CHAPTER 17 MAGNESIUM WATER-ACTIVATED …chemecar.wikispaces.asu.edu/file/view/water-activated...

17.1

CHAPTER 17MAGNESIUM WATER-ACTIVATEDBATTERIES

Ralph F. Koontz and R. David Lucero

17.1 GENERAL CHARACTERISTICS

The water-activated battery was first developed in the 1940s to meet a need for a high-energy-density, long-shelf-life battery, with good low-temperature performance, for militaryapplications.

The battery is constructed dry, stored in the dry condition, and activated at the time ofuse by the addition of water or an aqueous electrolyte. Most of the water-activated batteriesuse magnesium as the anode material. Several cathode materials have been used successfullyin different types of designs and applications.

The magnesium/silver chloride seawater-activated battery was developed by Bell Tele-phone Laboratories as the power source for electric torpedoes.1 This work resulted in thedevelopment of small high-energy-density batteries readily adaptable for use as powersources for sonobuoys, electric torpedoes, weather balloons, air-sea rescue equipment, py-rotechnic devices, marine markers, and emergency lights.

The magnesium/cuprous chloride system became commercially available in 1949.2,3

Compared with the magnesium/silver chloride battery, this system has lower energy density,lower rate capability, and less resistance to storage at high humidities, but its cost is signif-icantly lower. Although the magnesium/cuprous chloride system can be used for the samepurposes as the magnesium/silver chloride battery, its major application was in airbornemeteorological equipment, where the use of the more expensive silver chloride system wasnot warranted. The cuprous chloride system does not have the physical or electrical char-acteristics required for use as the power source for electric torpedoes. Recently, themagnesium/cuprous chloride chemistry has been developed for aviation and marine lifejacketlights (see Sec. 17.5.5).

Because of the high cost of silver, the impracticality of recovering it after use, othernonsilver water-activated batteries were developed, primarily as the power source for anti-submarine warfare (ASW) equipment.

The systems which have been developed and used successfully are magnesium/lead chlo-ride,4 magnesium/cuprous iodide-sulfur,5–7 magnesium/cuprous thiocyanate-sulfur,8 andmagnesium/manganese dioxide utilizing an aqueous magnesium perchlorate electrolyte.9–11

None of these systems can compete with the magnesium/silver chloride system in almostevery attribute except cost.

Magnesium seawater-activated batteries, using dissolved oxygen in the seawater as thecathode reactant, also have been developed for application in buoys, communications, andunderwater propulsion. These batteries, as well as the use of other metals as anodes forwater-activated batteries, are covered in Chaps. 16 and 38.

17.2 CHAPTER SEVENTEEN

Another seawater battery system being investigated for low rate long duration underseavehicle applications consists of a magnesium anode, a palladium and iridium catalyzed car-bon paper cathode and a solution-phased catholyte of seawater, acid and hydrogen peroxide.The magnesium/hydrogen peroxide system has a voltage of 2.12 volts and is expected tobe capable of more than 500 Wh/kg when configured for large scale unmanned underseavehicles.12

The advantages and disadvantages of the various water-activated magnesium batteries aregiven in Table 17.1.

TABLE 17.1 Comparison of Silver and Nonsilver Cathode Batteries

Advantages Disadvantages

Silver chloride cathodes

ReliableSafeHigh power densityHigh energy densityGood response to pulse loadingInstantaneous activationLong unactivated shelf-lifeNo maintenance

High raw material costsHigh rate of self-discharge after activation

Nonsilver cathodes

Abundant domestic supplyLow raw-material costInstantaneous activationReliable, safeLong unactivated shelf lifeNo maintenance

Requires supporting conductive gridOperates at low current densitiesLow energy density compared to silverHigh rate of self-discharge after activation

17.2 CHEMISTRY

The principal overall and current-producing reactions for the water-activated magnesiumbatteries are as follows:

