Battery Performance Testing | Summary of Mechanical Performance Test Items for Lithium-Ion Batteries
Mechanical performance testing is used to simulate the effects of external forces on lithium-ion cells/batteries during handling and transportation, including drops and impacts in transit. It is also used to verify the battery’s overall structural strength, the resistance of tabs and separator to mechanical damage from external forces, and the trigger boundaries for thermal runaway. Compared with purely electrical verification, mechanical testing more closely reflects logistics/transport scenarios for batteries and can effectively reveal “invisible” structural hazards.
1、Overview of Mechanical Performance Test Items
| No. | Test Item | Test Purpose | Judgment Criteria |
|---|---|---|---|
|
1 |
Crush test |
Simulate strong compression causing internal short risk |
No smoke / no fire / no explosion. |
|
2 |
Heavy-object impact test |
Simulate crushing/impact by a heavy object |
Appearance deformation allowed; no fire, no explosion. |
|
3 |
Acceleration (half-sine) shock test |
Simulate transportation half-sine shocks |
No leakage / no smoke / no fire / no explosion. |
|
4 |
Vibration test |
Simulate transportation vibration fatigue |
No leakage / no smoke / no fire / no explosion. |
|
5 |
Free-drop test |
Simulate sudden battery drop |
No leakage, no smoke, no fire, no explosion. |
|
6 |
Post-packaging full-carton drop test |
Simulate drop of a full carton of batteries |
No fire, no explosion, no leakage; carton remains intact. |
2、Detailed Explanations of Mechanical Performance Test Items
2.1 Crush Test
Test Purpose:
Simulate whether, during compression of the cell, an internal short circuit causes excessive temperature rise and thus ignition.
Test Steps:
Iray Energy standard (UL1642/UL2054/IEC62133)
① Charge to full at 0.5C (use 1.0C for high-rate batteries);
② Place the battery between two flat plates and apply crushing perpendicular to the electrode plate direction; apply a compressive force of 13.0 kN ± 0.78 kN between the two plates;
③ Observe the pressure display; once the pressure reaches the maximum value, stop the crush test.
UN38.3 standard
Each test sample must be fitted with a thermocouple to measure the surface temperature of the sample;
① Charge to full at 0.5C (use 1.0C for high-rate batteries);
② Crush test: place the cell between two test plates and crush at a plate speed of 1.5 cm/s.
Stop the test when any of the following occurs:
① Applied pressure reaches 13 ± 0.78 kN;
② Cell voltage drops by 100 mV;
③ Cell thickness increases to or exceeds 50% of the original thickness.
Judgment Criteria:
Iray Energy standard:
The cell shall show no smoke, no fire, and no explosion.
UN38.3 standard:
① No fire, no explosion, and no rupture during the test and within six hours after completion;
② The maximum surface temperature of the cell does not exceed 170 °C.
Figure 1. Cell placement schematic for the crush test
Figure 2. Battery undergoing a crush test
2.2 Heavy-Object Impact Test
Test Purpose:
Simulate the condition of a cell or battery being struck.
Test Steps:
① Charge to full at 0.5C (use 1.0C for high-rate batteries);
② Place the sample on the impact tester’s table. Position a solid steel rod with a diameter of 15.8 ± 0.2 mm perpendicular to the long-axis face of the battery and resting at the center of the battery. Drop a cylindrical steel weight of 9.1 ± 0.1 kg from a height of 610 ± 25 mm so that it impacts the battery via the steel rod;
③ After the test, visually inspect the battery appearance.
Note: Each cell is subjected to only one impact; use a different cell for each impact.
Acceptance Criteria:
Deformation of the battery is permitted, but there shall be no fire and no explosion.
Figure 3. Cylindrical cell undergoing a heavy-object impact test
2.3 Acceleration Shock Test
Test Purpose:
Simulate whether the cell or battery can withstand shocks during transportation.
Test Steps:
① Charge to full at 0.5C (use 1.0C for high-rate batteries);
② Mount the sample on a shock table and perform a half-sine pulse shock test: within the first 3 ms, the minimum average acceleration is 75 gn (735 m/s²), the peak acceleration is 150 ± 25 gn (1225–1715 m/s²), and the pulse duration is 6 ± 1 ms. Conduct three acceleration shocks in each direction.
