Three sizes of small valve regulated (VRLA) commercially available lead-aci
d cells were investigated and characterized for their dynamic properties by
ac impedance spectroscopy and other electrochemical techniques. All cells
were of the limited electrolyte type and no additional electrolyte was intr
oduced during the studies.
The data indicates a very significant increase in cell impedance at lower s
tates of charge, as expected. In charging studies close to the fully charge
d state, some unexpected impedance data were observed.
Complex impedance plots indicate a passive film formation, probably associa
ted with the recombination surface film. The investigations included cells
in various states of charge as well as cycling history including positional
orientation studies. Equivalent circuits were derived from ac impedance sp
ectroscopy and the parameters studied as a function of the cell's state-of-
charge. Furthermore, the voltage response of the cells was theoretically ge
nerated from the ac impedance spectroscopy using Fourier transform analysis
and found to be similar to the measured cell responses. (C) 2001 Published
by Elsevier Science B.V.