Linden D., Reddy T.B. (eds.) Handbook of batteries
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SILVER OXIDE BATTERIES 33.21
FIGURE 33.19 Typical charge curve of silver-zinc
battery at 20⬚C, 10-h charge rate.
monovalent to the divalent silver oxide (AgO), which occurs at approximately 1.9 V. It should
be noted that during this transition from the monovalent to the divalent state of charge, a
momentary increase in the charge voltage, of up to 2.00 V, may occur prior to stabilizing at
the 1.90 to 1.95-V plateau. To ensure a full charge, the charging system must be designed
to ignore this temporary rise in voltage.
Charging is normally terminated when the voltage during charge rises to 2.0 V. Above
2.1 V the cell begins to generate oxygen at the silver electrode and/ or hydrogen at the zinc
electrode, decomposing water from the electrolyte. Overcharge is also detrimental to cell life
in that it promotes the growth of zinc dendrites and subsequent short circuits.
The importance of proper charging to the life of these batteries cannot be overemphasized.
Special provisions must be made for those applications which do not permit the use of a
constant current with preset voltage cutoff or a similar controlled charging method.
33.5.3 Cadmium/Silver Oxide Batteries
Except for lower voltages on each of the plateaus (1.2 V on the lower level, 1.5 V on the
upper level), the charging characteristics of the silver-cadmium battery are similar to those
of silver-zinc. A typical charge curve is shown in Fig. 33.20.
As with silver-zinc, silver-cadmium batteries are usually charged at constant current at
the 10 to 20-h rates. The recommended cutoff voltage during charge is normally 1.6 V per
cell.
The silver-cadmium battery, however, is less sensitive to overcharge than the silver-zinc
battery. Other charge methods can be and have been adapted to specific applications.
33.22 CHAPTER THIRTY-THREE
FIGURE 33.20 Typical charge curve of silver-
cadmium cell at 20⬚C, 10-h charge rate.
33.6 CELL TYPES AND SIZES
Tables 33.6 to 33.8 present excerpts from the catalogs of two major silver battery manufac-
turers—Yardney Technical Products Inc., and Eagle-Picher Industries, Inc. They are intended
as a guide only, since the design parameters can be varied to meet specific customer re-
quirements. Many applications for the high-energy silver batteries, in fact, require special
designs, which often dictate new cell case and cover designs and tooling. These then become
the ‘‘available’’ models for future applications.
SILVER OXIDE BATTERIES 33.23
TABLE 33.6 Nominal Characteristics of Typical Vented Zinc / Silver Oxide Batteries
Cell type
Capacity,
Ah
Cell dimensions, mm
including terminals)
Length Width Height
Cell
weight, g
including
electrolyte)
Maximum
continuous
rate, A
HR-02
HR-05
HR-1
HR-2
PMV-2(4.5)*
HR-5
PM-15*
HR-21
PM-30*
HR-40
HR-105
HR-140
PML-170*
HR-190
PML-2500*
0.2
1.3
2.0
4.5
5.0
8.5
21.8
35.9
44.0
46.0
121
190
221
238
2750
5.6
13.7
13.7
15.0
15.2
20.3
20.3
20.6
25.4
25.1
35.2
72.4
35.3
39.4
107.2
16.0
27.4
27.4
43.7
43.7
52.8
58.9
58.4
77.7
82.6
96.9
82.5
97.0
152.6
107.2
49.3
39.6
51.3
63.5
64.3
73.7
125.5
191.5
166.4
180.3
137.4
183.4
184.4
165.4
479.0
6.5
21.3
31.2
68.0
72.6
127.6
295
439
607
646
950
1721
1520
2217
18,150
2.0
4.0
6.0
20.0
100
60.0
200
160
400
200
120
600
120
800
600
Low-rate types
LR-1
LR-4
LR-8
LR-12
LR-40
LR-70
LR-90
LR-190
LR-350
LR-360
LR-660
2.1
7.5
10.0
16.0
64.0
100
155
270
560
570
840
13.7
15.0
16.3
19.1
25.1
36.1
54.9
39.1
107.4
69.9
79.2
27.4
43.7
29.9
47.2
82.6
92.5
82.9
151.6
107.4
147.3
161.3
51.3
85.3
120.1
100.1
180.3
155.4
179.3
162.6
222.3
162.6
177.8
30.1
99.2
116.3
163.0
638
1055
1588
2048
5615
4391
6183
4.5
16.0
16.0
20.0
64.0
160
150
200
350
300
180
Special deep submersible types
LR-700(DS)†
LR-750(DS)†
LR-850-21
LR-875
LR-1000(DS)†
1060
1075
1200
1050
1072
107
142
119
160
137
107
97
114
787
137
486
513
479
183
513
11,200
12,500
13,200
7,000
18,500
900
750
800
125
1250
* Primary, manually activated.