Note: Cylindrical cells are tested along both the axial and radial directions; prismatic and irregular cells are tested sequentially along three mutually perpendicular directions.
Judgment Criteria:
No leakage, no smoke, no fire, no explosion.
Figure 4. Energy-storage battery pack undergoing an acceleration (mechanical) shock test
2.4 Vibration Test
Test Purpose:
Simulate the shocks that may occur to the cell or battery during transportation.
Test Steps:
① Charge to full at 0.5C (use 1.0C for high-rate batteries) and record the internal resistance;
② Mount the battery on the vibration table (or via a fixture) without deforming it, and test according to the parameters in the table below.
Judgment Criteria:
a) No leakage, no smoke, no fire, no explosion;
b) Open-circuit voltage after the test > 3.6 V;
c) Post-test impedance increase shall not exceed 50% of the initial impedance.
Table 1. Test parameters
Note: logarithmic sweep method as follows: 7 Hz–18 Hz maintain a peak acceleration of 9.8 m/s². Keep the amplitude at 0.8 mm (displacement 1.6 mm) until the peak acceleration reaches 78.4 m/s² (frequency ≈ 50 Hz). Maintain a peak acceleration of 78.4 m/s² until the frequency increases to 200 Hz.
Figure 5. Energy-storage battery pack undergoing a vibration test
2.5 Free-Fall Drop Test
Test Purpose:
Simulate the situation in which a single cell or battery suddenly drops during use.
Test Steps:
① Charge at 0.5C (use 1.0C for high-rate batteries) to full and rest for 10 min; then discharge at 0.5C (use 1.0C for high-rate batteries) to 3.0 V, and record the discharge capacity A;
② Charge at 0.5C (use 1.0C for high-rate batteries) to full, rest for 10 min, and record the internal resistance;
③ Drop the battery freely from a height of 1.0 m onto a concrete slab;
④ After the drop, rest for 2 h, measure its voltage and internal resistance, then discharge at 0.5C (use 1.0C for high-rate batteries) to 3.0 V, and record the discharge capacity B.
Note: For cylindrical cells, drop once on each end and twice on the cylindrical surface, for a total of four drops. For prismatic and irregular cells, drop once on each face, for a total of six tests.
Judgment Criteria:
a) No leakage, no smoke, no fire, no explosion;
b) Capacity B / Capacity A > 90%.
Figure 6. Lithium-ion battery undergoing a free-fall drop test
2.6 Post-Packaging Full-Carton Drop Test
Test Purpose:
Simulate the situation of a full carton of batteries being dropped during transportation.
Test Steps:
Packaging requirements: Unless installed in equipment, if each package contains more than 24 primary cells or 12 batteries, the gross weight of each package shall not exceed 30 kg;
① At room temperature, drop a fully packed carton of lithium-ion batteries from 1.2 m (measured from the lowest point of the carton) onto a hardwood board 18–20 mm thick (the board laid on a concrete floor);
② Drop once on each of the ±X, ±Y, and ±Z directions, for a total of 6 drops.
Judgment Criteria:
Cells shall not catch fire, explode, or leak; and the carton shall not disintegrate or be damaged.
Figure 7. Full carton of batteries undergoing a packaged-carton drop test
3、Referenced Standards and Applicable Specifications
The above mechanical performance tests are conducted with reference to the following industry standards:
- UL1642
- UL2054
- IEC62133
- GB/T 18287
- UN38.3
- Certain customer-specific standards
4、Summary and Recommendations
Mechanical performance testing of batteries plays a crucial role in products that use batteries across various industries. Through different categories of test methods, the performance and reliability of battery systems under various stress conditions can be comprehensively evaluated. The application of these methods not only helps improve the design and structure of battery systems, enhancing their safety and stability, but also ensures their reliability during transportation and in special environments. By gaining an in-depth understanding of and applying these mechanical stress testing methods, the widespread application of lithium-ion batteries across industries can be promoted. In particular, for lithium-ion batteries—products that are flammable and potentially explosive—thorough safety testing is very important; it demonstrates responsibility to oneself and to customers.
