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I'm using this Battery Charger IC

I completely charge the battery to 4.17V and it is indicated by the STAT2 pin, turning ON of the GREEN LED.

After a couple of minutes, I unplug the USB cable and plug it back. The battery charger again starts charging for 80 seconds and then only the charge cycle gets completed which is indicated by the turn-on of the GREEN LED.

I wanted to understand why the charge cycle is starting again even though the charge was completed only a couple of minutes back.

At one point, when the battery voltage reaches 4.17V, the charging is complete. GREEN LED turns ON. After some time, despite having the same 4.17V, the battery charger shows the status as charging by turning ON the RED LED. This is Interesting.

Any idea why this is happening?

I was going through this site and saw this question

I had a query on the accepted answer of the above question. The accepted answer mentions that "The voltage where it switches from CC to CV charging is V_REG in the datasheet, which is factory fixed at one of 4.10/4.20/4.35/4.40V ± 0.5%"

Where in the datasheet does it mention like above?

So, my V_REG is 4.2V. So, can someone tell me when will it switch from CC to CV? Also, any idea whether the accepted answer above is related to the answer of my original question?

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Datasheet page 1 and 23: "... four available options: 4.10V, 4.20V, 4.35V or 4.40V ..."

The chip is switching at the end of the CV-mode after the current is under the "Charge Termination Set Point"-value to the green light, but this means that there could go some energy in the cell.

Sometimes the voltage in the LiIon-cell is falling a bit after the end of the loading process. It is possible too, that your cell is a bit damaged and have created a parallel resistor inside of the cell.

An other possibility is that the Vref on the chip is reduced because of the heat development during the loading. After the chip could cool down for 80 seconds Vref is now higher and this means the loading-voltage is higher.

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  • \$\begingroup\$ Thank you for your answer. I'm still not clear on when the charger switching from CC to CV and when from CV to charge completed state? Could you please clarify it in simpler terms? Does the CC to CV happen when the voltage is close to 4.2V? Or when does it happen? And when, at what voltage does the CV mode end? \$\endgroup\$
    – Freshman
    Mar 20, 2023 at 2:49
  • \$\begingroup\$ Also, what is the Vref value that you are referring to? \$\endgroup\$
    – Freshman
    Mar 20, 2023 at 2:50
  • \$\begingroup\$ @Freshman Vref = 1.21V, but there is no diagram with a voltage-temperature curve available in this data sheet. From experience I know that the temperature is changing the reference voltage. \$\endgroup\$
    – MikroPower
    Mar 20, 2023 at 14:51

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