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  • TI Thinks Resolved

BQ34Z100-G1: SoC, SoH, control status, temperature, current and voltage jump while ambient temp is -35 degC

Intellectual 280 points

Replies: 6

Views: 114

Part Number: BQ34Z100-G1

I see abrupt changes in  SoC, SoH, temperature, current and voltage. Below is FuelGauge trace from my equipment

Qsns

1.  What could cause below abrupt changes in  SoC, SoH, temperature, current and voltage?

2.  We can reproduce this reliably in 4-12 hrs span. What other parameters from bq34z100-G1 do you want us to record that may help with investigation?

3.  I have two other devices on same I2C bus as bq34z100-G1 (total 3). Is this okay? 

4.  Can I issue reset 0x0041 command when I see SOH = 0 or cstatus=0? Is there a better indicator of FuelGauge fault that warrants a reset 0x0041 command?

"10/21/2019 6:58:01 PM",vbat = 12056, ibat = -131, temp = -33.15, soc = 26, soh = 100, rcap = 135, fcap = 528, avgcur = -116, cycles = 8, cstatus = 0005

"10/21/2019 6:58:02 PM",vbat = 12000, ibat = -131, temp = -33.15, soc = 26, soh = 100, rcap = 135, fcap = 528, avgcur = -117, cycles = 8, cstatus = 0005

"10/21/2019 6:58:03 PM",vbat = 11964, ibat = -121, temp = -33.15, soc = 26, soh = 100, rcap = 135, fcap = 528, avgcur = -118, cycles = 8, cstatus = 0005

"10/21/2019 6:58:05 PM",vbat = 14400, ibat = 0, temp = 19.85, soc = 0, soh = 0, rcap = 0, fcap = 4500, avgcur = 0, cycles = 8, cstatus = 0000

"10/21/2019 6:58:05 PM",vbat = 14400, ibat = 0, temp = 19.85, soc = 0, soh = 0, rcap = 0, fcap = 4500, avgcur = 0, cycles = 8, cstatus = 0000

"10/21/2019 6:58:06 PM",vbat = 12052, ibat = -112, temp = -33.15, soc = 0, soh = 0, rcap = 0, fcap = 375, avgcur = -7, cycles = 8, cstatus = 0005

  • HI Padam,

    Are you saying the values measured by the gauge  for voltage, current and temperature were inaccurate? What condition was the gauge operating in when this occurred? Was  this in a lab/controlled environment or was the chip susceptible to ESD/EMI? ESD/EMI are two factors that could cause wrong readings. 

    What does your schematic look like? Do you have any components inbetween the cell and the voltage measurement terminals of the chip. Can you reproduce this issue while logging with bqstudio so we could have proper log files of the events? Can you also share your schematics?

    thanks

    Onyx

  • In reply to Onyx Ahiakwo:

    Hi Onyx --

    I am the software engineer on this project for Padam, he is out of office this morning. I don't know the answers to all of your questions, but this is reproducible consistently by putting our board at -40 C, after about 3-4 hours we will see state of charge drop to 0 from ~90+ %. We have also seen other variables read out from the the gauge be incorrect at these times as well.

    Unfortunately I am not sure about the finer details of our board design, and am not sure how much from the schematic I am allowed to share, so will wait for Padam to return answer these questions.

    Thanks!

    JD

  • In reply to Onyx Ahiakwo:

    Hi Onyx

    With new debug traces I am seeing Battery Voltage at temperature -35 to -40 degC momentarily drops below 11V and bounces back to 11.5 or higher within 1 sec. My system's average current draw is 125mA and peak current is 2A for 300ms (once a minute). 

    My Current Cell Term V is set to 2750mV/cell. With 4s3p config it is set to 11V. 

    Is there a way to attach time interval to Cell Term V so that FuelGauge ignores momentary voltage drops below < 1 sec?    

    I am looking into NDA situation so that we can share files, schematic, layout etc. More on that later.  

    Padam 

  • In reply to Padam Swar:

    Hi Padam,

    Unfortunately not on this gauge.I would suggest you use the reserve capacity function so there gauge reports 0% SOC at a higher voltage.

    thanks

    Onyx

  • In reply to Onyx Ahiakwo:

    Hi Onyx

    Is there another model fuel gauge that supports terminate voltage threshold with time interval?

    Ideally that fuel gauge needs to support LiFePO4 and lead acid chemistry. At a minimum must support LiFePO4.

    Padam

  • In reply to Padam Swar:

    Hi Padam

    The bq40z50-R3 supports LFP

    thanks

    Onyx

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