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BQ34Z100-G1: Full Charge Termination bit not set

BattMan
Prodigy 60 points
Part Number: BQ34Z100-G1
We have been running charge/discharge cycles to test and understand when State of Health is updated, and have noticed an anomaly:
 
With three back-to back charge cycles, the SoH is updated each time. However, on two of the three cycles, the Full Charge Termination bit  (FC bit in Alert Configuration Register ) has not been set. However, in each of the three cycles, OCV taken occurs properly after charge termination. Can you explain why the FC bit would not get set yet a post-charge OCV is obtained?
These are on Lead Acid batteries, 12v AGM with 105ah capacity.
Thanks in advance!

  • 0
    TI__Mastermind 25955 points
    Hi BattMan,

    An OCV post charge may be obtained with a partial charge, however, the device may not have met the conditions required for FC to set.

    For FC to set with FC Set% = -1, the following must occur:
    1. During two consecutive periods of Current Taper Window, the Average Current is < Taper Current
    2. During the same periods, the accumulated change in capacity > 0.25 mAh per Current Taper Window
    3. Voltage > Charging Voltage - Taper Voltage

    SOH is calculated using the ratio of FCC and design capacity where the load for FCC used is defined by SOH Load Current.

    Sincerely,
    Bryan Kahler
  • 0 in reply to Bryan Kahler
    Expert 1232 points
    Hi, I'm looking at BatMans data:

    Taper current was 100 mA
    Taper window is 40s x windows = 80s
    1. Average current was (90mA) less than taper current for more than 80s.. CHECK

    Current flowing during two consecutive windows less than taper current and above 90 mA
    Cummulated capacity = (40secs / 60secs per hr ) * 90mA (aprox) = 60 mAhr per window
    2. 60mAhr > 0.25 mAhr per window.. CHECK

    ChargeV :14.28V -Taper V: 0.3 = 13.98V
    3. Voltage during windows was rising above 14.4 V during both widows... CHECK

    No FC occured
  • 0 in reply to BatMan
    TI__Mastermind 25955 points
    Hi Tim,

    Could you please share these logs as well as the gg.csv file?

    Without seeing the files, please also investigate the following:

    With 105 Ah of capacity in the system, current scaling will have had to been implemented. Please ensure that all capacity/current/energy based parameters in the data memory of the device have been scaled by the scale factor utilized when calibrating current for the device. A scale factor of 4 or greater was most likely used.

    If the issue still persists after a modification of the values in dataflash (if this has not been done), please determine the following: Has the chemID been verified to be a good match to these cells? Which chemID is being used?

    Sincerely,
    Bryan Kahler
  • 0 in reply to BatMan
    TI__Mastermind 25955 points
    Hi Tim,

    Thank you for the files. In addition, please answer the following:

    Has the chemID been verified to match these cells?
    What was the process followed?
    Which chemID # is being used?

    What is the value of your current sense resistor?
    What is your current scale factor?

    Sincerely,
    Bryan Kahler
  • 0 in reply to Bryan Kahler
    Expert 1232 points
    Yes we used GPC tool: Best chemical ID : 807 Best chemical ID max. deviation, % : 5.63

    We are using a scale factor of 20 and the shunt resistor is 100uOhm and it is calibrated.
    SOC tracks very well. OCV taken occurs after charge and discharges.
  • 0 in reply to BatMan
    TI__Mastermind 25955 points
    Hi Tim,

    The device has not been validated with such a small current sense resistor.

    What are the design decisions prompting this size and very large scale factor?

    Changing the size of the current sense resistor may be the solution. FC may not be setting due to resolution.

    If this is not possible, Please send a log and the gg.csv file of the device for further analysis.

    Sincerely,
    Bryan Kahler
  • 0 in reply to Bryan Kahler
    TI__Mastermind 25955 points
    Hi Tim,

    Haven't heard back since this answer was suggested - hope the issue is resolved. If not, please let us know.

    If this answer resolved the issue, please hit the green 'resolved' button to help improve question/answer searchability on the forums. Thank you!

    Sincerely,
    Bryan Kahler