Linden D., Reddy T.B. (eds.) Handbook of batteries

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MAGNESIUM WATER-ACTIVATED BATTERIES 17.25

Because the salt added to the cathode makes the cathode even more hygroscopic than it

would otherwise be, the batteries are preferably stored with a removable pull-plug used to

seal the holes in the battery case.

The characteristics of the lifejacket lights are given in Table 17.7.

TABLE 17.7 Characteristics of Lifejacket Lights

Electric fuel

model no.

Nominal

voltage, V

Nominal size, cm

Length Width Height

Nominal discharge capacity

Time Wh Normal usage mode

WAB-H12

WAB-H18

WAB-MX8

1.7

3.6

2.9

3.1

1.6

3.3

9.3

9.5

12h

⫹

8h⫹

4.4

3.3

10.7

Aviation/ Marine

Lifejacket light

Aviation

Lifejacket light

Marine

Lifejacket light

Source: Electric Fuel Ltd.

17.6.2 Magnesium/Silver Chloride Batteries

Figure 17.28 illustrates two of the magnesium/ silver chloride batteries currently manufac-

tured. These batteries are used in the following types of applications:

Lifeboat emergency equipment on commercial airlines

Sonobuoys

Radio and light beacons

Underwater Ordnance

Radiosonde units—balloon transport equipment, high altitude low ambient temperature

operation.

FIGURE 17.28 Magnesium/ silver chloride batteries; 12023-1

and 12073.

17.26 CHAPTER SEVENTEEN

17.7 BATTERY TYPES AND SIZES

Although ‘‘standard lines’’ of water-activated batteries were once manufactured, most bat-

teries now are designed and manufactured for speciﬁc applications. Tables 17.8 and 17.9 list

some of the standard and special purpose magnesium/ cuprous chloride and magnesium/

silver chloride batteries that were manufactured. Of these, only the two batteries illustrated

in Fig. 17.28 are currently manufactured.

TABLE 17.8 Magnesium / Cuprous Chloride Water-Activated Batteries

E-P number

Other

designation

Nominal

voltage/

selection, V

Nominal size, cm

Length Width Height

Nominal discharge

capacity

Time Wh Normal usage mode

MAP-12037

MAP-12051

PIBAL

—

3.0

18.0

1.3

6.8

3.2

3.8

5.1

5.7

30 min

120 min

0.8

2.16

Airborne, lighting type

Airborne, radiosonde

MAP-12053 BA-259

A-1.5

B-6.0

冦冧

C-115.0

11.7 10.2 6.0

A-90 min

B-90 min

冦

C-90 min

0.34

1.89

冧

650.4

Airborne, radiosonde

MAP-12060

MAP-12061

MAP-12064

MAP-12071

—

BA-253

—

18.0

22.5

6.0

20.0

5.1

10.2

6.3

5.4

7.0

3.8

7.6

5.1

3.8

16.0

120 min

90 min

45 min

8.1 h

5.4

7.59

2.25

53.46

Airborne, radiosonde

Airborne, lighting, type

Submerged, buoy system

Source: Eagle-Picher Technologies, LLC

TABLE 17.9 Magnesium / Silver Chloride Water-Activated Batteries

E-P number

Other

designation

Nominal

voltage, V

Approximate size, cm

Length Width Height

Nominal discharge capacity

Time Wh Ah

MAP-2023-1 Squib ﬁring

battery

5.5 5.1 2.5 5.4 1 min 0.315 0.0572

MAP-12062

MAP-12065

MAP-12066

MAP-12067

—

MK-72

Squib ﬁring

battery

4.5

7.5

0.75

12.1

6.3

5.1

2.8

dia.

6.7

5.1

dia.

13.9

16.5

2.5

20 min

50 h

14 h

13 s

400

157.5

138

0.0010

8.33

18.4

0.0014

MAP-12069

MAP-12070

MAP-12073

MAP-12074

—

14.5

10.5

7.6

5.1

7.6

4.1

2.5

2.6

2.8

5.1

8.9

5.1

15 h

48 h

1.5

53.2

14.55

95.35

0.15

4.44

Source: Eagle-Picher Technologies, LLC

MAGNESIUM WATER-ACTIVATED BATTERIES 17.27

REFERENCES

1. National Defense Research Committee, Final Report on Seawater Batteries, Bell Telephone Labo-

ratories, New York, 1945.