† Pressure compensated
Source: Yardney Technical Products, Inc.
33.24
TABLE 33.7 Nominal Characteristics of Typical Vented Zinc / Silver Oxide Cells
High rate
Cell type
Rated
capacity
Amp-hr
Nominal capacity
Amp-hr rates
15 min. 30 min. 60 min.
Weight,
g
Low rate
Cell type
Rated
capacity
Amp-hr
Nominal capacity
Amp-hr rates
4 hr 10 hr. 20 hr.
Physical dimensions, mm
Weight,
gLWH
SZHR 0.8
1.5
2.8
5.0
6.5
10.5
15
26
48
65
100
140
0.8
1.5
2.8
5.0
6.5
10.5
15
26
48
65
100
140
0.7
1.4
2.6
4.8
6.2
10.0
12
20
*
*
*
*
0.7
1.5
2.7
5.0
6.4
10.3
14
24
40
50
80
*
0.8
1.5
2.8
5.0
6.5
10.5
15
26
48
65
100
140
22.7
39.7
53.9
76.6
119.1
170.2
210.0
312.1
595.9
737.8
1107
1944
SZLR 0.8
1.5
3.0
5.3
7.5
11.5
16.5
30
51
70
115
160
0.8
1.5
3.0
5.3
7.5
11.5
16.5
30
51
70
115
160
0.8
1.5
3.0
5.3
7.4
11.5
15.5
28.0
48
65
100
*
0.8
1.5
3.0
5.3
7.5
11.4
16.5
30.0
51
70
110
150
0.8
1.5
3.0
5.3
7.5
11.5
16.5
30.0
51
70
115
160
22.7
42.6
56.7
85.1
124.8
184.4
215.6
326.3
624.2
780.3
1220
2049
10.9
12.4
14.2
16.3
14.9
20.1
21.3
25.4
18.5
26.9
37.3
74.17
26.9
30.7
35.1
40.1
43.7
49.5
41.1
62.7
89.9
83.1
92.7
75.7
51.6
57.2
63.2
70.9
90.2
84.8
120.7
103.9
167.9
155.4
150.9
161.8
* Not applicable at this rate.
Source: Eagle-Picher Technologies.
SILVER OXIDE BATTERIES 33.25
TABLE 33.8 Nominal Characteristics of Typical Cadmium-Silver Oxide Batteries
Cell type
Capacity,
Ah
Cell dimensions, mm
(including terminals)
Length Width Height
Cell
weight, g
(including
electrolyte)
Maximum
continuous
rate, A
YS-1
YS-3
YS-5
YS-5 (sealed)
YS-10
YS-16 (sealed)
YS-20
YS-40
YS-100
YS-150
YS-300
1.5
4.2
7.8
6.8
14.5
21.0
32
54
132
240
420
13.7
15.2
19.1
20.1
18.8
20.6
43.9
25.1
70.6
45.2
45.2
27.4
43.7
51.1
52.8
58.9
58.4
52.1
82.6
87.4
106.4
106.4
51.3
72.6
73.9
73.9
122.2
146.1
108.7
179.8
122.2
272.0
444.5
31.2
82.2
130.5
141.8
246.7
348.8
450.9
745.9
1503
2978
5190
5.0
12.0
25.0
15.0
30.0
50.0
40.0
100
150
150
150
Source: Yardney Technical Products, Inc.
