After years in which consumers and researchers faced sharp trade-offs in weight, safety, and power for high-power batteries, promising variants are emerging. Nanotechnology is enabling a new lithium-ion battery that can unleash five times as much power as existing versions, and this summer, tool manufacturer DeWalt, of Baltimore, MD, plans to sell a line of 36-volt cordless tools that use it. Progress in the field even includes an upgrade to the age-old lead-acid battery.

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