An equation-based battery cycle life model for various battery chemistries

Abstract

The evaluation of the cycle life of batteries is an essential task in the assessment of the reliability and cost of battery-operated devices. Several compact cycle life models have been proposed in the literature, that exhibit a general trade-off between generality and accuracy. Some models are based on a compact equation derived from experimental data and try to extract a general relationship between cycle life and the relevant parameters (mostly the depth of discharge), but suffer from poor accuracy. At the other extreme, more accurate models, based on incorporating the aging effect into an equivalent circuit, tend to be focused on a specific device and are seldom applicable to another battery. In this work we propose an equation-based model that tries to overcome the accuracy limits of previous similar models. The model parameters are obtained by fitting the curve based on information reported in datasheets, and can be adapted (with different accuracy levels) to the amount of available information. We applied the model to various commercial batteries for which full information on their cycle life is available. Results show an average estimation error, in terms of the number of cycles, generally smaller than 10%, which is consistent with the typical tolerance provided in the datasheets, and much lower than previous equation-based models.