[wizzwizz4]

I'd argue you can't cram any electrons into any finite space without infinite energy. But we're not really talking quantum physics, here.

[danparsonson]

I'm not sure what you mean - any battery you have would seem to contradict you - would you elaborate?

[wizzwizz4]

The electrons are not wholly within the battery; they are mostly within the battery. (Batteries discharge over time for an almost completely unrelated reason.)

[danparsonson]

I think you're misinterpreting the meaning of the wave equation. Batteries self-discharge due to chemical reactions not quantum tunneling.