Nickel cadmium cells were the most commonly used rechargeable batteries until recently. NiCads come in sizes like non-rechargeable cells and can directly replace non-rechargeables like alkalines. NiCads do have a lower voltage output 1.2 volts as opposed to non-rechargeable cells at 1.5 volts. That voltage drop will not make much of a difference under most application.
See The Full Article Here: http://wp.me/p1rtTO-vs