What is BMS battery management system
The Battery Management System (BMS) is used to manage batteries. It usually measures the Battery voltage to prevent over-discharge, overcharge, and overtemperature of the battery. With the development of technology, many features have been gradually added.
The battery management system and the electric vehicle power lithium batteries together, through the sensor to the battery voltage, current, temperature, the real-time detection, as well as detect the leakage, thermal management, balanced battery management, alarm to remind, the residual capacity of computing (SOC), discharge power, the report of the residual capacity of battery degradation (SOH) and state of (SOC), It also uses algorithms to control the maximum output power according to the voltage, current and temperature of the battery to obtain the maximum mileage and uses algorithms to control the charger to charge the best current. The CAN bus interface communicates with the vehicle master controller, motor controller, energy control system, and vehicle display system in real-time.
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Why do lithium batteries need BMS?
The battery management system can effectively monitor, protect, energy balance, and fault alarm of the lithium-ion battery pack, improving the entire power lithium battery pack's working efficiency and service life. Lithium-ion batteries are widely used in various precision equipment due to their high working voltage, small size, lightweight, high energy density, no memory effect, no pollution, low self-discharge, long cycle life and many other advantages. However, lithium batteries have serious shortcomings. In summary, there are the following two aspects:
(1) Security
The lithium batteries have poor safety and have defects such as explosions from time to time. In particular, lithium 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 over-discharge can cause irreversible damage to the cells. Lithium batteries are also susceptible to temperature: if used at too high a temperature, 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 and affect the regular use of the device.
Due to the limitations of the battery manufacturing process, each battery cell's internal resistance and capacity will vary. When multiple battery cells are used in series, each battery cell's charging, and discharging rate will be inconsistent, leading to low battery capacity utilization. Because of this, in the actual use of lithium-ion batteries, a special protection system is usually required to monitor the battery's health to manage the use of the lithium-ion battery.
(2) Maintainability
We cannot accurately predict the capacity decay and power consumption of lithium batteries 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 maintenance workload and maintenance cost, the lithium-ion battery BMS management system 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 practical design of the lithium-ion battery BMS management system is of great significance to the maintenance of the equipment.
