ABSTRACT

Batteries store electrical energy in the form of chemical energy. Rechargeable batteries supply electrical energy at the expense of chemical energy through direct conversion, and they can be reverted nearly to their original state by charging them with electrical energy. My talk will cover functioning of some of the important batteries, and characteristics of their performance. There are three general features common to all: (i) the battery voltage drops with time when a battery is discharged at constant current, and precipitously so towards the end of discharge, (ii) though energy stored in a battery is constant, increasingly smaller fractions can be recovered with increasing discharge current, (iii) a battery cannot be recharged fully, even at the expense of energy excess of that withdrawn, beyond a finite number of cycles of discharge and charging, i.e., it has a finite life. My work uses mathematical modeling for describing some of these features, but is specialized to lead-acid battery. Models are very classical and easily accessible to one and all. Battery reactions produce electrical energy by conversion of neutral species into ionic species and vice versa. Models consist of classical diffusion-chemical reaction equations, and as ionic species are present, diffusion will be governed, in addition to the usual concentration gradients, by electrical fields. For the same reason, chemical reactions will also be influenced by electrical potential. It is known that, with repeated cycles of charge and discharge, the electronic resistance of a lead-acid battery increases and that lead sulfate, a product of the discharge reaction, accumulates. Existing models of lead-acid batteries do not contain elements that, at least potentially, can quantitatively describe these features. I will discuss my efforts to introduce these features. Though I have not solved the problem of prediction of the life of a lead-acid battery, I will present some results report the progress I made.

ABOUT THE SPEAKER

Professor K. S. Gandhi studied Chemical Engineering and obtained his Bachelor’s degree with honours from Andhra University, his Master’s degree from Ohio State University (USA), and his Ph. D. from the University of California, Berkeley. Gandhi taught at IIT Kanpur till 1984, and then moved to the Indian Institute of Science, Bangalore. He worked for two years in the R&D Centre of Pilkington Brothers, UK, on the fluid mechanics of glass- fiber filled molding compounds. His research interests are in the analysis of transport processes in polymer processing and reactors, liquid-liquid systems, gas-liquid systems, sono-chemical reactors, and electrochemical power sources. He is a Fellow of the Indian Academy of Sciences, Bangalore (IASc) and of the Indian National Academy of Engineering (INAE). He has also been honoured with the “Dr. B. P. Godrej Life Time Achievement Award” of the Indian Institute of Chemical Engineers (IIChE) in 2012. He has written the popular textbook: K. S. Gandhi, Heat and Mass Transfer, a Transport Phenomena Approach, New Age Intl., New Delhi, 2011.