You sure can, and I have the set up exactly as you describe.
I have 3 12V house batteries and 2-12V starting batteries.
My solar charge set up is a 40W that I fabricated a mount and mounted it to a building next to my motorhome. I have about a 15 foot run to my battery compartment where the solar panel goes into a waterproof solar controller.
The solar controller runs then to the + - leads on the house batteries.
The Chassis batteries a charge via a trikLstart, which was already on the motorhome.
The batteries are consistently maintained at the float level of 13.6 or so of this controller.
Cost of panel approx. 60-70 or so and the controller around 12 bucks or so, from memory and Ebay prices.
There is extra wiring and Velcro to attach controller etc, but I don't think I have more than $150. in it.
