Did I understand that you deduct that if the batteries are certified (=theoretically good for) 1h in emergency situation, that you can expect to perform a 1h turnaround on batteries only? If so, the I see a logic mistake here. I'm flying the 747 and without going into too much detail (in other words, I forgot))), there is a nice load-shedding logic build into the electrical system, and almost all ancillary power consumers (including most of the cabin lights, baggage door operation etc) are load shredded on batteries only.