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BQ27320: Battery Low %

K.Yaita
Guru 29720 points
Part Number: BQ27320

Hi Team,

I understand EDV2 threshold can be set by parameter of "Battery Low %".
*Default value of "Battery Low %" is 7%.



I beleive 7%(default) is recommended however could you tell me what situation it should be set another value? 

Best Regards,
Yaita

  • 0
    TI__Guru* 76230 points
    Hi Yaita
    We wouldn't recommend changing that value except if the 7% does not fall close to the knee region of the OCV curve. Those values are chosen to ensure the cell is below the knee region.

    thanks
    Onyx
  • 0 in reply to Onyx Ahiakwo
    Guru 29720 points

    Hi Onyx-san,

    Thank you always for your support.
    I would like to ask further questions.

    My customer wants to set "Battery Low %" from default (7%) to another (8%, 9%, 10% etc..).
    The purpose of it is they wants to change update timing of FCC because of their system requirement.

    1)
    I believe changing "Battery Low %" is only method to change FCC update timing.
    Is my understand correct?

    2)
    If they set "Battery Low %" from default (7%) to another (8%, 9%, 10% etc..), what is concern about?

    Best Regarads,
    Yaita

  • 0 in reply to K.Yaita
    TI__Guru* 76230 points
    Hi Yaita
    1. Yes
    2. There is no concern. 7% was just a arbitrary no, and customer can modify as needed.

    thanks
    Onyx
  • 0 in reply to Onyx Ahiakwo
    Guru 29720 points

    Hi Onyx-san,

    Thank you always for your support.

    My customer changed Battery Low% from 7%(default) to 80%, then he found RSOC doesn't decrease from 99% although battery is discharging.
    Do you know if it is expected behavior for BQ27320?

    The background of setting Battery Low% to 80% is he just wants to update FCC at battery voltage is around 3.55V.

    Best Regards,
    Yaita

  • 0 in reply to K.Yaita
    TI__Guru* 76230 points
    Hi Yaita,


    I am sorry i was mistaken. I thought this gauge was like our other IT gauges where battery low is just a point that is set where the gauge will just indicate that the battery is low. This is totally different in this gauge. I looked at the TRM and it is indeed used for FCC learning. Your customer definitely not set that value to 80%. Does 3.55V correspond to 80% SOC on your device?


    thanks
    Onyx
  • 0 in reply to Onyx Ahiakwo
    Guru 29720 points

    Hi Onyx-san,

    Thank you for your reply!

    >Does 3.55V correspond to 80% SOC on your device?
    I heard 3.55V is 74% (nearly 80%) , so my customer tested in Battery Low%=80% in this case.

    I understand my customer shouldn't change Battery Low% to 80%.
    Is there any criteria to change Battery Low% value? Is there recommended range?
    I also heard my customer changed Battery Low% to 10% then he confirmed the operation is expected (no ploblem).

    Best Regards,
    Yaita

  • 0 in reply to K.Yaita
    TI__Guru* 76230 points
    Hi Yaita
    So the idea for the gauge to learn FCC is that you need to be around the knee region of the OCV of the cell. Your battery low can't be higher than that.

    thanks
    Onyx
  • 0 in reply to Onyx Ahiakwo
    Guru 29720 points

    Hi Onyx-san,

    Thank you always for your support.

    >So the idea for the gauge to learn FCC is that you need to be around the knee region of the OCV of the cell.
    If my customer wants to set Battery Low % as high as possible, how should he consider?
    I would like to ask further about "around the knee region".



    Best Regards,
    Yaita

  • 0 in reply to K.Yaita
    TI__Guru* 76230 points
    I do not believe that is possibe with this gauge because as you have seen setting that higher caused you problems. You will want to consider our IT gauges.
    thanks
    Onyx