The ancestors of today's batteries Radio technology has always been very dependent on batteries . The history of batteries goes back 200 years, twice that of radio itself. During this long period, some very interesting ways of producing an electric current have evolved. There is a common belief that the Operation could be restored by either ing the positive electrode were em- first practical battery was invented by removing the bubbles physically or rest- ployed, as in the Leclanche and Edison Georges Leclanche in 1868, but in fact ing the battery, but these remedies were cells. Leclanche's battery was a relative late- both inconvenient. comer in a long line of developments — The 19th century was the age of indi- Grove's cell some successful, some bizarre, others vidual rather than corporate research, In 1839, Sir William Grove intro- dangerous, but most now forgotten. and experimenters were soon at work duced a cell that performed excellently, The history of the battery actually improving on Volta's pile. Various elec- but was expensive and produced a poi- starts in 1790, when Luigi Galvani of trolytes and electrode materials were sonous gas. Grove's cell consisted of a Bologna was experimenting with mus- tried. Zinc was found to be the most glass jar containing dilute sulphuric acid cles from frog's legs. The story goes satisfactory negative electrode and its and a semicircular amalgamated zinc that he hung them on copper hooks, use was universal. As acids will attack electrode, surrounding a porous earth- suspended from an iron railing. When commercial grade zinc, in some in- enware pot. Inside the pot was a sheet the legs touched the iron, their muscles stances the negative electrode was re- platinum positive electrode and nitric twitched from the stimulus of the elec- moved when the battery was idle, or it acid. Hydrogen from the zinc and tric current produced by contact with was coated with mercury as this was sulphuric acid reaction migrated through the dissimilar metals. found to minimise wastage. Positive the walls of the porous pot to be oxi- Another Italian, Alessandro Volta in- electrodes could be made from copper, dised by the nitric acid, producing water vestigated the phenomenon further and silver, platinum or carbon and did not and nitric oxide fumes. in 1793, created the first battery — his deteriorate. Platinum is not exactly cheap, and the `Crown of Cups'. A row of glass cells One of the earliest developments was German chemist Bunsen substituted a filled with salt water was fitted with al- Wollaston's battery, an adaptation of carbon positive electrode. Both the ternating series-connected copper and the Crown of Cups using jars filled with Grove and Bunsen cells were rated at zinc plates. He discovered that the de- dilute sulphuric acid. The electrodes 1.93 volts and the internal resistance of gree of muscle stimulus was propor- were made as large as possible to lower the 'quart' size (about 1 litre) was only tional to the number of cells. the internal resistance and delay the 0.15 ohms, comparable to a small lead In 1800 Volta produced his 'Pile', a onset of polarisation, and were mounted acid accumulator. These cells had ideal much more compact arrangement. on a frame, so that they could be lifted characteristics for experiments and were Paired discs of copper and zinc were al- out of the electrolyte when not in use. used well into the 20th century for lab- ternated with cardboard discs moistened Mechanical depolarisation was im- oratories and class room demonstra- with acidulated water. Initially, like the practical, and experimenters concen- tions. crown of cups, the pile used containers trated on chemical methods which of dilute acid as terminals. It is worth Edison used a Bunsen battery in his worked by persuading the hydrogen to development of the electric lamp. How- noting that physically Volta's pile was combine with oxygen. This entailed sur- identical to today's standard layer-built ever, nitric acid is a dangerous material, rounding the positive electrode with an and nitric oxide fumes require ventilat- 9.0 volt carbon-zinc batteries — a space oxidising material that reacted with hy- saving method of construction intro- ing. Furthermore, when finished with, drogen — but not at the expense of the the cells had to be dismantled, the nitric duced to radio batteries about 60 years normal operation of the electrolyte. ago. acid and any free mercury bottled, and The first method was to use a liquid the electrodes and pots washed! Polarisation problem oxidiser with a porous container sepa- The Fuller cell substituted a mixture Volta's battery had made possible re- rating it from the acid electrolyte. In of sulphuric and chromic acids for the search into 'current electricity' (as op- one popular variation, the bichromate nitric acid of the Bunsen cell, to pro- posed to 'static electricity'), but it had a cell, the electrolyte and depolariser duce a more docile but still very useful major weakness. Under load, hydrogen were mixed together. A very important source of current. It had the further ad- bubbles built up on the copper elec- type used gravity to separate the liq- vantage that it did not require disman- trode until the current was cut off. uids. Later, solid depolarisers surround- tling. 