dwh
Tail-End Charlie
A good solar controller for what you're doing would be the Morningstar SunSaver Duo. It's a PWM controller, usually comes with the Morningstar RM-1 remote control panel, and does two batteries or banks. Controller with optional control panel generally runs around $125-$150.
You can set dip switches to control the bias between banks, for instance 90/10 or 50/50. Say you set it 90/10 bias toward the main battery. 90% will go to the main battery and 10% to the aux battery, until the main is topped off (won't take long, probably be done with just the bit of power you get in the morning before the true good sun hits the panels), then 100% will go to the aux battery. That's the way to make sure your main battery is always topped off and ready to start the truck
You can set dip switches to control the bias between banks, for instance 90/10 or 50/50. Say you set it 90/10 bias toward the main battery. 90% will go to the main battery and 10% to the aux battery, until the main is topped off (won't take long, probably be done with just the bit of power you get in the morning before the true good sun hits the panels), then 100% will go to the aux battery. That's the way to make sure your main battery is always topped off and ready to start the truck