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BQ35100: Is there possibility the battery voltage goes less than minimum system voltage before reaching EOS condition?

Guru 29280 points
Part Number: BQ35100

Hi Team,

My customer considers using BQ35100 for SAFT LSH20 (Li-SOCl2) with EOS mode.
We already got chemID for LSH20 that TI has prepared.

He concerns if there is possibility the battery voltage goes less than minimum system voltage (=3.0V) before reaching EOS condition.
Is it possible case?
If the answer is yes, I would like to know how to set parameters (EOS Trent Detection, etc.) to prevent it.

Best Regards,
Yaita

  • Hello Yaita,

    I would need to know more information on the system to help further.

    If the gauge is being woken up often and there is not a large load on the battery, I think it would be possible to get an EOS alert before the battery drops below 3V (from review the datasheet)

    If they are doing pulsed high current loads and not sampling often, then it is possible the battery would drop below 3V before the EOS alert is triggered, since we base this trigger off of a moving average comparison.

    file:///C:/Users/a0485467/Downloads/LSH20_1006.4b1c2431-3028-48be-b4f2-a0b19f4a6e1e.pdf

    Sincerely,

    Wyatt Keller

  • Hi Wyatt-san,

    Thank you for your support.
    I want to clarify "pulsed high current loads" that you referred.

    Regarding the following thread, the high load pulse is required to measure impedance when EOS mode.
    Is it correct?
    -----------------------------------------
    The bq35100 is designed to gauge pulse with an amplitude of tens of mA (~50mA+) that last for tens of mSec (~100mS+).
    https://e2e.ti.com/support/power-management-group/power-management/f/power-management-forum/1025312/bq35100-what-does-the-high-load-pulse-indicate
    -----------------------------------------
    If the answer is yes, I would also like to know if ~200mA is applicable for the high load pulse.
    My customer estimated ~200mA for the high load pulse in his application.

    Best Regards,
    Yaita

  • Hello Yaita,

    Yes the post has a lot of valid information in it. The load must be large enough to cause at least a 100mV drop in voltage. This will allow us to get valid impedance measurements of the battery. If you are concerned about hitting the terminate voltage early (the minimum voltage for the system at 3V) I would recommend sampling as frequently as possible, so the moving averages have time to diverge before the voltage is too low for the system.

    Sincerely,

    Wyatt Keller