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As the North American energy storage market continues to expand, safety compliance for Stationary Energy Storage Systems (ESS) has increasingly drawn attention from regulatory agencies, insurers, and end users. UL 1973:2022, as a U.S.-Canada joint national standard, enjoys high recognition in the energy storage field and serves as a critical technical compliance threshold for energy storage products entering the U.S. and Canadian markets.
On February 25, 2022, ANSI/CA/UL 1973 Third Edition was officially released. The new edition introduced several significant updates, including new test requirements for sodium-ion batteries and metal-air batteries, the introduction of Functional Safety assessment, and additional Electromagnetic Compatibility (EMC) requirements, further raising the safety compliance threshold for energy storage systems in the North American market.
UL 1973:2022 Scope of Application
Applicable Product Categories
UL 1973:2022 applies to battery systems in the following application scenarios:
- Stationary Applications: PV energy storage, wind energy storage, grid-side energy storage, user-side energy storage, telecommunication base station backup power, UPS uninterruptible power supply, etc.
- Vehicle Auxiliary Power: Non-propulsion vehicle battery systems
- Light Electric Rail (LER): Auxiliary power systems for rail transit such as trams and light rail
Exclusions
- Traction batteries (for road vehicles) — applicable to UL 2580 standard
- Small consumer batteries (for portable electronic devices) — applicable to UL 2054 or IEC 62133-2 standards
- Electric Vehicle Supply Equipment (EVSE) — applicable to UL 2594 and related standards
Core Test System of the Standard
The UL 1973:2022 test system can be divided into four major categories: Electrical Safety Tests, Mechanical Safety Tests, Environmental Reliability Tests, and Functional Safety Assessment, forming a complete energy storage battery safety evaluation matrix.
I. Electrical Safety Tests
Electrical safety tests are the foundational component of the entire evaluation system, mainly verifying the safety performance of battery systems under electrical stress.
| Test Item | Test Purpose | Pass Criteria |
|---|---|---|
| Overcharge Test | Verify tolerance to overcharge conditions | No fire, no explosion, no leakage |
| External Short Circuit Test | Simulate external short circuit, verify protection | No fire, no explosion, enclosure temp. within limits |
| Overdischarge Protection Test | Verify overdischarge protection reliability | Protection operates normally, voltage above lower limit |
| Charge/Discharge Endurance Test | Verify safety under long-term cycling | No safety incidents during cycling |
| Dielectric Voltage Withstand Test | Verify electrical insulation strength | No breakdown, no flashover |
II. Mechanical Safety Tests
Mechanical safety tests simulate the mechanical stresses that battery systems may endure during transportation, installation, and operation.
| Test Item | Test Purpose |
|---|---|
| Vibration Test | Simulate vibration stress during transport and operation |
| Shock Test | Simulate mechanical shock during handling and installation |
| Crush Test | Evaluate safety performance under external mechanical force |
| Drop Test | Simulate accidental drop conditions |
III. Environmental Reliability Tests
Environmental reliability tests verify the safety performance of battery systems under different environmental conditions.
| Test Item | Test Condition |
|---|---|
| Temperature Cycling Test | -20°C to +60°C temperature cycling |
| Humidity Test | High temperature and high humidity (e.g., 85°C/85%RH) |
| Salt Spray Test | Evaluate corrosion resistance in coastal/corrosive environments |
| Enclosure Protection Rating Test (IP Code) | Verify dust and water protection (e.g., IP54, IP65) |
IV. New Requirements: Functional Safety & EMC
Functional Safety Assessment: UL 1973:2022 introduces Functional Safety assessment requirements, based on IEC 61508/ISO 26262, reviewing the hardware and software safety functions of the BMS.
EMC Requirements: The 2022 edition adds EMC testing requirements to ensure stable operation in electromagnetic interference environments and prevent unacceptable interference to surrounding equipment.
Collaborative Standard System for North American ESS Certification
UL 1973 is typically used in conjunction with the following standards, forming a complete North American ESS certification system:
| Standard | Standard Name | Scope |
|---|---|---|
| UL 1973:2022 | Standard for Batteries for Use in Stationary Applications | Cells, modules, battery systems |
| UL 9540:2024 | Energy Storage Systems and Equipment | Complete ESS (including PCS) system integration safety |
| UL 9540A | Test Method for Evaluating Thermal Runaway Fire Propagation in ESS | Cell/module/unit/installation level thermal runaway evaluation |
| IEEE 1547:2018 | Standard for Interconnecting Distributed Energy Resources | ESS grid interconnection technical requirements |
| NFPA 855 | Standard for the Installation of ESS | Installation locations, spacing, fire protection requirements |
