Lithium battery series problem
Since the battery is in the production process, there are many processes from the beginning of the film to the finished product. Even after a rigorous testing procedure, the voltage, resistance, and capacity of each group of power supplies are the same, but when used for a while, there will be one or the other difference. Like a mother's twins, they may grow exactly the same when they are born. It is difficult to distinguish them as mothers. However, as the two children grow up, there will be one or the other difference. Lithium-powered batteries are also the same. After using the difference for a period of time, the overall voltage control method is difficult to apply to lithium-powered batteries. For example, a 36V battery stack must be connected in series with 10 batteries. The overall charge control voltage is 42V and the discharge control voltage is 26V. With the overall voltage control method, there may be no problem in the initial use phase due to the particularly good battery consistency. After a period of use, the internal resistance and voltage of the battery fluctuate, forming an inconsistent state (inconsistent is absolute, the consistency is relative). At this time, the overall voltage control is still unable to achieve its purpose. For example, when 10 batteries are discharged, the voltage of two of the batteries is 2.8V, the voltage of the four batteries is 3.2V, the fourth is only 3.4V, and the current overall voltage is 32V. We let it continue to discharge until 26V. In this way, the two 2.8V batteries are in an over-discharge state below 2.6V. A lithium battery that is over-discharged several times is equivalent to scrapping. Conversely, charging with the overall voltage control charging will also result in overcharging. For example, charging with the voltage state of the above 10 batteries. When the overall voltage reaches 42V, the two 2.8V batteries are in a "starved" state, and the rapid absorption of power will exceed 4.2V, while the overcharged battery exceeding 4.2V will not only be scrapped due to excessive voltage, but even There is also danger, which is the characteristics of lithium-powered batteries.