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BQ34Z100-G1: How does Learning Cycle continue after depleting battery?

Jacob Lewis
Intellectual 280 points
Part Number: BQ34Z100-G1
Other Parts Discussed in Thread: BQSTUDIO, BQ34Z100

In the learning cycle you discharge the battery to empty and then let it sit for at least 5 hours which usually turns into 14+ hours over night.  During those 5-14 hours you're constantly querying data with bqStudio for the logs so the device doesn't get into SLEEP much if at all.  Because of the device's constant drain on the remaining battery in this state I end up with Li Ion batteries draining to under 2V.

It's bad for the batteries.  Is it bad for the learning cycle?  Is there a way around this problem?  What are others doing?  Do you power the BQ device externally for this test?

  • 0
    TI__Guru* 76230 points

    hi  Jacob 

     Is your battery so small such that it is drained by the gauge negligible current in under 14 hours. That seems not practical. Your cells should not discharge below 2V. Are you using 1s configuration?

    thanks

    Onyx

  • 0 in reply to Onyx Ahiakwo
    Intellectual 280 points

    Thanks for the response.

    It is probably something to do with my board pulling more than it should while "powered off".  It is a 1p12s stack.

    So is the general idea that even though we've discharged the cells down to 2.5V, the gauge should have enough energy to continue running and draws so little current (145uA or 84uA in SLEEP mode) that it can run for a day or more still logging data and not make a significant hit on the battery?

  • 0 in reply to Jacob Lewis
    TI__Genius 12215 points

    Jacob

       Please check how much current draws when the VEN pin turns high for measuring cell stack voltage, the cell stack is typically measured with a resistor string, this could generate additional current if the resistor is not high enough

       You also need to make sure the LDO circuit consumes as littler current as possible.

       Above are 2 major possible current consumption reasons caused by bq34z100, had better to be minimized