New nicads are sold discharged, and they must be charged before they can be used. For best results, manufacturers recommend charging their batteries with a charger of the same brand. Left unused, nicad batteries lose about 1 percent of their charge each day, so they're not suitable for devices such as remote controls, or for flashlights stored for emergency use. We didn't see that in our tests. But in, say, a cordless phone, which charges whenever it's in its cradle, nicads may be more susceptible to that phenomenon.
Some chargers can now completely drain the batteries before recharging to avoid that problem.
Rechargeable alkaline batteries. The Rayovac Renewal , a compromise between regular alkalines and nicads, comes in AAA, AA, C, and D sizes and is sold fully charged. Rayovac says it can be recharged 25 times or more. We didn't test the Renewal batteries this time. In our tests three years ago, the first use of the Renewal was its finest, and each subsequent recharging shrank its capacity.