Nickel-cadmium cells and batteries:
You have probably seen, NICAD cells and batteries. They have become common in consumer devices like those little radios and cassette players you can wear while going for aerobics or just sitting around. You can buy 2 sets of cells and switch them every couple of hours of use, charging 1 set where as using the other. Plug in charger units just cost a few dollars.
Types of NICAD cells
Nickel-cadmium cells are made in several types. The cylindrical cells are the standard cells; they look just like dry cells. Button cells are those little things which are used in the cameras, watches, memory backup applications, and places where miniaturization is significant. Flooded cells are generally used in heavy-duty applications and can have a charge capacity of 1,000 Ah. Spacecraft cells are made in the packages which can with- stand the vacuum and temperature changes of the spaceborne environment.
Uses of NICADs
There are other uses for NICADs besides in the portable entertainment equipment. Most orbiting satellites are in the darkness half the time and in sunlight half the time. Solar panels can be taken in use while the satellite is in sunlight, but during the times when the earth eclipses the sun, batteries are required to power the electronic equipment on board satellite. The solar panels can charge a set of NICADs, in addition to powering satellite, for half of each orbit. The NICADs can give the power during the dark half of each orbit.
Nickel cadmium batteries are available in packs of cells. These packs are plugged into the equipment, and may even form part of the case for a device. An instance of this is the battery pack for a handheld ham radio tranceiver. Two of these packs are bought, and they can be used alternately, with 1 installed in the handie talkie while the other is getting charged.
There are things which you should know about NICAD cells and batteries, to get the most out of them.
One rule, which is mentioned, is that you should never discharge them all the way until they die. This can cause polarity of a cell, or more cells in a battery, to reverse. Once this takes place, the cell or battery can be ruined. Another phenomenon, peculiar to this type of cell and battery, is called memory. This is uncommon; lab scientists have trouble forcing it to occur so they can study it. But when it happens, it can give illusion that the cell or battery has lost some of its storage capacity and the memory problems can be solved.
NICADS do best using wall chargers which take several hours to replenish the cells. There are high-rate available, but these can sometimes force too much current through a NICAD. It is best if the charger is made especially for the cell or battery type being charged. An electronics dealer, like the manager at a Radio Shack store, must be able to tell you which chargers are best for which cells.