Evolution of a voltage-time model of thermal batteries

A temperature time model of thermal batteries has almost been completed and validated against experimental data. Early attempts to integrate a voltage time model into this, taking advantage of the instantaneous predictions of temperature, thermodynamic potentials, and internal resistance which the thermal model provides are described. Recent refinements of the voltage time model have led to improved simulation of the discharges of a wide range of sizes and types of thermal battery under an equally wide range of test conditions. The semi empirical approach adopted was to provide a universally applicable framework based on logical concepts to cover various effects such as polarization etc., but with adjustable numerical parameters. It is shown that a moderately good simulation may be obtained for the majority of available discharge curves, using this one set of equations and without altering parameter values. Further improvements can be obtained when parameter values are optimized for one particular type of battery.