I am trying to figure out what size battery I will need to power my RPi and 2 components with it. I want to build a "tablet" of sorts, mainly because I don't want to spend $800 on a Wacom tablet when I can spend $200-$300 building my own (The point is to do digital sketches and take colorful and digital math notes).
I prefer for the battery to last for 10 hours as I don't want to have to constantly charge it. However, I don't need a $300 battery with a billion mAh on it either.
Since I have never calculated mAh before, I don't know if I screwed any of the math or formulas up, so I would like to know if I calculated it correctly and what pointers I could use to become more knowledgeable about building battery powered electronics.
The intended battery size I am looking for is under the Average Usage column.
Edit: The 30 hours is supposed to be 10. I just lazily dragged the sum(...) command across the columns.
Also, I cannot seem to find any actual sources of power requirements for the touch screen. I am looking at the 7 inch official RPi touch screen screen. I just randomly found on Google that is may use around .5 amps. It is similar for the camera being 200-250 milliamps. The last thing is, would I be right in believing these devices around around 5 volts. If not, how would I find out what voltage they use?