Some analysts predict that the trend of vehicle electrification will accelerate even more in the next decade. Lithium-ion battery technology is considered a big part of this, continuing to grow up to 2028. One of the most significant advances in rechargeable technology is Li-ion batteries. They are used for computers and cell phones, yet their use is also expanding in hybrid and electric vehicles with an increased demand for these technologies.
Li-ion batteries do have a number of safe features, but certain factors can lead to thermal runaway such as short-circuiting, mechanical malfunctioning, and electrochemical failure. Thermal and electrochemical energies are then released into the surrounding area, this can produce disastrous consequences. To be accurate, Li-ion batteries are abused to see what happens when there is thermal or mechanical failure which often results in the exothermic decomposition known as thermal runaway.
The primary objective of Li-ion battery testing is to make sure battery function and safety are maintained in any environment and that high-quality batteries are produced. Li-ion battery tests are performed according to industry standards, including the IEC, SAE, and UL, which test temperature cycling and short-circuiting under heat. To test a battery, there are 3 ways:
First, you can test primary (non-rechargeable) and secondary (rechargeable) cells or modules.
Safety for Household and Commercial Batteries pertains to battery level tests. Primary and secondary batteries are tested depending on their size and quantity, which includes electrical, mechanical, battery enclosure, fire exposure, and environmental tests. The reach-in or walk-in temperature chamber can accomplish the mold stress relief test at 70°C (5 degrees Celsius), heating test of 5°C per minute to 150°C (131 F), and voltage cycling from 70°C to 20°C to -40°C.
As with other IEC standards, Safety Requirements for Portable Sealed Secondary Cells address general, safety, and transportation specifications for Li-ion cells. The standard also includes short circuit testing at 55°C, Mold stress relief testing at 70°C, and temperature cycling from 75°C to 20°C to -20°C at 30-minute intervals.
There are many different kinds of tests that should be conducted and completed before purchasing Li-ion cells for the propulsion of an electric vehicle. A temperature chamber can be used to test the durability and function of such cells, including temperature cycling from 85°C to -40°C at 1°C per minute (or 65°C to -20°C with electrical operation) and a capacity discharge test at -20°C, 0°C, 25°C, or 45°C.
Tests exist for abuse testing of vehicle rechargeable batteries to determine the response to conditions or events which are above their normal operating range. Temperature chambers can be used for thermal stability testing by increasing temperature in 5°C increments, while a thermal shock chamber would be effective for temperature cycling from 70°C to -40°C in 15-minute transitions.
Li-ion batteries are becoming the standard of power for both automobiles and electronics. Different companies use different variations of Li-ion to make them more reliable, last longer, and be more cost effective. It’s difficult to test these batteries because they can become unstable in a test chamber.
| Hazard Level | Description | Classification Criteria & Effect |
|---|---|---|
| 0 | No effect | No effect. No loss of functionality. |
| 1 | Passive protection activated | No defect; no leakage; no venting, fire, or flame; no rupture; no explosion; no exothermic reaction or thermal runaway. Cell reversibly damaged. Repair of protection device needed. |
| 2 | Defect/Damage | No leakage; no venting, fire, or flame; no rupture; no explosion; no exothermic reaction or thermal runaway. Cell irreversibly damaged. Repair needed. |
| 3 | Leakage Δ mass < 50% | No venting, fire, or flame; no rupture; no explosion. Weight loss < 50% of electrolyte weight (electrolyte = solvent + salt). |
| 4 | Venting Δ mass ≥ 50% | No fire or flame; no rupture; no explosion. Weight loss ≥ 50% of electrolyte weight (electrolyte = solvent + salt). |
| 5 | Fire or Flame | No rupture; no explosion (i.e., no flying parts). |
| 6 | Rupture | No explosion, but flying parts of the active mass. |
| 7 | Explosion | Explosion (i.e., disintegration of the cell). |
Hazard levels are determined by how hazardous a battery is at any given time, with higher hazardous levels having a more significant effect on the person performing the test. EUCAR is an international organization that sets these hazard levels in order to prevent accidents caused by handling and testing batteries during testing.
Temperature-limited sheath heaters are needed in environments where flammable gas is present, fire suppression systems can be found in environments where extreme events (e.g. explosions) take place, and test enclosures are needed to protect the environment from hazardous events.
As the use of lithium-ion batteries continues to grow, so does the need for reliable and safe testing methods. The chambers described in this article are just one example of how companies are working to ensure that their products meet the highest standards for safety and quality. By investing in reliable testing methods, companies can provide their customers with the peace of mind that comes from knowing that their products are safe and effective.