Life without batteries would be a step back into time, nearly a century ago, when the only source of portable power was steam or clockwork. There would be no cellphones, laptops, no flashlights, no heart pacemakers, hearing aids, portable audio-video recording devices, no portable radios, portable power tools, no electric cars. As a matter of fact, the automobile, as we know it, could not function without a portable power source. Even though they have a huge environmental impact, we could not live our lives without them.
What is a battery? A battery is a self-contained chemical power-pack that can produce a limited amount of electrical energy wherever it is needed. Electricity in your home (alternating current) flows to your home through wires that start off in a power plant. A battery, on the other hand, slowly converts chemicals packed inside it into electrical energy, released over a period of days, weeks, months, or even years.
What are the main parts of a battery? The basic power unit inside a battery is called a cell, which is comprised of three main components. There are two electrodes (electrical terminals) and a chemical called an electrolyte between them. These parts are usually packed inside a metal or plastic outer case. There are two more electrical terminals, marked with a plus (positive) and minus (negative) on the outside connected to the electrodes that are inside.
When you connect a battery’s outside terminals into a circuit (for example, when you place them in a flashlight), the chemicals inside the battery are converted into other substances. Ions (atoms with too few or too many electrons) are formed from the materials in the electrodes and take part in the chemical reactions with the electrolyte. At the same time, electrons flow from one terminal to the other through the external circuit, for example, a flashlight. This process continues until the electrolyte is completely transformed. At that point, the ions stop moving through the electrolyte, the electrons stop flowing through the circuit and the battery is dead.
Why do batteries need two different materials?
The electrodes inside a battery are always made from two dissimilar materials (two different metals), which are conductors of electricity. This is the secret to how and why a battery works. One of the materials gives up electrons and the other material receives them. If both electrodes were made of the same material, there would be no current flow.
To understand this process, we need to go back through the history of electricity to 1792, when Italian scientist Luigi Galvani found he could make electricity from a frog’s leg. Galvani stuck a couple of different materials into a dead frog’s leg and produced an electrical current. He thought he was releasing “animal electricity.” However, as his countryman, Alessandro Volta (the unit of measurement called a volt is named after him) soon realized, the significant fact was that Galvani used two different metals. The frog was merely acting as an electrolyte.
Types of batteries-Batteries come in all shapes, sizes, and capacities (amounts of stored energy). There are two main types of batteries, disposable and rechargeable. With a rechargeable battery, the process of recharging is merely passing a current through it in the opposite direction. You can’t do this with a disposable battery. The three main kinds of disposable batteries are: zinc-carbon, alkaline, and lithium.
Zinc-carbon-The cheapest, everyday battery is a zinc-carbon battery. Disposable zinc-carbon batteries date back to 1865 when they were invented by French engineer Georges Leclanche. They are inexpensive; however, they do not last very long.
Alkaline-These disposable batteries store more energy and last longer. They stay charged for several years. Although they look like zinc-carbon batteries, they use different chemicals and different reactions take place inside them.
Rechargeable batteries-The lead-acid battery has been around since the end of the 19th century. They are rated at 12 volts (6-2 volt cells). Each cell has a lead electrode (negative), a lead-dioxide electrode (positive) and a sulfuric acid electrolyte. Lead-acid batteries make it possible to start our cars without hand-cranking them.
Nickel-Cadmium- these 1.5 volt batteries are used in flashlights, toys, and power tools. Nickel-cadmium batteries should be regularly discharged then recharged.
Nickel-metal-hydride-these batteries work similarly to Nickel-cadmium but suffer less from the “memory effect.” (They won’t fully charge.)
Lithium-ion-These are the fastest growing type of rechargeables. What is so good about Lithium? It is a lightweight metal that easily forms ions, so it is excellent for making batteries. The latest lithium-ion batteries can store twice as much energy as NiCad (nickel-cadmium) batteries and produce higher voltages. However, they have a shorter charge life cycle (they can be charged fewer times) than NiCad batteries.
Measuring batteries-Batteries are like boxes: just as bigger boxes hold more stuff, the size of a battery is a measurement of how much electrical energy it can store. Bigger batteries contain more electrolyte so they can release more energy (or the same energy over a longer period of time). If you want a more precise idea of how much electrical energy a battery holds, look on the side for a measurement in mAh (milliampere hours), which is a measurement of stored electrical charge often printed on small batteries or Watt hours (a measurement of electrical energy used on bigger batteries).