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BQ2040 based fuel gauging

sandeep srivastava
Prodigy 10 points
Other Parts Discussed in Thread: BQ2040, BQ3060, BQ78PL114, BQ78PL116

Hi All,

I am using BQ2040 for fuel gauging for battery pack of 6 Li-ion(2200mAH) cells in series, it incorporates cell balancing during charging cycle.

I am facing the below mentioned problems.Kindly revert back if you have any suggestions

1)Since the rate of discharge is 2A continuous and 4A for 100ms(pulse anytime during discharging) , the vooltage of the battery pack dips faster. out of 6 batteries in series one of the battery goes to lower threshold cut-off of discharge earlier than other causing abrupt shutdown. The fuel gauge RSC may be 30 %, 20% 25% etc. at the time of shutdown which is not acceptable to consumer. How to take care of this issue?

2) If in the system of 6 batteries ,any one battery becomes weak and the voltage of the battery reduces drastically while discharging , how and what parameter of fuel gauge BQ2040 can help us in determing this bad battery condition in order to indicate to consumer that it's time for recalibration or replacement of the battey pack.

3)The fuel gauge BQ2040 recalibrates itself when it reaches EDVF but in my system an individual battery is reaching threshold voltage of 2.5V (where the system shuts down) before the pack reaching EDVF value of 16.5V. So the chances of system recalibration becomes rare. Then how does BQ2040 willl take care of aging of the pack ?

 

Regards.

Sandeep Srivastava

  • 0
    TI__Intellectual 930 points

    1) Since the bq2040 uses EDV and not CEDV, it does not have the capability to account for pulses.

    2) and 3) The bq2040 cannot measure individual cell voltages, it only senses total battery pack voltage therefore both of these are not possible.

    To solve these problems, my suggestions are:

    For 2-4 cells I would recommend using either the bq20z45 (IT part) or the bq3060 (CEDV part).

    For more than 4 cells, I would recommend either the bq78pl114 or bq78pl116.

    Regards,

    Viktoriya