Estimation of Coulombic Efficiency of Lead Acid Battery for range determination of Electric Vehicle Santanu Sharma PabanSarma sss@tezu.ernet.in pabans@iitk.ac.in Department of Electronics Department of Electrical and Communication Engineering Engineering IIT Kanpur, India Tezpur University, India Abstract-.The coulomb counting method gives vital information for determination of state-of-charge (SOC) of battery, which in turn is a useful method for range determination of an electric vehicle. By investigating the charging and discharging characteristics for a number of cycles of operation, coulombic efficiency of the battery is determined. The variation observed in coulombic efficiency with respect to the number of cycle was empirically modeled with the help of polynomial as well as exponential curve fitting method in Matlab. Models thus developed was again validated for the later cycles of operation. The empirical model derived with the polynomial curve fitting was found to be the best suited for the requirement of the range detection system of an electric vehicle. A hardware related to this work is also developed. Keywords—Lead Acid Battery, Coulombic Efficiency, Range Determination, Efficiency Profiling, Electric Vehicle (EV), Hybrid Electric Vehicle (HEV) I. INTRODUCTION The plug in electric vehicle and hybrid electric vehicle market is entirely dependent on the development of the advanced battery technology. The major challenges associated in battery research are boosting of their energy and power densities with significantly reducing production costs [1]. Battery range and cost are the two prominent factors that determine whether EV is affordable in the vehicle market. To attempt the range enhancement, the development of advanced batteries such as lithium ion, lead acid, nickel metal hydride, lithium polymers etc are in progress. Lead acid batteries were the common choice of energy source since 19 th century in vehicular applications. In terms of cost to energy ratio, lead acid technology is very useful in low priced electric cars [2].On the other hand these batteries shows relatively low cycle life compared to other secondary batteries. Therefore efficiency calculation and understanding the characteristic of charging and discharging cycles is very crucial in lead acid batteries. The most common features of a lead acid battery for electric vehicle are listed down in the table. [3]. SushantaBordoloi Pranjal Barman b.sushanta@iitg.ernet.in pra2014@tezu.ernet.in Department of Electronics Department of Electronics and Electrical Engineering and Communication IIT Guwahati, India Engineering Tezpur University, India TABLE I. CHARACTERISTICS OF LEAD ACID BATTERY Parameters Values (PbPbO 2 ) Working Temperature ( 0 C) -20 to 60 Specific Energy (Wh/Kg) 161 Energy Density (Wh/l) 60-80 Specific Power (W/Kg) 75-100 Cell Voltage (V) 2 Cycle Durability (Cycle) 500-800 Self Discharge 3%-4% The capacity of lead acid battery is well denoted by coulombic efficiency, which is a key factor that helps in range determination of an electric vehicle [4]. The coulombic efficiency of a battery is simply expressed as the ratio of number of electrons discharged to the electrons charged for a particular cycle of operation. The efficiency of a battery is also a function of the mode of operations. The lead acid battery involves formation of PbSO 4 in anode and cathode electrodes during discharge process by the following chemical equations [5]. Anode: Pb Pb 2+ + 2e Pb 2+ + SO 4 2 PbSO 4 Cathode: PbO 2 + 4H + + 2e Pb 2+ + 2H 2 O Pb 2+ + SO 4 2 PbSO 4 The charging process on the other hand is completely reverse to the discharging process which facilitate retrieve of Pb and PbO 2 at respective electrodes. However the efficiency at each cycle gradually decreases due to the presence of competing processes like gassing, grid corrosion, self discharge and recombination [6]. Aging type discharge is also a factor that degrades coulombic efficiency [7].As the battery grows older, poor efficiency is result of sulfation and charge deterioration [8][9]. The degradation of efficiency is a prime concern for all those electric vehicles that rely on battery for better range. ,&3'(1    ,(((