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Original question:

BQ76940EVM: What are the conditions required to enable cell balancing on the BQ76940EVM

BQ76940EVM: Dumb Charger

g h
Prodigy 25 points
Part Number: BQ76940EVM
Other Parts Discussed in Thread: BQ78350, BQ76940, , BQ78350-R1, BQ78350-R1A

I have the BQ7640EVM and have set it up.  My question is whare are the recommendation to use a "dumb charger".

Parameter configuration and schematics we help a lot.

How dos the bq78350 know to enter charging mode.

my definition: dumb charger - a charger you only need to connect the BAT+ and BAT-, maybe the balance wires.

  • 0
    TI__Mastermind 27321 points

    Hello,

    g h said:
    My question is whare are the recommendation to use a "dumb charger".

    I am not sure I am understanding your question. We do not use the term "dumb charger". I do not know what you mean by this. Please elaborate more.

    g h said:
    How dos the bq78350 know to enter charging mode.

    The BQ76940 will sense positive or negative current through the sense resistor. Then, this current will be read from the BQ78350. The BQ78350 has a Fuel Gauge Operating algorithm which will detect charging, relax, and discharging depending on the current value obtained from BQ76940. You can reference to section 9.1.2 Fuel Gauge Operating Modes in the Technical Reference Manual.

    Also, in Section 2.2  Current and Coulomb Counting. The BQ769x0 AFE is the BQ76940 in this case.


    Note: The BQ76940 is a monitor and current sensing device and needs the interaction of an MCU. In this case, the MCU is the BQ78350 which is also a gauge.

    Regards,
    Jose Couso

  • 0 in reply to Jose Couso
    Prodigy 25 points

    thank you for the replay. I now understand how the BQ76940 know how to start charging.

    Do you know if there is any setting/ paraments I need to set that are not default?  for charging to work with the BQ76940EVM.

    About the "dumb" charger, I was trying to use the term as I understand it from - Using the bq78350-R1 page 12

  • +1 in reply to g h
    TI__Mastermind 27321 points

    Hello g h,

    I see there are two documents called "Using the bq78350-R1". You probably want to reference to this ONE. This one in particular includes the configurations required for good gauging. Reference to section 2.3 Gas Gauging. 

    g h said:
    Do you know if there is any setting/ paraments I need to set that are not default?  for charging to work with the BQ76940EVM.

    To ensure the BQ78350 uses the operating mode algorithm without any issues, you want to follow the following conditions.

    1- Taper Current > Chg Current Threshold > Quit Current
    2- DSG Current Threshold > Quit Current

    Other than the above, I think you should be following the configurations in section 2.3 mentioned above. Also, you want to read about the Charge Algorithm in section 5 of the Technical Reference Manual.

    g h said:
    About the "dumb" charger, I was trying to use the term as I understand it from - Using the bq78350-R1 page 12

    As for the dumb charger terminology, this is simply saying that the gauge supports smart or dumb chargers. "which means chargers that read or receive charge control data from the bq78350, or not." You can also search online for "smart vs dumb chargers".

    g h said:
    my definition: dumb charger - a charger you only need to connect the BAT+ and BAT-, maybe the balance wires.

    Regardless of smart or dumb, the charger will be attached to PACK+ and PACK-. 

    On another point, you may want to use the BQ78350-R1A version. And also, if cell balancing is required at rest, I suggest to look at  SLUUCM2A. The other versions only support cell balancing during charging.

    Regards,
    Jose Couso