My Johnny 5 light is not much to look at, but it is a pretty good emergency light. It has 2 13w HID lights (one spot, the other flood). You can run either light singlely or both lights.
Batteries are 2x4.5 Ah 12v Li-Ion with LED charge level indicators. It will run for 4 to 4.5 hrs with both lights on or approx 9 hrs with only one light on.
If you want it to run FOREVER (how long will half a dozen 35K mcd LEDs run on a 12v 9 Ah battery), you could replace one of the HID lights with a led light, or just add a LED light.
I think I just gave myself my next mod - add LED light.
Here's some pics. The pics show the light with only one battery. I have since added a second battery to increase the run time.