Building Construction, Renovation, Maintenance & Advice

Batteries

Batteries

All about batteries, how and who invented them, how they work, the ongoing development of batteries, different types of battery and the advantages and disadvantages of them.


See the full Fixed Abode article "Seeking The Holy Frog" here


The Invention of the Electrical Battery

“Heya Luigi, youra frog eet a tweetched.”
“Tweetched? Thata eesa impooossible.
“Heya Luigi, looka ‘ere, eeta tweetched again.”
“Noa mya friend eeta cannot be. You aff beena drinking tooa much offa datah Lemoncello”
“Looka Luigi, Seea ‘ere.”
“Whoa, dat eeza crazey. ‘ow can theesa be? Theesa frog ‘as gone to meet itsa maker, eet eez a very, very latea frog.”

The year was 1780 and the frog in question was being disembowelled by one Luigi Galvani, an Italian who, having just enjoyed a particularly stimulating bottle of Cianti decided to take up an iron scalpel to explore the inner workings of an unfortunate frog which was fastened to a board with a copper hook. Luigi decided the frog contained electricity and this made it twitch.

Luigi’s friend disagreed with the idea that the frog contained electricity, he believed that the twitch was caused by electricity generated by having two different metals (the brass hook and the iron scalpel) connected by a moist interface (the poor unfortunate frog). His name (the friend not the frog) was Alessandro Volta and he was right. In 1800, Alessandro created the world’s first battery by piling up pairs of copper and zinc discs on top of each other, each pair separated by cloth soaked in brine. It was called the Voltaic pile. Now Voltaic piles are not the nicest of things to have but in spite of this his name has become a household word being used for the volt - the measurement of electrical potential we see used on virtually any electrical equipment we use.

How does a battery work

In another article (see article at www.mrfixitbali.com/electrical/electricity-what-is-it-228.html) I bored you to tears with a diatribe about what electricity is, ie. a flow of negatively charged electrons, I also mentioned their tendency to flow from one type of metal to another. This is the principle that Alessandro used to develop the first battery.

We have two electrodes of different metals which are separated by a liquid, a gell or a paste which is called an “electrolyte”. This forms a “cell”. I won’t go into the chemical reactions that take place but all we need to know is that the electrolyte allows, sometimes stimulating and sometimes restricting, electricity to flow from one electrode to the other. The components break down as the electricity passes and the battery is “flat” once the electrolyte or the electrodes are depleted.

Many, many different kinds of batteries have been invented over the years, they all follow the same basic principle but use different materials for the electrodes and electrolyte. The battery has, in may respects, changed the world, they start our cars, power our torches and every mobile device imaginable from mobile phones and laptops to electric toothbrushes, nasal hair removers and vibrators.

Alessandro Volta’s pile, with it’s electrodes of copper and zinc and brine as it’s electrolyte, only lasted about an hour but it gave a constant reliable source of electricity and back in 1800 this was an enormous step forward.

The Develeopment of the Flooded Battery

The next logical step was to lay the pile on its side in a box full of liquid electrolyte, this is known as a “flooded cell” (for rather obvious reasons). A single cell has a voltage of around 2 volts depending on the type of battery.

We can divide this box into seperate sections each is a cell within itself and by connecting these together we can make a “battery” with higher electrical potential (the volts of electricity) produced. 1 cell = 2 volts, 2 cells = 4 volts, car battery 6 cells = 12 volts, etc.

This type of battery has had many developments over the years but really has not changed much at all. It is still used to start our cars and motorbikes.

Different Types of Battery

Many, many different kinds of batteries have been invented over the years and here are some of the more common types:

Primary Batteries

Non rechargeable batteries are known as primary batteries. The most commonly used batteries across the world are primary “dry cell” batteries which come in C, D, AA, AAA, N and 9v (and a couple of other) sizes which are widely used in all sorts of devices including wall clocks, torches, remote controls, etc.

Zinc Carbon and Zinc Chloride batteries

Dr Carl Gassner invented the zinc carbon “dry” cell in 1886 which, until very recently made up the vast majority of disposable household batteries used. The battery is made up of an outer zinc canister (negative electrode) with a carbon rod down the centre (positive electrode). A mixture of powdered carbon and manganese dioxide is packed around the carbon rod which is separated from the zinc canister by paper impregnated with a salty moist paste of ammonium chloride (electrolyte). In the “Heavy Duty” version the ammonium chloride is replaced with zinc chloride.

