ALKALINE DISPOSABLES

They still exist because of convenience, not chemistry: You can buy them—for a pittance—from New York to Nepal. Perfect for occasional-use devices, such as smoke detectors and TV remotes, because of their long shelf life.


NICKEL-CADMIUM (NiCd)

Good for 1,000 discharge cycles. They’re toxic and suffer “memory effect,” when damaging crystals form if the cell isn’t often fully discharged. NiCds are rare except in power tools; their high discharge rates suit big-current draws.