You can never have too many batteries, well within limits. Anyway when I use my 350 mod I carry four extra batts in a plastic case, when vaping sub ohm I have use sony 30A 2000 mah with on in the mod and two extra in a case. I never seem to go batt dry when doing so, oh I do also keep a charger in my truck just in case. Hum, the word "case" keeps coming up, just never keep loose batteries in you pockets or such, not that your are, just some advice.