Methods, systems, and apparatus, including computer programs encoded on computer storage media, for the generation and use of an electro-thermal battery model. One of the methods includes obtaining battery data comprising voltage values, with each voltage value corresponding to an operating state of the battery. The method includes selecting a battery model, the battery model having convex parameters and non-convex parameters. The method includes processing the battery data by performing a fitting procedure to determine values of the convex parameters and non-convex parameters. The fitting procedure includes fitting the convex parameters with respect to the battery data during which the non-convex parameters are held fixed. The fitting procedure includes fitting the non-convex parameters with respect to the battery data. The fitting procedure also includes creating an electro-thermal model for a battery from the selected battery model using the fitted values of the convex and non-convex parameters.