Can I jump start my toad from my motor home?

We have found our toad battery dead, after towing the vehicle with the Unified Tow Brake hooked up. We had the battery (which is new) and the charging system tested, and everything is fine. Until we can figure out the cause of this problem, our question is this:

Can we jump start the toad from our 6 6-vol house batteries, or our chassis batteries? Is so, what is the correct procedure to perform this safely?

(Also, if anyone has any ideas about the discharge of our toad battery, we would appreciate it.)