Introduction
For those interested in determining the characteristics of batteries, especially by discharging them to see their changes in impedance, Gamry Instruments offers the Reference™ 3000 potentiostat plus our 30k Booster. This combination of instruments is useful for running stress tests on batteries, by applying rapid, high-current pulses singly or repeatedly.
As a cell, we used our 30k Test and Cal cell. The 30k Test and Cal cell printed circuit board was carefully designed for:
- True four-terminal sensing on both the Test and Calibration sides of the Cell
- Minimal inductance in the current-carrying connections
- Minimal mutual inductance between the current-carrying and sensing circuits.
Gamry Instruments uses the Calibration side of the cell to galvanostatically measure impedance spectra
at frequencies up to 300 kHz with less than 2° of phase error.
This Application Note shows results of our own research into the characteristics of our equipment.
Experimental
The tests were run on a Reference 3000 and Reference 30k Booster. A Gamry Reference 30k Test and Cal cell was connected to the booster in all tests. The cell connections used the standard cables supplied with the system: a 1 m current-carrying cable and a 1.5 m sense cable.
Most of the testing was done on the Calibration side of the Test and Cal cell. This side is a 200 mΩ resistor with a 2.5 A fast-blow fuse in the counter electrode lead. The fuse protects the 1 W resistor from damage caused by excessive current flow. The resistance of a sample fuse was measured to be 34 mΩ. Fast current pulses larger than the 2.5 A fuse rating will not blow the fuse if the pulses are short enough.
The Test side of the Test and Cal Cell is a 3 mΩ four-terminal resistor. It does not require a fuse because it can safely pass 30 A currents.
Many tests were performed at different CA (control amplifier) Speed settings. The faster the CA Speed is, the better time-resolution is achieved, but at the cost of stability in the amplifier.
Most data were recorded using our signature Framework™ software. Some of the tests required use of a Tektronix 2024C digital oscilloscope instead.
Results
Please visit Gamry.com’s application note for the ‘results’ and to download a PDF version of the complete application note,