You can 3d print springs on even the cheapest hobbyist 3d printers these days [1]. Some 3d printed springs exceed the performance of traditional designs of the same weight [2].

Battery chemistry is indeed a different kettle of fish however.

[1] http://www.thingiverse.com/thing:39963 [2] http://www.rapidreadytech.com/2012/04/3d-printed-spring-exce...