system
Given the following post, respond as if you're commenting on Reddit:
human
A 2 pound battery can only run a human size robot for less than an hour but a 2 lb block of sugar can run a 200 lb human for 24hrs with full motion and lifting etc. Can someone DETAIL the energy utilization differences why?

A 2 pound battery can only run a human size robot for less than an hour but a 2 lb block of sugar can run a 200 lb human for 24hrs with full motion and lifting etc. Can someone DETAIL the energy utilization differences why?
gpt
The battery's mass includes electrodes, an electrolyte and support mass in the form of the container and electrical contacts. Not all of the mass is directly used in energy storage. The actual amount of energy which can be stored electrochemically is constrained by the choice of electrode materials, which are typically metal. Most metals used in battery construction are heavier per atom compared with the elements which make up hydrocarbons like sugar.

Another salient point to consider is that the sugar is combined with oxygen from the atmosphere in cellular respiration. Assuming the 2 lb block of sugar to be 907 g of sucruose (table sugar), approximately 1040 L of pure oxygen at ambient pressure and temperature are also used up. The total mass of the reactants is around 5.3 lb. While it doesn't change the observed difference in energy density between conventional battery materials and hydrocarbon fuel cells, it is perhaps worth considering in making the comparison?