They all differ, but they're closer to one another than to other types.
If a V2 is really a kr808d, you could use any battery with a 808 connection.
Or, you could use a 510 connection on a proper e-cig with a 510/808 adapter.
Consider what you're looking for and whether a V2 is really what you want.
They are extraordinarily over priced for what they are.
If you really must look like you're smoking, check out a Volt, a far better cigarette lookalike.
Little cigarette lookalikes have serious limitations that no manufacturer can overcome.
Their
batteries are too small to produce a good vapor for very long between charges.
Small
batteries will keep their charge for shorter and shorter periods of time.
You'll soon find yourself with a whole handful of little batteries with a combined cost far in excess of what a couple larger batteries would have cost you.
If you absoutely must have a mini-cig type PV, there are better models out there than a V2.
Look at the Volt and the Bloog. Those are the two best mini-cigs, according to most fans of that class.
If you aren't hung up on a PV that looks like a cigarette, you broaden your horizon immensely.
You'll spend less money in the long run and end up with a PV you'll be happy with for a long time.
Chances are that if you smoke more than a 1/2 pack a day of analogs, you'll end up getting away from the mini-cigs anyway. So you might as well skip it right from the start and save yourself some time and money.