Charging battery wihle towing behind RV

Needed to add a battery charge wire to keep my D2 battery charged while being towed.

Currently have a wire going direct from the RV battery to the D2 via the Trailer/tow cable. Haven't hooked it up to the D2 battery yet as I wanted to check and see if there is a better or more proper way to connect it.

Already have all the diodes on the tail lights to stop any power going back into the elec system

Will I need to add anything else for elec circuit protection as the ignition is ON while towing.

Thanks

Well all the tail lights/turn sig/brake lamps are powered by the RV power through separate wires going from the RV to the D2 Lights through the trailer/Tow hook ups.

The battery wire would (in theory) on trickle charge the Battery for the computers as they are on while the key is in the on position to unlock the wheel.

They do make those DC chargers, but have read that they are really not needed.

I just need to know if i have a separate charge going back to the D2 am I going to blow anything - Alt/ ECU, etc. I'm thinking not as they would be getting their power from the on-board Batt/Alt while the D2 in on and running.

Thanks