I have a 65 mAh thin Li-Po pouch cell. I tried measuring the internal resistance of the same using the foll. steps: (The battery was fully charged before this process)
- Battery open circuit voltage measurement: 4.0662 V
- Connect a 560 ohm resistor across the battery
- Voltage measured across the resistor: 4.0562 ohm
- Current through the circuit: 4.0562/560 = 0.00724 A
- Voltage drop across battery's internal resistor: 0.01 V
- Battery Internal Resistance: 0.01/0.00724 = 1.38 ohm
I repeated this process with 150 ohm and 47 ohm resistors and got the internal resistance to be 1.55 ohm and 2 ohm respectively.
From what I have read in the literature, battery internal resistance is generally in double-digit milliohms whereas the resistance of my battery is 2000 milliohms.
- Is such high resistance possible?
- Is this because I'm measuring the resistance at a fully charged state?
- I know the SoC affects the battery resistance, but would it make the resistance so large?
- If not what is the mistake I'm making in the resistance measurement process?