33.7 SPECIAL FEATURES AND HANDLING
Silver cells are capable of providing extremely high currents if short-circuited. Accordingly,
provisions must be made to insulate all tools used with the batteries and to protect the cells
against grounding in their application.
The electrolyte is a caustic solution of potassium hydroxide. Precautions such as the use
of gloves and safety goggles are required when handling the electrolyte. In most applications,
addition of electrolyte or water is not required. However, the manufacturer’s recommenda-
tions for periodic maintenance and electrolyte checks should be followed closely.
Proper ventilation of these as well as other vented batteries, although not as much a
problem here as with other battery systems, is required to avoid the accumulation of haz-
ardous hydrogen, especially during charge. For larger installations, forced air or fans may
also be required to prevent undesirable temperature buildups. When close voltage regulation
is required at cold temperatures, thermostatically controlled heaters are often used with the
batteries.
Because of the sheer size and power of the batteries used, and because of critical personnel
safety requirements (for example, the U.S. Navy’s NR-1 submersible has a 240-V, 850-Ah
silver-zinc backup battery installed under the deck and venting into the operator’s quarters),
a whole new body of engineering technology has been developed for the application of these
batteries for underwater power. Some of the special features developed include removal of
all mercury, provision for fire walls inside cells, and provision for pressure compensation
for those batteries that are external to the vessels’ pressure hulls.
8
Electronic systems have
also been developed to permit continuous scanning of individual cell voltages to maximize
battery life. Special applications such as these can be successfully developed only if the
battery designers, manufacturers, and users work closely together during the design of the
product.
33.8 APPLICATIONS
Because of the high cost of silver, the major applications of these batteries have historically
been, and continue to be, governmental. However, because of their high power and energy
density, these batteries have found many varied uses where space and weight limitations are
critical. In addition, the cost of silver for most applications can be offset by reclaiming the
metal after the battery completes its useful life.
33.26 CHAPTER THIRTY-THREE
One of the original applications for the silver-zinc battery was for use in torpedoes.
22
Much of the original development work was sponsored by the U.S. Navy. Later, development
expanded to other underwater applications, including mines, buoys, special test vehicles,
swimmer aids, and, at present, deep submergence and rescue vehicles (DSRV), such ex-
ploratory underwater vehicles as UUV and NR-1, and various antisubmarine warfare (ASW)
applications. The MK 66 torpedo battery is illustrated in Fig. 33.21. The discharge rate for
this nominal 245-V battery is 580 A; operating time is 4 min. The deep submergence and
rescue vehicle (DSRV) battery illustrated in Fig. 33.22 is a pressure compensated design
using mineral oil to fill the cell and battery void during ocean descent. It is a 115 V, 700
Ah rated battery and the pressure compensation allows it to be mounted outside of the
pressurized vessel.
FIGURE 33.21 MK 66 torpedo battery. (Courtesy of Yardney Technical Products, Inc.)
Silver-zinc batteries have found wide use on numerous space applications, including
launch-vehicle guidance and control, telemetry, and destruct power: Apollo lunar spacecraft,
lunar and Mars rovers, and lunar drill power; space shuttle payload launch and get-away
special batteries: as well as power for the life-support equipment used by the U.S. astronauts
during Extra-Vehicular Activities (EVA). Figure 33.23 shows a typical aerospace battery
consisting of ten 145-Ah silver-zinc cells housed in a cast magnesium case, equipped with
a pressure relief valve, a pressurizing valve, and a battery connector.
Silver-cadmium batteries have been used in a number of space applications requiring
nonmagnetic properties. One such battery provided the main power for the Giotto Halley
Comet intercept spacecraft.
Ground applications include communications equipment, portable television cameras,
portable lights, camera drives, medical equipment, vehicle motive power, and similar uses
requiring high-energy-density rechargeable batteries.
The user should keep in mind that no one type of battery is suitable for all applications.
