Maxim fuel gauge battery characterization for customer's batteries is done at 0֯C, +20֯C and +40֯C.
Regarding the characterization at 70֯C, we characterize up to 60֯C. The reason being that the cells do not change behavior at high temperature as they do at cold; the cell model changes are minimal, if any, from 60C to 70֯ C – assuming the cell is safe to operate. So no new model is needed. Test data on run-times at 60 ֯C and 20 ֯ C is virtually the same.
From a high-level perspective, it is disruptive to run characterization at temperatures other than 0, 20 and 40 ֯C because the temp chamber cannot be used for anything else during that time. We can do a special case for customers if it is absolutely necessary. However, it looks like the battery characteristics change in a very minor way.