Linden D., Reddy T.B. (eds.) Handbook of batteries
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MAGNESIUM WATER-ACTIVATED BATTERIES 17.15
FIGURE 17.13 Magnesium / cuprous iodide seawater-activated cell discharged continuously at
0⬚C in simulated ocean water, 1.5% salinity.
FIGURE 17.14 Magnesium / lead chloride seawater-activated cell discharged continuously at 35⬚C
in simulated ocean water, 3.6% salinity.
17.16 CHAPTER SEVENTEEN
FIGURE 17.15 Magnesium / lead chloride seawater-activated cell discharged continuously at 0⬚C
in simulated ocean water, 1.5% salinity.
FIGURE 17.16 Capacity vs. power output of seawater-activated cells discharged continuously
at 35⬚C in simulated ocean water, 3.6% salinity.
MAGNESIUM WATER-ACTIVATED BATTERIES 17.17
FIGURE 17.17 Capacity vs. power output of seawater-activated cells discharged
continuously 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 the
physical, 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 Ⳳ 2 ⍀
Life 9 h
Voltage 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 Nonsilver
Height, 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
Ⳳ 14 482 Ⳳ 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
Ⳳ 1⬚C
High temperature Ocean water of 3.6% salinity by weight at
⫹34 Ⳳ 1⬚C
* Battery preconditioned at ⫺20⬚C prior to immersion in ocean water of 1.5% salinity by weight
at 0
Ⳳ 1⬚C.
† In equipment packed in sealed plastic container with appropriate desiccant.
17.18 CHAPTER SEVENTEEN
FIGURE 17.18 Discharge curves of seawater-activated batteries at 35⬚C.
FIGURE 17.19 Discharge curves of seawater-activated batteries at 0⬚C.
MAGNESIUM WATER-ACTIVATED BATTERIES 17.19
FIGURE 17.20 Discharge curves of seawater-activated batteries, 10-day humidity.
TABLE 17.6 Performance Summary of Seawater-Activated Batteries
Silver
chloride
Cuprous
iodide
Cuprous
thiocyanate
Lead
chloride
Number of cells 11 12 13 16
Battery dimensions:
Height, cm 7.5 9.8 10.2 10.5
Width, cm 5.5 7.6 7.4 7.5
Thickness, cm 3.9 4.4 5.7 4.5
Weight, g 252 516 478 458
Activation:
Low temp.:
To 13.5 V, s
⬍15 ⬍15 ⬍15 ⬍15
To 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 9.5
Low temp., h 9.80 10.3 10.3 10.7
Load resistance (per cell),
⍀* 7.27 6.67 6.15 5.0
Cutoff voltage (per cell), V* 1.364 1.25 1.154 0.9375
Average current, A 0.206 0.220 0.236 0.219
Average volts per cell, V* 1.497 1.463 1.378 1.048
Wh/ L 204 110 90 100
Wh/ kg 130 70 79 75
* As each battery system contains a different number of cells, cell load resistances and cell
voltages are different for each battery.
17.20 CHAPTER SEVENTEEN
17.5.3 Forced-Flow Batteries
With the development of the recirculation system in which the inflow of fresh electrolyte
can be controlled, thereby maintaining the temperature and conductivity of the electrolyte,
the performance of electric torpedo batteries has been improved markedly. With recirculation
and flow control, a recirculation pump (see Fig. 17.2) and a voltage-sensing mechanism are
added 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 controlling
the intake of electrolyte by means of the voltage-sensing mechanism.
The performance of one type of torpedo battery with and without recirculation voltage
control is shown in Fig. 17.21.
17
The blocked-in area represents the limits within which an
electric torpedo battery with recirculation and flow control will perform when discharged
under any of the conditions shown by the three individual curves. All voltages pertinent to
the 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 was
widely used in applications requiring low-temperature performance, such as radiosondes,
having replaced the more expensive magnesium/ silver chloride system in applications where
weight and volume are not critical. Figure 17.22 illustrates a typical magnesium/cuprous
chloride 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 to
10 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 on
high current drains, and self-discharge limits the life after activation. For best service these
batteries should be put into use soon after activation. The heat that is developed during
discharge 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 shows
the discharge curve for this battery at various temperatures. Figure 17.24 gives some typical
discharge curves for this type of battery with a similar design at various discharge loads.
MAGNESIUM WATER-ACTIVATED BATTERIES 17.21
FIGURE 17.22 Magnesium / cuprous chloride radiosonde bat-
tery. Size: 10.2 ⫻ 11.7 ⫻ 1.9 cm; weight: 450 g, rated capacity:
A
1
section—1.5 V, 0.3 Ah; A
2
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 ⍀.
17.22 CHAPTER SEVENTEEN
FIGURE 17.24 Discharge curves of magnesium/ cuprous chloride water-activated batteries at
20⬚C; electrolyte: tapwater.
Magnesium/ Manganese Dioxide Battery. This reserve battery consists of a magnesium
anode 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 or
more 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
⫺40
to
⫹45⬚C at the 10–20-h discharge rate. Over 75% of the battery’s fresh capacity is available
after 7 days’ activated stand at 20
⬚C and 4 days’ storage at 45⬚C. Typical discharge curves
are shown in Fig. 17.25 for a five-cell 10-Ah battery, weighing about 1 kg and being 655
cm
3
in size.
MAGNESIUM WATER-ACTIVATED BATTERIES 17.23
FIGURE 17.25 Typical discharge curves of magnesium /manganese dioxide cell, 10-Ah size. (Courtesy of Eagle-Picher
Industries.)
17.6 BATTERY APPLICATIONS
Water-activated batteries can be viable candidates as the power source for many types of
equipment. The choice of which battery to use becomes one of economics. By proper design
all 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-type
batteries; 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 the
magnesium/ 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 and
U.S. Coast Guard approved aviation and marine lifejacket lifts. A typical light is shown in
Fig. 17.26.
The single cell battery has a cathode approximately 5 mm thick with a footprint of 7.25
by 2 mm. Table salt is added to the cathode mix
19
to obtain an adequate voltage in freshwater.
(The holes in the battery case are optimized to maintain electrolyte salinity while allowing
flushing 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 cathode
is pressed with a titanium wire current collector, which is wire brushed before manufacture
to 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 a
sharp voltage drop signaling the end of discharge. Voltages in fresh water are about 0.1V
lower. Total capacity is about 3000 mAh.
A battery, with two cells wired in series for international marine use, uses a AT61 sheet
because 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 1.87V
early in the discharge and drops to about 1.8V after 8 hours. Again, the voltage is fresh
water voltage is about 100 mV less per cell. This discharge is shown in Fig. 17.27.
17.24 CHAPTER SEVENTEEN
FIGURE 17.26 Lifejacket light, using
magnesium / 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 of
Electric Fuel Ltd.
20
)