Configuring the Frequency Sweep Characteristics for EIS Measurements

For electrochemical impedance spectroscopy (EIS) measurements, configure frequency sweep characteristics.

Configuring Frequency Sweep Characteristics for EIS Measurements

For EIS measurements, the Battery Cell Quality Toolkit directs the SMU to move through a set of frequencies at a rate that you specify. The software stores the test parameters in an array. For each frequency value in the array, the SMU sends one sine wave to excite the battery cell and measure its impedance.

Configuration Guidelines for a Frequency Signal Current Amplitude

  • Abide by the maximum current allowed depending on the cell voltage. Refer to Configuring the SMU for EIS Measurements through Test Parameters for information about the maximum current allowed.
  • Select current based upon the charge rate of the battery. NI recommends starting at one-tenth of the charge rate of the battery. Then, increase or decrease the current based on the measurement repeatability.
  • The ideal test current depends on the cabling, fixture, and DUT.
  • If you are using the PXIe-2525, the maximum current amplitude with multiplexing is 2 A.
  • Source as little current as possible to avoid disturbing the DUT.
  • If the current is too low, the resulting potential changes (voltage responses) might not accurately reflect the behavior of the battery at high frequencies.

Configuration Guidelines for the Number of Periods

  • As the number of periods increases, the accuracy and the test time increase.
  • Empirically determine the number of periods at which the measurement repeatability does not improve.

Configuration Guidelines for Specifying the Power Line Frequency

  • In the United States, the power line frequency is 60 Hz.
  • In Europe, China, and parts of Japan, the power line frequency is 50 Hz.

Example Configuration of Frequency Sweep Characteristics for EIS Measurements

The following table is an example configuration of frequency sweep characteristics. The example shows a configuration to evaluate low, mid, and high frequency behaviors of an 18650 cell with the following specifications:

  • 0.5 A charging rate
  • 2500 mAh capacity

The total test time of the example is approximately 248 seconds.

Table 6. Example Sweep Configuration
Frequency (Hz) Periods Current (A) Test time in seconds for context
0.01 2 0.25 200
0.1 4 0.25 40
1 4 0.25 4
4 4 0.25 1
10 4 0.25 0.4
20 4 0.25 0.2
30 4 0.25 0.13333333
40 4 0.25 0.1
50 5 0.25 0.1
60 6 0.25 0.1
80 8 0.25 0.1
100 10 0.25 0.1
120 12 0.25 0.1
140 14 0.25 0.1
200 20 0.25 0.1
300 30 0.25 0.1
400 40 0.25 0.1
500 50 0.25 0.1
600 60 0.25 0.1
800 80 0.25 0.1
1000 100 0.25 0.1
1200 120 0.25 0.1
1400 140 0.25 0.1
1800 180 0.25 0.1
2000 200 0.25 0.1