RobertS975:
The ETOPS time doesn't matter if your airplane is burning!
That's the point of the metal box.
Look at it this way: Without the box, a battery fire is a critical safety issue. Because it has the potential for bringing down the plane, it must be extremely improbable (< 10E-9 per flight hour). Since it appears that this is not the case, we get the fireproof box. The sales pitch for the box doesn't appear to have a time limit for withstanding a fire (at least none that I've heard). So that means diversion range in the event of a fire will be based on the remaining system capabilities. If you had ETOPS-180 before the battery caught fire, you still have it. That's the position we will be in if the FAA buys the battery in a box solution.