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BQ34Z100-G1: Large swings in full charge capacity after charging

richard mcdougall
Prodigy 185 points
Part Number: BQ34Z100-G1
Other Parts Discussed in Thread: BQSTUDIO

Hi,

 I have several systems having the same issue of large swings of FCC after charge completion -- swinging back and forth by as much as 80%.

These are 38AH packs, so the FCC starts and ends correct, but for some time during relaxation the FCC seems to jump around.

(full capacity = reading 0x06, 0x07)'

Everything else seems to work accurately and as expected.

I have another board which swings more -- from 38AH down to 10 and back again.

What could explain these large swings?

Thanks,

Richard

PS. I'm sorry I don't have the BQ log, because these systems are remote -- but I do have a log of the flags/registers -- see csv below:

fcc_swings.csv.txt

  • 0
    Prodigy 185 points
    Note: I see the last increase bump from 32 to 36 occurs when OCV_TAKEN occurs.
  • 0 in reply to richard mcdougall
    TI__Guru* 76230 points
    Hi Richard,
    Do you have the smoothen flag set? If smoothening is enabled then the value that the gauge will be reporting for FCC will be the filtered values which does not have meaning but is just a mathematical manipulation of the true FCC to prevent SOC jumps. What you should be checking is true FCC. If true FCC is changing to extreme values, then you need to check your system to see if temperature is varying significantly.

    You will need to try to get one of your boards and connect to bqstudio and run evaluation tests while logging so we can see exactly what is going on.

    thanks
    Onyx