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Original question:

BQ27Z561-R1: Checksum Valid

BQ27Z561-R1: AMB_PRED

Ryan Wang
Expert 5470 points
Part Number: BQ27Z561-R1

Dear expert,

"This can be useful in system applications that experience large increases in ambient temperature during discharges and/or charges without entry to RELAX mode."

So for this situation, I should enable AMB_PRED and TAMB_SYNC_SIM. And let host manually launch TambientSync() during temperature change?

Can T_ambient be gotten automatically without host involve?

What's relationship between AMB_PRED and TAMB_SYNC_SIM? What if I only enable one of them?

T_ambient is useless if either AMB_PRED and TAMB_SYNC_SIM is disabled?

T_ambient = cell temperature during TambientSync()? So why NOT just use cell temperature directly?

Thanks

  • 0
    TI__Guru 51346 points

    The gauge needs to know the ambient temperature so that it can predict how cell temperature behaves during a discharge simulation (capacity prediction). By default (if AMB_PRED is off), the gauge will assume that the ambient temperature equals the temperature in relax before charge or discharge. If AMB_PRED is on, the gauge will, after some time, even if it's not in relax, attempt to update ambient temperature by adjusting measured temperature with estimated temperature due to energy dissipated in the cell.

    TAMB_SYNC_SIM just controls, if the gauge will run a discharge capacity simulation, if the host forces a ambient temperature update (with the TAMBIENT SYNC command).

  • 0 in reply to Dominik Hartl11
    TI__Expert 5470 points

    Dominik,

    Battery always head itself and ambient temperature during discharge/charge, so AMB_PRED should better be always ON, right? But why we turn AMB_PRED off by default? Is there any risk for it ON?

    And we have Tk, Ta to simulate battery self heat, why do we still need AMB_PRED ?

    And AMB_PRED take care of temperature raised by cell discharge/charge. This has nothing to do with whether customer do temperature ramp test or not, right?

    If AMB_PRED is on, how long it will ambient temperature ?

    Thanks

  • 0 in reply to Ryan Wang
    TI__Expert 5470 points

    Dominik,

    "If AMB_PRED is on, how long it will ambient temperature ?" Is it ""Predict Ambient Time""?

  • 0 in reply to Ryan Wang
    TI__Guru 51346 points

    The gauge will wait for Predict Ambient Time when not in relax before it starts to calculate an update (prediction) to Ambient Time.

  • 0 in reply to Dominik Hartl11
    TI__Expert 5470 points

    Dominik,

    It seems AMB_PRED is a good feature, why we turn it off by default?

    And even when it is ON, Predict Ambient Time = 2000s by default which is very long. Is there any risk to turn it ON?

  • +1 in reply to Ryan Wang
    TI__Guru 51346 points

    This feature relies on a high quality estimate of heat generated over the internal cell resistance. That's why it has to be out of relax for a certain time.

    Also, if there's any inaccuracy in the cell model, the error can be unacceptable, hence it's an option that is supposed to be enabled only if one is sure that everything else is configured accurately.