So I'm working on a new project, and I only have room for 1 charging/wall wart jack. I spent a while trying to figure out how to wire things up to a DPDT switch like we normally use to "play and charge" because well, that's what I had available here. Long story short, its not possible. There is no way to isolate the batteries completely from the wall wart and prevent explosions. So I had to get off my ass and make the 5 minute trek to the local rat shack to pick up a SP3T switch (three way switch).
Anyway, I was browsing the voltage section here and I didn't see a diagram for this type of situation. Not that its all that complicated, but I like visual flax:
Highly modified SS's diagram to suit my needs rather than have to draw all that flax myself.
Now, understand that this type of power switch wiring WILL NOT
allow you to play and charge. Also understand that, if your switch is in the charge position and you plug in a regular wall wart (not a smart charger) your batteries will likely go boom if you leave it there. So you'll need to be careful.