2. L. Pucher, ‘‘Cuprous Chloride-Magnesium Reserve Battery,’’ J. Electrochem. Soc. 99:203C (1952).

3. B. N. Adams, ‘‘Batteries,’’ U.S. Patent 2,322,210, 1943.

4. H. N. Honer, F. P. Malaspina, and W. J. Martini, ‘‘Lead Chloride Electrode for Seawater Batteries,’’

U.S. Patent 3,943,004, 1976.

5. H. N. Honor, ‘‘Deferred Action Battery,’’ U.S. Patent 3,205,896, 1965.

6. N. Margalit, ‘‘Cathodes for Seawater Activated Cells,’’ J. Electrochem. Soc. 122:1005 (1975).

7. J. Root, ‘‘Method of Producing Semi-Conductive Electronegative Element of a Battery,’’ U.S. Patent

3,450,570, 1969.

8. R. F. Koontz and L. E. Klein, ‘‘Deferred Action Battery Having an Improved Depolarizer,’’ U.S.

Patent 4,192,913, 1980.

9. E. P. Cupp, ‘‘Magnesium Perchlorate Batteries for Low Temperature Operation,’’ Proc. 23d Annual

Power Sources Conf., Electrochemical Society, Pennington, N.J., 1969, p. 90.

10. N. T. Wilburn, ‘‘Magnesium Perchlorate Reserve Battery,’’ Proc. 21st Annual Power Sources Conf.,

Electrochemical Society, Pennington, N.J., 1967, p. 113.

11. W. A. West-Freeman and J. A. Barnes, ‘‘Snake Battery; Power Source Selection Alternatives,’’

NAVSWX TR 90-366, Naval Surface Warfare Center, Silver Spring, Md., 1990.

12. M. G. Medeiros and R. R. Bessette, ‘‘Magnesium-Solution Phase Catholyte Seawater Electrochem-

ical System,’’ Proc. 39th Power Sources Conf., Cherry Hill, N.J., June 2000, p. 453.

13. M. E. Wilkie and T. H. Loverude, ‘‘Reserve Electric Battery with Combined Electrode and Separator

Member,’’ U.S. Patent 3,061,659, 1962.

14. K. R. Jones, J. L. Burant, and D. R. Wolter, ‘‘Deferred Action Battery,’’ U.S. Patent 3,451,855,

1969.

15. H. N. Honor, ‘‘Seawater Battery,’’ U.S. Patent 3,966,497, 1976.

16. H. N. Honer, ‘‘Multicell Seawater Battery,’’ U.S. Patent 2,953,238, 1976.

17. J. F. Donahue and S. D. Pierce, ‘‘A Discussion of Silver Chloride Seawater Batteries,’’ Winter

Meeting, American Institute of Electrical Engineers, New York, 1963.

18. H. R. Knapp and A. L. Almerini, ‘‘Perchlorate Reserve Batteries,’’ Proc. 17th Annual Power Sources

Conf., Electrochemical Society, Pennington, N.J., 1963, p. 125.

19. U.S. Patent No. 5,424,147.

20. Electric Fuel, Ltd., Beit Shemesh, Israel.

21. Eagle-Picher Technologies, LLC, Power Systems Dept., Colorado Springs, CO.

18.1

CHAPTER 18

ZINC/SILVER OXIDE

RESERVE BATTERIES

James M. Dines and Elliott M. Morse

Revised by Curtis Brown

18.1 GENERAL CHARACTERISTICS

An important reserve battery, particularly for missile and aerospace applications, is the zinc/

silver oxide electrochemical system, which is noted for its high-rate capability and high

energy density. The cell is designed with thin plates and large-surface-area electrodes, which

augment its high-rate and low-temperature capability and provide a ﬂat discharge character-

istic. This design, however, reduces the activated or wet shelf life of the battery, necessitating

the use of a reserve-battery design to meet storage requirements.

The zinc/silver oxide electrochemical system was the metallic couple with which Volta

demonstrated the possibility of using dissimilar metals in a ‘‘pile-type’’ multicell construction

to obtain a substantial electric voltage. The system existed somewhat as a laboratory device

until Professor Andre´ designed a practical secondary cell early in World War II.

Subsequent to World War II, the U.S. military became interested in a dry-charged primary

version for use in airborne electronics and missiles because of its very high energy output

per unit weight and volume and high-rate capability. The ultimate result of this interest was

the development of lightweight batteries for the aerospace industry, both military and civilian.

The entire manned space program was keyed to zinc/silver oxide reserve batteries as the

power sources for the various ﬂight vehicles.

