Abstract
This paper proposes a new testing method for detecting a local short circuit cell which causes unusual high temperature rise and unusual cell voltage rise of the adjoing cell at the operating stack.
The method utilizes lower cell voltage of the local short circuit cell than that of normal cells when small constant DC current is supplied for some time.
As low cell voltage of the short circuit portion spread all over the cell, the test after stacking can be carried out by measuring cell voltages of exposed edge part of each cell at the stack side.
In order to increase detecting sensitivity, low testing temperature is recomended.
At the test in air, current density and the duration of current flow must be strictly limited within the level which the cell voltage does not saturate or carbon dioxide will generate from the electrode due to oxidation of carbon.
At the test in nitrogen, detecting sensitivity can increase by using higher current density and longer duration of current flow than that at the test in air without any oxidation of the electrode.
This method is shown to have enough sensitity to detect harmful level of local short circuit resistance.
