One thing to remember, a standby unit will slowly run the battery down when not in use, if not connected to the AC line, since the controller always draws current. You could just pull the fuse feeding the controller or add a battery switch.
Thanks UPS, I didn't think of that.
Add a breaker to the panel feeding the battery charger to keep the battery up when running.
No need to switch the full battery current.
Just add a toggle switch in the 12v feed to the controller, and turn that off whenever you shut down the genset.