> work at a coffee shop

That doesn't sound super secure to me.

> for five hours.

My experience with anything that is not designed to be an office is that it will be uncomfortable in the long run. I can't see myself working for 5 hours in that kind of place.

Also it seems it is quite easily solved with an external battery pack. They may not last 12hours but they should last 4 to 6 hours without a charge in powersaving mode.