To "Oversimplify things" as a "guideline only"
Using Single Coil Atty/Cartos
1.7-2 Ohm is Low Resistance (hotter coil) > 2 .5 Ohm is standard resistance (3-3.2 probably most common) Using too low resistance at too high voltage will cause problems at the very least (blown atty/carto coils, trip protection circuits in PV or batteries etc. )