system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why can't you just mount two or more batteries in an electric car to extend its range?
gpt
You can!  But batteries are big, and heavy, and expensive.  Manufacturers are currently going with their best balance of weight, cost, and range.  They're always striving to improve upon the current model.

Let's take the cost out of the picture, though.  Let's say you've got plenty of money to throw at your SuperPrius™ and just want to fill it with batteries.  You've still got the issue of weight.  The SuperPrius™ is now way heavier, so its already sluggish 0-60 time is even worse.  Breaking distance increases as well, since it takes more to stop that car once it gets going.  And the added weight means it taxes the batteries even more when accelerating.