18650 battery lithium ion 2200mah

What is the difference between energy storage battery BMS and 18650 battery lithium ion 2200mah?

1 Application scenarios of large-scale energy storage systems

In order to achieve the purpose of smoothing output power fluctuations, more and more power plants are equipped with energy storage systems, such as new energy power stations, wind power stations or solar power stations.

Independent energy storage power stations, as the reform of the power system gradually enters people's field of vision, independent energy storage power stations that make a living by reselling electricity gradually appear.

Microgrid, a small power supply and distribution network that includes distributed power sources, power loads, energy storage systems and power grid management systems. In order to ensure the continuity and stability of power consumption of loads, each microgrid will be equipped with an energy storage system.

Indoor energy storage power station

2 Differences between energy storage battery management system (ESBMS) and power battery management system (BMS)

Energy storage battery management system is very similar to power battery management system. However, the power battery system is in high-speed electric vehicles, and has higher requirements for battery power response speed and power characteristics, SOC estimation accuracy, and the number of state parameter calculations.

The scale of energy storage system is extremely large, and the centralized battery management system is significantly different from the energy storage battery management system. Here we only compare it with the distributed battery management system of power batteries.

2.1 The positions of batteries and their management systems in their respective systems are different.

In the energy storage system, the energy storage battery only interacts with the energy storage converter at high voltage. The converter draws power from the AC power grid to charge the battery pack; or the battery pack supplies power to the converter, and the electric energy is converted into AC by the converter and sent to the AC power grid.

For the communication of the energy storage system, the battery management system mainly has information interaction with the converter and the energy storage power station dispatching system. On the one hand, the battery management system sends important status information to the converter to determine the high-voltage power interaction; on the other hand, the battery management system sends the most comprehensive monitoring information to the dispatching system PCS of the energy storage power station. As shown in the figure below.

Basic topology of energy storage system

The BMS of electric vehicles has energy exchange relationships with both the motor and the charger at high voltage; in terms of communication, it has information interaction with the charger during the charging process, and has the most detailed information interaction with the vehicle controller during the entire application process. As shown in the figure below.

Electric vehicle electrical topology

2.2 Different hardware logical structures

Energy storage management system, hardware generally adopts a two-layer or three-layer mode, and the larger scale tends to use a three-layer management system, as shown in the figure below.

Block diagram of three-layer energy storage battery management system

Power battery management system, only one layer of centralized or two distributed, basically no three-layer situation. Small cars mainly use a centralized battery management system. Two-layer distributed power battery management system, as shown in the figure below.

Block diagram of distributed electric vehicle battery management system

From the functional point of view, the first and second layer modules of the energy storage battery management system are basically equivalent to the first layer acquisition module and the second layer main control module of the power battery. The third layer of the energy storage battery management system is an additional layer on this basis to cope with the huge scale of energy storage batteries.

Let's make an analogy that is not so appropriate. The best number of subordinates for a manager is 7 people. If the department continues to expand and 49 people appear, then 7 people have to choose a team leader, and then appoint a manager to manage these 7 team leaders. Beyond personal ability, management is prone to confusion.

Mapped to the energy storage battery management system, this management capability is the computing power of the chip and the complexity of the software program.

2.3 Communication protocols are different

The energy storage battery management system basically uses the CAN protocol for internal communication, but its external communication, mainly the PCS of the energy storage power station dispatching system, often uses the Internet protocol format TCP/IP protocol.

The power battery and the electric vehicle environment in which it is located all use the CAN protocol, but the internal CAN is used between the internal components of the battery pack, and the whole vehicle CAN is used between the battery pack and the whole vehicle.

2.4 The parameters of the management system are quite different for different types of cells used in energy storage power stations.

For safety and economic considerations, when selecting lithium batteries, energy storage power stations often use lithium iron phosphate, and some energy storage power stations use lead-acid batteries and lead-carbon batteries. The current mainstream battery types for electric vehicles are lithium iron phosphate batteries and ternary lithium batteries.

Different battery types have huge differences in external characteristics, and battery models cannot be universal at all. The battery management system and cell parameters must be one-to-one corresponding. The same type of battery cells produced by different manufacturers will have different detailed parameter settings.

2.5 Different threshold setting tendencies

Energy storage power stations have more space and can accommodate more batteries, but some power stations are located in remote areas and transportation is inconvenient, so large-scale replacement of batteries is difficult. Energy storage power stations expect batteries to have a long life and not fail. Based on this, the upper limit of its working current will be set relatively low to prevent the battery cells from working at full load. The energy and power characteristics of the battery cells do not need to be particularly high. The main consideration is cost performance.

Power batteries are different. In the limited space of the vehicle, the battery that is finally installed hopes to maximize its capabilities. Therefore, the system parameters will refer to the battery's limit parameters, and such application conditions are harsh for the battery.

2.6 The number of state parameters required to be calculated by both

SOC is a state parameter that both need to calculate. But until today, there is no unified requirement for energy storage systems, which state parameter calculation capabilities must be required for energy storage battery management systems. In addition, the application environment of energy storage batteries has relatively abundant space and a stable environment, and small deviations are not easily perceived in large systems. Therefore, the computing power requirements of the energy storage battery management system are relatively lower than those of the power battery management system, and the corresponding single-string battery management cost is not as high as that of the power battery.

2.7 The passive balancing conditions for the application of the energy storage battery management system are relatively good

The energy storage power station has an urgent requirement for the balancing ability of the management system. The scale of the energy storage battery module is relatively large, and multiple strings of batteries are connected in series. The larger single-cell voltage difference will cause the capacity of the entire box to decrease. The more batteries are connected in series, the more capacity is lost. From the perspective of economic efficiency, energy storage power stations need full balancing.

In addition, due to ample space and good heat dissipation conditions, passive balancing can play a better role. With a relatively large balancing current, there is no need to worry about excessive temperature rise. Low-cost passive balancing can be used in energy storage power stations.

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