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BQ4050: FCC capacity jump

LVJIAORNG1 LVJIARONG1
Prodigy 20 points
Part Number: BQ4050
Other Parts Discussed in Thread: BQSTUDIO

Tool/software:

Hello, engineers at TI,
The aging test of the lithium iron phosphate battery has been completed, and the FCC shows that the updated value is 3603mAh. During the static process of the product, it is found that the FCC jumps to 4118mAh, but the Soc value of the product is correct. What may be the cause of the FCC jump during the static process of the product?

The attachment is the data of the aging test.

Aging test data.xlsx
  • 0
    TI__Mastermind 25355 points

    Hello,

    This question has been assigned and will be reviewed when possible.

    Thank you,
    Alan

  • 0 in reply to Alan Frias
    TI__Intellectual 752 points

    Hello,

    The CEDV gauging will update FCC when the EDVx thresholds are reached. The TRM states on section 6.3 the new FCC updates after:

    FCC (new) = DCR (final) = DCR (initial) + Measured Discharge to EDV2 + (FCCx Battery Low%)

    Do you know if what is the EDV2 value when they got the FCC jump?

  • 0 in reply to Miguel Castro Gonzalez
    Prodigy 20 points

    EVD0 2.5V   EVD1 2.67V    EVD2 2.95v

  • 0 in reply to LVJIAORNG1 LVJIARONG1
    TI__Intellectual 752 points

    The key here is to know if the device was in qualified discharge event. The TRM states it needs multiple conditions to meet this:

    • • No valid charge activity occurs during the discharge period. A valid charge is defined as a charge of 10 mAh into the battery. •
    • No more than 256 mAh of self-discharge or battery load estimation occurs during the discharge period. •
    • The temperature does not drop below the low temperature thresholds programmed in Learning Low Temp during the discharge period. •
    • The battery voltage reaches the EDV2 threshold during the discharge period and the voltage is greater than or equal to the EDV2 threshold minus 256 mV when the BQ4050 detected EDV2. •
    • No midrange voltage correction occurs during the discharge period. •
    • Current remains ≥3C/32 when EDV2 or Battery Low % level is reached. • No overload condition exists when EDV2 threshold is reached or if RM() has dropped to Battery Low% × FCC.

    I looked into your gg file closer.There seems to be multiple protection events on this part. Did you test this part before? I also see a permanent fail (PF) of voltage on CELL1 of ~1V which is very low. If the voltage of one the cells is getting too low, it might be triggering the qualified discharge event. However, the part needs to remain on that EDV2 + ~256 mV voltage for a period of time.

    Can you elaborate what was the state of the gauge and the battery pack during "static"?

    Is this issue repeatable? If so, can you capture a log from Bqstudio I can take a look closer?