Battery Cell Impedance Measurement

This is a python script for interfacing with several pieces of bench equipment in order to make AC impedance measurements of battery cells.

Equipment and Setup

• 2x Keithley 2110 Bench Multimeter
• 1x Tektronix AFG1022 Arbitrary Function Generator

Dependencies

• A VISA implementation on the host computer. NI-VISA is a popular one. Download it from https://www.ni.com/support/downloads/drivers/download.ni-visa.html#442805.
  • For Linux/Mac: note that only the runtime is strictly required for this program, but you can install the full suite if you wish
• PyVISA library, for interfacing with VISA-enabled instruments from Python

Program Setup

First time setup to run the program is as follows:

1. Install a VISA Implementation such as NI-VISA
2. Create a python virtual environment

python -m venv venv

3. Install python dependencies

python -m pip install --upgrade pip
python -m pip install -r requirements.txt

Program Use

1. Activate virtual environment

. venv/bin/activate # Linux / Mac
venv/Scripts/activate # Windows

2. Make sure instruments are connected
3. Run the script

python main.py

4. Follow the instructions given by the program to identify the instruments, confirm the instrument identification and run the test.

The script will save all of the measurements to a new file in the data folder called impedances <timestamp>.csv.

Any time the program prints an ERROR during the measurement routine, it will not save the measurement. If this occurs, make sure the problem is corrected and re-run the test on the battery cell. If a WARNING is printed, it will still save a measurement.

Don't worry about measuring the same cell twice. The program will never overwrite existing data, and a timestamp is saved with each entry of data from a run of the test.