Modeling and simulation of nickel-cadmium batteries during discharge

A battery is an essential component of any aircraft. It has several functions such as to start the aircraft propulsion engines and to provide power during electrical emergencies. The aircraft designer must know the electrical behaviour of the batteries that have been preselected for possible use in the aircraft at several operating conditions. Typically, the manufacturers of batteries for aircrafts provide proprietary software that can be used to generate the battery voltage curves over time for constant and user-specified room temperature and discharge current, assuming that the battery is initially fully charged. This paper shows how these battery voltage curves can be used to generate and validate a battery discharge model. By using such a model, the aircraft designers can simulate the battery behaviour at several operating conditions such as a variable room temperature, a variable discharge current and a partially charged battery. As a case study, it is shown how to generate and validate the battery discharge model for a specified nickel-cadmium aeronautical battery. The model is then used to simulate the battery during an electrical emergency situation considering three types of loads: linear (constant resistance) load, constant power load and constant current load. In all three cases, the simulation results were as expected.