Optimum performance of a battery in an application can usually be achieved only by meeting
the critical needs of the application and subordinating the others. The best approach for
battery selection is to work with the battery manufacturers during the early stages of equip-
ment design, rather than asking the battery designers, as is often done, to ‘‘design a battery
that meets all my requirements and fits into this remaining cavity in my equipment.’’
SILVER OXIDE BATTERIES 33.27
FIGURE 33.22 DSRV pressure compensated battery. (Courtesy of Yardney Technical Prod-
ucts, Inc).
33.28 CHAPTER THIRTY-THREE
FIGURE 33.23 Silver-zinc aerospace battery, 15 V, 145 Ah. (Courtesy of Yardney
Technical Products, Inc.)
33.9 RECENT DEVELOPMENTS
The vast majority of recent efforts in secondary silver cells has been concentrated in the
areas of negative electrode and separator improvements for the zinc/silver oxide system
because of its proportionally larger market volume.
7
The major developments are summarized
in Table 33.9. Some of the most recent work has been quite successful, including:
•
Use of bismuth oxide as an inexpensive additive to the zinc electrodes to improve the
capacity retention and the cycle life of the cells.
25
•
The development of new separators, including:
1. Microporous polypropylene with a proprietary coating,
26
which is very thin and has
improved resistance to attack by the electrolyte.
2. A polyolefin film with inorganic fillers, which has demonstrated to more than double
the cycle life of the cells built with it, by inhibiting the ‘‘shape change’’ of the zinc
electrodes.
Both separators are currently costly, and require further development work prior to produc-
tion.
SILVER OXIDE BATTERIES 33.29
TABLE 33.9 Summary of Recent Developments in Silver Oxide Secondary Batteries and Components
Development area Advantages Disadvantages
Zinc electrode
Increased zinc-to-silver-weight ratio Delays onset of capacity losses Gains not proportional to extra
material used; reduces energy
density
Oversized negatives Reduce current density at plate edges
where shape changes start
Reduce energy density
‘‘Contoured’’ negatives Reinforce areas of maximum erosion Reduce energy density; high cost
PTFE binder Reduces shape changes and dendrite
growth; improves low-temperature
performance
High cost; difficult to disperse
evenly; may interfere with normal
electrode reactions
Potassium titanate fibers Reduce shape changes and dendritic
growth; reduce probability of
‘‘hot’’ short circuits
Somewhat higher cost; hazardous
during fabrication; restricted
availability
Lead, lead/ cadmium, bismuth
additives as mercury substitutes
Reduce hazard to health and
equipment in cases of ‘‘hot’’ short
circuits; improve capacity
maintenance
Smaller performance database
Main separator
Inorganic separators Resist temperature above 150⬚C:
resist attack by silver oxides and
electrolyte
High electrolytic resistance; bulky,
difficult to handle: high cost
Cellulosics with metallic groups in
molecule
Improved resistance to attack by
silver oxides and electrolyte:
extend cycle life
Somewhat higher cost
Microporous polypropylene Proven resistance to attack by the
electrolyte
Higher cost
Polyolefin film/ inorganic fillers Major improvement in cycle life High cost; needs additional
development work
Interseparators
Positive: asbestos Prevents or reduces magnitude of
short circuits: acts as silver stopper
Bulky: reacts with silver oxides; may
contaminate cell with iron:
hazardous during fabrication
Zirconium oxide Reduce hazard to health during cell
manufacture
Higher cost
Negative: potassium titanate mat Reduces zinc shape changes; reduces
incidence and magnitude of short
circuits
Bulky; reduces energy density;
somewhat costly; hazardous during
fabrication
Silver electrode
Close control of particle-size
distribution
Improves control of cell voltage and
capacity
Hardware
New plastics for cases and covers
(e.g., modified PPO, polysulfone)
High-temperature operation: better
mechanical properties
Higher cost
New adhesives More efficient at high temperatures:
comply with EPA requirements
33.30 CHAPTER THIRTY-THREE
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th
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