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bq34z100g1 behavior

Ben Duvenage22
Expert 1250 points

Hi All

I'm seeing funny things in the field and trying to understand what is going on.

1) I have a 2 cell in series battery LiOn when I charge the battery to 95% stop and wait then after a while when I cycle the power on the battery and then the gauge indicate 83 % it then stays there for about 4 days before it drops to 82.

2) I charge a 14.8 Volt 4.3Ah LiOn to 100% then leave for a while when I cycle the power on the bettery it drops to 92 % and stay there.

3) 80%of the battery packs does not do this,  just here and there I have this issue.

I have a protection board on the battery and a NTC.

Inputs please?

Kind regards

Ben

  • 0
    TI__Guru 73830 points

    The issue resolves around the OCV table and charging. The gauge will run an FCC simulation after it has been reset and the new SOC will be based on how the cell voltages compare to the OCV table. The gauge uses coulomb counting to update the capacities during charging, so there can be some error between the SOC and actual capacity of the pack. This could be due to being over discharged, a poor ChemID match, poor learning, etc. The error should be reduced, if the pack is charged to charge termination. That could also be the case with the second issue. Maybe the pack is not fully charged to charge termination. The gauge will also run an FCC simulation every 5 hours during rest and update the capacities based on the OCV. The 92% must reflect the true state of the cells as compared to the OCV table. The fact that most packs do not exhibit this performance indicates that there may be some imbalance between cells causing one of the cells to not get full charged and then the voltage drops during rest.

  • 0 in reply to ThomasCosby
    Expert 1250 points
    Thank you Thomas
    Kind regards
    Ben