466 



MECHANICAL AND ACOUSTICAL SENSES 



drop during discharge, environmental effects, and the availability of desired 

 sizes and shapes. The commonly used mercury and silver-oxide cells have 

 been standard in biotelemetric applications, but the recently developed 

 lithium cells appear superior in many respects and may become the standard 

 in the future, especially in applications in which battery cost is not limiting. 

 There seems little reason to consider other battery types for UST use. The 

 common carbon-zinc and alkaline cells, while inexpensive, are poorer in 

 both energy density and voltage stability. A comparison of some primary 

 (nonrechargeable) batteries is given in the following paragraphs, in Table 9, 

 and by HeUer (1975). 



Mercury (mercuric oxide): Frequently used for UST applications because 

 of its compactness, moderately flat voltage discharge curve, and moderate 

 cost. Readily available from several manufacturers in a large variety of 

 sizes and shapes, including series-wired stacks for higher voltages. 



Silver oxide: About the same energy density as mercury but with a higher 

 voltage and a flatter voltage discharge curve. Made only in small sizes (up to 

 160 mAh), therefore not convenient for the main battery for higher powered 

 USTs. Useful for powering sections of circuits where quite stable voltage is 

 needed. 



Lithium: A major improvement over mercury or silver oxide in terms of 

 energy density, especially per unit weight. These cells also possess very flat 

 voltage discharge curves. Lithium -battery chemistry is of two distinct types, 

 the organic-electrolyte type and the inorganic -electrolyte type. At this 

 writing, the former is more readily available and less costly per cell, but the 



Table 9. Performance characteristics of some nonrechargeable types of 

 batteries.* 



*Data from Heller (1975) and various battery, manufacturer specifications. The ranges of 

 voltages and energy densities are due to variations in manufacturer, specific chemistry 

 involved, and size and shape of cell. 



