UL1642 - Testing for Lithium Batteries
UL 1642 is a safety standard specifically for lithium batteries, developed by Underwriters Laboratories (UL). It focuses on ensuring that lithium cells (both lithium-metal and lithium-ion) are designed and manufactured to be safe for use in consumer and industrial products. Any company making or using lithium cells in products such as phones, laptops, power tools, medical devices, or wearables should consider UL 1642 certification.
The purpose of the test is to reduce risk of fire, explosion, leakage, electric shock and ensure batteries are robust against abuse such as short circuits, overcharge, impact, or crushing.
UL1642 test applies to:
- Individual lithium cells, not complete battery packs.
- Covers primary (non-rechargeable) and secondary (rechargeable) lithium cells.
- Focuses on electrical, mechanical, and environmental safety.
| Test Name | Description | Requirements | Number of Primary Cells to be Tested | Number of Secondary Cells to be Tested |
|---|---|---|---|---|
| Low Pressure (Altitude Simulation) Test | • Cells will be stored for 6 hours at an absolute pressure of 11.6 kPa and temperature of 20±3°C | Cells should not explode or catch fire due to low pressure, as well as no leaking or venting | 5 fully charged, 5 half charged, & 5 fully discharged | 5 fully charged & 5 conditioned by cycling |
| Heating Test |
• Cell will be heated in a gravity convection or circulating air oven with initial temperature of 20±5°C, raised at a rate of 5±2°C per minute to 130±2°C and remain for 10 min then returned to 20±5°C and examined. • For cells specified for temperatures above 100°C, conditioning temperature will be 30±2°C above manufacturer’s maximum specified temperature and for lithium metal batteries, conditioning temperature will be 170±2°C. |
Cells should not explode or catch fire | 5 fully charged & 5 half charged | 5 fully charged & 5 conditioned by cycling (10 if operating conditioning is needed) |
| Temperature Cycling Test |
Cell will be placed in a test chamber and subjected to the following tests: • Raising chamber temperature to 70±3°C within 30 min and maintaining for 4 hours • Reducing chamber to 20±3°C within 30 min and maintaining for 2 hours • Reducing chamber to -40±3°C within 30 min and maintaining for 4 hours • Raising chamber to 20±3°C within 30 min • Sequence will be repeated for 9 cycles, stored after the tenth at 20±5°C for minimum 24 hours before examining |
Cells should not explode or catch fire, as well as no leaking or venting | 5 fully charged, 5 half charged, & 5 fully discharged | 5 fully charged & 5 conditioned by cycling |
| Vibration Test |
• Cell will be subjected to harmonic motion with amplitude of 0.8 mm (1.6 mm total maximum excursion) • Frequency will be varied at a rate of 1 Hz/min between 10 and 55 Hz and return in more than 90 but less than 100 minutes • Battery will be tested in each of its mutually perpendicular directions |
Cells should not explode or catch fire, as well as no leaking or venting | 5 fully charged, 5 half charged, & 5 fully discharged | 5 fully charged & 5 conditioned by cycling |
| Shock Test |
• Cells will be tested at a temperature of 20±5°C • Cell will be secured to the testing machine with a rigid mount which supports all mounting surfaces of the cell • Each cell will be subjected to a total of three shocks of equal magnitude applied in each of the three mutually perpendicular directions (if only two axes of symmetry, only two shocks will be applied) • For each shock, cell will accelerate in such a manner that during the initial 3 ms the minimum average acceleration is 75 g. Peak acceleration will be between 125 and 175 g. |
Cells should not explode or catch fire, as well as no leaking or venting | 5 fully charged, 5 half charged, & 5 fully discharged | 5 fully charged & 5 conditioned by cycling |
| Short-Circuit Test |
• Tests will be conducted at 20±5°C and 55±5°C • Test sample will be short-circuited with a circuit load having a resistance load of 80±20 mΩ • Battery will be discharged until fire or explosion, or until it has reached a completely discharged state of <0.2 V and the battery case temperature return to ambient temperature±10°C • If battery is to be used in series or parallel, additional tests on five sets of batteries will be conducted using the maximum number of batteries for each configuration |
Cells should not explode or catch fire | 5 fully charged and 5 half charged (for both temperatures) | 5 fully charged & 5 conditioned by cycling (for both temperatures) |
| Crush Test |
• Cell will be crushed between two flat surfaces, crushing continued until an applied force of 13±1 kN is reached • For cylindrical, pouch, or prismatic cells: crushed with its longitudinal axis parallel to the flat surfaces of the crushing apparatus (prismatic cell is also to be rotated 90° around its longitudinal axis) • For coin or button cells: crushed with flat surface of the battery parallel with the flat surfaces of the crushing apparatus • Separate samples will be used for each test |