Alkaline Batteries

Zinc Carbon batteries have been largely replaced by longer lasting and safer “alkaline” manganese batteries invented by Lew Urry in 1949. They are more expensive but have 40% more power than the zinc carbon battery. These have now taken over 80% of the world’s zinc carbon battery market.

Alkaline batteries have a steel outer canister lined with a compressed paste of manganese oxide powder mixed with carbon (positive electrode). In the centre is a gel of zinc powder mixed with potassium hydroxide (negative electrode), the two are separated by a membrane that allows ions to flow between the paste and the gel.

Alkaline batteries are also produced these days as “button” or “coin” batteries for use in watches and other small devices.

Note that the potassium hydroxide is caustic so care is needed if a battery should leak. Also it is dangerous to try to recharge a non rechargeable battery.

A version of the alkaline “dry” battery has been developed that can be recharged.

Secondary Batteries

Rechargeable batteries are known as secondary batteries. The most common ones are:

Lead Acid Battery.

The old trusted lead acid battery was the first rechargeable battery and was invented by Frenchman Gaston Plante way back when Adam was a lad in 1859. They are not very efficient, heavy and contain lead but they are cheap, rugged and reliable and are able to provide bursts of high electrical current. They are still widely used today to start motor vehicles and for powering fork lift trucks, golf carts and the like.

Nickel Cadmium (NiCd) Battery.

Invented by Waldmar Jungner in 1899, they became widely used for all sorts of uses but cadmium is highly toxic and was banned by the European Union in 2004.

Nickel Metal Hydride (NiMH) Battery.

Introduced in 1989 these replaced Nickel Cadmium using a hydrogen absorbing alloy instead of cadmium for the negative electrode.

Lithium Ion (Li-ion) Battery.

Introduced in 1991 Li-ion are very efficient, tough, small, very forgiving when being recharged and retain their charge well when not in use. They have become the battery of choice for most of our consumer electronics.

Energy Density

In many applications the important consideration for any battery is the ratio of the electrical energy it can hold for its weight. This ratio is known as the “Energy Density” of a battery and is measured in watt hours per kilogram (Wh/kg). The pursuit of high energy density is “Seeking the Holy Frog” for battery developers.

Remember early mobile phones - very useful for chocking the back wheel of a broken down truck. It is only the development of smaller, lighter batteries that has made compact mobile phones a reality. Even so vehicles like fork lift trucks still use very heavy large lead acid batteries.

Battery Type Energy Density Wh/kg Volts per cell Comments
Primary Batteries      
Zinc Carbon 36 1.5v Standard dry cell, low cost, low energy density.
Zinc Chloride 45 1,5v "Heavy Duty" dry cell, low cost.
Alkaline Zinc Manganese Dioxide 112-165 1.55v High energy density medium cost.
Silver Oxide 132 1.55v Very expensive, high energy density, used for "button" batteries in watches etc.
Secondary Batteries      
Lead Acid 30-50 2.2v Low cost, low energy density, high toxicity, used for car and motorcycles batteries.
Nickel Cadmium (NiCd) 45-80 1.2v Low cost, moderate energy density, rugged, memory effect, high toxicity, banned.
Nickel Metal Hydride (NiMH) 60-120 1.2v Low cost, high energy density but self discharges, low toxicity.
Lithium Ion (Li-ion) 150-250 3.6v Very expensive, very high energy density, low toxicity, used in laptops, cell phones, etc. Chance of explosion.

New Developments

With a new worldwide push for renewable energy and the inherent need to store energy, battery technology will have a much needed boost. Much of the recent development work has been towards different types of lithium battery there is, of course, the “Saltwater Battery”.

That’s the name but in fact it isn’t. Developed over the last ten years it is an Aqueous Hybrid Ion (AHI) Battery and has a manganese oxide cathode, a carbon composite anode, a synthetic cotton separator and saltwater electrolyte.

These batteries may well be heavy and not very efficient as modern batteries go but, because they are low cost and use non toxic materials, they might prove a turning point in battery development.

It should be noted that the energy density of a ham and cheese sandwich is around 10.13 MJ/kg (that’s about 2,800 watts per kilogram) considerably more than any of the batteries above (is this the holy frog?). Rumour has it that Apple are working on a new battery technology that will allow you to charge your mobile phone and then eat it for lunch.


Copyright © Phil Wilson December 2015
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