system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why are Tesla batteries lots of little batteries wired together. Can't they just make big ones?

Is it more efficient to use little ones, or is it technology limitations?
gpt
Making a semantic comment rather than a technical one.  If there was only one electrolytic cell it wouldn't be a battery.  For example, a 9V battery is a battery of six 1.5V cells in series.  In contrast, a AA cell is not a battery at all; only a cell.  The word battery means many units working together, as in a battery of guns.

Back to the technical.  Electrolytic cells produce only a low voltage so it's necessary to connect them in series, multiplying the voltage in a battery.  It's impractical to drive high-power motors with a low voltage because the extremely high current required would need thick and expensive cables.  Also, some of the losses involved in the power control electronics are of a constant voltage; losing 0.5V might be acceptable with a 100V supply but if you're only working with 3V the loss of efficiency is too great.  Much the same issue would arise in any attempt to step up the battery voltage with a DC to DC converter.