Ⅰ: Briefly describe the BMS lithium battery management system
As we all know, the BMS is mainly used in lithium batteries, and lead-acid batteries generally do not have this management system. The trend of lithium batteries on the market is steadily rising, precisely because lithium batteries require one more BMS than lead-acid batteries to protect the cells. In short, BMS is a system to manage, control, and use lithium battery packs. BMS is the "Brain" of the lithium battery operating system, receiving and sending information from the battery and each external port, in-depth analysis and processing of the information, and outgoing work orders. Therefore, BMS is a bridge between the battery and the user, supervising the battery state, preventing the battery from overcharging and over-discharging, and ensuring safety. BMS determines the status of the entire battery system by detecting every single cell in the battery pack. BMS adjusts the battery system according to the single cell status and realizes charge and discharge management to ensure a safe and stable operation.
Ⅱ: Why do lithium batteries need BMS
Lithium batteries need protection, according to the characteristics of lithium batteries. Excessive charging and discharging will damage the chemical composition inside the battery, shorten
the battery life, and even cause serious consequences. Overcharging will also cause the battery to heat up and cause safety hazards such as fire. To ensure safety, the use of lithium batteries needs to meet safety requirements:
1. Basic protection requirements: overcharge protection, over-discharge protection;
2. Strengthen protection requirements: Over-current protection, high-temperature protection, low-temperature protection, short circuit protection, reverse polarity protection;
3. Expansion requirements: good balance performance, low-pressure difference, a low-temperature difference;
Therefore, a special protection system is required to monitor the health of the lithium battery and manage its normal operation. To reduce maintenance workload and cost, BMS has the function of charge estimation, which can accurately grasp the charge state. At the same time, BMS has lower power consumption to reduce the maintenance frequency and prolong the service life of lithium batteries.
Ⅲ: The BMS role
A lithium battery is a kind of battery with a large power reserve, and the market popularity continues to rise. Some unscrupulous merchants put fake and shoddy batteries into the market. Bad lithium batteries have many critical problems，and even explode due to overcharge and over-discharge, or may explode due to a short circuit in the internal circuit. However, the BMS role is to guarantee the safety of lithium batteries. A lithium battery pack is composed of small lithium batteries connected in parallel. Put a protective plate in the gap of the internal lithium battery to separate them.
The protective board is made of non-conductive fiberboard, and the outside is covered with a layer of oil. Everyone knows oil is non-conductive, so BMS can isolate lithium batteries to avoid short circuits.
Secondly, BMS also has the function of avoiding battery overcharging. When the external power supply continuously and rapidly charges the battery, the internal power of the lithium battery reaches a certain level, and the BMS will automatically cut off the external charging power. External power will not continue to enter the battery. BMS also has the function of avoiding the over-discharge of lithium batteries. When the lithium battery is over-discharged, the BMS can sense that the battery content will change, then quickly cut off the discharge power supply so that the lithium battery will not discharge all the electricity.
Therefore, we can mainly summarize the role of BMS as the following three points:
1. Ensure battery safety and prolong battery life, which is a necessary condition for lithium-ion batteries;
2. Avoid overcharging, over-discharging, over-current, short-circuit, etc. of the battery pack, and avoid the lithium battery catching fire due to failure;
3. Equilibrium function to ensure the stability of internal current and superior performance;
Ⅳ: Additional functions of BMS
The common BMS topology diagram structure is two major blocks: the master control module and the slave control module. It consists of a central processing unit, a data acquisition module, a data detection module, a display unit module, a control component, and the like. The data information communication between modules is realized by adopting CAN bus technology.
Based on the functions of each module, BMS can realize real-time monitoring of parameters such as voltage, current, and temperature of lithium batteries. BMS can also perform thermal management, equalization management, high voltage, and insulation detection, etc. on the battery, and can estimate the remaining battery capacity, charge and discharge power, and state of charge (SOC) & state of health (SOH). A good BMS also has a temperature sensor that can monitor the voltage of a single battery pack and detect under-performing batteries.
Therefore, we can conclude that in addition to solving the basic security problems, the additional working principles of BMS are as follows:
1. Communication function—customers need to know the operating status information of the battery pack, RS232/RS485/CAN, etc；
2. 2.SOC (State Of Charge) calculation / SOH estimation；
3.Alarm function - when there is a problem with the battery, you need to inform the customer in time；
4.Recording function - it is best to record the historical running process data, including alarm data, etc；
5.Fault diagnosis function - the protection board or the management system should be able to diagnose if there is a problem ；
6.Display function-customers can directly read information and set parameters through the display screen；
7.Balance function - according to the information of the single battery, make the capacity of the battery pack as close to the smallest single cell as possible；
