By: Flore Chiang, principal engineer, Consumer, Medical and Information Technologies
Overview and purpose of UL 4900, the Standard for Micromobility Charging Equipment
The first edition of ANSI/CAN/UL 4900, the Standard for Micromobility Charging Equipment, was published as a binational consensus Standard for the United States and Canada on Feb. 19, 2025. This Standard is the result of a collaborative effort initiated in 2023, involving industry representatives, manufacturers, fire services, testing and certification bodies, and code authorities.
The increasing prevalence of lithium-ion batteries across a wide range of consumer and industrial products has brought greater convenience and portability. From personal electronics like smartphones and laptops to micromobility devices such as e-bikes and e-scooters — and even energy storage systems — lithium-ion batteries have become indispensable. However, this widespread adoption has also raised safety concerns, particularly around the risk of fires and thermal runaway events.
Recognizing the escalating dangers associated with battery-powered products, particularly the fire risks in micromobility devices, the U.S. Consumer Product Safety Commission (CPSC) has stressed the urgent need for manufacturers to adhere to robust safety standards. This concern is echoed by authorities like the New York City Fire Department (FDNY), which has actively responded to a surge in lithium-ion battery fires.
Established safety Standards exist for micromobility, such as UL 2272, the Standard for Electrical Systems for Personal E-Mobility Devices, UL 2849, the Standard for Electrical Systems for eBikes, and UL 2271, the Standard for Batteries for Use In Light Electric Vehicle (LEV) Applications. But a crucial gap has been identified: the absence of specific safety standards tailored to the unique charging equipment used for the rapidly growing category of micromobility devices like e-bikes and e-scooters.
UL 4900 was developed to directly address this void, providing the necessary safety framework for these distinct charging systems, especially for public charging equipment.
Scope and applicability of UL 4900
UL 4900 specifically addresses the safety of charging equipment designed for use with a defined range of micromobility systems and their components. This Standard applies to charging equipment with rated voltages not exceeding 600 V, exclusively intended for use with micromobility systems, subassemblies or components covered by UL 2849, UL 2272 and UL/ULC 2271.
Examples of charging equipment covered by UL 4900 include, but are not limited to:
- Charging piles or stations specifically designed for micromobility devices
- Charging racks intended to simultaneously charge multiple e-bikes or e-scooters
- Battery swappable systems that include charging docks for individual battery packs used in micromobility devices
- Battery charging racks designed to charge multiple removable batteries for e-bikes or personal e-mobility devices
Key hazards and UL 4900 requirements
Micromobility charging equipment introduces distinct safety considerations. To mitigate these potential hazards, UL 4900 supplements the hazard-based safety engineering (HBSE) approach of UL 62368-1, the Standard for Audio/Video, Information and Communication Technology Equipment, by addressing the specific risks associated with micromobility charging.
Here's a summary of the main focus points:
- Protection against weather and other outdoor influences – UL 4900 addresses the need for charging equipment intended for outdoor use to withstand various environmental conditions. This includes requirements for protection against rain, dust, temperature fluctuations, and other factors that could compromise the safety and functionality of the charger.
- Protection of interconnecting (charging) cables – The Standard emphasizes the safety and durability of the cables that connect the charger to the micromobility device. This includes requirements for cable construction, protection against mechanical damage and evaluating the integrity of electrical connections to prevent hazards like short circuits or overheating.
- Protection of charging interface – UL 4900 includes specific requirements for the design and safety of the charging interface (the point of connection between the charger and the micromobility device). This aims to prevent electrical shock, support proper connection, and minimize the risk of damage or malfunction during the charging process.
- Battery swappable systems – UL 4900 addresses the safety of swappable battery systems, focusing on secure connections and preventing accidental contact during exchange. Safe storage, charging and handling of these batteries are essential, requiring continuous parameter monitoring and appropriate safety actions. Automated systems must verify device compatibility before charging. For emergencies, a readily accessible stop button is necessary for personnel present during battery exchange.
- Additional protection – Commercial or public micromobility charging equipment requires additional protection against weather and reasonably foreseeable misuse, including automatic supply disconnection upon failure of basic or supplementary safeguards, utilizing devices like ground fault circuit interrupters (GFCIs) or specific residual current circuit breakers (RCCBs) incorporating over-current protection (RCBOs) within 300 mm of the mains connection to disconnect all phase conductors with a specified air gap or personnel protection system.
- Safety of field wiring connections – The Standard also covers the safety of connections made during the installation of permanently connected charging equipment. This includes requirements for proper wiring methods, secure terminations and confirming that field wiring connections do not pose electrical shock or fire hazards.
- Temperature limits for current-carrying parts – Temperatures of current-carrying parts must not exceed the specified limits.
- Protection against inrush current – Micromobility charging equipment must be designed to minimize the risk of ignition during the charging interface’s initial connection.
- Protection against load dump – Micromobility charging equipment designed to charge multiple batteries simultaneously must maintain the effectiveness of all safeguards when subjected to a load dump condition.
- Protection against arc interruption – Connections intended for disconnection under load in micromobility charging equipment must be protected against arc interruption to prevent ignition during use.
- Thermal burn – Wireless power transmitters for near-field charging must incorporate safeguards to prevent burns from heated foreign metallic objects placed on or near them.
- Assessment of unforeseen hazards – For technologies, components, materials or construction methods not specifically covered by existing standards, UL 4900 requires a risk assessment of safeguard effectiveness to verify that the residual risk is no greater than that generally accepted by UL/CSA C22.2 No. 62368-1.
- Functional safety – Defined actions implemented electronically (e.g., sensors, actuators, software) to maintain a safe state regarding specific hazardous events or situations must be assessed against relevant standards (e.g., UL 991, the Standard for Tests for Safety-Related Controls Employing Solid-State Devices; UL 1998, the Standard for Software in Programmable Components; CSA C22.2 No. 0.8; CSA/UL 60730-1, the Standard for Automatic Electrical Controls — Part 1: General Requirements; IEC 61508) for appropriate performance classifications.
- Equipment markings, instructions and instructional safeguards – Specific operating instructions, instructional safeguards and appropriate equipment warning markings are required, such as “Risk of electric shock and fire.” Operating instructions are based on the micromobility charging equipment and the specific micromobility devices it is intended to charge.
UL 1487, the Standard for Battery Containment Enclosures and UL 4900
Days before UL 4900 was published, UL 1487, the Standard for Battery Containment Enclosures, was also published to address the explosion and fire hazard of batteries that are stored in a containment enclosure. Both Standards work in tandem with each other. UL 1487 focuses on the explosion and fire hazard that storing lithium batteries can present. UL 4900 focuses on the fire/electric shock hazard of charging lithium batteries in various environments.
A UL 1487 battery containment enclosure is not intended for charging micromobility equipment. Similarly, a UL 4900 micromobility charging equipment system is not intended to evaluate for battery thermal runaway containment. Both Standards are necessary to address the explosion, fire and electric shock hazards that are present when storing and charging lithium batteries. For fire and shock safety, any equipment that charges micromobility must meet UL 4900 requirements, and any equipment that is acting as battery containment must meet UL 1487 requirements. If a system performs both functions — charging and containment — it must comply with UL 4900 and UL 1487.
For more information about UL 1487, read our fact sheet.
Summary
UL 4900 provides a crucial framework for supporting the safe operation of micromobility charging equipment. By addressing the various hazards associated with this equipment, and supplementing the requirements of UL/CSA C22.2 No. 62368-1, this Standard helps to mitigate the risks of fire, electrical shock and other dangers. Adherence to UL 4900 is therefore essential to help protect users and property as the use of micromobility devices continues to expand.