A battery management system (BMS) is a system for battery management. It usually has the function of measuring battery voltage to prevent or prevent abnormal conditions such as battery over-discharge, over-charge, and over-temperature. With the development of technology, many functions have been gradually added.
The battery management system is closely integrated with the lithium battery, and the voltage, current, and temperature of the battery are detected in real time through sensors. At the same time, it also performs leakage detection, thermal management, battery balance management, alarm reminders, and calculation of remaining capacity (SOC) and discharge power , Report the battery degradation degree (SOH) and remaining capacity (SOC) status, and also use an algorithm to control the maximum output power according to the battery voltage, current and temperature, and communicate in real time through the port. The function of BMS should include basic battery protection function, battery equalization function, battery reserve energy calculation function and network communication function
The battery management system (BMS) can effectively monitor, protect, energy balance and fault alarms for lithium-ion battery packs, thereby improving the working efficiency and service life of the entire lithium-ion battery pack. Lithium-ion batteries are widely used in various precision equipment due to their high working voltage, small size, light weight, high energy density, no memory effect, no pollution, low self-discharge, long cycle life and many other advantages. However, lithium-ion batteries have serious defects. In summary, there are two aspects:
1 safety
Lithium-ion batteries have poor safety and have defects such as explosions. In particular, lithium-ion batteries with lithium cobalt oxide as the cathode material cannot be discharged at a large current, and their safety is poor. In addition, almost all types of lithium-ion batteries overcharge or overdischarge can cause irreversible damage to the cells. Lithium-ion batteries are also extremely sensitive to temperature: if they are used at too high a temperature, they 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 and affect the normal use of the device.
Due to the limitations of the battery manufacturing process, the internal resistance and capacity of each battery cell will vary. When multiple battery cells are used in series, the charging and discharging rate of each battery cell will be inconsistent, which leads to low utilization of battery capacity. In view of this, a special protection system is usually required to monitor the health of the lithium-ion battery during actual use, so as to manage the use of the lithium-ion battery.
2 maintainability
The capacity decay and power consumption of lithium-ion batteries cannot be accurately predicted at low temperatures, which makes the maintainability of the equipment poor. Long-term online instruments need to replace the battery regularly, while the remote monitoring equipment work sites are scattered, and the distance between the sites is long. Therefore, the workload of replacing the battery is huge and the cost is high.
In order to reduce the workload of maintenance and reduce maintenance costs, the battery management system (BMS) must have an accurate state of charge estimation function to accurately grasp the state of charge of the battery and perform battery replacement work more purposefully; at the same time, the battery management system must have Low power consumption to reduce maintenance frequency and extend battery life. Therefore, for the long-term continuous power supply remote monitoring instrument, the reasonable design of the battery management system (BMS) is of great significance to the maintenance of the equipment.