Battery Hub

Batteries overview

Present in devices the world over, the battery has become a staple of modern living. As a source of portable power it has been implicated in the development of many items that we take for granted, ranging from the handheld torch to the Ipod. Its many applications mean that far from being a humble relic of the pre electrical age, it continues to play a major role in current and future technologies.

In its most basic form, a battery is an electrochemical cell that converts chemical energy into electrical energy by means of negative and positive electrodes. An electrolyte - essentially a liquid that conducts electricity – faciliates the movement of ions between these electrodes, thus producing electrical current via the battery terminals.

In every day use, batteries are commonly classified as “primary” or “secondary” use power sources. Most batteries used in domestic situations, for example, are designed for “once only” (primary) use. When the power has drained from the cell, the battery is discarded and a replacement sought. Rechargeable batteries can – as the name suggests – be restored to a gainful state by recharging them – usually by means of a battery recharging kit.

 

History of the Battery

Before the general adoption of grid power and industrial scale electrical generation, at the end of the nineteenth century, batteries provided the main source of electrical power. What is less well known is that the term “battery” goes back as far as the 18th century. Originally coined by American inventor Benjamin Franklin in 1749, the first “batteries” were little more than capacitors linked together and charged by a static generator. When metal was applied to their electrodes, the capactitors would discharge. The discharge effect was increased when the capacitors were linked together in a “battery”.

The nineteenth century saw many more innovations in the physical sciences, including the pioneering electro magnetic induction work completed by the British scientist Michael Faraday (1791-1867). Elswhere, continental Europe was also playing a significant role in the development of power sources. As early as 1800, Italian physicist Alessandro Volta (1745-1827) invented what is now considered the first battery proper. Fashioned from discs of copper and zinc arranged in an alternating sequence and filled with brine-soaked cardboard layers, the “Voltic Pile” was the first “wet cell” battery to produce a steady supply of current.

Volta’s invention proved to be a turning point in the development of battery technologies. Despite technical flaws that included short circuits borne of leaking electrolytes (the discs arranged in a “stack” would compress the brine cloth), inventors in other parts of the world were inspired to refine the design and look for ways of providing more current over an extended period of time. In 1836, English scientist John F.Daniell constructed a cell (subsequently dubbed the Daniell Cell) that used copper sulfate and zinc sulfate as electrolytes. The experiment was a success – this new battery produced 1.1 volts of power and was able to deliver electrical charge for significantly longer than its venerable predecessor. It also meant that new innovations – such as the telegraph and – eventually – the telephone had a reliable source of power.

The first “dry cell” battery was created by a German scientist in 1887. Carl Gassner’s design did not use a liquid electrolyte. Instead, ammonium chloride (a soluble crystalline salt that was a regular feature of earlier “wet” battery designs) was combined with Plaster of Paris and zinc chloride, which ultimately produced a cell capable of a consistent potential of 1.5 volts – a considerable achievement for the time. The resultant “dry” design gave birth to many of the leading kinds of batteries in use today.

 

Overview of battery types

 

Battery

A battery may refer to any cell that converts chemical energy to electrical energy. Ubiqitous in industry, commerce and domestic settings, batteries are used to provide power sources in a whole of host of places, including personal computers, vehicles, handheld devices and white goods. Common types of batteries include the dry cell zinc chloride batteries and alkaline batteries.

 

Recharageable batteries

Rechargeable batteries are classified as “secondary” cells to distinguish them from their primary – or use once – cousins. In all respects they produce current in the same way as primary cells, but in the case of the rechargeable battery the process of discharge is reversible. As soon as electrical energy from a charger or other source is applied, the flow of electrons (negative to positive in the case of discharge) reverses and the cell is capable of producing power again. Today’s rechargeable battery is usually of the lithium-ion variety – though nickel-cadmium and nickel-metal hydride were also widespread until relatively recently.

 

CR2032 batteries

A favourite amongst horologists, the CR2032 battery – or pen cell battery – is often found in wristwatches and other devices where discrete power sources (such as the “hard” controllers in computers like CMOS chips) that hold charge for a sustained period are required. In general terms a CR2032 battery has a slow and low discharge, which means that the cell maintains a lengthy period of operational life. A single cell lithium battery, the CR2032 is rated at 3.0 volts.

 

Battery Charger

Battery chargers replace the charge in secondary cells by pushing electrical current back through them. At their most basic level, either a constant or pulsed DC power source is forced back into the battery, which then starts to charge. Basic – or simple chargers – do not have the capacity to adjust output relative to the charge in the battery and are not usually supplied with timer devices. For this reason, they usually charge at a slower rate than other types of recharging device and can weaken or destroy a battery’s capacity to “power up” if left charging for too long.

Other types of battery charger include “trickle” chargers and timer-based chargers. The former are usually used for charging batteries with a small capacity – typically 2-30 Ah. They are also used to charge batteries on vehicles as diverse as boats and cars, but given their low current output, largely function as a way of topping up a battery should it be relatively close to full power.

