Although my earlier post #16 (
https://www.trailmanorowners.com/for...5&postcount=16 described how to wire a Relay, powering the brakes from the bargman "TBC" pwer source when the on-board batteries fail, it is my opinion that the addition of that feature is not worth the trouble.
I offer a "wild guess" estimate that 99% of hitch connection failures (with the Trailer falling loose from the Tow Vehicle while traveling), the bargman cable will have ripped loose from the Tow Vehicle at the same time as the hitch.
Power from the on-board batteries will power the brakes when the breakaway cable fails. But in the case of the no voltage from the on-board batteries AND breakaway cable ripped out, the TBC wire probably has no power either. (The relay will have switched over, but the TM brakes wil not be activated.)
Rob, if you choose to skip the relay - I don''t disagree with that choice. (Even though RIAA woul not approve of such "missed" wiring in a new trailer.) i do NOT have such a relay in my own TM.