I did that on my 2003 Suncruiser 33V as well as on my Allegro Bus.
The existing wire is way too small for any real solar panels. It winds up down in the battery box. I can't remember exactly where it was, but I "think" that it was on the "hot" side of the battery disconnect solenoid, rather than the batteries themselves. Now, I may be wrong on that (swiss cheese memory - really good but very short
) but I do do know that it is down there. Either way, it's not a big deal to remove it and assign it to the chassis battery. I relocated it to the chassis side of the Auxiliary Start solenoid rather than going over to the battery. It was easier that way.
I then put two Shell-Siemens 110 watt solar panels on the roof of the 33V. I thought I may want to add more in the future (I did, but I waited for the Allegro Bus to go to 4 panels) so I spec'd everything accordingly. 440 watts divided by 10 volts = 44 amps, so I bought a 50 amp charge controller rather than a 30 amp controller. This meant I had to run #8-2 wire, instead of #10-2 (which is only good for 30 amps). The wire I picked up looked just like Romex that is used in a home except it was 12 volts and stranded. But the nice white PVC jacket made for a clean installation. I bought my solar panels from www.windsun.com
and also ordered some Z brackets to mount them. I then mounted the aluminum Z brackets to the roof with 3/16" stainless steel rivets (screws would have pulled out in the thin fiberglass). Then I ran the #8-2 wire assembly down through the refrigerator vent. I had to unscrew the assembly, drill a hole in the side, fish the "romex" through, and recaulk the vent cap. Once behind I routed the cable under 'fridge to the converter area and then down through one of the existing plumbing access holes into the large basement compartment immediately aft of the entrance door. There I mounted my Charge Controller and continued the wires through the steel bulkhead into the battery box area, where I attached the leads to the coach batteries themselves so that when the coach battery disconnect switch was thrown, I'd still have solar chargeing. I then ran a Cat5 cable up from the Charge Controller to a remote display panel which I mounted above the breaker panel in the cabinet by the stepwell.
Moving the existing solar panel to the chassis helps a little but it's so small it doesn't do much. It did keep the battery up over winter enough that it cranked slow, but never was dead after 1 month of winter storage. So, it helps extend the interval but won't keep it charged all winter long on it's own.
220 watts of solar power was marginal, but we are power hogs so the 440 watts was much better. However, some RVers can go a long time on very little power so where you fit in is up to you.
Solar power's biggest problem is that it's greatly misunderstood. An inverter will let you run AC loads off your batteries. Either way, whether it's 12 VDC or 120 VAC, the load comes off your batteries. The less batteries you have, the quicker they'll go dead. The more you have, the longer you can run between recharges. Unless you live like a hermit (in bright sun all the time
) you'll never be self sufficient with 200-400 watts of solar power. But, solar power will help extend the time between battery recharges. Under normal usage you will still have to recharge the batteries, with either the generator set or the vehicle's alternator. If you stay a short time and drive around a lot the vehicle alternator may just do it for you. If not, you have to fire up the Onan every now and then. But, solar power is great in that you can extend your batteries to the point in time where it's convenient for you (and not disturbing to your fellow campers) to recharge them. It's tough to justify them oin a "cost effective" basis but it sure does help in that it removes some of the limitations you may otherwise have. It helps you be that much more self-sufficient and enjoy RVing that much more.