Dry cell

For the heavy metal band, seeDry Cell (band).For prison dry cells, seeDry cell (prison).

Line art drawing of a dry cell: 1. brass cap, 2. plastic seal, 3. expansion space, 4. porous cardboard, 5. zinc can, 6. carbon rod, 7. chemical mixture

Adry cellis a type ofelectric battery,commonly used for portable electrical devices. Unlike wet cell batteries, which have a liquid electrolyte, dry cells use an electrolyte in the form of a paste, and are thus less susceptible toleakage.

The dry cell was developed in 1886 by the German scientistCarl Gassner,after the development of wetzinc–carbon batteriesbyGeorges Leclanchéin 1866. A type of dry cell was also developed by the Japanese inventorSakizō Yaiin 1887.

History

Dry cell battery byWilhelm Hellesen1890

Many experimenters tried to immobilize the electrolyte of an electrochemical cell to make it more convenient to use. TheZamboni pileof 1812 is a high-voltage dry battery but capable of delivering only minute currents. Various experiments were made with cellulose, sawdust, spun glass, asbestos fibers, and gelatine.

In 1886,Carl Gassnerobtained a German patent (No. 37,758) on a variant of the (wet)Leclanché cell,which came to be known as the dry cell because it did not have a free liquid electrolyte. Instead, the ammonium chloride was mixed withPlaster of Paristo create a paste, with a small amount ofzinc chlorideadded in to extend the shelf life. Themanganese dioxidecathode was dipped in this paste, and both were sealed in a zinc shell, which also acts as the anode. In November 1887, he obtainedU.S. patent 373,064for the same device.A dry-battery was invented in Japan during theMeiji Erain 1887. The inventor wasSakizō Yai.However, Yai didn't have enough money to file the patent,the first patent holder of a battery in Japan was not Yai, butTakahashi Ichisaburo.Wilhelm Hellesenalso invented a dry-battery in 1887 and obtainedU.S. patent 439,151in 1890.

Unlike previous wet cells, Gassner's dry cell is more solid, does not require maintenance, does not spill, and can be used in any orientation. It provides a potential of 1.5 volts. The first mass-produced model was the Columbia dry cell, first marketed by theNational Carbon Companyin 1896.The NCC improved Gassner's model by replacing the plaster of Paris with coiled cardboard, an innovation that leaves more space for the cathode and makes the battery easier to assemble. It was the first convenient battery for the masses and made portable electrical devices practical.

Thezinc–carbon cell(as it came to be known) is still manufactured today.

Design

Ray-O-Vac Advertisement USA 1949

A dry cell uses a pasteelectrolyte,with only enoughmoistureto allow current to flow. Unlike awet cell,a dry cell can operate in any orientation without spilling, as it contains no free liquid, making it suitable for portable equipment. By comparison, the first wet cells were typically fragile glass containers with lead rods hanging from the open top and needed careful handling to avoidspillage.Lead–acid batteriesdid not achieve the safety and portability of the dry cell until the development of thegel battery.Wet cells have continued to be used for high-drain applications, such as startinginternal combustion engines,because inhibiting the electrolyte flow tends to reduce the current capability.

A common dry cell is thezinc–carbon cell,sometimes called the dryLeclanché cell,with a nominal voltage of 1.5volts,the same as thealkaline cell(since both use the samezinc–manganese dioxidecombination).

A standard dry cell comprises azincanode,usually in the form of a cylindrical pot, with acarboncathodein the form of a central rod. Theelectrolyteisammonium chloridein the form of a paste next to the zinc anode. The remaining space between the electrolyte and carbon cathode is taken up by a second paste consisting ofammonium chlorideandmanganese dioxide,the latter acting as adepolariser.In some designs, often marketed as "heavy duty", the ammonium chloride is replaced withzinc chloride.

Types

Primary cells are notrechargeableand are generally disposed of after the cell's internal reaction has consumed the reactive starting chemicals.

Secondary cells are rechargeable, and may be reused multiple times.

• Primary cell
  • Zinc–carbon cell
  • Alkaline cell
  • Lithium cell
  • Mercury cell
  • Silver-oxide cell
• Secondary cell
  • Nickel–cadmium cell
  • Lithium-ion cell
  • Nickel–metal hydride cell

See also

• List of battery sizes
• List of battery types
• Rechargeable battery
• Wet cell