Comment by jdietrich
Lithium primary cells have a shallower discharge curve than alkaline, but not completely flat; measuring state-of-charge is essentially trivial for any competent design engineer. Medtronic specifically recommend FR6 lithium cells in their insulin pumps.
https://data.energizer.com/pdfs/l91.pdf
https://www.medtronicdiabetes.com/sites/default/files/librar...
While the Medtronic pump has a setting to toggle between "Alkaline" and "Lithium" to adjust how it reads the battery percentage, the Dana i is primarily calibrated for Alkaline (LR03).
So your mileage may vary...