Are you not getting off the thread's focus question. Why should the fuel spill out of the vents just because there was no AC power? I have to assume the battery was not depeleted, as 30mins of fuelling (but don't the NG's have 60mins batteries?) would be an enormous quantity of fuel. The valves are spring loaded shut unless the fueler was activating the red buttons and forgot to close them. Was this just a coincidence? But all this AC DC battery only techno babble is not answering th question. I'm curious too.