An innovative battery concept has been designed by Huang Kun, Meng Xun, He Ting & Liu Yuan, called the One = Two. Which is already a 2011 red dot design concept winning entry, and provides a great way to be able to use every last drop of power from each battery.
The concept behind the spring batteries is that when two batteries become drained enough that they are unable to power your electronic device, they can be compressed and combined into one battery slot. Allowing you to drain every last drop of power from the older batteries before replacing with a new fully charged one.
Source: YankoFiled Under: Concepts & Design, Design News