Battery Management System
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What is Battery Management System?

A battery management system (BMS) is an electronic system that manages a rechargeable battery (battery cell or battery
pack), for example, to protect the battery from operating outside its safe working area, monitor its status, calculate data auxiliary data, report the data, control Its environment, verify it and/or balance it. The built-inbattery pack and the battery management system with an external communication data bus is a smart battery pack. The smart battery must be charged with a smart battery charger.
 

Function

BMS can monitor the battery status represented by various elements, for example:  

Voltage: total voltage, single-cell voltage, or periodic tap voltage  

Temperature: average temperature, coolant inlet temperature, refrigerant outlet temperature, or single battery Temperature

 

Electric vehicle systems-Energy
recovery

BMS will also redirect the recovered energy (ie from regenerative braking) back to the battery pack Control battery
charging (usually composed of multiple battery modules, each module is composed of multiple batteries). The battery thermal management system can be passive or active, and the cooling medium can be air, liquid, or some form of phase
change. The advantage of air cooling is its simplicity. This system can be passive, relying only on the convection of the surrounding air, or it can bemactive, using fans for airflow. Commercially, Honda Insight and Toyota Prius
use active air cooling for their battery systems. The main disadvantage of air cooling is its inefficiency. A large amount of energy must be used to operate the cooling mechanism, far exceeding active liquid cooling. The additional components of the cooling mechanism also increase the weight of the BMS and reduce the efficiency of the battery used for transport.
  

Liquid cooling has a higher natural cooling potential than air cooling because the thermal conductivity of liquid refrigerants is often higher than that of air. The battery can be directly immersed in the coolant, or the coolant can flow through the BMS without direct contact with the battery. Due to the long length of the cooling channel, indirect cooling may generate a large thermal gradient across the entire BMS.
This can be reduced by pumping the coolant through the system faster, with a trade-off between pumping speed and thermal consistency.
 

  

Communication  

The central controller of the BMS and its unit The hardware that runs in the advanced stage communicates internally or communicates with external advanced hardware such as computer notebooks or HMI. high-level external communication
is very simple, using several methods: different types of serial
communication. CAN bus communication, often used in the automotive
environment.
 

  

Different types of wireless communication.

Most centralized low-voltage BMSs have no internal communication.  

Distributed or modular BMS must use some internal low-level unit controllers (modular architecture) or communicate with the controller (distributed architecture). These types of communication are difficult, especially for high voltage systems. The problem is the voltage compensation between the batteries. The ground signal from the first unit can be hundreds of volts higher than the ground signals from the other unit. In addition to the software protocol, the voltage conversion system also has two known hardware communication methods: optical isolator and wireless communication. Another limitation of internal communication is the maximum number of units. For modular architectures, most hardware is limited to a maximum of 255 nodes. For high-voltage systems, the search time for all units
is another limitation, limiting the minimum bus speed and losing some hardware options. The cost of a modular system is important because it can be comparable to the price of a battery.
 

Protection

BMS can protect your battery by preventing it from running outside its safe working area, for example:  

leakage current or ground fault detection (system monitoring) The high-voltage battery is disconnected from any conductive objects that can be touched for use as a car body)  

BMS can prevent the operation of the battery outside the safe working area in the following ways: includes internal switches (such as ar
elé or solid-state equipment) if it is operated safely If the battery is used outside the area, the device will open to ask about the device connected to the battery to reduce or even eventually use the battery.
 

   

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