Research status of power lithium battery pack protection

In the final analysis, the safety of lithium batteries depends on the thermal stability of lithium battery materials. The inconsistency of single cells makes the problem of thermal stability particularly prominent when power lithium batteries are used in groups or in series. Because the characteristics of lithium battery materials determine that it is more sensitive to overheating, the research on protection circuits used in lithium batteries is particularly important. In view of the protection of the use of power lithium battery packs, some measures have been taken in battery product design and use control. According to the decomposition of battery overcharge resistance, it is found that the stronger the overcharge resistance performance of the battery cathode material, the stronger the battery overcharge resistance performance. Therefore, in order to improve the overcharge resistance performance of the lithium battery, on the one hand, in the battery product design In the process, use safety devices such as PTC[B8], Vent/CID, use overcharge-resistant cathode material B9.40], use thermal shutdown isolation film, use PTC effect electrodes[4], use voltage-sensitive isolation film[42 ] Or add overcharge additives [434]. On the one hand, in order to guard against excessive charging and discharging of lithium batteries and ensure the safety of the battery, in actual use, a single battery and battery pack are loaded with protection circuits and a dedicated charging management system is used. Major semiconductor companies have also introduced integrated management chips for lithium battery protection, such as TI's bq77910 and OMicro's OZ890. The method is straightforward and effective, but it is not foolproof. Especially with regard to the use of high-voltage electric vehicles, such as BYD’s upcoming second-generation dual-mode electric vehicle called Qin, the voltage level has reached 500V, the number of batteries is several hundred, and the management of any single battery is out of control Both may bring serious security problems. In addition, the energy consumption of the single battery management circuit has gradually become a problem to be considered for battery protection. Aiming at the energy consumption problem of the single battery management circuit, a low power consumption design is carried out on the single battery voltage, temperature and other parameter tests in the single battery management circuit. However, when the battery pack is overloaded to output a large current, or the battery is left for too long and leaks and the battery voltage is very low (less than 2.65V), the single battery management circuit connected in parallel at both ends of the battery will still consume battery power. Especially for electric vehicles that have been left unused for a long time, the single battery management circuit connected in parallel at both ends of the battery will over-discharge the battery pack until the internal single battery is discharged to a damaged state. At present, there is very little research on the automatic power-down design of single-cell battery management circuits at home and abroad when the single-cell battery is over-discharged. Most battery management methods are to automatically power-off through the relay when the battery pack is under voltage. However, the disadvantages of this method are low reliability and high energy consumption. For this reason, it is necessary to design an automatic cut-off power-down circuit, which can cut off the single battery management circuit from both ends of the single battery when the single battery is under voltage under test. Disclaimer: Some pictures and content of articles published on this site are from the Internet. If there is any infringement, please contact to delete. Previous post: Comparison of the structure and performance of cylindrical 32650 lithium batteries