Suppose that through a "hand-wavium" genetic engineering coupled with nanotechnology the humanity was able to develop a body battery.
How does this work? It provides enough energy for the human body. No need to use glycogen/glucose ATP mechanism.
Let's suppose that heat regulation is also solved by this technology.
I suppose humans would still need to feed themselves (because of proteins/vitamins/minerals) and drink water.
So what would happen if this battery-human is lost in a desert without access to water? Would he/she die as fast as a regular human? What would be the difference? How can this be circumvented?