I too installed a separate battery and a Trik-L-Start to charge it. Did all of this after checking all connections and grounding. Since the AGS does not energize the Boost/charging solenoid, I lacked confidence in the system to start while we were away. Plus the White-Rogers boost/charge solenoids are failure prone.
Like the idea of hooking it to the start batteries
& if it can easily done, sounds like a great option.