The problem in a semi truck isn't the battery life (or lack of), its being able to fiddle with it while driving. Changing batteries, adding juice, or cleaning up a mess when those go wrong is a bigger challenge. You just don't have the room for error doing stuff like that as you would in a car or small truck. Not to mention that every stop has to be planned more carefully. You can't just whip a 75' long 40 ton truck into a parking lot somewhere to wipe up a juice spill or top off your cart.
What's worked best for me so far is a 650mAh eGo passthru with a type B atty and mega cart. The only fiddly part is putting drops into the cart. One of these filled to the rim at a stop will go for 2-4 hours depending on how hard you hit it. Plan ahead and don't vape it dry. Get on a long stretch without traffic and it's easy enough to pull the cart and squirt some juice in it without taking your eyes off the road for more than a glance. With practice, you can get enough in there, even in the dark, to last an hour or more. The downside to that assembly is that you have to be careful of leaks. I either drop mine in a cupholder when I need both hands (shifting or steering thru traffic) or lay it on my lap. Cupholder mouth end down on a recently filled cart, mouth end up when getting dry. Lap is ok in between. USB charge from the cig lighter socket is all you need. Battery has enough life to run off the cable while going into a truck stop for food or shower, or waiting around at a shipping manager's window. About the only other downside is new carts don't fill easy the first time. Once they've been soaked with juice, the process is much faster. So your friend would need to fill new ones while stopped. Or on I-10 in west Texas or something LOL.
With that said, I just recently started using eGo Vision clearomizers. I've had a love/hate/love relationship with cartos. When they work, they work great. When they don't, it's 3X the fiddle factor versus an atty/cart combo. With about two weeks of practice now, I could see using these OTR. Pre-fill about a half dozen and have them stored somewhere easy to reach. You could change them without even looking.
Aside from all that, this is what I told a driver that works for me: learn your vaping habit on home time or when you're on your break parked at a truck stop. Once you figure out the gear and what it takes to keep it working, you're in a far better position to safely do that while driving.
Oh yeah, bring spares. At least 2-3 attys, a couple empty carts, and at least one spare battery.
