DISCHARGE TIME — ^ HOuHS 



Fig, 7 3 Voltage profile of tfiree secondary batteries 



high enough to boil off the electrolyte, deteri- 

 orate the separators or distort the battery 

 case. In deep submersible operations, consid- 

 eration is generally given to low, rather than 

 high temperatures because the operating en- 



vironment is on the low temperature side. 

 Normal operating temperatures of most sec- 

 ondary batteries are between 65° and 90°F. 

 While water temperatures in excess of 90°F 

 are quite unusual, deck temperatures in the 

 tropics can exceed this value and should be 

 considered when the submersible is out of 

 the water. Water temperatures as low as 

 30°F may be encountered in the ocean, and 

 deck temperatures below 0°F can be antici- 

 pated in the high latitudes. Performance 

 data from various cells are presented in Ta- 

 ble 7.3 and show the effects of temperature 

 and discharge rate. The dashes in this table 

 indicate the need for heaters to warm the 

 cells. Cohn and Wetch (1), who present an 

 excellent technical summary of all present 

 and potential undersea power sources, rec- 

 ommend heaters in extreme cold to assure a 

 more normal voltage profile throughout the 

 discharge, and they point out that it is possi- 

 ble to have a higher voltage at cut off than 

 at starting because of the warming of the 

 active surfaces during normal discharge. 



TABLE 7.3 RELATIONSHIP OF TEMPERATURE, DISCHARGE RATE, AND PERFORMANCE 



[FROM REF. (10)] 



321 



