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BQ27750: BQ27750: QMax update; Gauge not resetting via I2C Commands

Praveen Pitchai
Prodigy 130 points

Part Number: BQ27750

Hello,

I am trying to reset the bq27750 gauge via the I2C commands provided in the technical reference document, i.e. 0x0012 or 0x0041 to the AltManufacturereAccess() location i.e. 0x3E, but it seems the gauge does not reset itself. This is so that the gauge can take the updated QMax value in the data flash according to section 6.4.2 .Unfortunately, the Qmax value does not get updated and the % readings on the system I am using are not correct.

Several Questions:

1. Is there a method to have QMax update taken immediately after the data flash update is done without a gauge reset?

2. If not, then is there any other mechanism by which the gauge is reset, i.e. if no voltage is applied to the gauge, by plugging out and plugging back in system batteries?

Any input into this would help.

 

  • 0
    TI__Guru* 76230 points

    Hi Praveen,

    What are you expecting when you sent the gauge reset command? A reset command does not cause qmax to update. 
    To get a qmax update, there has to be two relax periods and a dicharge of atleast 90% of design capacity. Ps follow the instructions in the app note below to get a successful learning cycle of which you will get qmax update and the update status would be 06.

    2. To reset the gauge to default settings, you need to reprogram the srec file on the device.

    thanks

    Onyx

  • 0 in reply to Onyx Ahiakwo
    Prodigy 130 points

    Hello Onyx,

    Thank you for your response. While I can try the learning cycle on a BQ27750, what I'm essentially trying to achieve is an update to HOST devices that are already using the bq27750 configurations without the correct QMax update. 

    In view of that: in the Tech Reference document provided, I see in section 6.4.2 QMax Update Conditions the following: " It will be cleared when the QMax update occurs, when the offset error for a QMax disqualification is met, or when there is a full reset" . 

    Also, with my HOST system, I have tried to Hook up the device to bqStudio (1.3.86), and have tried the RESET Command (i.e. 0x0041) via I2C which takes the updated QMax. I am trying to replicate this on my HOST system, as I cannot do it on all devices that have already been shipped out.

    Hence my question.

    Thank you,

    Praveen

  • 0 in reply to Praveen Pitchai
    TI__Guru* 76230 points

    Hi Preaveen

    A reset command (0x41) will not cause qmax to update. Qmax only updates when the conditions for learning has been met. You need to cycle your packs- charge to rull rest, discharge to empty, rest and charge to full to get a qmax update.

    thanks

    Onyx