1. Magnesium/silver chlorideAnode Mg � 2e → Mg2�

Cathode 2AgCl � 2e → 2Ag � 2Cl�

Overall Mg � 2AgCl → MgCl2 � 2Ag2. Magnesium/cuprous chloride

Anode Mg � 2e → Mg2�

Cathode 2CuCl � 2e → 2Cu � 2Cl�

Overall Mg � 2CuCl → MgCl2 � 2Cu

MAGNESIUM WATER-ACTIVATED BATTERIES 17.3

3. Magnesium/lead chlorideAnode Mg � 2e → Mg2�

Cathode PbCl2 � 2e → Pb � 2Cl�

Overall Mg � PbCl2 → MgCl2 � Pb4. Magnesium/cuprous iodide, sulfur


Cathode Cu2I2 � 2e → 2Cu � 2I�

Overall Mg � Cu2I2 → MgI2 � 2Cu5. Magnesium/cuprous thiocyanate, sulfur


Cathode 2CuSCN � 2e → 2Cu � 2SCN�

Overall Mg � 2CuSCN → Mg(SCN)2 � 2Cu6. Magnesium/manganese dioxide


Cathode 2MnO2 � H2O � 2e → Mn2O3 � 2OH�

Overall Mg � 2MnO2 � H2O → Mn2O3 � Mg(OH)2

A side reaction also occurs between the magnesium anode and the aqueous electrolyte,resulting in the formation of magnesium hydroxide, hydrogen gas, and heat.

Mg � 2H O → Mg(OH) � H2 2 2

In immersion-type batteries the hydrogen evolved creates a pumping action which helpspurge the insoluble magnesium hydroxide from the battery. Magnesium hydroxide remainingwithin a cell can fill the space between the electrodes which can become devoid of electro-lyte, prevent ionic flow, and cause premature cell and battery failure.

The heat evolved improves the performance of immersion-type batteries; it enables dunk-type batteries to operate at low ambient temperatures and forced-flow batteries to operate athigh current densities.

Those cathodes containing sulfur exhibit a higher potential versus magnesium than cath-odes possessing only the prime depolarizer. During discharge the sulfur probably reacts withthe highly active copper formed when the prime depolarizer is reduced producing a coppersulfide, thus accounting for the fact that no copper is observed at end of discharge. Thisreaction may also prevent copper from plating out on the magnesium, thus deterring pre-mature voltage drop. In those cases where the battery is allowed to discharge past the pointwhere all prime depolarizer is gone and magnesium is present, hydrogen sulfide can beproduced. Hydrogen sulfide can also result if the cell is short-circuited.

17.3 TYPES OF WATER-ACTIVATED BATTERIES

Water-activated batteries are manufactured in the following basic types:

1. Immersion batteries are designed to be activated by immersion in the electrolyte. Theyhave been constructed in sizes to produce from 1.0 V to several hundred volts at currentsup to 50 A. Discharge times can vary from a few seconds to several days. A typicalimmersion-type water-activated battery is shown in Fig. 17.1.


FIGURE 17.1 Seawater battery, immersion type.

2. Forced-flow batteries are designed for use as the power source for electric torpedoes. Thename is derived from the fact that seawater is forced through the battery as the torpedois driven through the water. Because of the heat generated during discharge and electrolyterecirculation, these systems can perform at current densities up to 500 mA/cm2 of cathodesurface area. Batteries containing from 118 to 460 cells which will produce from 25 to460 kW of power have been developed. Discharge times are about 10–15 min. A dia-grammatic representation of a torpedo battery and a torpedo battery with recirculationvoltage control is shown in Fig. 17.2.

FIGURE 17.2 Diagrammatic representation of torpedo battery construction. (a)Cell construction. (b) Battery configuration.


FIGURE 17.2 (c) Recirculation voltage control (Continued ).

3. Dunk-type batteries are designed with an absorbent separator between the electrodes andare activated by pouring the electrolyte into the battery, where it is absorbed by theseparator. Batteries of this type have been designed to produce from 1.5 to 130 V atcurrents up to about 10 A. Lengths of discharge vary from about 0.5 to 15 h. Figure 17.3is a diagrammatic representation of a magnesium/cuprous chloride battery used in radio-sonde applications. A pile-type construction is used. A sheet of magnesium is separatedfrom the cuprous chloride cathode by a porous separator which also serves to retain theelectrolyte. The cathode is a pasted type made by applying a paste of powdered cuprouschloride and a liquid binder onto a copper grid or screen. The assembly is taped togetherto form the battery. The batteries are also made in spiral or jelly-roll design. (See Figure17.22 for an illustration of this battery.)

