That is, a battery that could supply the nation's electrical needs for a few
days during a blackout.

The author computes it could be done with a sufficiently large, or
sufficiently numerous, lead-acid batteries. The whole shebang would need
only 5 billion tons of lead. The US has 7 million tons of lead reserves,
while the entire world has approximately 80 million tons.

We'd better get busy looking for more. Chinese toys might be a good place to
start...


(Caution: Real maths in use)
http://physics.ucsd.edu/do-the-math/...sized-battery/