Accession Number : AD0427070


Title :   CELL EQUALIZATION TECHNIQUES.


Descriptive Note : Final rept.,


Corporate Author : MALLORY (P R) AND CO INC BURLINGTON MASS


Personal Author(s) : Whoriskey,Peter J


Report Date : Dec 1963


Pagination or Media Count : 28


Abstract : A space vehicle power supply consists of certain types of hermetically sealed alkaline battery cells coupled with solar cells. During usage these alkaline battery cells, series connected, are repeatedly subjected to charge-discharge cycles that can produce cell failure. These failures are, in turn, attributable to inherent cell differences intensified by cycling rate, overall cycling time and depth of discharge. The prime failure modes consist of: (a) unequal cell charge which causes the evolution of gas in sufficient quantities to destroy the cell, and (b) cell reversal on discharge that effectively cancels the cell from the circuit and ultimately results in cell failure. The objectives of this program were, accordingly, to investigate: (1) methods of equalizing the terminal voltage of the individual cells on charge, and (2) methods of preventing cell reversal upon discharge. To achieve cell equalization, the logarithmic forward volt-ampere characteristic of semiconductor P-N junctions was investigated in depth. Semiconductor diodes were designed and tested for specific V-I slopes and current handling capability. Similarly, the anti-reversal approach consisted of utilizing the low forward drop of especially fabricated Ge diodes which were placed across the cell terminals, in parallel to, but in polarity opposing the equalizer diodes. These diode assemblies materially increased the cycle life of Ni-Cd cells. (Author)


Descriptors :   *ALKALINE BATTERIES , STORAGE BATTERIES , SOLAR CELLS , SOLAR CELLS , NICKEL , CADMIUM , SEMICONDUCTOR DIODES , GERMANIUM , LIFE EXPECTANCY(SERVICE LIFE) , SILICON , SILVER , ZINC , BATTERY COMPONENTS


Distribution Statement : APPROVED FOR PUBLIC RELEASE