An electric battery comprises one or more electrochemical cells that convert stored chemical energy into electrical energy. Each cell contains a positive terminal, cathode, and a negative terminal, or anode. Electrolytes allow ions to move between the electrodes and terminals, which allows current to flow out of the battery to perform work.
Primary (single-use or “disposable”) batteries are used once and discarded; the electrode materials are irreversibly changed during discharge. Typical examples are the alkaline battery used for flashlights and many portable devices.
Secondary (rechargeable batteries) can be discharged and recharged multiple times; the original composition of the electrodes can be restored by reverse current. Examples include the lead-acid batteries used in vehicles and lithium-ion batteries used for portable electronics.
Batteries come in many shapes and sizes, from small cells used to power hearing aids and wristwatches to battery banks the size of rooms that provide standby power for telephone exchanges and computer data centers.
According to a 2005 estimate, the worldwide battery industry generates US$48 billion in sales annually, with 6% annual growth. Batteries have much lower specific energy (energy per unit mass) than standard fuels such as gasoline. This is somewhat offset by the higher efficiency of electric motors in producing mechanical work compared to combustion engines.
What are some examples of devices that use primary batteries?
Primary batteries, also known as non-rechargeable batteries, are used once and then discarded. They can maintain their charge for long periods when not in use. Here are some examples of devices that often use primary batteries:
- Remote Controls: Many remote controls for TVs, garage doors, or other appliances use primary batteries, often AA or AAA.
- Smoke Detectors: Smoke detectors often use 9-volt primary batteries. Some models can run for several years on a single battery.
- Flashlights: Many flashlights use primary batteries, especially those designed for emergencies, as they can hold their charge for a long time when not in use.
- Portable Radios: Some portable radios, particularly those designed for emergencies, run on primary batteries.
- Clocks: Many wall clocks and alarm clocks run on primary batteries.
- Toys: Many children’s toys run on primary batteries, especially those that don’t require frequent battery changes.
- Medical Devices: Certain medical devices, such as hearing aids, glucose meters, and digital thermometers, often use primary batteries.
- Cameras: Some cameras, particularly disposable or “single-use” cameras, use primary batteries.
- Watches: Many wristwatches use small primary batteries, often button cells.
Remember, while primary batteries can be convenient, they generate a lot of waste since they’re discarded after a single use. Where possible, consider using rechargeable batteries instead. They can be more cost-effective in the long run and are more environmentally friendly.
How are secondary batteries recharged?
Secondary batteries, also known as rechargeable batteries, can be recharged after they have been drained. This is done by applying an external electrical power source to the battery, which reverses the chemical reactions that occur during discharge. Here’s a general overview of how this process works:
- Connection to Power Source: The first step in recharging a secondary battery is to connect it to a power source. This is typically done using a battery charger, designed to supply electricity at the correct voltage and current levels for the specific type of battery.
- Reverse Chemical Reaction: When the battery is connected to the charger, the power source’s electrical energy drives a reverse discharge process reaction. This reverse reaction converts the electrical energy back into chemical potential energy stored within the battery.
- End of Charging Process: As the battery charges, its voltage increases, and the charging current decreases. Most modern battery chargers are designed to detect when the battery is fully charged, either by monitoring the battery voltage or the rate at which the voltage increases. Once the battery is fully charged, the charger will either shut off or switch to a trickle charge mode to maintain its charge without overcharging it.
The exact chemical reactions involved in charging a battery depend on the type of battery. For example, in a lithium-ion battery, the charging process requires lithium ions to move from the positive electrode through an electrolyte to the negative electrode. In a lead-acid battery, the charging process involves the conversion of lead sulfate and water into lead, lead dioxide, and sulfuric acid.
Using the correct charger for the charged battery is essential, as different types of batteries require different charging voltages and currents. Using the wrong charger can damage the battery or even cause safety issues.
What is the specific energy of batteries compared to gasoline?
The specific energy of a substance is the amount of energy stored per unit mass. In the context of batteries and fuels, it measures how much power they can deliver per unit weight.
It is essential to consider that gasoline currently possesses around 100 times greater energy density than lithium batteries. Nonetheless, the efficiency of electric motors in transforming stored energy into motion is remarkably high, usually ranging from 60-80%. This substantially compensates for the contrast in energy density.
Lithium-ion batteries, commonly used in electric vehicles and portable electronics, typically have a specific energy range of 100-265 Wh/kg (watt-hours per kilogram).
On the other hand, gasoline, a standard fuel for internal combustion engines, has a much higher specific energy, around 12,000 Wh/kg.
This difference in specific energy is one of the reasons why gasoline-powered vehicles typically have longer ranges than electric vehicles. However, electric cars and batteries have other advantages, such as higher energy efficiency, lower emissions, and the ability to be recharged with renewable sources.
