On February 25, 2022, ANSI/CAN/UL 1973 the third edition was officially released. UL 1973, as the United States-Canada joint national standard, has a very high degree of recognition in the field of energy storage.
This standard update involves a number of major changes, including: cell test evaluation, battery system test evaluation, functional safety evaluation, new EMC requirements, metal-air batteries and sodium-ion batteries and other new product test evaluation methods. The new standard comprehensively upgrades the safety requirements for energy storage batteries, further raising the market access threshold for energy storage products in North America.
UL1973 the main applicable product range:
1. Batteries and parts for light electric rails (LER) or fixtures
2. Batteries and parts for fixing and/or transportation
3. Stationary batteries for energy storage (PV systems, wind power stations, household energy storage, etc.)
4. Battery for vehicle auxiliary power supply (excluding power battery)
5. Unlimited chemical substances, including various types of batteries, supercapacitors, batteries and electrochemical capacitor hybrid systems, such as beta sodium batteries and fluid batteries
UL1973 fixed energy storage battery regular test items:
1. overcharge Overcharge
2. External short circuit Short Circuit
3. Protection of over-discharge protection Overdischarge
4. Temperature rise and working limit confirmation Temperature and Operating Limits Check
5. Unbalanced charging Imbalanced Charging
6. Withstand voltage test Dielectric Voltage Withstand
7. Grounding continuity Continuity
8. Failure Failure of cooling/thermal management system of Cooling/Thermal Stability System
9. Voltage Measurements of working voltage measurement Working
10. Locked-Rotor Test
11. Input Test Input
12. Wire stress relief test Stain Relief/Push-Back Relief
13. Vibration Vibration
14. Mechanical shock Shock
15. Crush
16. Static Force
17. Steel ball impact Impact
18. Drop (rack fixed module) Drop Impact (rack mounted module)
19. Wall Mount Fixture/Handle Test
20. Mold Stress Relief
21. Pressure release Pressure Release
22. Validation of pressure relief start value Start-to-Discharge
23. Temperature cycle Thermal Cycling
24. Moisture-proof Resistance to Moisture
25. Salt Fog
26. External flame exposure External Fire Exposure
27. Single Cell Failure Tolerance Test Single Cell Failure Design Tolerance
UL 1973:2022 Key Changes:
add Clause 16: High-rate discharge test;
added Clause 18: Discharge Overload Test;
add Clause 27: Electromagnetic immunity test, I .e. EMC test requirements (refer to relevant requirements of IEC 61000-4 series);
The battery cells and battery packs with echelon utilization of the energy storage battery shall meet the UL 1974 echelon utilization battery evaluation standard;
regarding the cell, the scheme referring to UL 1642 + difference test is no longer valid. The cell needs to be tested according to Annex E, and there are two cell test schemes available;
added clause 7.7 for transformers to meet UL 1562, UL 1310 or other equivalent standards, and the primary side of the transformer should be equipped with overcurrent protection devices. Transformers located in low-voltage circuits (I. e. ≤ 60 VDC) can also be evaluated according to the test in clause 26.6;
the reference to the relevant requirements for high-voltage isolation is replaced by UL 62368-1 from UL 60950-1;
added test requirements for sodium ion cells, refer to test methods for lithium ion cells;
the concept of SELV is introduced, and the definition of dangerous voltage in Canada is unified with that in the United States: greater than 42.4 Vpeak or 60 Vdc;
it is specified that the backup energy storage system used in automobiles/saloon cars shall comply with UL1973, and refer to the evaluation method of LER battery;
short-circuit testing adds to the test assessment of the risk of short-circuit when the module is installed or maintained on site, in which case the battery module short-circuit test should also be considered;
refined the requirements related to functional safety assessment;
requirements for cell identification added;
the requirements for capacity inspection before cell test are specified, and the test capacity shall not be less than the declared capacity;
added metal-air battery test evaluation method;
the test and evaluation methods for lead-acid batteries and nickel-cadmium batteries are added.
Some notes on UL1973 certification:
1. The plastic shell shall meet the combustion level of 5VA, and the impact temperature level of RTI(Impact) shall be ≥ 80 ℃. Outdoor but also to meet the corresponding UV (anti-ultraviolet) grade and waterproof grade; if the metal shell to meet the requirements of anti-corrosion.
2. Insulating materials in direct contact with live parts shall meet the insulation requirements of UL746C (CTI,IPT,HAI,HWI,RTI).
3. In addition to reliable fixing, the connection terminal should also prevent short circuit, accidental disconnection or reverse connection and bear 10N thrust.
4. The junction box meets the wiring space requirements of NFPA70 Table 312.6 (A) or (B); The electrical parameters of terminals and cables should be greater than or equal to 125 times the electrical parameters of the product.
5. The cooling system requires the container to be corrosion-resistant and pass UL157 test. Hazardous containers or high pressure containers conform to ASME B31.3; When the cooling system fails, there is no danger. Reasonable wiring to prevent liquid leakage to live parts.
6. Electrical spacing conforms to Table 5.1, UL60950-1, UL840.
7. Insulation class and grounding requirements: double insulation/reinforced insulation/basic insulation, and grounding; grounding impedance needs to be less than 0.1 Ω.
8. Batteries installed in ≥ 50V circuits must be equipped with manual disconnect devices.
9. Electronically protected circuits need to be evaluated for functional safety, meeting UL991 and UL1998, or IEC61508
10. System safety analysis considers a single fault in the protection line.
11. Key components need to meet UL certification, usually including: batteries, cables, connectors, fuses and bases, PWBs, seals and labels.
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