The battery is rated at 2000 mAh which gives a lot of hours if you are not using the projector, but then I’m not sure that the projector would be feasible for other than on the spot, short presentations.
I like the projector; I’ll let the early adopters pay for the R&D because you can be sure that this will lead to a new generation of small, cheap projectors that could make big-screen TVs obsolete.
My question would be how long the projector bulb lasts...
I can usually plug in the phone for power...