FIGURE 17.3 Diagrammatic representation of magnesium/cuprouschloride dunk-type battery. (Courtesy of Eagle-Picher Industries.)


FIGURE 17.4 Basic water-activated cell.

17.4 CONSTRUCTION

Water-activated cells consist of an anode, a cathode, a separator, terminations, and someform of encasement. A battery consists of a multiplicity of cells connected in series or series-parallel. Such an assembly requires a method to connect the cells in the desired configurationplus a method to control leakage currents. The voltage of a cell depends primarily on theelectrochemical system involved. To increase voltage, a number of cells must be connectedin series. The capacity of a cell in ampere-hours is primarily dependent on the quantity ofactive material in the electrodes. The ability of a cell to produce a given current at a usablevoltage depends on the area of the electrode. To decrease current density so as to increaseload voltage, the electrode area must be increased. Power output depends on the temperatureand salinity of the electrolyte. Power output can be increased by increasing the temperatureor the salinity of the electrolyte.

The basic components of a single cell, a duplex assembly for connecting cells in series,and a finished battery are illustrated in Figs. 17.4, 17.5, and 17.1, respectively.12–16 Theillustrations represent batteries designed for use by immersion in the electrolyte as contrastedto a dunk-type (radiosonde) battery, which is activated by pouring the electrolyte into thebattery, or a forced-flow electric torpedo battery. The construction principles with slightvariations are similar in all cases.


FIGURE 17.5 Duplex electrode assemblies. (a) Silver. (b) Nonsilver.

17.4.1 Components

A more detailed description of the various cell and battery components and constructionelements follows.

Anode (Negative Plate). The anode is made from sheet magnesium. Magnesium AZ61Ais preferred because it tends to sludge and polarize less. In some cases AZ31B alloy is used;however, this alloy gives slightly lower voltage, polarizes at high current densities, andsludges more. In recent years magnesium alloys AP65 and MTA75 have been developed and


evaluated. These are high-voltage alloys giving load voltages of 0.1–0.3 V higher thanAZ61A. MTA75 is a higher-voltage alloy than AP65. These alloys sludge more; however,under some forced-flow discharge conditions, the sludging problem may be controlled. Thesealloys are not used extensively in the United States; however, they are used in the UnitedKingdom and Europe in electric torpedo batteries. Composition ranges of these alloys areshown in Table 17.2.

TABLE 17.2 Composition Range for Battery Plate Alloys

Element

AZ31

% Min. % Max.

AZ61

% Min. % Max.

AP65

% Min. % Max.

MELMAG 75

% Min. % Max.

AlZnPbTlMnSiCaCuNiFe

2.50.6——

0.15—————

3.51.4

——

0.70.10.040.050.0050.006

5.80.4——

0.15——

0.05——

7.21.5

——

0.250.050.30.050.0050.006

6.00.54.4

—0.15

——

0.005——

6.71.55.0

—0.300.30.3

—0.0050.010

4.6——6.6——0.3———

5.60.3

—7.60.250.3

——

0.0050.006

Cathode (Positive Plate). The cathode consists of a depolarizer and a current collector.These depolarizers are powders and are nonconductive. In order for the depolarizer to func-tion, a form of carbon is added to impart conductivity; a binder is added for cohesion, anda metal grid is used as a current collector, a base for the cathode, to facilitate intercelconnections and battery terminations. Possible cathode formulations are shown in Table17.31,3–5,8

TABLE 17.3 Cathode Compositions

Silverchloride1

Cuprousiodide5,6

Cuprousthiocyanate8

Leadchloride4

Cuprouschloride

Depolarizer, %/w 100 73 75–80 80.7–82.5 95–100Sulfur, %/w — 20 10–12 — —Additive, %/w — — 0–4 2.3–4.4 —Carbon, %/w — 7 7–10 9.6–9.8 —Binder, %/w — — 0–2 1.5–1.6 0–5Wax, %/w — — — 3.8 —

Silver chloride is a special case. Silver chloride can be melted, cast into ingots, and rolledinto sheet stock in thicknesses from about 0.08 mm up. Since this material is malleable andductile, it can be used in almost any configuration. Silver chloride is nonconductive and ismade conductive by superficially reducing the surface to silver by immersion in a photo-graphic developing solution. No base grid need be used with silver chloride.

