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Understanding Batteries

Introduction
A battery is a portable source of energy. We use batteries to power a wide range of items from our watches to our vehicles. All batteries consist of an anode, a cathode and an electrolyte. The materials that make up those parts, as well as the way the parts are put together, make it possible to choose from a wide variety of batteries with different properties and power capabilities.

Terms:
Anode: An electrode at which an oxidation reaction occurs.
Battery: One or more cells that connect to form one unit—having provisions for external connections. 
Capacity: The ability of the battery or cell to supply current to an external circuit. 
Cathode: An electrode at which a reduction reaction occurs. 
Cell: An electrochemical device which can store electrical energy 
Cycle: A charge followed by a discharge in a rechargeable battery. 
Duty Cycle: The pattern a battery uses that includes charge, overcharge, rest and discharge. 
Electrode: A part of the cell where an electrochemical reaction occurs. 
Electrolyte: An electrical conductor for the movement of ions within a cell. 
Life: The length of time a battery performs and measured in years or charge/discharge cycles. 
Overcharge: The application of charge current after the battery has reached full charge. 
Oxidation: Occurs when the cells active material releases electrons to the external circuit. 
Parallel: To link or interconnect cells or batteries by joining all like terminals. 
Plates: Common name for electrodes. 
Primary Cell/Battery: A cell designed to be used only once and then discarded. 
Rechargeable Battery or Secondary Battery: A battery capable of repeated use because the chemical reactions are reversible. Reduction: The gain of electrons. 
Series: To join or interconnect cells or batteries by connecting the positive terminal of one unit to the negative terminal of the next unit.

How a Battery Works

All batteries work on the principle of converting chemical energy into electrical energy or power. This is accomplished by establishing a flow of negatively charged particles called electrons (e - ). These electrons flow from the anode to the object requiring the power, and then flow back to the cathode. Throughout this process the energy level of the battery steadily decreases. The electrical energy/electron flow continues until the anode can no longer donate electrons and the cathode can no longer accept them. Once this happens, the battery is “dead”—no longer able to provide energy to the equipment.

Types of Batteries

Primary Batteries
Primary batteries are batteries that are discarded once the chemical/electrical energy in them has been used up. There are several different kinds of these disposable batteries:

Alkaline: This is one of the most commonly-used batteries. Alkaline batteries provide long service life for high drain devices such as flash cameras or portable stereos. They are composed of manganese dioxide, graphite, and an electrolyte. The service life is directly related to the purity of materials and the construction of the battery. Alkaline batteries work best within a –4°F to 130°F temperature range. 
Zinc Chloride: Good for moderate- to low-drain uses such as clocks, flashlights and radios. These batteries don’t last as long as alkaline but are generally less expensive than alkaline. Zinc chloride batteries are most effective at a 35°F to130°F temperature range.
Carbon Zinc: This older technology battery has nearly been replaced by alkaline and zinc chloride batteries. These batteries have half the service life of zinc chloride batteries. 
Lithium: Lithium batteries are mainly used when a long shelf and a long service life are required. Products that require battery backup generally use lithium including computers and other electronic equipment. In some instances lithium batteries can be stored for as long as 10 years and still be activated. The temperature range on a lithium battery is 40°F to 185°F.

Secondary Batteries
Secondary batteries can be used repeatedly (charged, discharged and recharged) because the chemical reactions are reversible. The two following battery types are examples of these secondary batteries: 

Lead-Acid: These batteries are extremely durable, have a long service life and account for more than half of the batteries sold worldwide. They are found in automobiles, trucks, forklifts, as well as other high-powered devices. These batteries are comprised of lead components and the electrolyte is sulfuric acid. They are reliable at fairly low to high temperatures. There are two basic types of lead-acid batteries, flooded or sealed. The flooded version is initially less expensive, but may cost more in the long run due to its high level of maintenance. With flooded batteries, the electrolyte level has to be constantly checked and changed. This can be hazardous because of its sulfuric acid content. Sealed batteries can initially cost twice as much as flooded batteries, but require little maintenance. Sealed batteries also have a low-risk factor due to the completely enclosed electrolyte which requires no changing or checking.

Ni-Cad: Ni-Cad batteries are extremely durable batteries used in equipment and can be discharged daily, recharged and used again the next day. Most Ni-Cads can be recharged more than 500 times. Ni-Cads are composed of nickel oxide, cadmium compounds and use potassium hydroxide as an electrolyte. Operating temperature range is –4°F to 140°F. Ni-Cads are ideal for use in low temperatures, displaying very little sluggishness that normally occurs in other types of batteries. Ni-Cads are used in cordless power tools, emergency lights, powered air purifying respirators, telecommunication equipment and more.

Commonly Asked Questions

Sources for more Information

www.rayovac.com

www.tadiranbat.com

www.duracell.com

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