I think the only adverse comment about running it on a battery is that it wouldn't run for long. And it wouldn't.
But that was before you said you only needed 45mins runtime.
But I can't give you absolute assurance that it will work OK.
Mains power supplies are regulated, and put out an accurate and pretty closely-controlled voltage even with variable current loading. So the camera has a good power supply feed.
Batteries on the other hand are not regulated, droop in voltage a little if heavily loaded, and may start to go outside the voltage that the camera is happy to work at as the batteries discharge, so there is some uncertainty here.
So - why don't you try it and see if it works? Too low a voltage to the camera will not break it - it will just stop functioning temporarily.
My example was based on the common Nickel metal hydride NiMH rechargeable batteries that have a nominal cell voltage of 1.2V.
So 4 of them in series would give 4.8V which is pretty close to what the camera needs.
5 would give 6V, which may be an overload for the camera.