Zinc/ silver oxide reserve batteries are divided into two classes, manually activated and

remotely activated. In general the manually activated types are used for space systems and

accessible terrestrial applications and are usually packaged in more conventional conﬁgura-

tions. The remote or automatically activated types are used principally for weapon and mis-

sile systems. This use requires a long period of readiness (in storage), a means for rapid

remote activation, and an efﬁcient discharge at high discharge rates, typically in the 2 to 20-

min. range. The performance of manually activated types ranges from about 60 to 220 Wh

/kg and 120 to 550 Wh/L. For remotely activated types, the speciﬁc energy and energy

density are reduced because of the self-contained activating device and ranges from about

11 to 88 Wh/kg and 24 to 320 Wh/L.

18.2 CHAPTER EIGHTEEN

18.2 CHEMISTRY

The electrochemical reactions associated with the discharge of a zinc/ silver oxide battery as

a primary system are generally considered to proceed as follows. The cathode or positive

electrode is silver oxide and may be either Ag

O (monovalent), AgO (divalent), or a mixture

of the two. The anode or negative electrode is metallic zinc, and the electrolyte is an aqueous

solution of potassium hydroxide. The chemical reactions and the associated voltages at stan-

dard conditions are

Zn ⫹ 2AgO ⫹ HO→ Zn(OH) ⫹ Ag O E ⫽ 1.815 V

222

Zn ⫹ Ag O ⫹ HO→ Zn(OH) ⫹ 2Ag E ⫽ 1.589 V

22 2

The total cell reaction with 31% KOH electrolyte at 25⬚Cis

⫹ AgO ⫹ HO→ Zn(OH) ⫹ Ag E ⫽ 1.852 V

18.3 CONSTRUCTION

A typical assembly of the manually activated reserve zinc /silver oxide cell is shown in Fig.

18.1. These batteries are designed to be ﬁlled with electrolyte, just before use. The conven-

tional cell design is a prismatic container with positive and negative terminals and a com-

bination ﬁll /vent cap. Batteries are formed by connecting single cells in series and packaging

them in a unit container. Batteries used in space programs utilize thin-gauge stainless-steel,

titanium, magnesium or composite containers to minimize weight.

FIGURE 18.1 Typical construction of primary reserve

zinc / silver oxide cell. (Courtesy of Eagle-Picher Industries.)

ZINC / SILVER OXIDE RESERVE BATTERIES 18.3

18.3.1 Cell Components

The components of a reserve zinc/silver oxide cell consist of the positive plates, the negative

plates, and the separators. The components are assembled such that each negative plate is

protected from direct contact with the adjacent positive plate by a separator. The cell com-

ponents are assembled and packaged in a container; the plates can be prepared in either a

dry and charged condition or dry and uncharged condition.

Positive Plates. The positive plates are prepared by applying silver or silver oxide powder

to a metallic grid. Copper, nickel, and silver have all been used for grid material, with silver

the most prevalent for reasons of electrochemical stability and conductivity. After the silver

powder is pressed or sintered to the grid, the plates are electroformed in an alkaline solution,

then washed thoroughly and air-dried at a moderate temperature (usually 20 to 50

⬚C). The

nominally divalent oxide thus formed is relatively stable at ambient temperatures but tends

to lose oxygen and degrade to the monovalent state with increasing temperatures and time.

Continuous exposure to high temperatures (70

⬚C) causes reduction to the monovalent oxide

in a few months.

Negative Plates. The negative plates may be prepared by pasting or pressing zinc powder

or zinc oxide onto a grid or by electroplating zinc from an alkaline bath to form a very

active spongy zinc deposit.

Both positive and negative electrodes may vary in thickness from 0.12 mm as a practical

minimum to 2.5 mm maximum for positives and 2 mm maximum for negatives. The ex-

tremely thin plates are utilized for very short-life, high-discharge-rate automatically activated

batteries; the thick plates are employed in manually activated batteries designed for contin-

uous discharge over several months at very low currents.

Separator Materials. Typical separator materials used in zinc/ silver oxide cells include

regenerated cellulose ﬁlms (cellophane, ﬁber-reinforced or silver-treated cellophane), non-

woven synthetic ﬁber mats of nylon, Dacron, and polypropylene, and nonwoven rayon ﬁber

mats. The synthetic ﬁber mats are frequently placed adjacent to the positives to protect the

cellophane from the highly oxidizing inﬂuence of that material. The cellophane, a semiper-

meable ﬁlm, prevents buildup of particles between plates (while allowing ionic transfer),

thus preventing interplate short circuits. The rayon mat absorbs the electrolyte solution and

distributes it over the plate surfaces. Cells intended for automatic activation normally are not

designed with the ﬁlm separators for they require too long for complete wetting. The open-

mat separators provide sufﬁcient protection from interplate short-circuiting for several hours.

