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BQ78350-R2-DEVICE-FW: BQ78350-R2-DEVICE-FW

sai praturu
Intellectual 280 points

Part Number: BQ78350-R2-DEVICE-FW

Hi:

We have an application where two identical  battery modules (labelled Pack 1 and Pack 2)  are connected in parallel. Each battery pack is running V2.02 R2 device firmware on the BQ78350-R1 and has BQ76930 AFE.

During the discharge cycle, if Pack 1 battery pack terminates discharge earlier than the Pack2, the Pack 2 appears as a low impedance source and causes the discharged Pack1 to trip the ASCD flag. This flag toggles based on its recovery time. 

Any way to avoid this in parallel battery connections? or do we have to disable ASCD detection?

  • 0
    Intellectual 280 points

    Would like to keep ASCD detection  and not have to disable.

  • 0 in reply to sai praturu
    TI__Guru* 81034 points

    Hi Sai,

    If you are seeing current flow from Pack 2 to Pack 1 after Pack 1 terminates discharge, there may be something wrong in your circuit because Pack 1 should disconnect. 

    Another thing that might be happening: Pack 1 and Pack 2 are both driving the same current. When Pack 1 terminates discharge, Pack 2 all of a sudden needs to supply double the amount of current. Could that be why ASCD is triggering? If so, you may need to adjust your ASCD threshold and / or sense resistor value to account for this scenario.

    Best regards,

    Matt

  • 0 in reply to Matt Sunna
    Intellectual 280 points

     

    The ASCD seems to be behaving as it should once we have adjusted the settings. Another behavior we have noticed on parallel connected packs is:

    If there is a slight imbalance between packs (even 1V  delta between packs), and if  one pack is charging the other, after they equalize, what we have noticed is that the pack which was getting charged, once it equalizes with the other pack (PACK OCV), the rem cap changes to 100% (from its current state for example 5%). 

    We are using fixed EDV and EDV_CMP is 0.

    FCC learn up and learn down are set to same as the design capacity.

    Not sure what can cause the Rem Cap to become equal to FCC, in this instance?

    We will repeat this for more cycles and log observations.

  • 0 in reply to sai praturu
    TI__Guru* 81034 points

    Hi Sai,

    That sounds like a good plan. If you still see this behavior, can you also send your data flash settings (.gg file) when you send the log file?

    Thanks,

    Matt