When I bought my first two P2.5's a little over a year ago I bought the AW batteries sold by Provape because I read a lot of confusing opinions on this, and I didn't want to think about this too hard
. And a year later I am satisfied with my decision. Provape now also sells E-Fest button top batteries (they only sold AW the last time I bought Provari batteries).
As best I understand it, the P2.5 is not terribly picky about the battery. But the battery's positive button must conform to the standards. For example, I have heard of button top batteries that did not work because the button was presumably either too small or too wide. The battery must be unprotected (IMR chemistry) and must be a high drain type.
Here is my argument for preferably buying the batteries directly from Provape or at least the identical models from very reputable dealers:
1. You are not a battery expert.
2. Nor do you want to be
How many hours of your life do you want to waste trying to save a couple bucks per battery ? (which presumably is the only reason to look elsewhere)
3. You are trying to vapocalypse proof yourself. You want your entire mod to be as reliable as possible
4. At the current price of $79 I think the P2.5 is an excellent vapocalypse proof-er and I've bought a couple more myself.
5. You get a one year warranty (real, meaningful warranty), why screw that up with a possibly questionable battery? If you buy the battery from Provape then there can never ever be any question about battery choice.
6. There are supposedly a lot of counterfeit batteries out there, and most you would find for much less would be at least suspect. How much time do you want to waste learning about cheap counterfeit batteries? And certainly don't buy them from eBay or Amazon unless you really know what you are doing.