A photoflash battery is a specialized zinc-carbon battery optimized to provide a high electric current output for a very short time, such as required to fire a flashbulb. Service life for this battery in applications where a lower but continuous current is required, such as for a flashlight with incandescent bulb, is short.

Photoflash cells were in production during the flashbulb era, and were phased out as alkaline cells came into general use, and one-use flashbulbs were replaced by electronic flash. The photoflash cell was produced in 1.5 volt D, C, and AA size.

The cathode of a zinc-carbon cell is usually made of powdered carbon black (or acetylene black), manganese dioxide and electrolyte. The MnO2 to carbon ratio varies between 10:1 and 3:1 for general purpose cells, but a 1:1 mixture is used for photoflash batteries, allowing a high current output with intermittent use, as required for photoflash use. These cells have lower capacity than those with a higher content of MnO2.[1]

Another common type of photoflash battery is a series assembly of cells, often providing 22.5 volts, used in battery–capacitor flash units. The battery slowly charges a capacitor, which is then discharged through a flashbulb to provide a high-current pulse to ignite the bulb.[2] Higher-voltage photoflash batteries were also made to fire reusable xenon electronic flash tubes, which require a high voltage, without the use of circuitry generating this voltage from low-voltage batteries. Eveready battery manufactured the 240-volt Eveready 491 (NEDA 729) battery, and the 497 battery providing 510 volts and 180 volts.

See also

References

  1. David Linden, Thomas B. Reddy (ed). Handbook Of Batteries, 3rd Edition. McGraw-Hill, New York, 2002 ISBN 0-07-135978-8 Chapter 8.
  2. Nikon Flash Unit BC-7 Instruction Manual (PDF)


This article is issued from Wikipedia. The text is licensed under Creative Commons - Attribution - Sharealike. Additional terms may apply for the media files.