What's the biggest alternator available?

I'm really jumping in late here, but try this idea. I did this myself, and it works really good.

I had enough room behind my stairs where the batteries are, to install a marine 4 bank battery charger. It's good for getting wet etc. It was smart, and would decide what charge you needed when you turned it on. It would even run a maintenance routine past them once a month. I hooked it up with a marine socket I put in just below the door. I carried a 100 foot extension cable with me, and I could plug in and run whatever I wanted, and the batteries would be more than fresh. No fuel needed, and if I wanted to run the truck's a/c, I always had more than enough juice flowing from the charger. Of course it didn't help during the winter obviously, except for not running the engine to nuke some food etc.

I can't remember the model number off-hand, but it was the ProMariner 4 bank monster.

So, all you have to worry about is parking near enough to a power source.