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Bq34z100 Cell V at ChgTerm?

Ryan Brown2
Intellectual 795 points
Other Parts Discussed in Thread: BQ34Z100

I have a question about the Impedance Track learning Cycle on the Bq34z100. 

Ok I'm doing a IT learning cycle by entering 21 into the control box. 

I'm starting with a discharged battery that has sat until the voltage has settled. 

Now I charge the cell up to 3.6v DC . I have the Cell V at Chg Term set at 3.6v in the Gas Gauging section in the Data Flash in BQ gas gauge software. 

I'm charging the cell with a power supply set to 3.6v. 

I initially set the battery capacity to 10000 mah because its a 10Ah cell. 

When I charge the cell to full I end up with a cell capacity of 10400 mah which means the FC "Full Charge" flag is set as soon as the passed charge hits 10,000 mah which is kinda early. 

Then it takes  OVC reading while the cell is right at the 3.6v dc peak charge and then sets the new Qmax and Charge V at Chg Term to the voltage that it took right after the FC flag was set. 

So my question is: What should the Cell V at Chg Term be? The actual cell charge voltage during the charge cycle or should this be the cell voltage after it has been fully charged to 3.6v and then sat for a few hours? 

And the other question is about the cell State of Health reading. If I am using a LiFePo4 battery that has a rated cycle life of 1500-2000 cycles do I or can I adjust this in the chip so the State of Health reading is accurage 1000 cycles into the future? How is State of Health calculated?

  • 0
    TI__Guru 73830 points

    Cell V at Chg Term is not programmable parameter, but it is set by the gauge after charge termination. The parameters that you need to set are Taper Current and Cell Taper Voltage. These are discussed in the datasheet and there is a section on them in the Configuring the bq34100 Data Flash document. The Taper Current is the final threshold that usually triggers charge complete. You should set FC Set% to –1 to set the FC flag with the charge termination thresholds.