Batteries are electochemical cells that store energy for release on demand when a switch is flipped or a circuit is closed. Battery development dates as far back as the late 18th century. The cause was championed by the work carried out by Luigi Galvani from 1780 to 1786. Through his experiments Galvani observed that, when connected pieces of iron and brass were applied to frog's legs, they caused them to twitch. However, Galvani thought that the effect originated in the leg tissue. Nevertheless, Galvani had laid the cornerstone for further developments in "voltaic" electricity.
From 1796 - 1799, Alessandro Volta experimented with zinc and silver plates to produce electric currents at the Pavia University. Volta stacked the two to form a "pile", the first "dry" battery. By 1800 Volta had created the "crown of cups", a modified arrangement of zinc and silver discs dipped in a salt solution.
In the years that ensued, other means of producing electricity were invented, all of which involved the use of liquid electrodes. Those developed by Bunsen (1842) and Grove (1839) were amongst the most successful systems, and, were used for many years.
By 1866, Georges Leclanche, a French engineer, patented a new system, which was immediately successful. In the space of two years, twenty thousand of his cells were being used in the telegraph system. Leclanche's original cell was assembled in a porous pot. The positive electrode consisted of crushed manganese dioxide with a little carbon mixed in. The negative pole was a zinc rod. The cathode was packed into the pot, and a carbon rod was inserted to act as a currency collector. The anode or zinc rod and the pot were then immersed in an ammonium chloride solution. The liquid acted as the electrolyte, readily seeping through the porous cup and making contact with the cathode material. Leclanche's "wet" cell (as it was popularly referred to) became the forerunner to the world's first widely used battery, the zinc carbon cell.
Leclanche's invention, which was quite heavy and prone to breakage, was steadily improved over the years. The idea of encapsulating both the negative electrode and porous pot into a zinc cup was first patented by J.A. Thiebaut in 1881. But, it was Carl Gassner of Mainz who is credited as constructing the first commercially successful "dry" cell. Variations followed. By 1889 there were at least six well-known dry batteries in circulation. Later battery manufacturing produced smaller, lighter batteries, and the application of the tungsten filament in 1909 created the impetus to develop batteries for use in torches.
The production of batteries was greatly increased during the First World War as a means of powering torches, field radios. Other milestones in battery production include the widespread radio broadcasting, which brought battery-operated wireless into the heart of many homes. But, it was during the inter-war years that battery performance was greatly enhanced. This was achieved through better selection of materials and methods of manufacture. Batteries have now become an essential part of everyday life. They are the power source for millions of consumer, business, medical, military and industrial appliances worldwide. This demand is growing. The battery industry is divided into two main sectors.
Prevention of Fire
Since batteries can cause explosion, if involved in a fire, all smoking, open flames and spark producing items such as grinders, welders or other electrical equipment, should be kept well clear of batteries. Non combustible material should be used for the canopies and ducting of lead and other toxic fume extraction systems. General safety aspects for storage of batteries and combustible raw materials like casings etc. should be followed. Also if casing is manufactured inside the battery manufacturing premises, it should be segregated from the rest of the process areas.
Due to the generation of hydrogen in battery manufacturing, this remains as a significant risk in the process which needs to be controlled by proper ventilation and detel OSHA1 states that "Ventilation shall be provided to ensure diffusion of the gasses from the battery and to prevent the accumulation of an explosive mixture." Most references define the explosive lower limit of hydrogen at 4 percent. These regulations are also referenced in the Uniform Fire Code (UFC)2 and the International Fire Code (IFC)3. The IEEE standards4 have established 2 percent as a non-hazardous limit. Those standards are in widespread use by both the Utility and the UPS Industries. The Fire Codes specify the use of an even lower 1 percent hydrogen concentration, or 25 percent of the lower explosive limit (LEL), as an appropriate hydrogen limit in order to determine ventilation requirements. The appropriate IEEE section is quoted completely here: "The battery area shall be ventilated, either by a natural or mechanical system, to prevent accumulation of hydrogen. The ventilation system shall limit hydrogen accumulation to less than 2% of the total volume of the battery area. The location should be free of areas that might collect pockets of hydrogen. Maximum hydrogen evolution rate is 1.27 x 10-7 m3/s (0.000269 ft3/min) per charging ampere per cell at 77oF (25oC) at standard pressure."
Detection of Hydrogen
A hydrogen gas monitor to give an alarm when the concentration goes beyond 1% or 25% of the lower explosive limit is recommended.
The information set out in this document constitutes a set of general guidelines and should not be construed or relied upon as specialist advice. Independent legal advice should always be sought. Therefore Risktechnik accepts no responsibility towards any person relying upon these Risk Management Guides nor any liability whatsoever for the accuracy of data supplied by another party or the consequences of reliance upon it.
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