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BQ40Z50-R2: Learing cycle step1. How main volts is required for step 1 discharge?

HJ_KIM
Intellectual 485 points
Part Number: BQ40Z50-R2

I want to do learning cycle for my battery.

My battery standard discharge spec is 3V/0.2C.

When discharging, it is difficult to adjust the voltage of all cells to 3V.

Some cells are 3.2V and some cells are 3V.

Does the learning cycle require the voltage to be equal to 3 volts individually?

Or is it acceptable to perform a Learning cycle if the overall voltage is 12V?

Can the learning cycle be performed in the voltage state shown below?

  • 0
    TI__Genius 12215 points

    Hi

        It is not a strict requirement for all voltage to go to same 3v at the end of discharge for learning cycle, you can discharge the battery to system terminate voltage, which in your case I think it is 12v, or a little bit lower to have all Ra values in the table to be updated.

       Please make sure the UVP threshold is set according the cell vendor spec, it is typically lower than 3v.

  • 0 in reply to Steven Yao
    Intellectual 485 points

    My cell spec is below;

    Standard discharge : 0.2C to 3.0V

    Over discharge : 2.75V / cell

    What is start voltage about Step1 of learning cycle?

    3.0V(12V) or 2.75(11V)?

  • 0 in reply to HJ_KIM
    TI__Genius 12215 points

    For Learning Cycle, it starts with a discharge step first from any voltage.

    For the discharge step in learning cycle, you can set the terminate voltage to Minimum System Voltage, which is Terminate Voltage in Dataflash

    Please also be noted to select cells with most approximate voltage and impedance to assemble the battery pack.

    Because if the cells are absolutely matched, when it is discharged to 12v, each cell is 3v. but as you know, this is not possible. So even with carefully selected cells, the cell voltage can be as approximate as possible when the battery voltage reaches to Terminate Voltage. for example some might be 3.1v, some might be 2.9v 

    You do not have to set the Terminate Voltage to base on single cell voltage, the stack voltage would be fine

    The UVP can be disabled if you have concern on some single cell hit the UVP threshold first when you do learning cycle