[Editor's Note] Part 3 of the four-part micromobility series explores the types of personal micromobility solutions available in the consumer market, the technical challenges they face, how technology is solving them, and the challenges posed to personal transportation and consumers, including battery fires.

[Order of contributions]
Part 1: On Micromobility
Part 2: Urban Infrastructure and Micromobility
Part 3: Personal Transportation and the Challenges for Consumers
Part 4: What will micromobility look like in the future?


■ Personal Micromobility Solutions

Personal micromobility solutions come in all shapes and sizes, from electric bicycles and scooters to electric skateboards and hoverboards. Some people may use it as a means of transportation instead of walking or driving, while others may use it as exercise equipment.

Among them, electric bicycles are the most important micromobility solution. According to market research firm Precedence Research, the electric bicycle market is expected to grow at a compound annual growth rate (CAGR) of 9.89 percent from 2023 to 2032, reaching a market size of $44.08 billion.

Early electric bikes were heavy bikes with attached batteries and hub motors, but today’s electric bikes are much lighter and designed from the start to accommodate electric drive systems and batteries. The wiring is carefully routed through tubing in the frame to prevent damage. Mid-range and higher models feature a mid-drive motor unit between the pedals to optimize drivetrain efficiency and weight distribution (Figure 1).

○ Other micromobility

In addition to electric bikes, there are a variety of micromobility solutions such as hoverboards, Segways, electric skateboards and electric scooters. While owning these is legal, using them in the UK and most of the EU is restricted to private property. Because entering public areas such as sidewalks, roads, and bicycle paths is prohibited.

From an electronic design perspective, these products are equipped with a motor, control interface, and battery pack, just like an electric bicycle. The difference with an electric bicycle is in the control of the movement. These solutions rely entirely on the electric powertrain to control the user's operation and speed, either through a throttle or, in the case of hoverboards and Segways, through gyroscopic sensors.

■ Challenges of personal micromobility

Personal micromobility solutions have grown incredibly rapidly over the past few decades and will likely continue to do so, but they are not without their challenges. In addition to regulatory issues that need to be addressed, there are still technical challenges that need to be addressed with the personal micromobility solutions currently available.

○ Battery fire

The biggest problem is battery fires caused by faulty individual cells or battery management systems (BMS). According to the London Fire Brigade, there were 116 fires involving electric bike and electric scooter batteries in 2022, and this number is increasing. As of the start of 2023, there are reports of electric bike and electric scooter battery fires every other day on average. This increase in fires has led Transport for London (TfL) to ban services involving electric scooters, hoverboards and skateboards from 2021.

Recent micromobility batteries use arrays of lithium-ion 18650 cells to provide the required charge capacity and voltage (typically 36 V, 48 V, or 52 V). The electrolyte used in lithium-ion cells is lithium salt. Although lithium salts are ideal for this application, lithium salts are volatile and flammable. Therefore, lithium cells are extremely sensitive to temperature changes and can undergo thermal runaway.

If a cell is damaged in any way, whether due to damage, manufacturing defects, external heat, overcharge/over-discharge, etc., the temperature can rise rapidly, causing a fire or explosion. This can then ignite the remaining cells in the battery pack and cause a runaway fire. Furthermore, since the cathode of a lithium-ion battery contains oxygen, any fire can be very difficult to extinguish by supplying fuel to itself.

■ Safety Improvement

Micromobility fires are quite common, and are mostly low-end products. Fires in mid- and premium-tier manufacturers are rare.

○ Safe battery design

For cost-saving reasons, low-end batteries often use a simple BMS that only balances cell charge and discharge, with fuses for the charging lines and output outlets.

By comparison, high-end models include much more sophisticated safety measures, such as those offered by Littelfuse. Littelfuse offers a variety of solutions for electric bicycles and other micromobility (Figure 2).


This battery block diagram suggests a negative temperature coefficient (NTC) thermistor, such as the Littelfuse KC series, which can be used to monitor the temperature of individual cells. Therefore, the microcontroller can take action before thermal runaway occurs.

In addition, battery-level overcurrent and overvoltage protection devices, such as the compact surface-mount 0805L series polymeric positive temperature coefficient (PPTC) devices, can be used together, and additional protection can be provided using Littelfuse ITV battery protection devices (Figure 3).


The ITV battery protection device, which is inserted between the combined output of the cells and the BMS unit, is a fast-responding, cost-effective surface-mount solution designed to shut down the circuit when the IC or FET detects overvoltage.

■ Conclusion

Micromobility fires can pose a significant risk to consumers and can be a barrier to gaining market confidence. To ensure the safety of lithium-ion batteries, designers must incorporate a variety of safety measures related to voltage, current, and temperature at both the battery pack level and the cell level. Additionally, rigorous third-party testing and compliance with local regulations will help prevent thermal runaway by reducing the potential for design defects and ensuring that any defects that do occur occur in a safe manner.

In Part 4, the final installment in this series, we explore the future of micromobility.

※ About the contributor

Mark Patrick is part of Mouser’s EMEA team and joined Mouser Electronics in July 2014. Prior to that, he held a senior marketing position at RS Components. Prior to RS, he spent eight years at Texas Instruments in applications support and technical sales roles. He holds a first class honours degree in electronic engineering from Coventry University.