The timer charger allows for charging to be switched off after a set period of time. Although popular in the last decade of the twentieth century, they exhibited limitations if different types of batteries were placed in them for recharging. This was especially true of devices that had “pre-set” timers that were designed with one type of battery in mind. The charger would be designed to switch off after a period of charging time suitable for bringing that specific kind of battery up to full power. When other types of batteries were charged using the same device, they were often either under or overcharged.

 

Laptop Batteries

Modern laptop batteries are lithium-ion batteries. Until comparatively recently however, they were Nickel Cadmium batteries that had the distinct disadvantage of creating environmental hazards when incorrectly disposed of. These were subsequently replaced by Nickel-Metal-Hydride batteries that offered better performance than their immediate predecessors. The current generation of lithium-ion laptop batteries have improved the discharge rate (a measure of how the battery lasts when charged) considerably and represent an equitable balance between price and performance.

Lithium-ion batteries work by forcing lithium ions from the negative to the positive electrode when the battery is discharged. In terms of their capacity to store charge, the highly reactive nature of lithium as an element means that energy can be densely packed into its atomic bonds, hence a standard lithium-ion battery has the capability of storing as much as 150 watt-hours of electricity in just 1 kilogram of battery. For users of mobile computing devices such as laptops the advantages are evident – particularly as batteries such as these have the capacity to deliver hundreds of charging cycles before they are finally disposed of.

 

SR44 batteries

SR44 batteries are a type of silver-oxide cells that are often used in watches and toys. Like their counterparts the LR44s, they offer a long shelf life (and a concomitantly slow discharge rate), which makes them ideal for powering devices that require constant charge to keep them moving. Their physical resemblance to the LR44 “button shape” can lead to a degree of confusion, but the voltage characteristics of each are subtly different and the SR usually has more storage headroom.

 

AA batteries

Ubiquitous in a domestic context, AA batteries are a staple of many pieces of electrical equipment. Consisting of a single cell and a positive and negative terminal, they are one of the most common standard battery sizes available on the market today. The capacity of the AA is dependent on the cell chemistry and the type of battery, but some zinc-chloride or alkaline batteries provide more milliamp hours (mAh) use than the standard zinc-carbon batteries (sometimes between 1000 – 3000 mAh) and are often used for devices that require more power.

AA batteries are also available in rechargeable form, where their relatively low cost and different chemistries (lithium-ion and nickel-cadmium are common) provide a useful alternative to primary cells of the same size.

 

Yuasa Battery

Yuasa batteries are lead-acid batteries manufactured by the Japanese company Yuasa. Used in motorcycles and other areas of the automotive industry, they are also a popular choice in manufacturing. The chemistry of the lead-acid design means these batteries are able to supply surge current, making them popular with engineers who require appropriate power sources for technologies such as starter motors in cars. Starter motors will draw their peak amount of input current when the ignition is first turned, making the lead-acid battery’s ability to meet these “high surge” demands a crucial part of the process of starting the engine.

 

Technical characteristics

A standard battery consists of two electrodes, called an anode and a cathode and a “conducting substance”, or electrolyte. When the battery is placed in a closed circuit, an electron flow is created between the electrodes outside and the electrolyte inside. The net result is that the charge within the battery is discharged and passed to whatever device it is housed in. In effect, the chemical energy store is depleted and turned into electrical power.

The two major types of battery are described as either being “wet” or “dry”. Wet batteries use a liquid form electrolyte and – despite the general shift towards dry cells – are still used in laboratories to demonstrate the fundamental principles of cell-based power and remain popular in the automotive industry.

Dry cells use a composite form of paste as an electrolyte and are sealed in a case with a zinc anode (the positive electrode) and a carbon cathode that forms a central rod down the middle. In a standard  zinc-carbon battery, the electrolyte is usually ammonium-chloride.


Capacity and efficiency

A battery’s capacity is defined as the amount of electrical charge the cell delivers at the voltage at which it is rated. This is dependent on the amount of electrode material occupying the cell, hence smaller cell sizes have a diminishing effect on capacity.

As with all sources of power, variable factors influence the ability to deliver a stored charge at optimum efficiency. Different battery chemistries, the amount of time the battery has spent in storage, and terminal voltage requirements are significant, as is the surrounding temperature in which the battery is required to do the work. Batteries that have been exposed to a long period of storage before commencing their useful life often suffer from reduced capacity, as reactions in the cell destroy charge carriers and lead to what is known as internal self-discharge.

 

Batteries from a manufacturing perspective  

Batteries remain a staple of industrial life. They are used to provide back up in the event of mains failure and are crucial to ensuring continuity of service in sectors such as logistics and manufacturing, where handheld devices are an essential part of checking, picking and despatching goods. There are also numerous applications of cell power of both the primary and secondary types across the entire sphere of human activity, ranging from hearing aids, to computers, to personal entertainment devices.