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BQ27510-G2: How to configure the fuel gauge to report SOC=0% at lowest system voltage point, without a instantaneous jump of SOC?

Stefan Ohlson
Prodigy 40 points
Part Number: BQ27510-G2

Hi

Reading your SLUA903 "Achieving The Successful Learning Cycle".

In 2.6:

"2.6 Term Voltage
Also called Terminate Voltage, this is essentially the empty pack voltage where the gauge should ensure
0% state of charge is reported. For learning cycle purposes, this should be set to the minimum voltage of
the battery as specified in the manufacturer’s data sheet. After the learning cycle is completed, this value
can be adjusted upwards if there is a need for the gauge to report 0% at a higher voltage."

We have generated some Golden Images with different configurations. Always we have instantaneous jump of SOC% from 10-13% to 0%, at lowest system voltage, 3.25V, see pict. Desirable we want the SOC=0% to hit the lowest system voltage continuously ie. a straight SOC line to 0%.

How shall we configure the generation for a continuously SOC line?

Running bq Evaluation Software bqEasy 0.9.71 and bq27510-g2

SOC jump 10.docx

SOC jump 10% to 0% at correct lowest system voltage, 3.25V, but want a continues SOC line to 0%

Regards

/Stefan O

  • 0
    TI__Guru 51266 points

    This requires that the gauge is configured for the correct chemistry (see http://www.ti.com/tool/GAUGEPARCAL) followed by a (lab-controlled, not with the end user system) learning cycle.

    After the learning cycle was successful, you will have to make sure that the gauge is configured to be compatible with your actual system (not just the battery). The most important settings are charge termination, terminate voltage and load mode/select as well as current thresholds so that the gauge is tracking the state of the battery (charge/discharge/relax).

    charge termination will determine when the gauge reports 100% SOC.

    terminate voltage is the cut-off voltage when the gauge will set SOC to 0%.

    The gauge determines SOC through discharge simulations (these require the correct chemistry and a learning cycle). Discharge simulations  are predicting how much capacity is still available from the cell under various assumptions (this is where load mode/select play a major role) and conditions (like temperature).

    If you observe a huge jump in SOC, then the gauge overestimated capacity. There are many potential reasons for this and it's not possible to solve this with the information that you provided.

    The best way to fix this is to make sure that you went through the correct ChemID selection, a proper learning cycle and a careful configuration for your system.

  • 0 in reply to Dominik Hartl11
    Prodigy 40 points

    Hi Dominik

    Thank you for the answer. We will adjust our running and double check the configuration data.

    Regards

    /Stefan O