Brewbear, I have multiples of all the Provaris. V 2.5 uses button top batts. They have a few in stock at provarifuel.com
The Proceyon is 50 watts. Flat top batt. The Radius comes in 40 or 60 watts. I already had two, when I saw a post by PLAN OF MAN, showing his Provari v1. Still going strong at 5 years. I commented that was when I was convinced I had made good choices. Also note that Creme de la cream E.U. has many Provaris left. Once you put in your U.S.A. address, the vat charges go away, so prices are comp. Good luck. Edited to add that all my units are run on 18650's, I get at least 24 hrs from a charge.