Page 158 - Battery Reference Book

Mercury-indium-bismuth and mercury-cadmium primary batteries 815
other primary systems just would not function. How- 1 .oo
ever, as the temperature drops, the operating volt-
age also drops as expected. Away from these very
low temperaturjes, mercury-indium shows a better 0.80
power-to-volume ratio than mercury-cadmium, and
still gives exceptional perfonnance in difficult environ- - 3 0.60
e
ments. Both these systems also have the advantage of -
I
level voltage discharge characteristics. Typical applica- 8 0.401
lions include reactor and high-temperature processing,
telemetry systems and military uses. 0.201
\
Table 8.2 Performance characteristics of 675
size mercury-zinc primary button cells 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7
Capacity (A h)
Energy density Figure 8.2 Operating characteristics for 0.6A h rnercury-cad-
W hl-1 650 mium cell at various temperatures. Hourly discharge rate is 2% of
W h/kg-' 110 capacity, i.e. C/50 (Courtesy of Crompton-Parkinson)
Voltage
Nominal 1.35
'Workmg 1.25 14
Nominal rate 13
Capacity - 12
m~illcm-l initid 80 2. 11
8 10
Pulse current z9
m.4 per cell 50
'8
Life capacity mA h/ceIl 275 7
Service 0 200 400 600 800 1000 12
625 S2 pert16 h day 8
Shelf years 3 Hours of service at 20 "C
Storage temperature -"C -40 to 60 Figure 8.3 Mallory No. 3041 16,12.6V mercury-cadmium battery;
Operating temperature ("67) -10 to 55 two-stage discharge curve. Current drain at 1 1.5 V: 13 k R,
0.884 mA (Courtesy of Mallory)
Capacity loss per annum
21°C (8) 4
(5-10 years) are its main advantage. These cells also
have inherently better high-temperature storage than
In mercury-cadmium batteries, the battery contains other primary batteries. Operating characteristics of
a cadmium anode (similar to that used in a mercury-cadmium cells are shown in Figure 8.2. The
nickel-cadmiurn cell), a mercuric oxide cathode, low voltage and high cost of materials are the main
and a potassium hydroxide electrolyte. Batteries are drawbacks of the system as a primary battery.
fabricated in prismatic or flat button designs. They Mallory also supply a mercury-cadmium battery in
have an open-circuit voltage of approximately 0.9 V their Duracell range. This battery (No. 304196) is of
and an operating voltage between 0.75 and 0.9V 12.6V with a capacity of 63QmA h to an end-point
depending on the discharge load. Energy densities of 10.3 V, or 900MA h to an end-point of 7.OV, both
for mercury-cadmium systems range between 44 on 13 000Q at 20°C. This cylindrical battery weighs
and 66Wh/kg depending on discharge rate, which 127 g and occupies a volume of 40.5 crn' and is recom-
is lower than that of a mercury-zinc cell. The mended for use in applications such as alarm systems
cell is characterized by good stability because both using voltage-sensitive low-battery indicators. Typical
electrodes exhibit a high degree of insolubility in the two-step discharge characteristics for this battery are
electrolyte. Resulting excellent storage characteristics shown in Figure 8.3.