@feld @tk >the rapid development in battery technology

The thing is: no.
Battery technology has principally remained unchanged for almost 50 years. Lithium-[Polymer/Ion/C/Mn/NMC], NiCad, Lead-Antimony and all the other mainstays were developed decades ago. We just found better ways to pack them into smaller packages. Now all that free space to stuff more cells into has run out.

All the new technologies we keep hearing about are fusion technology -- perpetually 5 to 20 years away. Carbon nano-tubes, anyone?

t. Guy who contracted for Briggs&Stratton "Flexpack" battery technoogy & Tesla Energy.