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DISPONIBILI
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ARTICLES IN THE BOOK

  1. AAAA battery
  2. AAA battery
  3. AA battery
  4. A battery
  5. Absorbent glass mat
  6. Alessandro Volta
  7. Alkaline battery
  8. Alkaline fuel cell
  9. Aluminium battery
  10. Ampere
  11. Atomic battery
  12. Backup battery
  13. Baghdad Battery
  14. Batteries
  15. Battery charger
  16. B battery
  17. Bernard S. Baker
  18. Beta-alumina solid electrolyte
  19. Betavoltaics
  20. Bio-nano generator
  21. Blue energy
  22. Bunsen cell
  23. Car battery
  24. C battery
  25. Clark cell
  26. Concentration cell
  27. Coulomb
  28. 2CR5
  29. Daniell cell
  30. Direct borohydride fuel cell
  31. Direct-ethanol fuel cell
  32. Direct methanol fuel cell
  33. Dry cell
  34. Dry pile
  35. Duracell
  36. Duracell Bunny
  37. Earth battery
  38. Electric charge
  39. Electric current
  40. Electricity
  41. Electrochemical cell
  42. Electrochemical potential
  43. Electro-galvanic fuel cell
  44. Electrolysis
  45. Electrolyte
  46. Electrolytic cell
  47. Electromagnetism
  48. Electromotive force
  49. Energizer Bunny
  50. Energy
  51. Energy density
  52. Energy storage
  53. Flashlight
  54. Float charging
  55. Flow Battery
  56. Formic acid fuel cell
  57. Fuel cell
  58. Fuel cell bus trial
  59. Galvanic cell
  60. Gel battery
  61. Grove cell
  62. Half cell
  63. History of the battery
  64. Hybrid vehicle
  65. Lead-acid battery
  66. Leclanché cell
  67. Lemon battery
  68. List of battery sizes
  69. List of battery types
  70. List of fuel cell vehicles
  71. Lithium battery
  72. Lithium ion batteries
  73. Lithium iron phosphate battery
  74. Lithium polymer cell
  75. LR44 battery
  76. Luigi Galvani
  77. Manganese dioxide
  78. Memory effect
  79. Mercury battery
  80. Metal hydride fuel cell
  81. Methane reformer
  82. Methanol reformer
  83. Michael Faraday
  84. Microbial fuel cell
  85. Molten carbonate fuel cell
  86. Molten salt battery
  87. Nickel-cadmium battery
  88. Nickel-iron battery
  89. Nickel metal hydride
  90. Nickel-zinc battery
  91. Open-circuit voltage
  92. Optoelectric nuclear battery
  93. Organic radical battery
  94. Oxyride battery
  95. Panasonic EV Energy Co
  96. Peukert's law
  97. Phosphoric acid fuel cell
  98. Photoelectrochemical cell
  99. Polymer-based battery
  100. Power density
  101. Power management
  102. Power outage
  103. PP3 battery
  104. Primary cell
  105. Prius
  106. Proton exchange membrane
  107. Proton exchange membrane fuel cell
  108. Protonic ceramic fuel cell
  109. Radioisotope piezoelectric generator
  110. Ragone chart
  111. RCR-V3
  112. Rechargeable alkaline battery
  113. Reverse charging
  114. Reversible fuel cell
  115. Searchlight
  116. Secondary cell
  117. Short circuit
  118. Silver-oxide battery
  119. Smart Battery Data
  120. Smart battery system
  121. Sodium-sulfur battery
  122. Solid oxide fuel cell
  123. Super iron battery
  124. Thermionic converter
  125. Trickle charging
  126. Vanadium redox battery
  127. Volt
  128. Voltage
  129. Voltaic pile
  130. Watch battery
  131. Water-activated battery
  132. Weston cell
  133. Wet cell
  134. Zinc-air battery
  135. Zinc-bromine flow battery
  136. Zinc-carbon battery
 



BATTERIES
This article is from:
http://en.wikipedia.org/wiki/Memory_effect

All text is available under the terms of the GNU Free Documentation License: http://en.wikipedia.org/wiki/Wikipedia:Text_of_the_GNU_Free_Documentation_License 

Memory effect

From Wikipedia, the free encyclopedia

 
This article is about the 'memory' observed in batteries. For other uses, see Memory (disambiguation).

The memory effect in electrical batteries, also known as lazy battery effect, is an effect observed in some rechargeable batteries that causes them to hold less charge. The term has become almost universal in describing any such effect, though in its original meaning it describes one very specific case. NiCd batteries gradually lose their maximum energy capacity if they are repeatedly recharged after being only partially discharged. This is termed the memory effect. A major advantage of NiMH battery technology, apart from lack of toxicity, is the absence of any memory effect — NiMH batteries are remarkably tolerant of frequent 'top-up' charging. Lithium ion batteries do not have the memory effect either.


 

Original meaning

Memory effect occurs when a sintered-plate nickel-cadmium (NiCd) battery is repeatedly discharged to a particular level above a full discharge, that is, only "partially used", and then recharged to an equally precise "full" level. This "real" memory effect is extremely rare and is found only on very expensive, rare, and older unattended electronics such as communications satellites (which repeatedly use exactly the same amount of power while in the Earth's shadow). Repeated attempts to duplicate it in the lab have proven difficult.

Voltage depression

A much more common process often ascribed to memory effect is voltage depression. In this case the peak voltage of the battery drops more quickly than normal as it is used, even though the total energy remains almost the same. In modern electronics equipment that monitors the voltage to indicate battery charge, the battery appears to be draining very quickly and therefore about to run out of energy. To the user it appears the battery is not holding its full charge, which seems similar to memory effect. This is a common problem with high-load devices such as digital cameras.

Voltage depression is caused by repeated over-charging of a battery, which causes the formation of small crystals of electrolyte on the plates. These can clog the plates, increasing resistance and lowering the voltage of some individual cells in the battery. This results in a seemingly rapid discharge as those individual cells discharge quickly and the voltage of the battery as a whole suddenly falls. This effect is very common, as consumer trickle chargers typically overcharge.

Possible fixes

There are numerous urban legends suggesting how to fix batteries in which voltage depression has occurred.

(This section needs updating. Information supporting this fix is available in the Gates manual. Also, voltage depression is caused by an alternate chemical reaction, not crystals. The part about cell reversal is true.) There is some scientific basis behind one of the most common recommendations: completely drain the battery in another device in order to dissolve the crystals. In practice, however, this technique more often damages the other cells in the battery pack, considerably shortening battery life. Because some cells may discharge before others, they are charged in reverse by the remaining cells, severely damaging them. To avoid damage to the other cells, each cell must be individually discharged, not the entire pack as a whole.

If your device malfunctions due to memory depression it is the fault of the power supply and charging circuits in the device, not the battery cells or how it's used. The definitive reference for EEs wanting to use NiCd technology has been available since at least 1992 from Gates Energy Products in the Rechargeable Batteries Applications Handbook. There is very little you can conveniently do if your device was designed cheaply or by an ignorant EE.

Wrapping the battery in a plastic bag (to avoid high humidity) and leaving it in a refrigerator overnight helps to 'reset' the battery sometimes.

External links

  • Battery Information
  • Battery FAQs
  • http://forum.notebookreview.com/showthread.php?t=91846
Retrieved from "http://en.wikipedia.org/wiki/Memory_effect"

 


 

 
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