Why do lithium-ion batteries need a lithium-ion battery management system?

Why do we need a lithium-ion battery management system? Remote meters have high requirements on batteries due to their special working environment and working methods. It requires the battery to have a long-term continuous power supply, usually for a year or more. Lithium-ion batteries are widely used in long-term standby remote monitoring instruments because of their high working voltage, small size, light weight, high energy density, no memory effect, no pollution, low self-discharge, and long cycle life. Compared with nickel-metal hydride batteries, lithium-ion batteries are 30-40% lighter and have a 60% higher energy ratio. However, lithium-ion batteries also have serious defects, which can be summarized in the following two aspects: (1) Safety Li-ion batteries have poor safety and have defects such as explosions. In particular, lithium-ion batteries using lithium cobalt oxide as the cathode material cannot be discharged under large currents, and their safety is poor. In addition, almost all lithium-ion batteries overcharge or overdischarge will cause irreversible damage to the battery. Lithium-ion batteries are also very sensitive to temperature: if the temperature is too high, it may cause the electrolyte to decompose, burn or even explode; if the temperature is too low, the performance of the lithium-ion battery will deteriorate significantly, affecting the normal use of the equipment. Due to the limitation of the battery manufacturing process, the internal resistance and capacity of each battery will be different. When multiple batteries are used in series, the charge and discharge rate of each battery is inconsistent, resulting in low battery capacity utilization. In view of this, in the process of actual use of lithium-ion batteries, a special protection system is required to monitor the health of the battery, so as to manage the use of lithium-ion batteries. Figure 1 shows the lithium ion battery after the electrolyte is decomposed. Figure 1 Lithium-ion battery after electrolyte decomposition (2) Maintainability At low temperatures, capacity decay and power cannot be accurately predicted, which reduces the maintainability of the equipment. Long-term online instruments need to be replaced regularly, and remote monitoring equipment works in scattered locations, and the distance between each location is very long, so the workload of replacing the battery is very large and the cost is also high. In order to reduce maintenance workload and maintenance costs, the battery management system must have an accurate power state estimation function, accurately grasp the battery power state, and perform battery replacement work more specifically. At the same time, the battery management system must have lower power consumption to reduce maintenance frequency and extend battery life. Therefore, a reasonable design of the battery management system is of great significance to the maintenance of long-term continuous power supply remote monitoring instruments. However, due to the operating characteristics of remote monitoring instruments and the inherent characteristics of lithium-ion batteries, it is difficult to develop a battery management system that meets the needs of this application. The following factors are important: First of all, from the working characteristics of the remote measuring instrument, in order to reduce power consumption, the remote measuring instrument generally sleeps and wakes up regularly. This is the dynamic change of the working current, and the working current of waking up is much higher than the static state. , But the working time after waking up is much shorter than that in the dormant phase; secondly, the discharge curve of lithium-ion battery is very flat, and the important power is concentrated at 3.6V and above. Subsequently, with the further decrease of the voltage, the battery power began to drop sharply, and the remote instrument and equipment could not issue a low battery alarm based on the battery voltage. Finally, the self-discharge rate of lithium-ion batteries fluctuates greatly with temperature. Instruments working in the field have extremely extreme temperature conditions, which further increases the difficulty of battery power prediction. Existing battery management systems are difficult to adapt to these functions and performance requirements. Disclaimer: Some pictures and content of articles published on this site are from the Internet. If there is any infringement, please contact to delete it. Previous: What should I pay attention to when using lithium-ion batteries?