Separator materials are necessary for cell operation because they prevent short circuits,

but they also impede current ﬂow, causing an IR drop within the cell. Very high discharge

rate cells must have very low internal impedance, hence a minimum of separator material.

As a result this type of cell is restricted to very short wet-life applications. The semiper-

meable ﬁlm is the separator which contributes most to IR drop and also to protection against

short circuits. Long-life cells may contain ﬁve or six layers of cellophane. They are therefore

better suited to medium or low discharge rates.

Electrolyte. The electrolyte used for reserve zinc/ silver oxide cells is an aqueous solution

of potassium hydroxide. High and medium discharge rate cells use a 31% by weight elec-

trolyte solution because this composition has the lowest freezing point and is close to the

minimum resistance which occurs at 28 wt. %. Low-rate cells may use a 40–45% solution

since lower rates of hydrolysis of cellulosic separators occur with the higher KOH concen-

trations.

18.4 CHAPTER EIGHTEEN

FIGURE 18.2 Zinc /silver oxide primary reserve battery designed for automatic activa-

tion. (Courtesy of Eagle-Picher Industries.)

18.3.2 High- and Low-Rate Designs

A battery intended to be discharged at a 5 to 60 min. rate is considered a high-rate design.

These cells are designed primarily to deliver high current and require a large plate surface

area. They therefore contain many very thin plates. The separators also have as low an

impedance as possible, that is, one or two layers of cellophane versus ﬁve or six layers for

low-rate cells. The 31% potassium hydroxide electrolyte has a high conductivity and is

therefore employed in high-rate cells.

Low-rate batteries are in a class intended for discharge at rates ranging from 10 to 1000

hours with emphasis on high speciﬁc energy and energy density. The plates are thick (2

mm), and relatively high impedance separator wraps are used. A higher concentration of

electrolyte (40%), which permits a greater Ampere-hour capacity, can also be used. This

design conﬁguration also gives a substantial improvement in the activated or wet stand

capability of the cell.

18.3.3 Automatically Activated Types

The automatically activated type battery is a class of reserve battery intended for quick

preparation for use after an undetermined period subsequent to installation. The very high

energy output of the primary zinc /silver oxide system and the use of an integrally designed

system for injecting the electrolyte into the cells combine to provide an efﬁcient power source

for weapons and other systems requiring a long-term ready state. Figure 18.2 shows a typical

automatically activated battery for a missile application.

ZINC / SILVER OXIDE RESERVE BATTERIES 18.5

Four kinds of activation systems have been utilized in this type of battery for transferring

electrolyte from a reservoir to the cells. All the systems depend on gas pressure to move the

electrolyte, and the most conventional source of gas is a pyrotechnic device.

The ‘‘gas generator’’ is a small cartridge which contains an ignitable propellant material

and an electrically ﬁred ignitor or ‘‘match.’’ Figure 18.3 shows the four types of battery

design.

The tubular reservoir (Fig. 18.3a) can assume many forms. It is usually coiled around the

battery, as shown in Fig. 18.4 (an assembly of a battery with a tubular reservoir), but it can

also be formed with 180

⬚ bends into a ﬂat shape, or it can be conﬁgured to ﬁt into available

nonstandard volumes into which a missile battery is often mounted. The tubular reservoir is

ﬁtted with foil diaphragms at each end. For activation, the gas generator located at one end

can be electrically ignited; the gas causes the diaphragms to break, and the electrolyte is

forced into a manifold which distributes it to the cells of the battery. The piston activator

(Fig. 18.3b) operates by pushing the electrolyte out of a cylindrical reservoir when a gas

generator is ﬁred behind it. The tank activator contains the electrolyte in a variable-geometry

tank with a gas generator located at the top. When the gas enters at the top, the electrolyte

is forced out through an aperture at the bottom. The system is position-sensitive and will

operate properly only when in an upright position relative to the components. The tank-

diaphragm activator (Fig. 18.3d) uses a sphere or spheroid tank with a diaphragm attached

internally at the major circumference. When the gas generator is ﬁred, the diaphragm moves

to the opposite side, forcing the electrolyte out through an aperture in the reservoir side of

the tank.

