RE: Simple 6/7-cell field charger?
Go with the Hobbico Quick field charger MKII. Will charge two packs of any configuration.
$50 at tower.
Best $50 I spent on a quick charger.
One note though: Notice they put a set of charge monitor jacks right next to each set of outputs. If you're not careful, you could plug your charging banana plugs into them (I did). Since you're not supposed to charge through those jacks, I guess you could screw somethign up.
My solution: Since I know I'll NEVER use those monitor jacks, I put hot glue into the 4 holes. I'll never mistakingly put the plugs into those jacks ever again. And, should I ever choose to monitor the charging, since the hot glue is soft, it would be pretty easy to dig it out of the jacks. Problem solved.
Nice, solid, well built charger.
Roger