If you want to be able to control the vape then yes, you will need one, especially as the dc to dc controllers above will keep your set voltage going to the vape as the battery slowly discharges(and drops voltage).
You can always use it at home too (pugged into the WS or higher voltage wall wart) for a cheap VVPS
I actually use my Makita LXT 18v power tool batteries to run my WS from DC as the ones above use up to 1 volt so a standing 100% charged car battery max output would only be 12.3 to 12.6 and it will drop as you use. Having an 18v to start with lets you use concentrates while camping as the DC output could be set at 13v and it will stay at 13v even as the Makita battery drains and is easier to lug around than a car battery!
Ok, interesting. Now, pardon my ignorance and high... but what do you mean by "control"? what would happen if i can't control the vape? would it be at the set dial level initially and eventually drop its power as the battery discharges? Damn I'm feeling dumb right now... feel it should be easier to grasp.
Oh, and I don't plan to carry a battery car around, but i do vape alot in my car, so being able to using the WS in it would great. As for camping, I haven't looked into battery packs yet, but that Makita battery pack seems like a cool idea... a power tool battery for a power vaporizer.