Nonsilver cathodes are usually prismatic in shape and are flat. Silver chloride cathodesare used flat and corrugated in many configurations.


Separators. Separators are nonconductive spacers placed between the electrodes of im-mersion- and forced-flow-type batteries to form a space for free ingress of electrolyte andegress of corrosion products. Separators in the form of disks, rods, glass beads, or wovenfabrics may be used.13–14

Dunk-type batteries utilize a nonwoven, absorbent, nonconductive material for the dualpurpose of separating the electrodes and absorbing the electrolyte.

Intercell Connections. In a series-arranged battery of pile construction, the anode of onecell is connected to the cathode of the adjacent cell. To accomplish this without producinga short-circuited cell, an insulating tape or film is placed between the electrodes on nonsilverbatteries. For silver batteries silver foil is used alone or in conjunction with an insulatingtape.

For nonsilver cells the connection is made by stapling the electrodes together through theinsulator.15 For silver cells, the silver chloride, surface-reduced to silver, is heat-sealed tosilver foil, which has been previously welded to the anode. Where large surface areas areinvolved, contact between silver and silver foil can be made by pressure alone.

Terminations. For silver chloride cathodes the lead is soldered directly to silver foil, whichhas been heat-sealed to one surface of the silver chloride. Leads are soldered directly to thecollector grid of nonsilver cathodes or soldered to a piece of copper foil, which has beenstapled to the collector grid.

The anode connection is made by soldering the lead to silver foil, which has been weldedto the anode, or by welding directly to the anode.

Encasement. The battery encasement must effectively rigidize the battery and provideopenings at opposite ends to allow free ingress and egress of electrolyte and corrosionproducts.

The periphery of the battery must be sealed in such a manner that the cells contact theexternal electrolyte only at the openings provided at the top and bottom of the battery. Theencasement can be accomplished by using premolded pieces, caulking compounds, epoxyresins, an insulating sheet, or hot-melt resins.13–16 For single-batteries these precautions arenot necessary.

17.4.2 Leakage Current

All the cells in the immersion- and forced-flow-type batteries operate in a common electro-lyte. Since the electrolyte is conductive and continuous from cell to cell, conductive pathsexist from each point in a battery to every other point. Current will flow through theseconductive paths to points of different potential. This current is referred to as ‘‘leakagecurrent’’ and is in addition to the current flowing through the load. Electrodes must bedesigned to compensate for these leakage currents.

Leakage currents for a small number of cells can be reduced by increasing the resistancepath from a cell to the common electrolyte or that of the common electrolyte betweenadjacent cells. Leakage currents for a large number of cells can be reduced by increasingthe resistance of the common electrolyte external to the individual cells.

By construction the conducting paths from cell to cell are made as long as possible. Inmany instances the negative or positive of the battery is connected to an external metalsurface. Leakage currents flow from the battery to this surface. These leakage currents arecontrolled by placing a cap containing a slot over the battery openings. If one terminal isconnected to an external conductive surface, the slot in the cap is opened to the electrolyte


only on that side of the battery. Where neither terminal is connected to an external conductivesurface, either end of the cap may be opened; however only that on one side of the batteryshould be opened.

The resistance (ohms) of the slot in the cap may be calculated using the formula

lR � p

a

where R � resistance, �l � length of slot, cma � cross-sectional area of slot, cm2

p � resistance of electrolyte for temperature and salinity in which battery is operat-ing, � � cm

For dunk-type batteries the electrolyte continuity from cell to cell is broken when theelectrolyte is absorbed in the separator. The excess is poured off the battery or spun awayfrom the cells by some external force applied to the battery.

17.4.3 Electrolyte

Seawater-activated batteries are designed to operate in an infinite electrolyte, namely, theoceans of the world. However, for design, development, and quality control purposes, it isnot practical to use ocean water. Thus it is common practice throughout the industry to usea simulated ocean water. A commercial product, composed of a blend of all the ingredientsrequired, simplifies the manufacture of simulated ocean water test solutions.

