for a large RV with 4 6v house batteries at 12v output, I would consider any 'trickle charger' to be something to avoid - more for a single battery car, maybe...it's unlikely it would give you the outcome you are looking for, at least for that size battery bank.
with such a small panel, it's likely you would be relying on something that will severely disappoint you, especially the first time you find dead batteries. The thing with solar is that it itself it severely limited by the amount of 'sun hours' during the day, ESPECIALLY during winter, the shortest days of the year.
Your best bet is to try to COMPLETELY disconnect all draws on the batteries....and not just the 'salesmans' switch near the door, but a true disconnect of the battery main wires themselves, either thru an installed disconnect 'switch' near the batteries, or removing the POS and NEG leads themselves, which is probably just as easy.
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