Circuit Simulation of Lithium Battery Balanced Charging Protection Board.18650 lithium battery 3.7 v

　　Based on the basic principle of the balanced charging protection board circuit mentioned above, a system simulation model was built in the Matlab/Simulink environment to simulate the operation of the protection board during the charging and discharging process of the lithium battery pack, and to verify the feasibility of the design scheme. For simplicity, a simulation model of a lithium battery pack consisting of only 2 lithium batteries in series is presented

　　In the model, a controlled voltage source is used instead of a single lithium battery to simulate the charging and discharging of the battery. In Figure 5, Rs represents the total internal resistance of the series battery pack, RL represents the load resistance, and Rd represents the shunt discharge branch resistance. The single lithium battery protection chip S28241 used is packaged as a subsystem, making the overall model expression more concise.

　　The protection chip subsystem model mainly uses logic operation module, symbol function module, one-dimensional table lookup module, integration module, delay module, switch module, mathematical operation module, etc. to simulate the timing and logic of protection actions. Due to the differences between the simulation environment and the real circuit, there is no need for filtering and strong/weak current isolation during simulation, and redundant modules can easily lead to lengthy simulation time. Therefore, in the actual simulation process, circuits such as filtering, optocoupler isolation, and level adjustment were removed, and the resistor network designed for high current shunt was changed to a single resistor, reducing the complexity of the simulation system. When establishing a complete system simulation model, it is important to note that there may be differences in the input and output data and signal types of different modules. It is necessary to correctly arrange the connection order of the modules, and if necessary, perform data type conversion. The voltage detection module is used in the model to achieve the problem of strong and weak signal conversion connection.

　　The given signal of the controlled voltage source in the simulation model can have slight differences under the premise of roughly the same waveform. The voltage detection simulation results of a single battery in the battery pack represent the differences in individual battery charging and discharging. It can be seen that the circuit can work normally by using the method of equalizing the charging of overcurrent discharge branches

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