Use of auxiliary channels for impedance analysis:
Detecting failure mechanisms within a fuel cell/battery stack
By John Harper and Brian Sayers
Keywords:
Electrochemical Impedance Spectroscopy (EIS), CellTest System,
impedance testing, multi-channel test stations, energy storage device
analysis, battery testing, fuel cells, supercapacitors
The introduction of the Solartron CellTest® System heralds a new era in
high performance DC and impedance testing for energy storage devices such as
batteries, fuel cells and supercapacitors. Its innovative design provides
measurements that are beyond the capabilities of other multi-channel test
stations. In this application note, we describe one such feature that allows
the COMPLETE characterization of a multi-cell battery. These techniques can
be applied to the investigation of any multi-cell energy storage device.
A fuel cell stack or multi-cell battery is a complicated system and it is
possible that failures can occur on any of the individual cells within the
system. Single channel impedance analyzers typically connect across the end
terminals of the entire stack and therefore measure the total impedance of
the stack. Whilst this is useful for assessing the overall performance of
the complete stack, it cannot provide information regarding the location and
cause of faults in individual cells. The Solartron CellTest System with the
14702 auxiliary voltage measurement option fitted, has been specifically
designed to provide impedance measurements from individual cells within the
stack, allowing rapid assessment of the behaviour of each cell.