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BQ34Z100 Battery Replacement

Other Parts Discussed in Thread: BQ34Z100

Hi All,

I've recently been evaluating the BQ34Z100 for use in a new product. It has been working well so far and performs Qmax and Resistance table updates correctly.

The fuel gauge is located system side.

However If I remove the battery pack and insert another battery pack from the same batch (should have similar Qmax and Rtables) the gauge does not correctly estimate the capacity based on an open circuit voltage measurement. 

Actual battery capacity is roughly 35% gauge shows 3%

The OCVTAKEN flag has been set and the pack voltage is 7228 mV (2S pack)

Is there something I need to do to tell the gauge that the pack has changed? I would rather not do a full charge/discharge cycle if I can help it.

  • Sam

    The gauge should show an accurate SOC if the Ra table and Qmax are truly the same. One thing that can affect the accuracy is the flatness of the OCV table. If the table is really flat, then even small differences in QMax and Ra table can affect how well the gauge can resolve the location on the table. It usually take one or two cycles for the gauge to tune itself to the new battery. You could try resetting the device to force an FCC simulation. It may improve the accuracy after the gauge has fully initialized.

    Tom

  • Thanks Tom,

    I was looking at the RESET command, but this can only be done on an UNSEALED gauge. (Made little difference regardless)

    What I have since found is changing the chemistry to more closely match the cells we are using has made the first OCV measurement far more accurate on a pack change.

    Thanks for your help.
    Sam