Battery testing is vital for ensuring safety and performance. From evaluating cycle life to rate performance and safety, these tests prevent issues like overheating and explosions, guaranteeing reliable battery function.
Why battery Testing is Important:
Batteries serve as the primary power source for products, driving their operation. Through detailed battery testing using testing tools, we can ensure battery safety, preventing issues like overheating leading to self-ignition or explosions. Given that cars are a major mode of transportation for many people, ensuring driver safety is crucial. Thus, battery testing is essential. It involves simulating various accident scenarios to assess battery quality and observe any risk of explosion. These tests help effectively mitigate risks and maintain stability.
Cycle life:
The number of cycles a lithium battery can undergo, representing how many times the battery can be charged and discharged repeatedly. The cycle life of a battery can be tested under different environmental conditions, including low temperature, room temperature, and high temperature, to determine its performance. The criteria for deeming a battery as unusable typically vary based on the battery’s intended application. For power batteries used in electric vehicles and forklifts, the standard parameter is often set at an 80% state of charge retention. On the other hand, for batteries used in energy storage and backup power applications, this standard can be relaxed to around 60%. In the case of common consumer batteries, if the state of charge falls below 60% of the initial capacity, they are typically considered no longer viable, as they won’t last very long.”
Rate performance:
Nowadays, lithium-ion batteries are not only used in 3C applications (computers, communications, consumer electronics) but are also increasingly used in power battery applications. Electric vehicles operate under different conditions and require variable currents. In the fast-paced modern life, the demand for rapid charging of lithium-ion batteries is increasing, especially with the shortage of electric vehicle charging stations. Therefore, it is necessary to test the rate performance of lithium-ion batteries. Testing can be conducted according to the national standards for power batteries. Battery manufacturers worldwide are now producing special high-rate batteries to meet market demand. The design of high-rate batteries can involve factors such as the type of active material, electrode density, compaction density, tab selection, welding processes, and assembly techniques.
Safety testing:
Safety is a major concern for battery users, with incidents like phone battery explosions and electric vehicle fires causing considerable alarm. The safety of lithium batteries is a critical aspect that requires thorough examination. Safety testing includes evaluations for overcharging, over-discharging, short circuits, drop tests, heating, vibration, compression, and puncture tests, among others. However, these safety tests are considered passive safety tests, which means that the batteries are subjected to external forces to assess their safety. When submitting batteries for testing, appropriate designs for the batteries and modules are necessary to conduct safety assessments. In real-world usage scenarios, such as irregular collisions like when an electric vehicle loses control and collides with another vehicle or object, more complex situations may arise. However, testing under such conditions can be costly, so relatively reliable test parameters are typically chosen.
Low Temperature Discharge High Temperature Discharge:
The impact of temperature on the discharge performance of batteries is directly reflected in the discharge capacity and discharge voltage. As the temperature decreases, the internal resistance of the battery increases, the electrochemical reaction rate slows down, the polarization internal resistance rapidly increases, leading to a decrease in the battery’s discharge capacity and discharge voltage, which affects the power and energy output of the battery.
For lithium-ion batteries, the discharge capacity sharply decreases under low-temperature conditions. However, under high-temperature conditions, the discharge capacity is not lower than at room temperature, and sometimes it may even be slightly higher. This is primarily because at high temperatures, the lithium-ion migration rate increases, and unlike nickel electrodes and hydrogen storage electrodes, lithium electrodes do not generate decomposition or hydrogen gas formation that leads to a capacity decrease at high temperatures. When discharging a battery module at low temperatures, as the discharge progresses, heat is generated due to reasons like resistance, causing the battery’s temperature to rise. This is reflected in a voltage increase. As the discharge continues, the voltage gradually decreases.
Currently, the batteries available in the market are primarily composed of ternary batteries and lithium iron phosphate batteries. Ternary batteries can be less stable than lithium iron phosphate batteries due to structural collapses of their materials at high temperatures. However, they offer a higher energy density than lithium iron phosphate batteries. As a result, both of these systems coexist and continue to develop.
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