Gandhi, K.S. and Shukla, A.K. and Maqrtha, S.K. and Gafoor, S.A.
(2009)
Simplified Mathematical Model for Effects of Freezing
on the Low-Temperature Performance of the Lead-Acid Battery.
Journal of the Electrochemical Society, 156 (3).
pp. 238-245.
ISSN 0013-4651
Abstract
Discharge periods of lead-acid batteries are significantly reduced at subzero centigrade temperatures. The reduction is more than
what can be expected due to decreased rates of various processes caused by a lowering of temperature and occurs despite the fact
that active materials are available for discharge. It is proposed that the major cause for this is the freezing of the electrolyte. The
concentration of acid decreases during battery discharge with a consequent increase in the freezing temperature. A battery freezes
when the discharge temperature falls below the freezing temperature. A mathematical model is developed for conditions where
charge-transfer reaction is the rate-limiting step, and Tafel kinetics are applicable. It is argued that freezing begins from the
midplanes of electrodes and proceeds toward the reservoir in-between. Ionic conduction stops when one of the electrodes freezes
fully and the time taken to reach that point, namely the discharge period, is calculated. The predictions of the model compare well
to observations made at low current density C/5 and at −20 and −40°C. At higher current densities, however, diffusional
resistances become important and a more complicated moving boundary problem needs to be solved to predict the discharge
periods.
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