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# BQ40Z60: BQ40Z60

Part Number: BQ40Z60

Hi TI Team,

We are using BQ40Z60 and 2 cells of Panasonic NCR18650B battery in series.

• As specified in NCR18650B datasheet, the charging voltage should be 4.2+/-0.03V.
• The output ripple & noise of the charger is 240mV max. The measured ripple is +30mV to -50mV.

I have done some test. I set Charging Current to be 1625mA, Charging Voltage to be 4200mV, Charger Term Taper Current to be 65mA and keep Charge Term Voltage to be 75mV. I found the battery is charged by 1625mA until the cell voltage reach 4275mV. Once the cell voltage reaches 4275mV, the current starts to taper. The charger terminate once the measured current is below 65mA.

As described in SLUUA04D, I through the charging current should start to taper once max cell voltage reaches 4125mV.

Per battery datasheet, the battery should be charged with constant current until the voltage reaches 4.20V. The charging voltage is required to be set to less than 4.23V/cell with considering the
accuracy of charger.

I have some questions about "Charge Term Voltage" in Termination Config:

• Is it correct to set the Charging Voltage to be 4200mV in "Advanced Charge Algorithm" section? Should I set the Charging Voltage to be 4.2V-Charge Term Voltage?
• The default value for "Charge Term Voltage" is 75mV. What would be a better value for NCR18650B and our charger?

Thank you very much.

Regards,

YB

• YB,

1) A Charge term Voltage value of 75mV means the gauge will start to look for Current < taper current. The current will start to taper when the battery voltage reaches the voltage the charger is trying to charge to. This is a physical property and has nothing to do with the gauge.

2) 75mV is normally good. I would lower the charging request so you are not violating the abs max of the battery cell.

thanks,
Eric Vos