Originally Posted by COTuscany
I was thinking about a line from the 7-pin but it sounds like the 6-pin on the Blue Ox cable has the same ability. But now for the complication: My MH doesn't power the 7-pin when the ignition is off.
If it was me, I would run that charge line to your toad battery, with sell-resetting circuit breakers on both ends. Then I would add a new 12 volt power point in your toad, powering it directly from the toad's battery with an inline fuse or circuit breaker. That way, it'll always be powered, either from the toad or MH.
And be careful with that 6 pin, it can be wired one of two ways, you need to double check that it's hooked up as a charge line. The most common pin arrangements:
4-pin: lights and ground
5-pin: adds a brake controller signal
6-pin: adds charge line OR reverse (back-up lights) signal
7-pin: has charge line AND reverse signal