I tested the internal resistance of a 18650 sanyo cell using the following method
No load test = 4.01 V
2 ohm 5 watt resistor load test = 3.80 V
ohms law 3.80 V / 2 ohm = 1.9 Amps
Kirchhoff voltage law (sum all algebraic values of V drops = 0)
4.01 - 3.80 = .21 V (4.01 - 3.80 - .21 = 0)
.21 V / 1.9Amps = .110 ohm (internal resistance of cell)
Does this value (.110 ohms) indicate that this cell has been over cycled/ charged? The internal resistance from the spec sheet indicates less than 100 milli ohms is normal
I tested another cell from the same pack, same voltage drop (3.80) was measured
Tested another cell from another set, charged at 4.10 no load 4.03 2 ohm resistor load, came up with .065 milli ohm
No load test = 4.01 V
2 ohm 5 watt resistor load test = 3.80 V
ohms law 3.80 V / 2 ohm = 1.9 Amps
Kirchhoff voltage law (sum all algebraic values of V drops = 0)
4.01 - 3.80 = .21 V (4.01 - 3.80 - .21 = 0)
.21 V / 1.9Amps = .110 ohm (internal resistance of cell)
Does this value (.110 ohms) indicate that this cell has been over cycled/ charged? The internal resistance from the spec sheet indicates less than 100 milli ohms is normal
I tested another cell from the same pack, same voltage drop (3.80) was measured
Tested another cell from another set, charged at 4.10 no load 4.03 2 ohm resistor load, came up with .065 milli ohm