Which battery model to use?

The use of mobile devices like cell phones, navigation systems, or laptop computers, is limited by the lifetime of the included batteries. This lifetime depends naturally on the rate at which energy is consumed, however, it also depends on the usage pattern of the battery. Continuous drawing of a high current results in an excessive drop of residual capacity. However, during intervals with no or very small currents, batteries do recover to a certain extend. The usage pattern of a device can be well modeled with stochastic workload models. However, one still needs a battery model to describe the effects of the power consumption on the state of the battery. Over the years many different types of battery models have been developed for different application areas. The best type of model to use in the setting of performance modelling are analytical models. In this paper we analyse two well-known analytical models, and show that one is actually an approximation of the other; this was not known previously. Furthermore, we tested the suitability of these models for performance evaluation purpose.