Can anyone comment on the design of the cell, specifically why it is long and thin, which would work against the square cube law. Is a large surface to volume chosen for thermal reasons?
The cells are pressure vessels, so normal cube-square scaling laws don't apply. Instead you need to use pressure vessel scaling laws, which also account for the needed wall thickness.
Pressure vessel scaling laws say that all cylinders have the same mass efficiency, and making long thin cylinders is easier than making short squat cylinders.
As I understand it, something like a lead-acid battery using volumes of acid and volumes of reactants so a cube gives them more power with the same surface area. NiMH batteries use boundaries between states instead of acid. Therefore, you want long thin batteries of alternating materials to make them more efficient.
Or, to put it a different way, NiMH batteries require a large interior surface area, and so the square/cube law forces them to look longer and thinner as they get larger.
As per the article, these Nickel Hydrogen batteries are very different to NiMH
> Nickel-hydrogen batteries look and work unlike any other battery. They consist of a stack of electrodes inside a pressurized gas tank. The cathode is nickel hydroxide while the anode is hydrogen. When the battery is charging, a catalytic reaction generates hydrogen gas. During discharge, the hydrogen oxidizes and converts back to water.
schiffern|2 years ago
Pressure vessel scaling laws say that all cylinders have the same mass efficiency, and making long thin cylinders is easier than making short squat cylinders.
HWR_14|2 years ago
Or, to put it a different way, NiMH batteries require a large interior surface area, and so the square/cube law forces them to look longer and thinner as they get larger.
h0l0cube|2 years ago
> Nickel-hydrogen batteries look and work unlike any other battery. They consist of a stack of electrodes inside a pressurized gas tank. The cathode is nickel hydroxide while the anode is hydrogen. When the battery is charging, a catalytic reaction generates hydrogen gas. During discharge, the hydrogen oxidizes and converts back to water.