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BQ34Z100-G1: SOC jump to 100%

Stefan Mueller
Prodigy 20 points
Part Number: BQ34Z100-G1

Hi all,

We're using the BQ34100-G1 fuel gauge with battery based on Lithium Iron Phosphate technology (LiFePO4) in 4-S configuration.

Our Problem:
We start charging some seconds after discharge. At the begin of charging sometimes the SOC jumps to 100 %. Charger Termination setup is OK and cell voltage is far below taper voltage at that time, also FC bit is not set then.

During charging TrueRC then counts up far beyond TrueFCC. At least the counting is correct,  only the offset is wrong which results in a SOC of 100 % during the whole charging.
On charger termination RC is set to FCC (with FC bit) which results in a (true) SOC of 100 %. All is OK then until the next charge-after-discharge cycle starts.

My understanding is the gauge will run a IT simulation at begin of charging. Could this simulation fail in some circumstances?
What can go wrong at that time?
Is it possible to start a new simulation or DOD measurement manually?


Thanks,
Stefan

  • 0
    Prodigy 20 points

    Hi,

    it seems that we have fixed our issue. Obviously we had the wrong ChemID programmed, for some reason it was 423.

    After characterizing our battery pack (Gauging Parameter Calculator) we had a match for ChemID 404. Although the deviation is above recomended level (6 %) this setup works fine and such jumps (> 50 %) had not been observed afterwards.

    Smaller jumps of some percent at begin of charging after discharge with high load current are sometimes left, but we can live with that. We will go over that with smoothing.

    Best regards,

    Stefan