Electric battery

An electric battery is a source of electric power made up of one or more electrochemical cells. These cells have positive and negative parts called terminals. When a battery powers something, like a flashlight, tiny particles called electrons move from the negative terminal through the device and back to the positive terminal. This movement of electrons is what makes things work.

There are two main types of batteries. Primary batteries, like the small ones used in remote controls or toys, can only be used once and then thrown away. But secondary (rechargeable) batteries, such as those in smartphones or cars, can be plugged in and used again many times. When you recharge a battery, you send electricity back through it, which resets the chemicals inside.

Batteries come in all kinds of sizes and shapes. Some are tiny, like the ones in your hearing aid or watch, while others are huge, big enough to fill a room and keep important places like phone systems running during power outages. Even though batteries don’t store as much energy as fuels like gasoline, they are very good at turning stored energy into power that makes things move or work.

History

Main article: History of the battery

The idea of using electricity stored in devices started with Benjamin Franklin. In 1749, he called a group of special jars a "battery."

In 1800, Alessandro Volta made the first true battery, called the voltaic pile. It was made of layers of copper and zinc with paper soaked in salty liquid in between. This could give a steady flow of electricity.

Over time, scientists made batteries better so they could be used in many everyday devices. Today, batteries are very important for powering cars, homes, and helping manage electricity on power grids. Researchers keep finding new ways to make even better batteries.

Chemistry and principles

Main articles: Electrochemical cell and Voltaic cell

Batteries turn chemical energy into electrical energy. They do this with special reactions between metals, oxides, or molecules. Metals like zinc or lithium can hold a lot of energy because of how their atoms are arranged.

A battery is made of one or more voltaic cells. Each cell has two parts called half-cells. These parts are linked by a special liquid called an electrolyte. The electrolyte helps tiny particles called ions move between the half-cells. One half-cell has the negative electrode, and the other has the positive electrode. When you use the battery, it creates a force called voltage that pushes electricity through a circuit.

Types

See also: Battery nomenclature and List of battery types

Batteries come in two main types: primary and secondary. Primary batteries are used until their energy runs out, and then they are thrown away. They cannot be recharged. Secondary batteries, also called rechargeable batteries, can be charged many times. When you charge a rechargeable battery, you reverse the chemical reactions that happen when it’s used.

Some common primary batteries include zinc–carbon and alkaline batteries, often used in flashlights or remote controls. Rechargeable batteries, like lead–acid, nickel–cadmium, nickel–metal hydride, and lithium-ion, are used in cars, computers, and many portable devices. Each type has its own advantages.

Performance, capacity and discharge

See also: State of charge, Depth of discharge, and Trickle charging

A battery’s performance can change depending on factors like temperature and how much power is being used. In cold weather, batteries don’t work as well, so some people use special heaters to keep car batteries warm.

The capacity of a battery is how much electric charge it can give before its voltage gets too low. Bigger batteries have more capacity than smaller ones, even if they are made of the same materials. Capacity is usually measured in ampere-hours (A·h). For example, a 100 A·h battery can give 5 A of current for 20 hours at normal room temperature. But if you use power faster, the battery will last a shorter time.

Batteries also lose charge over time even when they’re not being used, because of natural chemical reactions inside them. This is called self-discharge. When batteries are recharged many times, their capacity can get smaller until they don’t work well anymore. How fast a battery charges or loses charge is described by its C-rate. A lower C-rate means the battery can give more of its capacity over a longer time, while a higher C-rate allows faster charging but can make the battery last shorter. Recent advances have led to experimental batteries that can charge very quickly, such as prototypes that can reach 80% charge in just a few minutes.

Lifespan and endurance

Battery life means how long a battery can power a device or how many times it can be recharged before it stops working well. For non-rechargeable batteries, like the ones in remote controls, life is just how long they can run before the power runs out. For rechargeable batteries, like those in smartphones, life means how many times you can charge and use them before they wear out.

Some batteries, like the very old Zamboni pile, can last a long time without needing to be recharged, but they don’t give much power. Most batteries lose a little bit of their power each year just sitting on a shelf. This is called “self-discharge.” Storing batteries in a cool place can help them last longer, but they should be brought back to room temperature before use. Different types of batteries last different amounts of time, with some lasting thousands of charges before they need to be replaced.

Hazards

See also: Lithium-ion battery § Safety, and Battery leakage

Batteries can be dangerous if not handled properly. They can sometimes explode if misused, like trying to recharge a battery that cannot be recharged or creating a short circuit. This can happen if a battery is charged too quickly.

Car batteries can also be risky if overcharged, as they may produce explosive hydrogen gas.

If a battery leaks, the chemicals inside can be harmful. It is important to dispose of batteries correctly to protect the environment. Batteries should never be swallowed, especially small button cells, as they can cause damage inside the body.

Legislation and regulation

Laws help keep electric batteries safe. They make sure batteries are thrown away and recycled properly. Some batteries can be dangerous if not handled right.

In the United States, a law from 1996 stopped selling batteries that contain mercury. It also made rules for labeling rechargeable batteries. Places like California and New York City do not allow people to throw away rechargeable batteries in the trash. Many areas have recycling programs for these batteries.

In the European Union, there are rules to help recycle batteries better. Batteries sold in the EU show a special symbol to remind people to recycle them. Starting in 2026, new rules will make it easier for people to remove and replace batteries in many devices.