Well its like the tyranny of the rocket equation. Yes the size increase isnt linear, but it isn't a free lunch either.
Don't forget, once you've added an extra tonne of batteries your suspension and chassis need upgrading (ie get heavier) to compensate, so you need to add more batteries to compensate....
Don't forget, once you've added an extra tonne of batteries your suspension and chassis need upgrading (ie get heavier) to compensate, so you need to add more batteries to compensate....