Battery in a drum rolled out
That's enough to power a computer workstation for 2 or 3 days, or to recharge a cell phone almost indefinitely, according to Younicos, the German company that invented the pack.
The mobile energy storage unit, called Yill, is a couple of feet in diameter, about the size of a small bass drum, with a handle and wheels. It recharges in about four hours in a 220-volt electric outlet.
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