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BQ76952: BQ76952

Mohit Aggarwal
Prodigy 90 points
Part Number: BQ76952

Hello Ti Team 

We are using BQ76052 AFE for 48volt BMS application.

We are facing issue of voltage fluctuation in the field.

Meaning of voltage Fluctuation means one cell is reading higher value and second corressponding cell is reading Lowe value but the actual value of cell is accurate.

Example :-  

Cell 1-10:-      3760

Cell 11:-         3657    Actual Voltage is 3760

Cell 12:-         3966    Actual Voltage is 3760

Cell 13-14 :-  3760

If we can divide cell 11 and cell 12 we will get approx same value with a difference of 30mV to 50mV.

Note :- We have deployed 8000 Battery pack with the same BMS.

Out of 8000 Battery pack we have faced two types of issues on the voltage fluctuation.

Issue 1 :- Voltage Fluctuation will be auto corrected (This type of issue we have seen in 100 Battery pack approx.)

Voltage Fluctuation will be auto corrected means one cell read higher voltage and second corresponding cell will read lower voltage and this issue will be autocorrected.

Issue 2 :- Voltage fluctuation will not be autocorrected (This type of issue we have 70-80 Battery packs approx)

Voltage Fluctuation will not be auto corrected means once the one cell reads higher voltage and second corresponding cell reads lower voltage then this scenario will be continue there.

This scenario can be rectified by two ways

1.Disconnect the sensing wire and again connect then this will be resolved.

2.ON cell balancing for that particular cell then this will be resolved.

 

We need your support to resolve this issue .or get to know what are the possible cases in which this type of issue occur

Thanks and Regards 

Mohit Aggarwal

  • 0
    TI__Mastermind 25980 points

    Hi Mohit,

    This sounds like the beginning of an open wire condition. If the connection to the board between the fluctuating cells is faulty then the measured voltage of the upper cell will drift upwards, and the lower cell will drift downwards.

    I recommend measuring the voltage between the cell inputs at the device's pins. If it is fluctuating with the measurements, then it is very likely to be a faulty cell connection, especially since reapplying the cell connection fixes the fluctuation. 

    Regards,

    Max Verboncoeur

  • 0 in reply to Max Verboncoeur
    Prodigy 90 points

    Hi Maxwell

    As i mentioned in the above two cases 

    One case is Voltage Fluctuation will be auto corrected in this case it is difficult to check the voltage at the input side because this type of issue automatically resolved without any interuption.

    But in the second case when voltage is not auto corrected in this case if there will be loose connection then how the  balancing ON for that particular cell resolved the issue.

  • 0 in reply to Mohit Aggarwal
    TI__Mastermind 25980 points

    Hi Mohit,

    Could you make a clarification for me? Does turning the cell balancing on completely fix the fluctuation, or does the fluctuation return once cell balancing is turned off?

    Regards,

    Max Verboncoeur

  • 0 in reply to Max Verboncoeur
    Prodigy 90 points

    Hi Mawell

    Yes When we ON the cell balancing then fluctutation completely fix.

    No after fix  fluctuation will not return back when balacning is OFF.

    Thanks & Regards

    Mohit Aggarwal

  • 0 in reply to Mohit Aggarwal
    TI__Mastermind 25980 points

    Hi Mohit,

    Can you share your schematic for me to check?

    Regards,

    Max Verboncoeur