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BQ40Z50-R3-DEVICE-FW: Golden File - Why Set Update Status to 0x2?

Eric Castle
Intellectual 710 points

Part Number: BQ40Z50-R3-DEVICE-FW

Hello,

I was creating yet-another learning cycle (as we iterate through hardware revisions), and following the instructions in "How to Complete a Successful Learning Cycle for the bq40z80". This time I noticed an additional step in the "Conclusion" section to set Update Status to 0x2. Why is this recommended? I thought part of the point of creating a "golden file" was to get Update Status to 0xE so that cell balancing would work. Is the assumption that the manufacturer will cycle each pack during testing, or that users will eventually do that themselves? What is the downside to leaving it set to 0xE?

Thanks,

-Eric 

  • 0
    TI__Genius 11535 points

    Hi Eric,

    It is okay to leave it at 0x06 in the final file for programming. The update status 0x02 corresponds to the Qmax and Ra learned but the impedance track algorithm is not active. 

    Although this post is talking about the BQ34z100, it goes into more detail about setting the update status to 0x02: https://e2e.ti.com/support/power-management-group/power-management/f/power-management-forum/1024042/bq34z100-g1-update-status-for-mass-production 

    Best,

    Jessica

  • 0 in reply to Jessica H.
    Intellectual 710 points

    Thanks for the reply. I'm trying to understand how production programming works for this part. I see there are two bits in the Update Status that I'm trying to understand why I would set one way or the other in the golden image: 

    1) Qmax: Is the idea that pack capacity can vary enough between packs that each pack should update it individually? What are the requirements for this update? The procedure that I followed was "charge all the way to 100% SOC, wait 2 hours, discharge all the way to 0%, wait 5 hours". I'm not sure how often packs will be used that way, and could see packs seeing a lot more "partial discharge, partial charge, etc." Is the assumption that manufacturers will cycle the packs themselves before shipping to customers? 

    2) Impedance Tracking: Assuming that we program the fuel gauge, and then attach cells, we don't want to have this enabled (as otherwise it will potentially mess up the fuel gauge). We then send a command to enable it after the cells are attached. Is that correct? Alternatively, if we are only programming the fuel gauge once cells are already attached, is it fine to have it already enabled?

    Thanks,

    -Eric

  • 0 in reply to Eric Castle
    TI__Guru** 105770 points

    Hello Eric,

    The Qmax bit only indicates if the Qmax has been updated, you don't need to modify this bit. Both the Ra table and Qmax should be updated in the learning cycle and included in the final production file uploaded to the gauge. The only bit that should be changed manually is the IT_EN (which is done by command.)

    Yes you are correct on your second point, I would recommend enabling the algorithm once the cells are attached.

    Sincerely,

    Wyatt Keller

  • 0 in reply to Wyatt Keller
    Intellectual 710 points

    Ok, so it's reasonable for my "golden file" to have an Update Status value of 0xA for production, or 0xE (for prototypes that have cells already attached). Agreed?

  • 0 in reply to Eric Castle
    TI__Genius 11535 points

    Hi Eric,

    It is reasonable for your golden image to have an Update Status value of 0x02 or 0x06. Anything higher should be updated by the gauge in the field.

    Best,

    Jessica

  • 0 in reply to Jessica H.
    Intellectual 710 points

    Hi Jessica,

    Huh, ok. I think I understand that the Impedance Track should only be enabled if the cells are already attached.

    I'm trying to understand the "QMax update in the field (Bit 3)" of Update Status. When you say it should be updated "in the field", do you mean by the end user? What are the requirements for it to be set? How strict are they? Do we need a large rest period in between discharging and charging? (I'm concerned that users will never fulfill the conditions necessary). 

    Thanks,

    -Eric

  • 0 in reply to Eric Castle
    TI__Guru** 105770 points

    Hello Eric,

    It's recommended to be done in the field, you should be getting Qmax updates regardless while the gauge is in the field so the gauge accuracy doesn't degrade. Qmax updates don't need to be every cycle but they should be often enough for the gauge to update when there's some battery degradation.

    The conditions are the same for a normal Qmax update, 37% change in DOD with 2 rest periods between with two valid OCV measurements. Or if you use the fast Qmax update that will also update the field Qmax.

    Sincerely,

    Wyatt Keller