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Why do lithium battery packs need an aging test?

The activation stage of the lithium battery pack includes the stages of pre-charging, formation, aging, and constant capacity. There are two main factors that affect the performance of the lithium battery pack by the aging system, namely, the aging temperature and the aging time. In addition, it is also more important whether the battery is in a sealed or open state during aging.

 

Aging generally refers to the placement of the battery after the first charge and formation after the battery is assembled and injected. It can be either normal temperature aging or high temperature aging. The function is to stabilize the properties and composition of the SEI film formed after the initial charging. The normal temperature aging temperature is 25 degrees, and the high temperature aging varies from factory to factory. Some are 38 degrees and 45 degrees. The time is between 48-72 hours.

 

Why do lithium battery packs need an aging test?

 

One is to make the infiltration of the electrolyte better, which is conducive to the stability of the performance of the lithium battery pack;

 

Second, the aging of the active substances in the positive and negative materials can accelerate some side effects, such as gas production, electrolyte decomposition, etc., so that the electrochemical performance of the lithium battery pack can quickly stabilize;

 

The third is to screen the consistency of lithium battery packs after aging for a period of time. After the formation, the voltage of the cell is unstable, and the measured value will deviate from the actual value. The voltage and internal resistance of the cell after aging are more stable, which is convenient for screening batteries with high consistency.

 

The battery performance after high temperature aging is more stable. Most lithium battery manufacturers adopt the high temperature aging operation method in the production process, and the temperature is 45~50 degrees Celsius for 1~3 days, and then shelved at room temperature. After high temperature aging, the potential adverse phenomena of the battery will be exposed: such as voltage changes, thickness changes, and internal resistance changes, which are the comprehensive indicators that directly test the safety and electrochemical performance of this batch of batteries.

 

Temperature has a great influence on the cyclic aging rate of Li-ion battery packs. Lower temperatures reduce cycle life due to enhanced lithium plating; too high temperatures shorten battery life due to Arrhenius-driven aging reactions; therefore, lithium battery packs can only achieve optimal cycle life at appropriate temperatures.

 

How to quickly judge the aging degree of lithium battery pack?

 

If you have a multimeter, you can test the quality of the lithium battery pack in one minute. The method is: find 3 to 5 power resistors with a power of 1 ohm and a power of 10W in series. How much, generally adjusted to 500 mA, if you want to buy a battery, you can connect the load to the positive and negative poles of the battery, and then measure the voltage drop of the battery, that is to say, measure the voltage before connecting the resistor. Measure the voltage after the load is connected. The smaller the difference between the two voltage values, the larger the battery capacity and the stronger the load capacity.

 

Look at the length of its standby time. If the time is getting shorter and shorter, it proves that the lithium battery pack is aging.

How to screen high temperature aging room equipment for lithium battery aging?

 

Lithium battery packs need to use a high temperature aging room for battery high temperature aging, low temperature, temperature cycling under various temperature conditions and changes, and integrate with the charging and discharging system to perform overcharge, discharge, and short circuit tests at various temperatures to evaluate the lithium battery during the test process. The accumulation of Joule heat will cause the temperature of the battery to rise, and the internal materials of the battery will have the risk of thermal runaway. Once the thermal runaway occurs, the battery will burn.

 

In order to ensure the safety of the test, a remote camera can be set up through the window to monitor the test, and the surface temperature of each battery can be detected. When the abnormal temperature rises, it is very likely to be dangerous, and the system immediately activates the safety protection mechanism. Assuming that the high-strength inner furnace body can withstand the power of BZ when the battery is instantaneously BZ, the standard explosion-proof hole will also vent the BZ pressure, and the lithium battery special testing machine will detect If the fire state is detected, it will immediately put out the fire and cool down. After the fire is extinguished, the organic volatile gas and peculiar gas in the box will be discharged through the exhaust mechanism to ensure the cleanliness of the laboratory. Through a number of international standards The required safety test of lithium batteries to avoid BZ burning in lithium batteries, etc.

 

In fact, what really accelerates the aging of lithium battery packs is not fast charging, but your charging habits! Fast charging will accelerate the aging of the battery. As the number of times and time of use of the lithium battery pack increases, aging is inevitable, but good maintenance methods can prolong the service life of the battery.

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