I did my own toad setup including Invisibrake, brake light diodes, etc. I simply powered the Invisibrake using the 12 volts supplied by the host motorhome through pin #4 on the 7-pin connector. The 7 pin connector has all necessary power for a trailer... it's the same principle for a toad vehicle. If wired properly, the toad receives all necessary power through that 7-pin connector. The toad battery should also receive a trickle charge from that 12 volt supply.
I've never had an issue with the toad battery running down. It's a matter of doing the wiring correctly.
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