Dunk-type batteries, activated by pouring the electrolyte into the battery where it is ab-sorbed by the separator, can utilize water or seawater when the temperature is above freezing.At lower temperatures special electrolytes can be used. The use of a conducting aqueouselectrolyte will result in faster voltage buildup. However, the introduction of salts in theelectrolyte will increase the rate of self-discharge.

17.5 PERFORMANCE CHARACTERISTICS

17.5.1 General

A summary of the performance characteristics of the major water-activated batteries currentlyavailable is given in Table 17.4.

Voltage versus Current Density. Figures 17.6 and 17.7 are representative voltage versuscurrent density curves for several water-activated battery systems at 35 and 0�C, respectively,using a simulated ocean water electrolyte.

Discharge Curves. Discharge curves of the magnesium/silver chloride, magnesium/cuprous thiocyanate-sulfur, magnesium/cuprous iodide-sulfur, and magnesium/lead chlorideelectrochemical systems, discharged continuously through various resistances in simulatedocean water and high and low temperatures and salinities, are shown in Figs. 17.8 to 17.15.These data show the advantageous performance of the silver chloride system.

Service Life. The capacities per unit of weight versus the average power output of thesesame electrochemical systems, at high and low temperatures and salinities, are shown in Fig.17.16 and 17.17.


TABLE 17.4 Performance Characteristics of Water-Activated Batteries

CathodeSilver

chlorideLead

chlorideCuprousiodide

Cuprousthiocyanate

Cuprouschloridea

Anode MagnesiumElectrolyte Tapwater, seawater, or other conductive aqueous solutionsOpen-circuit voltage, V 1.6–17 1.1–1.2 1.5–1.6 1.5–1.6 1.5–1.6V per cell at 5 mA/cm2 b 1.42–1.52 0.90–1.06 1.33–1.49 1.24–1.43 1.2–1.4

Activation, s:35�Cc �1 �1 �1 �1RT d — — — — 1–100�Ce 45–90 45–90 45–90 45–90

Internal resistance, � f 0.1–2 1–4 1–4 1–4 2Ah/g cath. theor.g 0.187 0.193 0.141 0.220 0.271Usable capacity, % of

theoretical60–75 60–75 60–75 60–75 60–75

Wh/kg 100–150 50–80 50–80 50–80 50–80Wh/L 180–300 50–120 50–120 50–120 20–200Operating temperatures, �C h �60 to �65

a All but cuprous chloride are immersion type. Cuprous chloride is dunk type.b See voltage vs. current density curves.c Battery preconditioned at �55�C, then immersed in simulated ocean water of 3.6 wt.%d Electrolyte at room temperature poured into battery and absorbed by separator.e Battery preconditioned at �20�C, then immersed in simulated ocean water of 1.5 wt. %.f Depends on battery design.g 100% active material.h Following activation at room temperature.

FIGURE 17.6 Representative cell voltages vs. current density at 35�C.


FIGURE 17.7 Representative cell voltages vs. current density at 0�C.

FIGURE 17.8 Magnesium/ silver chloride seawater-activated cell discharged continuously at 35�Cin simulated ocean water, 3.6% salinity.


FIGURE 17.9 Magnesium/ silver chloride seawater-activated cell discharged continuously at 0�Cin simulated ocean water, 1.5% salinity.

FIGURE 17.10 Magnesium/cuprous thiocyanate seawater-activated cell discharged continuouslyat 35�C in simulated ocean water, 3.6% salinity.


FIGURE 17.11 Magnesium/cuprous thiocyanate seawater-activated cell discharged continuously at0�C in simulated ocean water, 1.5% salinity.

FIGURE 17.12 Magnesium/cuprous iodide seawater-activated cell discharged continuously at35�C in simulated ocean water, 3.6% salinity.


FIGURE 17.13 Magnesium/cuprous iodide seawater-activated cell discharged continuously at0�C in simulated ocean water, 1.5% salinity.

FIGURE 17.14 Magnesium/ lead chloride seawater-activated cell discharged continuously at 35�Cin simulated ocean water, 3.6% salinity.


FIGURE 17.15 Magnesium/ lead chloride seawater-activated cell discharged continuously at 0�Cin simulated ocean water, 1.5% salinity.

