# How Batteries Work

## Battery Arrangement and Power

In many devices that use batteries -- such as portable radios and flashlights -- you don't use just one cell at a time. You normally group them together in a serial arrangement to increase the voltage or in a parallel arrangement to increase current. The diagram shows these two arrangements.

The upper diagram shows a parallel arrangement. The four batteries in parallel will together produce the voltage of one cell, but the current they supply will be four times that of a single cell. Current is the rate at which electric charge passes through a circuit, and is measured in amperes. Batteries are rated in amp-hours, or, in the case of smaller household batteries, milliamp-hours (mAH). A typical household cell rated at 500 milliamp-hours should be able to supply 500 milliamps of current to the load for one hour. You can slice and dice the milliamp-hour rating in lots of different ways. A 500 milliamp-hour battery could also produce 5 milliamps for 100 hours, 10 milliamps for 50 hours, or, theoretically, 1,000 milliamps for 30 minutes. Generally speaking, batteries with higher amp-hour ratings have greater capacities.

The lower diagram depicts a serial arrangement. The four batteries in series will together produce the current of one cell, but the voltage they supply will be four times that of a single cell. Voltage is a measure of energy per unit charge and is measured in volts. In a battery, voltage determines how strongly electrons are pushed through a circuit, much like pressure determines how strongly water is pushed through a hose. Most AAA, AA, C and D batteries are around 1.5 volts.

Imagine the batteries shown in the diagram are rated at 1.5 volts and 500 milliamp-hours. The four batteries in parallel arrangement will produce 1.5 volts at 2,000 milliamp-hours. The four batteries arranged in a series will produce 6 volts at 500 milliamp-hours.

Battery technology has advanced dramatically since the days of the Voltaic pile. These developments are clearly reflected in our fast-paced, portable world, which is more dependent than ever on the portable power source that batteries provide. One can only imagine what the next generation of smaller, more powerful and longer-lasting batteries will bring.

For more information on batteries and related topics, check out the links below.

### Battery FAQ

##### What is battery energy?
Energy in a battery is expressed in Watt-hours (the symbol Wh), which is the voltage (V) that the battery provides multiplied by how much current (Amps) it can provide for a given amount of time (typically in hours).
##### What are the different types of batteries?
Common battery chemistries (or types) include: zinc-carbon, alkaline, lithium-ion (which are rechargeable), and lead-acid (also rechargeable). Researchers are also currently developing an "air" battery in which the electrodes would be lithium and oxygen from the air.
##### How much is a car battery?
Expect to pay between \$50 and \$120 for a typical car battery and \$90-\$200 or more for one with a longer warranty, better cold-weather performance, or for use in a luxury vehicle.
##### What is the energy source of a battery?
Batteries create energy through an electrochemical reaction. Simply put, the reaction in the anode creates electrons, and the reaction in the cathode absorbs them. The net product is electricity.
##### What type are rechargeable batteries?
The most common rechargeable batteries on the market are lithium-ion (LiOn), though nickel-metal hydride (NiMH) and nickel-cadmium (NiCd) batteries used to be quite prevalent as well.

### More Great Links

Sources

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• "Batteries." Intro to Physical Computing, New York University. April 19, 2011. (June 23, 2011) http://itp.nyu.edu/physcomp/Notes/Batteries
• Brand, Mike, Shannon Neaves, and Emily Smith. "Museum of Electricity and Magnetism." National High Magnetic Field Laboratory. 2011. (June 25, 2011) http://www.magnet.fsu.edu/education/tutorials/museum/index.html
• Buckle, Kenneth. "How Do Batteries Store and Discharge Electricity?" Scientific American. May 29, 2006. (June 23, 2011) http://www.scientificamerican.com/article.cfm?id=how-do-batteries-store-an
• CalRecycle. "Rechargeable Batteries and Chargers: A Personal Perspective." Sept. 9, 2009. (June 25, 2011) http://www.calrecycle.ca.gov/ReduceWaste/power/rechbattinfo.htm
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• Duracell. "Power Education." 2010. (June 23, 2011) http://www.duracell.com.au/en-AU/power-education/index.jspx
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• Environmental Protection Agency. "Batteries." Dec. 1, 2010. (June 22, 2011) http://www.epa.gov/osw/conserve/materials/battery.htm
• Frood, Arran. "Riddle of 'Baghdad's Batteries.'" BBC News. Feb. 27, 2003. (June 23, 2011) http://news.bbc.co.uk/2/hi/science/nature/2804257.stm
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• Manjoo, Farhad. "Better Batteries Will Save the World." Slate. June 21, 2011. (June 23, 2011) http://www.slate.com/id/2297125/
• Rahim, Saqib. "Will Lithium-Air Battery Rescue Electric Car Drivers from 'Range Anxiety?'" The New York Times. May 7, 2010. (June 22, 2011) http://www.nytimes.com/cwire/2010/05/07/07climatewire-will-lithium-air-battery-rescue-electric-car-37498.html?pagewanted=1
• Savage, Neil. "Batteries That Breathe." DiscoveryNews. Feb. 8, 2011. (June 22, 2011) http://news.discovery.com/tech/batteries-that-breathe-110208.html
• University of Hawaii HAM Club. "Batteries in Fact and Fiction." August 1999. (June 22, 2011) http://www.chem.hawaii.edu/uham/bat.html