Degradation in nickel-cadmium cells studied by impedance measurements

✍ Scribed by Ron Haak; Cameron Ogden; Dennis Tench; Sal Di Stefano

• Book ID: 103897966
• Publisher: Elsevier Science
• Year: 1984
• Tongue: English
• Weight: 762 KB
• Volume: 12
• Category: Article
• ISSN: 0378-7753
• DOI: 10.1016/0378-7753(84)80026-9

✦ Synopsis

The impedance of 12 A h Ni-Cd sealed cells was evaluated as a nondestructive, m sdu means of determmmg cell hfetime, particularly with respect to the probabihty of premature failure The Nr-Cd cell impedance was measured (10000 to 0.0004 Hz) as cells were subjected to charge/ discharge cycle testmg under a variety of temperature and depth-of-discharge conditions

The results mdicate that cell degradation is reflected m the low frequency impedance characteristics associated with diffusional processes. The slope (W) of the low frequency portion of complex plane impedance plots obtained from totally discharged Ni-Cd cells was found to increase with charge/discharge cycling In addition, based on data for two cells, a high or rapidly Increasing W value signals unmment cell failure by one mechanism.

Degradation by another mechanism is apparently reflected m a fall-off of the lmagmary impedance component at low frequencies.

The frequency dependence of the absolute cell impedance at low frequencies (0.5 -0.005 Hz) was found to vary monotomcally with cell state-of-charge.