want_to_know
Newbie level 4
Hi all,
I am working on a simple system working to balance charge among four Li-ion cells in Matlab-Simulink. All the controller and Li-ion cell models are in Matlab-Simulink.
I want to discharge four cells within an hour (3600 seconds), so I work around with the R,V, and I values so that the cells would take an hour to discharge from 100% to 0% in terms of state of charge. (SOC from 100% to 0%, 100%= full cell; 0% = empty cell)
Without connecting any controller, the four cells work well where I can see in the graphs that each cell is going from SOC=100% to SOC=0% at the end of simulation of an hour period.
However, when I connect my controller to the four cells, weird thing happens where all the four cells take only 135 seconds to go from SOC=100% to SOC=0%.
Perhaps I should mention about what my controller is doing, cause I suspect it is the main culprit, though I have no idea why and how.
Basically, cell terminal voltage serves as the inputs to the controller, then the controller will sort the cell terminal voltage in descending order so that the cell with highest voltage is utilized first, for example, if I have cells voltage = [3.8 4.2 3.5 3.9], the controller will sort it to [4.2 3.9 3.8 3.5]. The controller is so simple that I have no idea how it caused the issue I am having here.
I appreciate any input, please.
I am working on a simple system working to balance charge among four Li-ion cells in Matlab-Simulink. All the controller and Li-ion cell models are in Matlab-Simulink.
I want to discharge four cells within an hour (3600 seconds), so I work around with the R,V, and I values so that the cells would take an hour to discharge from 100% to 0% in terms of state of charge. (SOC from 100% to 0%, 100%= full cell; 0% = empty cell)
Without connecting any controller, the four cells work well where I can see in the graphs that each cell is going from SOC=100% to SOC=0% at the end of simulation of an hour period.
However, when I connect my controller to the four cells, weird thing happens where all the four cells take only 135 seconds to go from SOC=100% to SOC=0%.
Perhaps I should mention about what my controller is doing, cause I suspect it is the main culprit, though I have no idea why and how.
Basically, cell terminal voltage serves as the inputs to the controller, then the controller will sort the cell terminal voltage in descending order so that the cell with highest voltage is utilized first, for example, if I have cells voltage = [3.8 4.2 3.5 3.9], the controller will sort it to [4.2 3.9 3.8 3.5]. The controller is so simple that I have no idea how it caused the issue I am having here.
I appreciate any input, please.
