Most campervans, and I assume most motorhomes in general, have their house batteries charge from the engine alternator through a battery isolator with no issues. My extended-body Sportsmobile has at least a 15-foot cable run from the engine compartment to a three-AGM battery bank in the rear of the van, and has always charged fine just from driving (we rarely plug-in while traveling, even up to a month on the road). As others have said, you will get some drop with a longer cable run, but proper cable sizing should mitigate that. Or, install solar?
AC charging via an inverter doesn’t make a whole lot of sense to me, as you are losing efficiency converting 12v DC alternator current to AC to run the charger and then back again to DC to charge the battery. A trickle charger is just that... a slow maintenance charge meant for long-term storage and not day to day recharging.
Consider also adding a AC-DC converter/charger, which takes AC from shore power and converts it to DC for running all your DC items, plus charges your battery. These are very common on pop-up trailers and the like, and can usually be found used pretty cheap, too. See if you have an RV junkyard near you and you’ll find a ton of them. Then just try to plug in every few days to top off batteries; you can find plug-in opportunities at lots of places, not just pay campsites.
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