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BQ28Z610: Obtaining ChemID

Miroslav Bozic42
Prodigy 30 points
Part Number: BQ28Z610
Other Parts Discussed in Thread: PMP40496, BQ24725A, , BQSTUDIO, GPCCHEM

Dear TI team,

Together with my team I been working on a device that integrate some of components from your portfolio. We designed consumer device that has backup battery support and for such purpose we decide to use BQ24725A as a charger and BQ28z610 as a battery protection and gauge. Our battery configuration is 2s1p and we are using 18650 Li-Ion cells inside pack. During the tests we have faced some inconsistencies with the estimation and figure it out that probably this is coming from the wrong chemical ID. Our hardware design is based on TI reference manual and the connection between charger and a gauge is almost identical to the PMP40496 Reference design.

We have found all the information how to log the data using BQstudio and how to get the ChemID based on these data from the TI. Our plan is to run the relax-dischg-relax in order to get logged data that are required by TI. Before we do this there are some concerns, we have and it would be very useful if you can provide some information so we can proceed with the process. Our concerns are following:

  1. Based on the information from How to Complete a Successful Learning Cycle for the BQ28Z610 (slua777) document we have found that for ChemID there is no need to do complete Learn cycle (dischg-relax-chg-relax). Since chemID requires logs for relax-dischg-relax our question is do we need to configure the registers as described in the chapter 4.2 in slua777 doc, and then charge the battery before first relax period? Should we need to monitor GaugingStatus[REST] flag to be sure that the relax period is done, or 2h relax after charge is enough?

  2. Since we are using a 2s1p battery without any protection, would it be ok to configure some safety params inside a gauge before we start charge/discharge procedure, and does this affects a procedure in any case?

  3. During the relax period, we are planning to leave the gauge in the normal mode, is this ok?

  4. We have never faced that our charger switch from constant current to constant voltage mode during the charge procedure with this battery, is this ok? We used BQ24725A in couple of applications and always at the end of charge the current went down until battery is fully charged.

  5. After obtaining ChemID we are planning to do a Learn Cycle, please tell me if LC is necessary for cell balancing, since we faced that some of the packs are not well balanced, both during the charge and discharge which lead us to the gauge shutdown due to over/under voltage protection?

 

I will really appreciate if you can provide answers on my questions because we are planning to rollout first batch of devices to end customers soon and this cannot be done before we finish complete battery commissioning and setup.

 

Thanks in advance.

  • 0
    TI__Mastermind 19195 points

    HI Miroslav,

    1. You must complete a full learning cycle, then the golden image from that pack can be flashed onto all others
    2. Most protections are enabled by default, you can refer to the TRM for more info
    3. Yes, this is ok
    4. CC/CV is the normal charging procedure for li-ion battery
    5. Yes, a learning cycle is necessary for cell balancing.

  • 0 in reply to Nick Brylski
    Prodigy 30 points

    Hi Nick,

    thank you very much for the fast response to our questions.

    I have a couple of more concerns so I will be thankful if you can give me just a bit more information about questions numbers 1 and 4.

    1. You said we need to do complete LC and after that, we will have a golden image, but before that, we need to find a chemical ID flash it inside the gauge before LC is started. Based on your answer, it seems like we need to do a complete learning cycle and log data during relax-discharge-relax to get the logs that should be uploaded to TI for obtaining a matched battery chemical ID, is this proper understanding of your answer?

    4. Yes this is fine, we know that CC/CV is the usual procedure, but we are facing that in our application charger never switch from CC to CV. We would like to detect the end of charge by measuring the voltage on BQ24725A_Iout and terminate the charging once the measured voltage is proportional to 18mA charging current. We set the charging voltage to 8.4V which is the same as the OVP on the gauge and the gauge terminate charging before the CV is activated. Do we need to set the BQ24725A charge voltage to 8.35V in order to reach CV mode and be able to measure 18mA taper current and terminate charging?

    Our procedure is the following:

    • Identify ChemID
    • Flash gauge with ChemID
    • Set all parameters regarding SLUA777
    • Do a learning cycle procedure
    • Dump complete register map and use it as a golden image for flashing all other gauges inside the devices

    Are these steps are ok?

    Thanks in advance. 

  • 0 in reply to Miroslav Bozic42
    TI__Mastermind 24870 points

    1. Yes, it is the GPCCHEM tool.

    4. As far as I know the charging voltage for smart chargers are configurable. You will set it to the max charging voltage for CV to begin.

    Yes the procedure looks correct, please add logging IVT and dump gg file prior to start of cycle.

  • 0 in reply to Kang Kang
    Prodigy 30 points

    Kang,

    thank you very much for the feedback you provided. This solved my doubts.

    Best regards.