NiCad, Lithium, and NiMH Batteries
Three main types of rechargeable batteries are used in newer technology hand held devices. Scientists are constantly trying to develop batteries with better technologies that make them faster, more powerful, and more lightweight. In the past, the only type of rechargeable battery available was a lead-acid battery, which contains liquid and must be kept ventilated in an upright position. Though still used in autos and motorcycles, scientists have developed gel-batteries, where the liquid is semi-solid and will not spill. These batteries, most commonly used in new had held devices are nickel-cadmium (NiCad), nickel metal-hydride (NiMH), and the newest, Lithium Ion (Li-Ion) batteries. Nickel Cadmium, or NiCad batteries are the least expensive of the three types, because it has the least power.
They are primarily used in portable phones, power tools, and other hand held devices. They are more practical than lead-acid batteries because of their increased power and light weight. They also have an advantage over alkaline batteries which are not usually rechargeable. NiCad are said to be the number one sufferer of the “memory effect” which in fact is really a lazy battery effect, where the battery discharges quickly after being fully charged. A NiCad battery only lasts 1000 full cycles, so eventually they need to be replaced.
NiMh batteries are next of the podium for newer, more powerful batteries. Though similar to the NiCad batteries, NiMh batteries do not contain toxic cadmium, so they are considered more of an environmentally-friendly battery. They are also higher capacity than NiCad and are said not to suffer from the “memory-effect” quite as much. Following the proper steps for charging and discharging in NiMH batteries is very important. NiMh batteries need smart chargers which prevent them from over-charging. It is also important that they are not run flat in a portable device, which creates reverse charging, which can completely damage the battery. Most devices detect safe discharge voltage and shut down automatically. In this case, NiMH batteries are much more effective in high drainage devices like digital cameras, while NiCad batteries are more effective in devices with a fast discharge rate such as power tools. NiMH batteries are also used in hybrid cars. The newest and most powerful of all rechargeable battery types is the Lithium Ion battery.
When compared to NiCad and NiMh batteries, Li-Ion batteries have the highest voltage density and the lowest self-discharge rate. It is the smallest and most light-weight of all the batteries, but all the advantages make it much more expensive as well. New Li-Ion batteries are said to charge 10 times faster than NiMH or NiCad batteries, and does so in a fraction of the time. Li-Ion are extremely susceptible to high temperatures which can great shorten their lifetime. Extremely high temperatures can also cause a Li-Ion battery to explode. Different types of batteries have their advantages and disadvantages. While some offer more convenience and higher capacity, there are still many limitations facing the development of batteries. However, battery technology is improving everyday to help portable devices last longer.
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