Of the four systems, the tubular system is the most versatile, but in simple battery shapes

may be heavier. The piston and diaphragm systems have moving parts and thus can be less

reliable; they are also less adaptable to special shapes. The tank is efﬁcient but position-

sensitive.

The operating sequence of an automatically activated battery involves: (1) application of

ignition current, (2) gas generator burning and associated gas production, (3) rupture of a

diaphragm, (4) movement of electrolyte out of the reservoir into the distribution manifold,

and (5) ﬁlling of the cells with electrolyte. In a typical operation the total sequence involves

less than one second. In many applications the electrical load is wired directly to the battery,

and so the battery activates under load. Figure 18.5 shows the rise times of the voltage under

load (A) and under no-load (B) condition for a battery not used until 6 hours later. The

delayed-use battery has ﬁlm separators, and the slower wetting is reﬂected by the longer rise

time.

Automatically activated batteries suffer a weight and volume penalty compared with man-

ually activated types, but the design permits the use of a high-performance battery when

there is no time available to activate manually or the unit is inaccessible. In many applications

both conditions exist. The volume penalty is usually about 2 times, and the weight penalty

about 1.6 times the basic battery. Most automatically activated battery designs utilize an

integral electric heater. The heater maintains the electrolyte at about 40

⬚C or at a temperature

which will raise a cold battery to 40

⬚C when activation occurs. The use of heaters permits

the design of batteries which can meet close voltage tolerances, thus improving the capability

of the weapons’ electric and electronic systems when operating over a wide temperature

range.

18.6 CHAPTER EIGHTEEN

FIGURE 18.3 Schematic drawings of four types of activation systems used in auto-

matically activated batteries. (a) Tubular reservoir. (b) Piston activator. (c) Tank activator.

(d ) Tank-diaphragm activator. (Courtesy of Eagle-Picher Industries.)

FIGURE 18.4 Assembly of automatically activated zinc/ silver oxide primary battery with

tubular coil reservoir. (Courtesy of Eagle-Picher Industries.)

ZINC / SILVER OXIDE RESERVE BATTERIES 18.7

FIGURE 18.5 Voltage rise time for automatically activated zinc/ silver oxide batteries at

25⬚C. (Courtesy of Eagle-Picher Industries.)

18.4 PERFORMANCE CHARACTERISTICS

Zinc/ silver oxide reserve batteries as a class are somewhat unique in that they are almost

entirely committed to speciﬁc applications. These applications require the ﬂat voltage proﬁle

and the high speciﬁc energy and energy density available from this system, and they often

demand a special design for each requirement. If a low-temperature environment is involved,

battery heaters are used. If the discharge requires a wide range of current with only a small

voltage variation, many very thin plates are used. A very high capacity requirement at low

rates requires the use of thick plates and more concentrated electrolyte. There is no standard

design or size because there is no typical application. The applications always demand the

maximum from the battery design in capacity and voltage regulation at a minimum weight

and volume. Multiple batteries are commonly packaged as a single unit, providing a range

of load current and Ampere hour capacity in one convenient package.

18.4.1 Voltage

The open-circuit voltage of the zinc /silver oxide cell will range from 1.6 to 1.85 V per cell.

The nominal load voltage is 1.5 V, and typical end voltages are 1.4 V for low-rate cells and

1.2 V for high-rate cells. At high rates, such as a 5 to 10-min. discharge rate, the output

voltage would be about 1.3 to 1.4 V per cell, whereas the 2-hour rate discharge voltage

would be slightly above 1.5 V. Figure 18.6 shows a family of discharge curves at four

different current densities. The voltage level is inversely related to the current density (cal-

culated from the area of the active plate surface). Thus based on 100 cm

of positive-plate

surface, a 10 A discharge rate would be a 0.1 A /cm

current density. If the discharge rate

is doubled to 0.2 A/ cm

, the voltage level would decrease, and if the rate is lowered to 0.05

A/cm

, the voltage level would increase.

In cell design, the Ampere-hour capacity of the cell is determined by the amount of silver

oxide active material present (zinc active material is provided in excess because of the cost

relationship to silver), but the voltage is determined by the current density. In a ﬁxed volume,

higher discharge rates can be obtained without lowering the battery voltage by using thinner

plates (thus providing more plates per cell element and lowering the current density), but

with a reduction of capacity. The lower the current density at which a battery can operate,

the better the voltage regulation with changing rates of discharge.