The independent sizing of the redox system's power and storage capacity makes it particularly attractive for long term electricity storage in remote areas where solar arrays or wind generators have been installed. An attractive feature of the vanadium redox battery is that since there is no solution contamination due to crossmixing, after the original capital investment, there would be negligible running and maintenance costs. Since the cell can be completely discharged without any deterioration in performance, it would be ideally suited for large scale energy storage in load leveling applications. A larger scale five-cell battery unit is currently under construction so that the system performance can be further tested before scaling up to a 1 kW unit.

A mathematical model has been developed to predict the time dependent behavior of a normalZn/normalNiOOH cell. The model uses experimentally determined polarization expressions to describe the losses between the positive and the negative electrodes. The electronic losses in the plane of the electrode are simulated by a network of resistors. The potential distribution, the current distribution, the cell voltage, the power capability, and the energy of a cell can be predicted. The mathematical model provides an analytical tool to evaluate, for example, the trade‐offs between power capability and current collector mass, needed to design an electric vehicle battery.

A mathematical model of a starved lead-acid cell has been developed to study the dynamic behavior of the cell during discharge. Concentrated binary electrolyte theory and a volume-averaging technique were used to model the transport of electrolyte. The model can be used to predict cell voltage and profile of: acid concentration, overpotential, porosity, reaction rate, and electrode capacity, as functions of time. The effects of separator thickness and its porosity were examined with respect to cold-cranking amperage and reserve capacity of the battery. The separator was found to be a significant factor governing performance.Starved lead-acid batteries are becoming increasingly popular in the secondary battery market due to many of their potential advantages: zero maintenance, operation in any position, internal gas pressure potentially usable as a built-in charge indicator, and low battery profile and weight, which is especially attractive in automotive SLI (starting-lighting-ignition) applications. A traditional flooded-type lead-acid battery contains excess acid to compensate for the water loss due to oxygen evolution on overcharge. A unit ceil of the battery is composed of a positive electrode, an acid reservoir, a separator, and a negative electrode. A starved lead-acid cell does not have an acid reservoir. Instead, a thicker and more porous separator is used to prevent physical contact of the positive and negative electrodes, serve as an electrolyte reservoir (this gives rise to the concept of an immobilized electrolyte), and promote oxygen gas transport from the positive electrode to the negative electrode for recombination on charging.The separator has always been thought to play a critical role in the operation of a starved lead-acid battery. Atlung and Fastrup (1), extending the work of Turner and Moseley (2), developed a mathematical model to study the effects of separator design on discharge rate and cell capacity. Their model, however, is of the separator alone, with constant reaction fluxes used as boundary conditions. We present here a detailed mathematical model of the whole starved lead-acid cell for discharge, which will allow the analysis of the total system and interactions between the components-positive electrode, separator, and negative electrode. This model is a modification of an earlier model by Gu et al. (3) for the flooded-type cell. With this model, the effects of porosity, tortuosity, thickness, and the level of electrolyte saturation of the separator, on the discharge performance of a starved lead-acid cell, can be studied, including any interactions between the separator and the electrodes.This paper is organized in the following manner. In the "Model Description" section, detailed formulation of the model is given. In the "Model Output" section, the model results are illustrated graphically using an example of a CCA calculation. Each plot is briefly discussed regarding its significance. In the latter section, the effects due to the separator on cold-cranking amperage (CCA) and res...