Paul,

Any idea how long it would take to charge a battery while driving?  Is is 1 to 1, in other words if you use the battery for an hour would you have to drive for an hour to charge it?

Depending upon the make and model, some trucks' B+ power is cut off when the engine is not running or the ignition is off. This eliminates any accidental draining of the trucks' batteries.

The trailer batteries will be recharged at whatever rate the alternator is designed for, in parallel with the truck's batteries. It could be as little as a few minutes, or the better part of an hour, depending upon the depletion of the batteries.

I have a Dodge and very much dislike the way it is wired, it is always hot which means I run the risk of dead batteries on my pickup, not sure why they aren't set up like the Ford and Chevy with keyed power.

I checked on an RV forum and some suggested a reley like this:

http://www.amazon.com/Tekonsha-7000-Terminal-Battery-Isolator/dp/B0002UHVYQ

but I'm not sure I like the idea of messing with my pickups electrical system.  I thought I would try just disconnecting the pickup when I got to my destination but the first time I did this I forgot to hook it up and drove home with no blinkers or brake lights.  I may just try making the hot wire on my pickup non active and understand I will have to charge my battery another way.