Cells should not explode or catch fire | 5 fully charged & 5 half charged | 5 fully charged & 5 conditioned by cycling (10 if prismatic cell due to 2 orientations) |
| Impact Test |
• Cell will be placed on a flat surface with a 15.8±0.1 mm diameter bar placed across the center of the sample • A 9.1±0.46 kg weight will be dropped from a height of 610±25 mm onto the sample • For cylindrical, pouch, or prismatic cells: impacted with its longitudinal axis parallel to the flat surface and perpendicular to the longitudinal axis of the 15.8 mm curved surface lying across the center of the test sample • For coin or button cells: impacted with the flat surface of the test sample parallel to the flat surface and the 15.8 mm curved surface lying across its center |
Cells should not explode or catch fire | 5 fully charged & 5 half charged | 5 fully charged & 5 conditioned by cycling (10 if prismatic cell due to 2 orientations) |
| Abnormal Charging Test |
• Tests will be carried out at ambient temperature of 20±5°C For Primary Cells: • Each battery will be subjected to a charging current of three times the current specified by the manufacturer, testing charging time determined with the following formula tc = 2.5 C / 3 (Ic) • Minimum charging time is 7 hours For Secondary Cells: • Each battery will be discharged at constant current of 0.2 C/1 hour to the manufacturer specified discharge end point voltage and then charged with constant maximum specified output voltage and current limit of 3 times the maximum charging current • Charging time is 7 hours or the time required to reach manufacturers specified end-of-charge condition |
Cells should not explode or catch fire | 5 fully charged, 5 half charged, & 5 fully discharged | 5 fully charged & 5 conditioned by cycling |
| Forced-Discharge Test |
• Test is intended for cells that are to be used in series-connected, multicell applications • A fully discharged cell will be force-discharged by connecting it in series with fully charged cells of the same kind. Five cells will be fully discharged at room temperature • Once fully discharged and fully charged cells are connected, battery pack will be short circuited. Cell will be discharged with a resistance load of 80±20 mΩ until fire or explosion, or until it has reached a completely discharged state of <0.2 V and the battery case temperature return to ambient temperature ±10°C . |
Cells should not explode or catch fire | 5 fully charged, 5 half charged | 5 fully charged & 5 conditioned by cycling |
| Projectile Test |
• Cell will be placed on a steel wire mesh screen that covers a 102 mm diameter hole in the center of a
platform table which will be mounted 38 mm above the burner. • Fuel and air flow rates will be set to provide a bright blue flame that causes the supporting screen to glow bright red • A metal screening eight-sided covered wire cage will be placed over the test sample which will be heated and remain on the screen until it explodes, or the cell has ignited and burned out. |
No part of the exploding cell should penetrate the wire screen such that some or all the cell protrudes through screen | 5(10) fully charged (based on cell application) | 5 fully charged (additional 5 needed if noncompliance within first 5 tests) |
FAQ:
1. Does UL 1642 apply to battery packs?
No. It applies to cells only, not full battery packs.
2. What tests are included?
UL 1642 includes a variety of mechanical, electrical, and environmental tests, such as:
- Short-circuit testing – simulates accidental external shorting.
- Overcharge testing – ensures the cell can handle excess voltage safely.
- Crush / impact testing – checks resistance to physical abuse.
- Thermal testing – evaluates stability under high and low temperatures.
- Forced discharge – ensures internal safety mechanisms prevent hazards.
3. Is UL 1642 mandatory?
It depends on the market and product. While not always legally required, many manufacturers and retailers demand UL certification as proof of product safety.
4. What happens if a battery fails UL 1642?
It cannot be certified. Manufacturers usually need to redesign the cell (e.g., add protection features, improve separator materials) and retest.
5. What is the difference between UN 38.3, UL 2054 and UL 1642?
- UL 1642: Focus on individual cells for operational safety.
- UL 2054: Focus on battery packs for operational safety.
- UN 38.3: Focus on transport safety for both cells and packs.
In short, UL 1642 ensures the safety of lithium cells themselves, UL 2054 ensures safety of the whole battery pack. While UN 38.3 ensures the battery (both cells and packs) are safe during shipping and transport.
Most manufacturers need both UL and UN 38.3 testing to sell and ship batteries safely worldwide.