NUMERICAL MODELING OF COUPLED ELECTROCHEMICAL AND TRANSPORT PROCESSESIN LEAD-ACID-BATTERIES

A numerical model is developed to predict transient behaviors of elect ric vehicle lead-acid batteries during discharge and charge processes. The model not only accounts for coupled processes of electrochemical kinetics and mass transport occurring in a battery cell, but also cons iders free convection resulting from density variations due to acid st ratification. A single set of conservation equations valid for both po rous electrodes and the free electrolyte region is derived and numeric ally solved using a computational fluid dynamics technique. This numer ical methodology is capable of simulating a two-dimensional cell with the fluid flow taken into consideration and requires only tens of minu tes of central processing unit time on engineering workstations. Four sample calculations are presented in this work to provide rigorous val idation of the developed simulator. The simulator is capable of predic ting the transient behavior of the acid concentration, the porosity of the electrodes, and the state of charge of the battery during dischar ge, rest, and charge cycles. The model can also be used to investigate the effects of various system parameters, such as electrode dimension s, separator design, temperature, and electrolyte composition on the b attery performance (voltage, power, cold cranking amperage, etc.).