Protection methods for lithium-ion battery charging and discharging equipment
[Power supply network] Lithium-ion batteries have to go through processes such as formation and capacity detection and sorting before leaving the factory, and a large number of charging and discharging equipment is required to detect the charging and discharging of the battery. Li-ion battery charging and discharging equipment includes formation system, capacity detection system, safety detection system, etc. During the detection process, the lithium-ion battery does not have a protection circuit to provide over-current and over-voltage protection, which requires the charging and discharging equipment to have the protection function of over-current and over-voltage when the lithium-ion battery is charged and discharged. When the fault causes the detection point to be short-circuited, it can effectively guard against the damage of the detection equipment. Since the processing of chemical power sources is irreversible, and lithium-ion batteries are prone to explode when overcharged and over-discharged, reliability is the most fundamental requirement for lithium-ion battery charging and discharging equipment. Large-scale battery processing uses many test points in the test equipment, and the structure is complex. To achieve high reliability, the protection design from the hardware is extremely important. 'Jb/T11142-2011 General Requirements for Lithium Ion Battery Charging Equipment' puts forward the protection requirements of overcurrent, overvoltage and short circuit for lithium ion charging and discharging equipment. When the DC output voltage and current of the equipment exceed the specified value and the detection point is short-circuited, It is required that the device can be disconnected from the battery, and after the fault is eliminated, the device can work normally without damage to parts or loss of function except for the protective device (fuse). Regarding processing plants with a daily production capacity of hundreds of thousands of batteries, the charging and discharging detection points have to undergo nearly a million charging and discharging operations every day, which is extremely prone to faults such as overcurrent, overvoltage and short circuit. If a one-time fuse protection device is used, the maintenance cost of the equipment is relatively high. The use of TE's PPTC and PolyZEN devices can more effectively achieve protection in the event of a failure, while reducing equipment maintenance costs. In addition to the charging and discharging circuit interface, the data acquisition communication interface is also prone to faults such as overcurrent. As described in 'JbT11143-2011 Lithium-ion Battery Charging Equipment Interface and Communication Protocolfigure 1. Usually the charging and discharging system will be realized through a two-level or three-level distributed structure. Data and commands are transmitted between all levels of control systems through communication interfaces. Due to the stability of the CAN bus and its wide use in industrial data transmission networks, the battery charging and discharging system uses CAN interfaces as the monitoring system between all levels Communication interface with test equipment. Regarding the CAN bus, the design of TEPPTC in series on CAN-H and CAN-L is usually used to achieve protection against overcurrent. At the same time, due to a large number of manual operations in the actual processing process, the electrostatic protection of the sampling contacts of the detection point is indispensable. TE's PESD and SESD devices can provide good electrostatic protection. Through these protection devices, the CAN communication system will be more reliable. In summary, TE's circuit protection devices can greatly improve the reliability of charging and discharging equipment such as lithium ion formation systems and capacity detection systems, reduce maintenance costs, and achieve safe and efficient processing.