DrewE wrote:
I think you're basically on the right track. It sounds like it could be a very fun project, though undoubtedly a good bit of work.
The entertainment systems are generally not going to be consuming their maximum rated power; this is particularly true for the receiver's audio amplifier, assuming it's not a very high end class A amplifier.
I would suggest a pure sine wave inverter for this use, not so much out of concern for the safety of the equipment as for the liklihood of picking up spurrious noise from many MSW inverters that put out a lot of electrical noise. A 1000W unit would be plenty; a 500W or 600W one would probably be sufficient; however, in my opinion the difference in price is small enough that the larger size seems more sensible.
Guessing at a system average power usage of about 200W, a pair of golf cart batteries would last about five hours before getting down to 50 percent charge. Lead acid batteries don't take well to being deeply discharged, and especially to being left in a discharged state; I wouldn't suggest going too much below 50 percent. Lighting, if any, and any fridges etc. would of course add to the power consumption.
For connecting to the vehicle electrical system, you do need an isolator of some sort, which you've basically described. Having a continuous duty contactor (or heavy-duty relay, which is basically the same thing under a different name) to connect the battery banks together when the engine running is pretty straightforward and can be done reliably. Often this is controlled by a switched circuit on the vehicle side, so it's engaged when the key is in the run position. Occasionally there are somewhat more sophisticated schemes, maybe with voltage sensing or time delays or such.
You would be very well served to have heavier wiring between the batteries than a 10 gauge wire. My class C motorhome has, as best as I can make out, 2 gauge wiring, fused at 175A at either end. Charge currents for golf cart batteries can easily be over 50A, and having a thin wire (with its resistance and voltage drop) will unnecessarily slow down charging from the vehicle electrical system.
It would not be a bad idea to also have some sort of an AC powered charger ("converter" in RV parlance). Depending on your usage, it could be a fairly small smart charger, mainly to maintain the battery's state of charge, or it could be a somewhat more powerful one that can recharge it in a reasonably short length of time. Progressive Dynamics makes some excellent ones for the latter use.
I do hope you've researched registration and driver's licensing laws for your proposed uses. In general this would not be able to be registered as an RV, and you'd probably need to have a class B CDL, quite possibly with a passenger endorsement (if it seats more than 15 including the driver), to legally drive it. An RV for personal use does not have these requirements, but does have certain minimal equipment requirements that may vary a little from state to state but typically include having at least some subset of permanently installed sanitation systems (a toilet), cooking systems, a permanent electrical system, sleeping bunks, etc.
Thanks for the quick reply. The thinner wire is definitely one of my concerns, it's gotta run from the left side of the bus underneath the body all the way up to floor level on the right side underneath a cabinent, which is at least 9 or 10 feet once all said and done. It doesn't have to charge terribly fast though.
We will charge the batteries up fully from a car battery charger I have already before each trip and we will drive 2-5 hours per trip then camp only 2-3 days typically, and only hang out inside at night, probably driving in between somewhat, I'm also considering a solar panel but that is another $150. Hardly any other 12v systems will be used though, no water pump, no fridge, ect.
As far as the inverter would this work alright for how low the price is? https://www.amazon.com/gp/aw/d/B01ALHANG2?psc=1
And the batteries: https://www.walmart.com/ip/12V-35AH-Light-Trolling-Motor-Sealed-Battery-Sevylor-Minn-Kota-Golf-Cart-AGM/149406140?wmlspartner=wlpa&selectedSellerId=1082&adid=22222222228049616421&wmlspartner=wmtlabs&wl0=&wl1=g&wl2=m&wl3=145272666681&wl4=pla-262099847748&wl5=9029683&wl6=&wl7=&wl8=&wl9=pla&wl10=112561763&wl11=online&wl12=149406140&wl13=&veh=sem
As far as lisencing I'm pretty sure I have that figured out. The previous owners already took out the seats and put in a new floor and some cabinents, they had it as an RV with AIS, and I'm going to do quite a bit more, kind of like the same systems a tent trailer has. Gravity fed sink and a portable toilet, no tank system is my plan, already have a stove and all that so I've just about covered all my bases.
