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Batteries

A battery is a means of storing electrical energy, usually in a portable form. The term battery was originally coined by Benjamin Franklin to describe an arrangement of multiple Leyden jars (a form of capacitor used to store static electricity). Batteries can be divided into the following categories.







In today’s world all these applications areas are expanding whether it be the demand for electric cars, or laptops that you can use on a 10 hour transatlantic flight assuming that the guy in front of you hasn’t put his seat so far back that you can’t open your notebook…

History of the Battery

It is generally acknowledged that Alessandro Volta at the University of Pavia in Italy invented the first practical multi-cell battery as a means of generating electricity. However, ancient devices looking  remarkably like batteries have been discovered near Baghdad. These devices have the characteristics of a battery: two dissimilar metals separated by an electrolyte. It has been suggested that they might have been used to electroplate jewelry, but there is no actual evidence. The single-cell battery was accidentally invented by Luigi Galvani in Bologna in 1786 when he was experimenting with the nervous systems of frogs (he discovered that touching a nerve with two dissimilar metals caused the frog’s leg to twitch).

In 1803 Nicholson and Carlisle in England were experimenting with the Volta battery and discovered electrolysis (the breaking down of molecules by the passage of electricity; for example, the conversion of water to hydrogen and oxygen). This was the beginning  of electro chemistry that would eventually lead to aluminum smelting, the preparation of elements like potassium, and electroplating.

In 1803 the German physicist Johann Wilhelm Ritter invented the rechargeable battery. Sadly, this never caught on at the time because there was no means of recharging batteries until the generator had been invented.

In 1859 The French inventor Gaston Planté constructed the first practical rechargeable lead acid battery. This is still used in automobiles today.

In 1866 George Leclanché in France invented the first battery that could be produced in commercial quantities. The Leclanché cell had a carbon cathode, a zinc anode and an electrolyte of ammonium chloride solution. The carbon cathode was surrounded by a depolarizer of manganese dioxide in a porous cylinder. Its output was 1.4 V and it was widely used during the early days of telegraphy.

In 1881 Carl Gassner invented the zinc-carbon cell. This was the first commercially successful dry cell battery. Up to this point all batteries involved liquids.

In 1900 Thomas Edison in the USA invented the nickel-cadmium rechargeable battery.

In 1949 the Canadian Lew Urry invented the alkaline battery, although its later versions did not go into large scale production until 1968. This is the type of battery widely used today to power small portable devices (when rechargeable batteries are not used).

In 1979 lithium-ion technology was perfected by John B. Goodenough. This is the basis of batteries in today’s laptops, cell phones, tablets, GPS, and digital cameras.

In 2013 the entire fleet of new Boeing 787 Dreamliners was grounded because of a fire in a lithium cell.  Modern battery technology has been so successful that  it has been incorporated in new aircraft to reduce weight. A series of incidents involving lithium-ion batteries (one incident was a fire) led to the grounding of an entire fleet. This demonstrated that battery technology still has some way to go.

How Batteries Work

A cell is a device that generates electricity by chemical means. If we stack cells together in series (daisy-chaining them together with positive terminal to negative terminal), we get a battery, although in common usage the term battery is used to describe devices with just a single cell. In general, the potential difference across the terminals of a cell is about 1.2 to 3.6 V and larger voltage are created by stacking cells in series; for example, a 9 V battery uses six 1.5 V carbon-zinc cells in series.

A cell consists of three components: a cathode which is the positive pole or terminal of the cell, an anode which is the negative pole of the cell, and an electrolyte which fills the space between anode and cathode and which conducts ions between the anode and cathode. An ion is an electrically charged atom.

A chemical reaction takes place at the anode which causes electrons to flow out of the anode into the external circuit and then back into the cathode. The battery is, therefore, an electron pump.  Positive ions move through the electrolyte from the anode to the cathode. At the cathode the negative electrons flowing in from the external circuit meet the positive ions flowing through the electrolyte where they neutralize each other.

The difference between batteries lies entirely in the form of the anode, cathode and electrolyte. Consider the following examples.

Size

Class

Typical applications

Large

Secondary (rechargable)

Backup power in hospitals, submarines

electric cars

Small

Primary (single use)

Portable appliances

Small

Secondary (rechargable)

Portable appliances

Computers, cell phones, digital cameras

The following diagram illustrates the operation of a cell. An oxidation reaction takes place at the anode and the released electrons travel via the external circuit to the cathode where a corresponding reduction reaction takes place.















Battery Characteristics

The specification of the ideal battery is simple: Its size and weight should be zero. You don’t really want to lug that laptop around, do you? Its cost should be zero. It should have an infinite capacity. Who wants to be in the Gobi desert when their MP3 player stops working?  It should recharge instantaneously. It should also be able to deliver large power surges. A few milliamps will run your digital camera, but you need rather more current to start your Mercedes on a cold morning. Its output voltage should be constant and not decay throughout its life. It should have a low self-discharge current; that is, if you leave it lying around for a hundred years or so, it should still be as good as the day you bought it. Finally, it should be reliable and show no inclination to burst into flame. In practice, we don’t usually get what we want.

Consider the lead-acid cell. It’s really quite horrid. It uses liquid acid in an unsealed container and it gives of hydrogen gas. It is very heavy and the energy stored per unit weight is one of the lowest of all batteries. However, it is very cheap and can supply a the massive current (e.g., 450 A) needed to supply the starter motor in an automobile.

Most batteries used to power laptops and similar devices use lithium ion technology. The energy density of a battery is measured in watt hours per kilogram (Wh/Kg). A battery’s energy density is largely determined by the material of its cathode;  a lithium nickel cobalt cathode has an energy density of 240 Wh/kg which makes lithium ion technology the first choice for designers.

History of Electronics

Semiconductors

Electronic Circuits

Battery

Type

Cathode

Anode

Electrolyte

Cell voltage







Carbon-zinc

Primary

Manganese dioxide

Zinc

Ammonium chloride

1.5 V

Alkaline

Primary

Manganese dioxide

Zinc

Potassium hydroxide

1.5 V

Lithium

Primary

Various

Lithium

Organic

3 V

Mercury

Primary

Mercuric oxide

Zinc

Potassium hydroxide


Zinc air

Primary

Oxygen

Zinc powder

Potassium hydroxide


Lead acid

Secondary

Lead dioxide

Lead

Sulfuric acid


Nickel cadmium (NiCad)

Secondary

Nickel oxyhydroxide

Cadmium

Potassium hydroxide

1.2

Nickel metal hydride (HiMH)

Secondary

Nickel oxyhydroxide

Nickel alloy

Potassium hydroxide


Lithium ion

Secondary

Manganese dioxide

Carbon

Solid material

3.6 V