It's actually better that there's no inline battery, or else you wouldn't have a 5V device. The passthroughs that have it (like the 510 for example) don't give you 5V, they charge the battery, and the battery delivers the normal 3.7V to your atomizer. *Well, I should say, closer to 4.2V that you get out of a freshly charged battery
Also Rob, I noticed that on your site it says not to use these with a wall charger, but unless there's something special about these that I don't know about, that's probably not accurate. The real problem is current - most wall chargers will only give you around 0.5A which won't power a cartomizer (or any other atomizer for that matter). Even some computers can't put out enough current to properly run this at 5V, depending on the type of computer you have and the amount of devices plugged in to your USB hub. I haven't tried it, but many people swear by these USB power adapters that deliver a full 2A of current which should have no problem with the passthrough, and it's cheap as hell:
USB Dual Power Adapter
I didn't know that a true 5v passthrough even existed for the 808. I think I'll throw one on my next order
Edit - if someone does buy that power adapter and use their passthrough in it, don't plug anything in to the second port!
Edit 2 - *