FIGURE 17.16 Capacity vs. power output of seawater-activated cells discharged continuouslyat 35�C in simulated ocean water, 3.6% salinity.


FIGURE 17.17 Capacity vs. power output of seawater-activated cells dischargedcontinuously at 0�C in simulated ocean water, 1.5% salinity.

17.5.2 Immersion-Type Batteries

The performance of these same systems, designed as immersion-type batteries to meet thephysical, electrical, and environmental specifications listed in Table 17.5, is shown in Figs.17.18 to 17.20. The performance characteristics are summarized in Table 17.6.

TABLE 17.5 Performance Specifications for Seawater-Activated Battery

Load 80 � 2 �Life 9 hVoltage 15.0 V in. from 90 s to 9 h

19.0 V max.Activation* 60 s to 13.5 V

90 s to 15.0 V

Battery size: Silver NonsilverHeight, cm 7.7 max. 10.6 max.Width, cm 5.7 max. 7.6 max.Thickness, cm 4.2 max 5.7 max.Weight, g 255 � 14 482 � 85

Environmental:Storage From �60 to �70�C for 5 years†

90 days at �50 to �40�C at 90% RH (see Table 17.5)10 days per MIL-T-5422E (see Table 17.5)

Vibration, Hz 5–500

Electrolyte:Low temperature Ocean water of 1.5% salinity by weight at 0 � 1�CHigh temperature Ocean water of 3.6% salinity by weight at �34 � 1�C

* Battery preconditioned at �20�C prior to immersion in ocean water of 1.5% salinity by weightat 0 � 1�C.

† In equipment packed in sealed plastic container with appropriate desiccant.


FIGURE 17.18 Discharge curves of seawater-activated batteries at 35�C.

FIGURE 17.19 Discharge curves of seawater-activated batteries at 0�C.


FIGURE 17.20 Discharge curves of seawater-activated batteries, 10-day humidity.

TABLE 17.6 Performance Summary of Seawater-Activated Batteries

Silverchloride

Cuprousiodide

Cuprousthiocyanate

Leadchloride

Number of cells 11 12 13 16

Battery dimensions:Height, cm 7.5 9.8 10.2 10.5Width, cm 5.5 7.6 7.4 7.5Thickness, cm 3.9 4.4 5.7 4.5Weight, g 252 516 478 458

Activation:Low temp.:

To 13.5 V, s �15 �15 �15 �15To 15.0 V, s 60 60 60 15

High temp.:To 15.0 V, s �1 �1 �1 �1

Life:High temp., h 9.67 9.4 9.3 9.5Low temp., h 9.80 10.3 10.3 10.7

Load resistance (per cell), �* 7.27 6.67 6.15 5.0Cutoff voltage (per cell), V* 1.364 1.25 1.154 0.9375Average current, A 0.206 0.220 0.236 0.219Average volts per cell, V* 1.497 1.463 1.378 1.048Wh/L 204 110 90 100Wh/kg 130 70 79 75

* As each battery system contains a different number of cells, cell load resistances and cellvoltages are different for each battery.


17.5.3 Forced-Flow Batteries

With the development of the recirculation system in which the inflow of fresh electrolytecan be controlled, thereby maintaining the temperature and conductivity of the electrolyte,the performance of electric torpedo batteries has been improved markedly. With recirculationand flow control, a recirculation pump (see Fig. 17.2) and a voltage-sensing mechanism areadded to the battery system. By this method the temperature of the battery and the conduc-tivity of the seawater electrolyte increase. Since battery voltage increases directly with tem-perature and conductivity, it is possible to control the output of the battery by controllingthe intake of electrolyte by means of the voltage-sensing mechanism.

The performance of one type of torpedo battery with and without recirculation voltagecontrol is shown in Fig. 17.21.17 The blocked-in area represents the limits within which anelectric torpedo battery with recirculation and flow control will perform when dischargedunder any of the conditions shown by the three individual curves. All voltages pertinent tothe start and finish of the battery are shown by the three individual curves.

FIGURE 17.21 Discharge curves of torpedo battery—effect of recirculation and flow control.

