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BQ78350-R1: Some registers do not update with BQstudio and BQ78350-R1

Marc Gera
Prodigy 10 points
Part Number: BQ78350-R1
Other Parts Discussed in Thread: TIDA-00792, BQSTUDIO, EV2400

Hello, 

We have designed a BMS + battery pack based on TIDA-00792. 

We have encountered several problems while performing charge and discharge cycles: 

Q1: 

FCC and RSOC do not update their values correctly unless a reset is performed. 

The RSOC updates as the voltage decreases, but several times it does not update correctly, resulting in an incorrect RSOC calculation (for example, 0%) when battery voltage corresponds to a higher or a different RSOC value. 

In these cases, a reset must be performed from BQstudio to recalculate the RSOC and FCC values correctly according to the cell characterization (after reset, for example, it goes from 0% to 20%). What could be causing this or how could we solve it? 

 

Q2:  

During vibration tests, the BMS loses SMBus communications and cuts the output voltage, and it does not reestablish until the activation button is pressed (making TS1 > Vboot). It seems that the battery goes into shutdown, but in this case the register with the shutdown entry counter (“No of shutdowns” in “Lifetimes”) does not increase. In what cases can this situation occur? 

Thank you very much, 

 

Marc Gera 

  • 0
    TI__Guru 62736 points

    This sounds like there's a problem with the bus (SCL/SDA) in your design. Which interface are you using (EV2400, EV2300)?

    The lifetimes shutdown counter only increases if there is a controlled shutdown event. It won't increase if the gauge suddenly loses power (which sounds likely during a vibration test).

  • 0 in reply to Dominik Hartl11
    Prodigy 10 points

    Hello Dominik,

    Regarding Q1:

    We are using the EV2400 bus interface.

    Regarding Q2:

    We believe our system is robust. The cells are securely attached to the BMS, and there is no loss of power to the BMS. Could it be something else?

    Thank you, best regards,

    Marc Gera

  • 0 in reply to Marc Gera
    TI__Guru 62736 points

    I can't say what else this could be. The vibration test hints at a mechanical problem. So I'd check that the part doesn't lose power or connection on the bus.

  • 0 in reply to Dominik Hartl11
    Prodigy 10 points

    Hello Dominik,

    We will recheck to ensure that the BMS does not lose power and that the communications are functioning correctly.

    Thank you, best regards,

    Marc Gera

  • 0 in reply to Marc Gera
    TI__Mastermind 37761 points

    Hello Marc,

    Sounds good, let us know any updates.

    Regards,

    Nick Richards