Lithium battery in uninterrupted power system(UPS) is increasingly widely used, and security has become the focus of industry attention. UL9540, as a safety standard for Energy Storage Systems and devices (Energy Storage Systems and Equipment,ESS), is widely used in battery system certification. So, does UPS lithium battery need to meet UL9540 certification? This article will focus on this issue and make an in-depth analysis from the aspects of standard scope, UPS system characteristics, safety requirements and practical suggestions.

1. Introduction to UL9540 standard

UL9540 is a safety standard for energy storage systems issued by the Underwriters Laboratory (UL), covering the design, manufacture, installation and operation safety of battery systems. This standard is mainly aimed at fixed energy storage systems, especially large-capacity lithium battery energy storage devices, and focuses on preventing battery thermal runaway, fire and electrical safety risks. The UL9540 standard includes the electrical performance, mechanical safety, thermal management, fire and explosion prevention and system monitoring of the battery system.

The certification of UL9540 not only improves the safety and reliability of the product, but also facilitates the promotion and application of the product in the North American market, meeting local regulations and insurance requirements.

II. Features of UPS system and lithium battery

UPS system is mainly used for key equipmentProvide power guarantee to ensure continuous power supply when mains power is interrupted. Traditional UPS mostly uses lead-acid batteries as energy storage units, but in recent years, lithium batteries have gradually replaced lead-acid batteries with their advantages of high energy density, long service life and lightweight.

The main features of UPS lithium batteries include:

• relatively small capacity: UPS battery pack capacity is usually smaller than energy storage power station battery pack, which is mainly used for short-term power supply.
• High system integration: The battery pack is often integrated within ups cabinet or adjacent to the device, with limited space.
• Strict security requirements: UPS is usually deployed in office buildings, data centers and other places, requiring extremely high security and reliability.
• The operating environment is relatively controlled.: UPS is generally deployed in a constant temperature and humidity environment, and the battery temperature and environmental conditions are relatively stable.

3. Does UPS lithium battery need UL9540 certification?

1. Analysis of the scope of application of the standard

UL9540 is mainly aimed at fixed energy storage systems, especially battery systems with large energy capacity and independent installation. Standard emphasis on batteryThe safety protection capability of the system under various abnormal conditions, including fire spread, explosion risk and electrical safety after thermal runaway.

However, the lithium battery system for UPS generally has a small capacity and exists as a part of the whole UPS system, which is usually not an independent energy storage system unit. Therefore, from the perspective of standard application, UPS lithium batteries do not necessarily require UL9540 certification.

2. Differentiation of relevant standards

for UPS battery, the more commonly used security certification standards in the industry are:

• UL1973: suitable for batteries used in power systems and telecommunications equipment, covering the safety performance of battery cells and battery packs.
• UL1642: mainly aiming at the safety performance test of lithium battery monomer.
• UL9540A: As the test method of UL9540, it is specially used to evaluate the battery thermal runaway and fire risk.

Generally, UPS uses lithium battery pack to meet UL1973 and UL1642 standards first, rather than complete UL9540 system certification.

3. Supervision and market demand

in the United States and other regions, if UPS equipment and its battery systems are put on the market, they must meet local electrical safety regulations and fire protection specifications. Some high-end UPS or data centers may require battery systems to have UL9540A test reports to prove the safety performance in case of thermal runaway.

In addition, if the UPS system design contains a large capacity lithium battery energy storage module, or the battery system is installed as an independent module, UL9540 certification may be required.

IV. Safety design and certification practice of lithium battery for UPS

although UL9540 certification is not necessarily mandatory, the safety design and certification of UPS lithium batteries cannot be ignored. The following are the key points of design and certification:

1. Battery selection and certification

select lithium battery monomer and battery pack that have passed UL1973 and UL1642 certification to ensure that the battery itself has good safety performance and quality assurance.

2. Battery management system (BMS)

3. Thermal Management design

reasonable thermal management schemes, such as air cooling or liquid cooling, ensure that the battery temperature is kept within a safe range and reduce the risk of thermal runaway.

4. Fire and explosion-proof measures

UPS battery system shall design isolation fire structure and explosion-proof device, adopt flame retardant materials and safety valves, etc. to reduce the impact of accidents.

5. Comply with national and regional standards

in addition to UL standards, it is necessary to meet the Electrical Safety and Fire Protection specifications of the country or region, such as NFPA 855 (fire protection specifications for energy storage systems in the United States), IEC 62485-2, etc.

Whether the lithium battery for UPS needs UL9540 certification depends mainly on the capacity scale of the battery system and the system integration method. Generally, lithium battery systems with small capacity, which are part of UPS, mainly meet UL1973 and UL1642 standards, while UL9540 certification is not mandatory. However, for UPS battery systems with large capacity or as independent energy storage units, UL9540 authentication will become an important security authentication indicator.

Whether UL9540 certification is required or not, UPS lithium battery system must attach great importance to safety in the design and application process. Through reasonable battery selection, perfect battery management, effective thermal management and fire and explosion prevention measures ensure the stable and reliable operation of the system and ensure the safety of users and equipment.