17.5.4 Dunk-Type Batteries

Magnesium/Cuprous Chloride Batteries. The magnesium/cuprous chloride battery waswidely used in applications requiring low-temperature performance, such as radiosondes,having replaced the more expensive magnesium/silver chloride system in applications whereweight and volume are not critical. Figure 17.22 illustrates a typical magnesium/cuprouschloride battery. The pile-type construction shown in Fig. 17.3 is used.

The battery is activated by filling it with water, and full voltage is reached within 1 to10 min. The battery is best suited for discharge at about the 1–3-h rate at temperatures from�60 to �50�C after activation at room temperature. Overheating and dry-out will occur onhigh current drains, and self-discharge limits the life after activation. For best service thesebatteries should be put into use soon after activation. The heat that is developed duringdischarge can be used to advantage in batteries which are operated at low temperatures;therefore, the energy output varies little with decreasing temperature. Figure 17.23 showsthe discharge curve for this battery at various temperatures. Figure 17.24 gives some typicaldischarge curves for this type of battery with a similar design at various discharge loads.


FIGURE 17.22 Magnesium/cuprous chloride radiosonde bat-tery. Size: 10.2 � 11.7 � 1.9 cm; weight: 450 g, rated capacity:A1 section—1.5 V, 0.3 Ah; A2 section—6.0 V, 0.4 Ah; B section—115 V, 0.08 Ah.

FIGURE 17.23 Discharge curves of magnesium/cuprous chloride ra-diosonde battery, 115-V section; discharge load: 3050 �.


FIGURE 17.24 Discharge curves of magnesium/cuprous chloride water-activated batteries at20�C; electrolyte: tapwater.

Magnesium/Manganese Dioxide Battery. This reserve battery consists of a magnesiumanode and a manganese dioxide cathode.10,18 It is activated by pouring an aqueous magne-sium perchlorate electrolyte into the cells of the battery, where it is absorbed by the sepa-rators. Electrolyte absorption occurs within a few seconds at 0�C or above, but 3 min ormore are required at �40�C due to the viscosity of the electrolyte.

The battery can deliver between 80 and 100 Wh/kg over the temperature range of �40to �45�C at the 10–20-h discharge rate. Over 75% of the battery’s fresh capacity is availableafter 7 days’ activated stand at 20�C and 4 days’ storage at 45�C. Typical discharge curvesare shown in Fig. 17.25 for a five-cell 10-Ah battery, weighing about 1 kg and being 655cm3 in size.


FIGURE 17.25 Typical discharge curves of magnesium/ manganese dioxide cell, 10-Ah size. (Courtesy of Eagle-PicherIndustries.)

17.6 BATTERY APPLICATIONS

Water-activated batteries can be viable candidates as the power source for many types ofequipment. The choice of which battery to use becomes one of economics. By proper designall will perform similarly. Where high current densities are required and cost is secondary,the magnesium/silver chloride system is best. All can be used as immersion or dunk-typebatteries; however, all but the magnesium/cuprous chloride system will withstand long stor-age times at high temperatures and high humidities. At the present state of the art only themagnesium/silver chloride system is suitable for use in forced-flow batteries.

17.6.1 Water-activated Batteries for Aviation and Marine Lifejacket Lights

The magnesium/cuprous chloride water-activated battery system is being used in FAA andU.S. Coast Guard approved aviation and marine lifejacket lifts. A typical light is shown inFig. 17.26.

The single cell battery has a cathode approximately 5 mm thick with a footprint of 7.25by 2 mm. Table salt is added to the cathode mix19 to obtain an adequate voltage in freshwater.(The holes in the battery case are optimized to maintain electrolyte salinity while allowingflushing of discharge products). After being mixed while heated, and then cooled and re-chopped, the powder is pressed and reheated in an automatic hydraulic press. The cathodeis pressed with a titanium wire current collector, which is wire brushed before manufactureto remove oxide buildup.

The cell is constructed with two anodes, each with the same footprint as the cathode,connected in parallel and placed on either side of the cathode. The anodes are AZ61 elec-trochemical magnesium sheet.

Typical cell voltage at a 220 to 240 mA (C/12) discharge (against a miniature incandes-cent lamp) starts at 1.77V in salt water and goes down gradually to about 1.65V before asharp voltage drop signaling the end of discharge. Voltages in fresh water are about 0.1Vlower. Total capacity is about 3000 mAh.

