10
Got the yocan uni pro and it's great.
Vaping a trainwreck cart from curaleaf, at 2.4 volts it rips and is quite tasty. Tastes like lemon and spicy pine, and the battery just sips the distillate but the effects are great.
Not to mention 3v burns the hell out of your throat.
Yes. 90% of the batteries out there that run higher then 3v as their stock or low setting too. You have to look for batteries that go sub 3v and not just in preheat mode. I use the Uni Pro and Yocan B-Smart pen style 2v-4v in 0.1v increments just like the pro, but it has a twist dial/analog.