Nickel-based cells include the nickel-cadmium (NICAD or NiCd) type and the nickel-metal-hydride (NiMH) type. Nickel-based batteries are available in packs of cells. These packs can be plugged into equipment, and sometimes form part of the case for a device such as a portable radio transceiver. All nickel-based cells are rechargeable, and can be put through hundreds or even thousands of charge/discharge cycles if they are properly cared for.
Configurations and Applications
Nickel-based cells are found in various sizes and shapes. Cylindrical cells look like ordinary dry cells. Button cells are those little things you find in cameras, watches, memory backup applications, and other places where miniaturization is important. Flooded cells are used in heavy-duty applications, and can have storage capacity in excess of 1000 Ah. Spacecraft cells are made in packages that can withstand the rigors of a deep-space environment.
Most orbiting satellites are in darkness half the time and in sunlight half the time. Solar panels can be used while the satellite is in sunlight, but during the times that the earth eclipses the sun, batteries are needed to power the electronic equipment on board the satellite. The solar panels can charge a nickel-based battery, in addition to powering the satellite, for the daylight half of each orbit. The nickel-based battery can provide the power during the dark half of each orbit.
Never discharge nickel-based cells all the way until they totally die. This can cause the polarity of a cell, or of one or more cells in a battery, to reverse. Once this happens, the cell or battery is ruined. A phenomenon peculiar to nickel-based cells and batteries is known as memory or memory drain. If a nickel-based unit is used over and over, and is discharged to the same extent every time, it might begin to die at that point in its discharge cycle. Memory problems can usually be solved. Use the cell or battery almost all the way up, and then fully recharge it. Repeat the process several times.
Nickel-based cells and batteries work best if used with charging units that take several hours to fully replenish the charge. So-called high-rate or quick chargers are available, but these can sometimes force too much current through a cell or battery. It’s best if the charger is made especially for the cell or battery type being charged. An electronics dealer, such as the manager at a RadioShack store, should be able to tell you which chargers are best for which cells and batteries. In recent years, concern has grown about the toxic environmental effects of discarded heavy metals, including cadmium. For this reason, NiMH cells and batteries have replaced NICAD types in many applications. In most practical scenarios, a NICAD battery can be directly replaced with a NiMH battery of the same voltage and current-delivering capacity, and the powered-up device will work satisfactorily.
Some vendors and dealers will call a nickel-based cell or battery a NICAD, even when it is actually a NiMH cell or battery.