A battery, with two cells wired in series for international marine use, uses a AT61 sheetbecause of the requirement for higher voltage. In salt water, the cell voltage at a 340 mA(C/8) discharge (against a highly efficient-gas-filled miniature lamp) is as high as 1.87Vearly in the discharge and drops to about 1.8V after 8 hours. Again, the voltage is freshwater voltage is about 100 mV less per cell. This discharge is shown in Fig. 17.27.


FIGURE 17.26 Lifejacket light, usingmagnesium/cuprous chloride water-activated bat-tery. (Courtesy of Electric Fuel Ltd.20)

FIGURE 17.27 Typical discharge of 6 WAB-MX8 batteries in fresh tap water at 330 mA (Courtesy ofElectric Fuel Ltd.20)


Because the salt added to the cathode makes the cathode even more hygroscopic than itwould otherwise be, the batteries are preferably stored with a removable pull-plug used toseal 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 fuelmodel no.

Nominalvoltage, V

Nominal size, cm

Length Width Height

Nominal discharge capacity

Time Wh Normal usage mode

WAB-H12

WAB-H18

WAB-MX8

1.7

1.7

3.6

2.9

2.9

3.1

1.6

1.6

3.3

9.3

9.3

9.5

12h

8h�

8h�

4.4

3.3

10.7

Aviation /MarineLifejacket light

AviationLifejacket light

MarineLifejacket light

Source: Electric Fuel Ltd.20

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 airlinesSonobuoysRadio and light beaconsUnderwater OrdnanceRadiosonde units—balloon transport equipment, high altitude low ambient temperatureoperation.

FIGURE 17.28 Magnesium/ silver chloride batteries; 12023-1and 12073.


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 listsome of the standard and special purpose magnesium/cuprous chloride and magnesium/silver chloride batteries that were manufactured. Of these, only the two batteries illustratedin Fig. 17.28 are currently manufactured.

TABLE 17.8 Magnesium/Cuprous Chloride Water-Activated Batteries

E-P numberOther

designation

Nominalvoltage /

selection, V

Nominal size, cm

Length Width Height

Nominal dischargecapacity

Time Wh Normal usage mode

MAP-12037MAP-12051

PIBAL—

3.018.0

1.36.8

3.23.8

5.15.7

30 min120 min

0.82.16

Airborne, lighting typeAirborne, radiosonde

MAP-12053 BA-259A-1.5B-6.0� �C-115.0

11.7 10.2 6.0A-90 minB-90 min�C-90 min

0.341.89�650.4

Airborne, radiosonde

MAP-12060MAP-12061MAP-12064MAP-12071

——

BA-253—

18.022.56.0

20.0

5.15.1

10.26.3

5.47.03.87.6

5.15.13.8

16.0

120 min90 min45 min

8.1 h

5.47.592.25

53.46

Airborne, radiosondeAirborne, radiosondeAirborne, lighting, typeSubmerged, buoy system

Source: Eagle-Picher Technologies, LLC21

TABLE 17.9 Magnesium/Silver Chloride Water-Activated Batteries

E-P numberOther

designationNominal

voltage, V

Approximate size, cm

Length Width Height

Nominal discharge capacity

Time Wh Ah

MAP-2023-1 Squib firingbattery

5.5 5.1 2.5 5.4 1 min 0.315 0.0572

MAP-12062MAP-12065MAP-12066MAP-12067

———

MK-72Squib firing

battery

484.57.50.75

12.16.35.12.8

dia.6.75.1dia.

3313.916.52.5

20 min50 h14 h13 s

400157.5138

0.0010

8.333518.40.0014

MAP-12069MAP-12070MAP-12073MAP-12074

————

101214.510.5

7.65.17.64.1

2.52.62.85.1

8.9105.1

25

6 h9 h

15 h48 h

1.553.214.5595.35

0.154.4419

Source: Eagle-Picher Technologies, LLC21


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. Patent3,450,570, 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 AnnualPower 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 SeparatorMember,’’ 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,’’ WinterMeeting, American Institute of Electrical Engineers, New York, 1963.

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

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