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I performed three charge tests on a single cell 190mAh Li-Po battery with Keithley Battery Simulator instrument. Charging started at 3V and stopped at 4.20V in all tests.

After completing the three charge tests, I plotted the LiPo Voltage and ESR results and the ESR curves came out a little strange.

In the ESR graph (2nd graph), the blue ESR curve (first charge of LiPo) suddenly drops (SOC: 80%) and I cannot explain why this happened. The other two curves in the same graph have a smoother curve.

  1. I cannot explain this sudden change in ESR in the first charge test (blue curve at SOC:80%)
  2. I cannot explain the difference between the first and the two following ESR test curves, since all three tests have been performed on the same battery

I searched for articles regarding Lipo ESR curves during charging but I have not found something.

If any ideas, please let me know.

Thank you.

Li-po Battery charge tests Voltage and ESR curves

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  • \$\begingroup\$ What is the specified accuracy and repeatability of the device measuring ESR? \$\endgroup\$
    – Andy aka
    Jan 29, 2020 at 11:34
  • \$\begingroup\$ According to the instrument's datasheet, only the voltage and current accuracy is mentioned, that is (+/- 0.02% + 2mV) and resolution (0.1mV). For current, accuracy for 100mA is +/-0.04% +10μΑ \$\endgroup\$
    – Sparky
    Jan 29, 2020 at 13:47

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