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Original question:

BQ78350-R1: CEDV Data Collection for Gauging Parameter Calculator (GPC)

BQ78350-R1: How does EDV_EXT_CELL affect UV and RSOC?

Marco Antonio Vega
Intellectual 365 points
Part Number: BQ78350-R1
Other Parts Discussed in Thread: BQ78350

Hi,

I open this new thread to solve a question previosuly asked on e2e.ti.com/.../3535917

I've one question: If I enable EDV_EXT_CELL = 1, the calculated EDV0,1,2 by CEDV algorithm will be based only on the External Average Cell Voltage?

In other words, if the External Average Cell Voltage is around 3,5V (which could means 7% of battery) but the lowest cell voltage is near of UV=3V. How it does affect to RSOC calculation? Would I see a jump from 7% to 0%? In this case, it seems better approach using the lowest cell voltage (not EDV_EXT_CELL=1).

For example, from the 6 log files that I've collected I've seen that cell7 reaches to 3V when the ExtAvgCellVolt=3,3V. It seems that cell7 has less capacity than others.. but it can occurs obviosusly because production process or aging. I've also checked the cell 7 balance during the charging process, and it's totally ok (maximum deviation of 20-30mV respect to the others).

Thanks,

Marco.

  • 0
    TI__Guru* 81034 points

    Hi Marco,

    Setting EDV_EXT_CELL to 1 means the CEDV algorithm will use the average cell voltage to determine when EDV2/EDV1/EDV0 have been reached. Setting EDV_EXT_CELL to 0 will use the lowest cell voltage. The original version of the Using the BQ78350 document (https://www.ti.com/lit/an/slua924/slua924.pdf) 

    The voltage difference you are observing does seem unusual though (500 mV difference between 3.5V and 3.0V) - I wouldn't expect that to be the case for all battery packs.

    Matt