Hi,
I am going to show a few quick measurements that I made on a Li-ion cell. This is the cell that I tested:
This a PKCELL 2200mAh ICR18650 cell. It is a few years old. I gave it a quick charge at 4.2V before I did the testing. The battery was probably around 20% depth of discharge (80% full).
HP4328A MilliohmmeterThis an old school meter that use 1kHz sinewave excitation. The meter was set on the 100m
scale. This conforms to the 1kHz test method described in the Battery University webpage.
The measured ESR was
79m Corrected, see messages below, 69m .
Electronic load and oscilloscopeThe battery was connected to an electronic load. A Tektronix current probe was used to monitor the current. This is the green trace.
The battery terminal voltage was measured, ac coupled, cyan trace.
The load was set to go between 0.25A and 1.25A, 1A pk-pk.
1 kHzThe peak to peak voltage is 76mV. A resistance of about 75m
10 Hz
The peak to amplitude increased to 98mV. The indicated ESR = 98m
LTspice ModelA quick LTspice model with similar behavior:
And the modeling results:
This set of test shows that measuring battery ESR different ways, you get different answers.
Regards,
Jay_Diddy_B