Your vehicle may be different but on my Honda CRv some of the circuits are live when the transmission is in neutral rather than park. We do not have a trickle charger from the RV. I did a battery voltage check and after 8 hours of towing we lose about 20% of battery power. You can pull the fuse for circuit #34 but it's a pain to get to it, so we simply run the vehicle if we don't plan to use it after a day of towing. Works for us.
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