132 ELECTRONICS Australia, October 1990 was that the zinc electrode had to be re- moved from the liquid 'electrolyte' when the cell was not in use. Known generally as the Bichromate battery, in its original form each cell consisted of a shapely flask with a long wide neck supporting the electrodes. A rod enabled the position of the zinc to be adjusted to give some degree of cur- rent control, or for its complete removal from the electrolyte. The Bichromate battery was used in early radio experiments. Producing about 2 volts per cell, and capable of supplying several amps, it was an inex- pensive and reliable source of power for spark coils used for transmission. Other applications were for powering small Fig.1: Volta's Tile', first made in electric motors and electroplating. 1800. Zinc/copper pairs of discs were Apart from its aesthetic appeal, there alternated with cardboard discs was no particular merit in the fancy bot- moistened with dilute acid. tle and satisfactory home made versions were more mundane. Harmsworth's Bichromate cell 1923 Radio Encyclopedia gives detailed Fig.3: Grenet's Flask or Bottle instructions for making a three-cell Bi- Bichromate Cell. When idle, the zinc It was found that Fuller's cell could chromate battery in jam jars. was withdrawn from the solution by be simplified by eliminating the porous The electrolyte in a freshly charged means of the rod. pot and separate sulphuric acid solution. cell was a most attractive orange colour, see, in its chief application, these were By immersing carbon and zinc elec- and I well remember as a youth making trodes directly in a mixture of dilute not significant problems. a Bichromate cell to provide the 2-volt In its original form, Daniell's cell con- sulphuric acid and either chromic acid filament power for a radio. It was most or potassium bichromate, results were sisted of a copper jar that was also the successful until an accident tipped the positive electrode, containing a satu- comparable to those from a Bunsen electrolyte down the wall. Somehow the cell. The only precaution to be observed rated solution of copper sulphate — the orange-stained wallpaper was not so ap- `bluestone' used in garden sprays. Inside pealing to my parents! a porous central container was the zinc negative electrode and a dilute sulphuric Daniell's cell acid, zinc sulphate or magnesium sul- phate solution. During operation, this We now go back to 1836 and Profes- solution reacted with the zinc to pro- sor Daniell of King's College, London. In that year he invented the principle of electroplating — and, at the same time, what was to be commercially the most important primary battery of all, until the close of the 19th century. Daniell's was unique among the 19th century cells in that the chemical makeup of the electrolytes did not change during operation, and provided that the consumables were replaced and liquid volumes adjusted, output was maintained indefinitely. Furthermore, as no free hydrogen was involved in the reaction, it never polarised. It also used inexpensive materials. Why then, if this was such a paragon of cells, were other types bothered with? Nothing is perfect, and the Daniell cell had limitations. Even in large sizes it had a high internal resistance, some- thing like 50 times that of a bichromate Fig.4: The shape of the zinc upper Fig.2: Bunsen's was a powerful but cell of the same size, severely limiting electrode suggested the name of the noxious cell. The carbon electrode its current capability. The voltage was `Crowfoot' Daniell gravity cell. It used inside the central unglazed only a fraction over 1.0 volt and if it saturated solutions of copper earthenware pot was surrounded by was not kept working, the electrolytes sulphate and zinc sulphate of strong nitric acid. would diffuse. However, as we shall different specific gravities. ELECTRONICS Australia, October 1990 133 VINTAGE RADIO duce zinc sulphate. Hydrogen ions mi- grated to the copper sulphate to pro- duce more sulphuric acid and metallic copper which was deposited on the cop- per electrode. Telegraph power In 1838, Wheatstone in Britain and Morse in America demonstrated the electric telegraph, one of the greatest 19th century inventions. There was an enormous investment in telegraph con- struction, with revenues to match. The telegraph had tremendous social, politi- Fig.5: This 19th century sketch of an elementary series-operation telegraph cal and economic influences, and it lead illustrates that the Crowfoot Gravity was a popular American form of Daniell directly to the development of the tele- battery.