[bq34z100-g1] can't be calibrated to "zero current"

You should calibrate the Voltage before calibrating the current. Voltage calibration may not be required, if you have a 1S configuration. If you have a multicell configuration, then you will need to set the VOLTSEL bit, number of series cells and calibrate the voltage first.

thanks for you quickly reply.

i do the test as your suggestion, calibrate the voltage first and then calibrate the curren offset. but the same phenomenon occur, the curren is still NOT "0".

You should complete the calibration before sending the IT_ENABLE, because the gauge limits changes after IT is enabled. If you cannot calibrated out the error, then there must be something in the external components or layout that is introducing an offset that the gauge cannot compensate. Do you see this on all of your boards? I also see that the GNDSEL flag is set. It should be set, if your VSS connection is to the PACK- side of the sense resistor. It should be set to 0, if your VSS connection is on the BAT- side of the sense resistor. You can also try manually entering Board Offset values to see if you can force the current to zero. this may tell you whether gauge has enough range to calibrate the error.

thansk for you useful information.
some units can be "zero current" by modify the Board Offset value, and these unit is also can been calibrate to "zero current". The others, who can't be calibrated to "zero current", also can't be "zero current" by manually entering Board offset values.
for more, it look like that the CC offset can't be modified by manually entering a value, is there something wrong with my operation?
and no matter the "good unit" or "bad unit", after calibrating the curren offset, the value of their CC offset is about "-14xx".

You can use the CC OFFSET calibration Control Subcommand button to force the gauge to calibrate the CC OFFSET. Values in in the -1400 to -1500 are common.

well, after calibrated, the value of CC offset of all the unit are in the range of "-1400 to -1500". it looks normal. But as i remember, the datasheet (SLUBZ5-JANUARY 2015)says that the range of CC offset is -32768 to 32767.

The +/- 32767 is the full scale range that can be used, but we typically see the CC OFFSET in the -1400 to -1500 range.

as you said, it means that the calibrating ability of BQ34 is not great as the Spec says, right?
And could you tell me the limit of the tolerance(Eg, +/-20mA, 50mA or any other value) can't be calibrated to "zero current", thanks