Today we are almost as dependent on batteries as we are on electricity. We use batteries everywhere – in our cars, cell phones, laptops, music players. So today we will investigate a little about how the batteries that power our many portable devices work and how we can use them effectively.
The modern development of batteries started in about 1800 when an Italian physicist, Alessandro Volta, invented the Voltaic pile. Volta made a large pile of pairs of alternating metal plates of zinc and silver (electrodes) separated by cardboard soaked in brine (electrolyte). When the top and bottom contacts were connected by a wire, an electric current flowed through the wire and the voltaic pile. Volta worked to measure the electro-force which is now measured in volts, after him. As the pile became higher, the force became stronger. Although in some countries batteries are called “piles” after the Voltaic pile, they are more commonly referred to as “batteries.” This was an expression that was coined by Benjamin Franklin after the term “artillery battery” which refers to a unit of artillery grouped together to facilitate better performance.
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In the most simplistic terms, the battery is a device that converts chemical energy into electrical energy. Today’s batteries like AA, C or D batteries have two terminals or ends. One is a (+) or positive terminal and one is a (-) or negative terminal. The interior of the battery has components that act like the Voltaic pile using a variety of different components, but all having metal for the electrodes and some sort of brine-like material for the electrolyte. The electrodes do not touch each other but are electrically connected by the electrolyte.
When you connect a wire between the negative and positive terminals, the electrons flow from the negative to the positive terminal. When something like a light bulb or electrical device is wired to the battery, it can be powered by the electron flow (i.e., electric current).
The electrical force across the terminals of a cell is known as the terminal voltage and is measured in volts. The force or the voltage is dependent of the chemical reactions inside the cell so using different chemicals can produce differing voltages.
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Batteries today are used in a wide variety of devices. They are classified into two broad categories: Primary and Secondary. These two types of batteries create energy in much the same way. The difference is that in Primary batteries when the supply of chemical reactants is used up, the battery is spent. Secondary batteries can be recharged and reused. This is done by having their chemical reactions reversed by supplying electrical energy to the cell. This restores their original composition and allows them to be reused. However, due to dissipation of the active materials, loss of electrolytes and internal corrosion, these batteries can only be recharged a certain number of times.
The zinc-carbon battery which is also known as a standard carbon battery is used in many inexpensive AA, C and D dry-cell batteries. The electrodes are zinc and carbon. The electrolyte is an acidic paste. These batteries produce 1.5 volts.
Alkaline batteries are commonly used in batteries from companies like Duracell and Energizer. The electrodes are zinc and manganese-oxide. The electrolyte is an alkaline substance. These batteries also have 1.5 volts.
Disposable batteries are shipped ready for immediate use. They are intended to be used until they are drained and then to be discarded. They are most commonly used in portable devices that have a low current drain and/or are used intermittently. These devices include clocks and remote controls. Regular disposable batteries do not fare well in high-drain devices like digital cameras. However, as we shall see later in this tutorial, newer, more high-tech disposable batteries have been developed for high-drain applications.
Secondary batteries are rechargeable.
Lead-acid batteries are used in automobiles. The electrodes are made of lead and lead-oxide. The electrolyte is a strong acid.
In nickel-cadmium (NiCd) batteries the electrodes are nickel-hydroxide and cadmium. Potassium-hydroxide is the electrolyte. NiCd batteries can deliver a high current and can be charged in short time with a high current, but they have one drawback. They suffer from a nasty disadvantage called memory-effect. When a NiCd battery is charged without being completely discharged, crystals grow in the battery. These crystals diminish the capacity of the battery and are difficult to remove. Click here to learn more about this subject.
Nickel-metal hydride (NiMH) batteries are replacing nickel-cadmium because they offer similar properties but do not suffer from the memory effect that plagues nickel-cadmiums.
Both nickel-cadmium and nickel-metal hydride batteries output 1.2 volts, which is slightly less than zinc-carbon or alkaline batteries. All rechargeable batteries lose their charge due to self-discharge. For example when not in use, nickel metal hydride batteries will lose 20% to 50% of their charge within six months due to self]discharge. Factors such as storage temperature can impact the self discharge rate.
Lithium-ion (Li-ion) batteries use lithium and carbon with an electrolyte. They have a very good power-to-weight ratio and fairly slow self-discharge rates when not in use, so they are often used in high-end laptop computers and cell phones.
Rechargeable batteries like NiMH batteries are usually shipped in a discharged state and need to be charged before use, but some pre-charged rechargeable batteries are now becoming available.
There are also several specialized types of batteries, both primary and secondary. Lithium-iodide batteries are often used in pacemakers because of their long life. Zinc-mercury oxide batteries are often used in hearing aids.
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Batteries were invented nearly two centuries ago but they keep getting better and better. Battery manufacturers are refining chemistries and production methods to make batteries last longer and weigh less.
Energizer claims that they have developed the world’s longest lasting AA and AAA batteries. They call these Energizer Ultimate Lithium batteries. They are said to last up to 8x longer than regular batteries and weigh 1/3 less than standard alkaline batteries. They also can perform in extremes temperatures from -40° F to 140° F (-40° C to 60° C). They boast a 15-year storage life and a more leak resistant construction. They are promoted for use in high-tech devices like cameras and MP3 players, handheld GPS devices and photo flash units.
Duracell has a battery called Ultra PowerPix which is designed with their proprietary NiOx technology to release more power for high-drain demand of today’s digital cameras and other devices. They claim that the Ultra PowerPix batteries allow you to take up to twice as many pictures as you can with ordinary alkaline batteries. The PowerPix battery is based on a Nickel Oxy Hydroxide formulation.
Panasonic has Oxyride batteries that use a finer grained graphite and manganese dioxide, permitting more material to be put in each battery. Oxyride batteries also utilize a vacuum-pouring technology that allows more electrolytes to be packed into each battery. These batteries propose to be able to take 2 x more pictures than regular alkaline batteries.
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Here are some facts about batteries you should know.
- All batteries degrade (self-discharge) over time — even if not used.
- The rate of self-discharge is lower at colder tempe
- Although freezing batteries has been used as storage solution, most battery manufacturers do not recommend freezing today’s commercial batteries.
- If you do freeze batteries, they must be allowed to return to room temperature before use.
- Using or storing batteries in high temperatures or using them in low temperatures can affect the voltage of the battery and may reduce battery performance.
- Loose batteries should not be carried in a purse or pocket. The batteries can be short-circuited by metal items such as keys, coins or paperclips. This can make the batteries produce heat that may result in leakage or personal injury.
- Batteries of different chemical compositions should never be mixed within any given device.
- Used batteries should not be mixed with fresh batteries within any given device.
- Rechargeable and non-rechargeable batteries should never be mixed within any given device.
- High drain devices like digital cameras will deplete a battery faster than a low drain device like a clock.
- Alkaline batteries do not leak under normal use or storage. However, the risk of leakage is increased significantly if battery chemistries are mixed within a device or if fresh and used batteries are mixed. High temperatures also increase the possibility of leakage.
- Battery leakage is extremely caustic and should not be allowed to come in contact with bare skin.
- You should never try to charge a primary, non-rechargeable battery. Doing so greatly increases the potential for leakage and rupture.
- To obtain maximum performance, rechargeable batteries that have not been used for an extended period of time should be recharged before being used.
- Batteries should be removed from any device is not expected to be in use for several months.
- All rechargeable batteries should be recycled.