). The VESC is a general purpose BLDC ESC build around the STM32F4 microcontroller and a customized firmware based on ChibiOS. Settings can be customized for your application and motor by using the BLDC tool application, available on OSX, Windows, and Ubuntu.
At this time the VESC is the only esc I recommend for use on a electric skateboard, smooth takeoff, 60V (12s Lipo), and programmable features make it in a class of its own. While there may be lower cost options, none of them have the adjustability, or advanced drive algorithms (FOC) that the current VESC can offer. The VESC is currently on version 4.12, while the new and improved version 6.0 is due sometime in early 2017. The highly anticipated new v6 features a redesigned compact board layout, higher current DirectFET package mosFETs, and even integrated nrf24l01+ 2.4ghz wireless radio module.
For a quick introduction to the different types of batteries, check out this video by GreatScott.
Early electric skateboards like the first z-board used sealed lead acid batteries, basically several motorcycle batteries connected together. These batteries are basically an ABS plastic box filled with lead metal and liquid. This meant early eboards were heavy, low power and worst of all they had horrible range.
The big bang of eSk8 came in recent years with advances of battery technology using Lithium (Li) which is the lightest metal on the periodic table of elements. Lithium batteries come in various types and chemical compounds that have different strengths and weaknesses. For eSk8 there are few key features we need, low weight, high discharge, and high capacity; Li-ion and LiPo (lithium polymer) are the best in all of these aspects. Although advances LiFE PO4 technology has made them a viable alternative for high discharge/charge application, but the max energy density of this type is only around half of Li-ion and Lipo. Energy density is the ratio of battery capacity to size or weight.
The typical Li-ion battery comes in a form factor called the 18650, these battery cells are around 18mm diameter and 65mm long. They have a capacity from 2000-3600 mah and useable voltage range from 3.3 – 4.2V. A popular 18650 cell for eSk8 is the samsung 25R and LG hg2, which are used for their high capacity (2500/3000 mah) and high discharge rate of 25 amps continuous each.
Series and Parallel
4. Remote Control
Hobby style radio control transmitters for scale cars and boats are they easiest and most reliable way to control your board. 3d printed enclosures to make remotes more portable are
But full DIY solutions are becoming more popular. more