On Feb 22, 11:16*am, Lee wrote:
On 22/02/2012 09:42, tony sayer wrote:

But there are still serious problems with implementing these the main
one is the primary power system. Batteries, unless someone does invent
one that is neigh on 100% efficient and has much greater capacity and
costs and weighs sod all, will always be their great limitation.

There is another problem here, namely that if a much higher density
portable energy solution was developed it would have too much potential
to be "unsafe".
Whether deliberately or not.

There is other technology on the horizon.
http://en.wikipedia.org/wiki/Super_capacitor

Instant charging is possible.