BIMONTHLY REPORT NO. 2 ON THE WATER-ACTIVATED BATTERY

• Document Type: CREST
• Collection: General CIA Records
• Document Number (FOIA) /ESDN (CREST): CIA-RDP78-03424A000500040002-2
• Release Decision: RIPPUB
• Original Classification: C
• Document Page Count: 17
• Document Creation Date: December 22, 2016
• Document Release Date: April 10, 2012
• Sequence Number: 2
• Publication Date: August 22, 1959
• Content Type: REPORT

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coNFI DENT I AL\
BINDNTHLY REPORT NO. 2
ON THE
WATER-ACTIVATED BATTERY
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Period:
22 August 1959 - 21 October 1959
0
ORIGINAL CL BY 3 5f 7
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DECL j
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EXT BYND '
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REASON
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TABLE OF CONTENTS
Page
I.
Abstract
1
II.
Purpose
1
III.
Factual Data
2
A. Lmge Battery Design
2
B. Drastic Reduction in the Number of Components
5
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C. Load Tests
9
IV.
Conclusions
13
V.
Future Plans
15
VI.
Personnel
15
0
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V
A detailed description of the construction and production of
the large model battery is given. This includes some drastic changes in
design, not included in the objectives for this contract. These changes
permit a substantial reduction in the number of battery components, which
in turn leads to a substantial simplification in operating procedures.
The electrical performance of this large battery, operating at an environ-
mental temperature of 25?C, exceeds the requirements by a substantial
margin. Its thermal performance, on the other hand, requires the develop-
ment of improved means for heat dissipation.
II. PURPOSE
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To demonstrate the feasibility of a large model, chemically
rechargeable, magnesium-silver chloride battery, activated by a 3 per
cent salt solution at room temperature and delivering an average current
of 3 A at 12V for at least 60 minutes. The voltage regulation at a maxi-
mum load current of 5.3 A shall equal or surpass the stability obtained
previously.
To demonstrate reasonably satisfactory performance of this
battery at environmental temperatures of -40?C and +40?C, using a
variety of electrolytes such as 3 per cent salt solution, tap water and
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others. It is recognized, however, that such performance cannot be ex-
pected to match that at room temperature.
Phase
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To fabricate and deliver six battery cases and thirty complete
sets of chemical recharges for field testing purposes, including instruc-
tions on the proper handling, activation, deactivation, disposal and
temperature control.
III. FACTUAL DATA
A. Large Battery Design
A comparison of the requirements, listed in Phase 1 of the
previous section, with those of the previous model reveals an increase
in power level for the new model by almost a factor 11. At a current
density of 0.25 A per inch2 this would require an AgCl surface area of
21 inch2. The rolled silver chloride, produced by the Rollief Corpora-
tion, is supplied by our Ordnance Department in Pittsfield, Massachusetts
as 12" x 30" sheets. The electrical conductivity of these silver chloride
sheets has been greatly enhanced by small perforations, 1/2" apart, and
a very thin coating of porous silver covering the entire area. It has
been found, that, for a given number of cells per sheet, the amount of
wasted AgCl leftovers is minimized at a cell-size of 9" x 2.68" = 24 inch2.
* Annual Report, pp. 55, 56
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These are the AgCl dimensions adopted for this battery. The thickness
of these sheets is about 0.015" as before. Since the cell-surface area
is somewhat larger (24) than the extrapolated value (21), the ampere-
minute capacity safety factor of this battery is slightly larger.
In order to minimize internal leakage processes*, the familiar
U-shaped spacers are being used, which require slightly larger magnesium
sheet dimensions (9,4" x 3.0"). These foils, 0.012" thick, are cut from
12" x 45" sheets, purchased from the Dow Chemical Company by our Ordnance
Department. The composition of this magnesium alloy, type Jl, is as
follows:
Aluminum: 5.8 - 7.2% by weight
Manganese: 0.15% (min.) for corrosion resistance
Zinc: 0.4 - 1.5%
Impurities: Approximately 0.5% (Si,Cu,Ni and Fe)
Magnesium: Balance
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The general outlay of the large battery design, including some
of the pertinent dimensions, is given in Figure 1. Only two cells have
been inserted in this illustration.
Provisions have to be made for the dissipation of heat, gener-
ated during discharge (Report No. 1, Section III). Consequently the two
large front and back panels are made of aluminum. These panels serve
also as battery terminals. Since aluminum is not a desirable electrode
* Annual Report, pp. 54, 61
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NEGATIVE
TERMINAL
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w
LARGE BATTERY DESIGN
FIGURE I
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material, the panels are separated from the battery proper by thin layers
of silver foil (not shown in Figure 1). The U-shaped bottom sidewall
piece is made of black cloth textolite, an insulator. Its width (1.050")
is the same as that used in the previous model. The amount of water
necessary to activate the battery is about 320 cm3 or 11 fluid ounces.
The other components, i.e. silver chloride and silver sheets, as well as
the separators necessary to prevent internal short-circuiting, cannot be
seen in Figure 1.
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It has been found, that the type of technology developed during
this project, in conjunction with a much larger size battery, can be used
to reduce effectively the required number of battery components. This re-
duction, in turn, leads to a considerable simplification of the manipula-
tions necessary for the storage, assembly, and disposal operations. In
view of the great importance of simple operating procedures it was decided
to explore such possibilities in spite of the fact that such a development
is not included as a specific objective for this contract.
Before reporting on these improvements it is desirable to
summarize first the present status of required battery components. Such
a listing can be found in Table I, under the column marked "Presently".
A total of 37 components are almost equally divided among permanent ones
(items 1-3) and those necessary for one chemical charge (items 4-7).
Items 2 and 3 require rather careful handling.
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Listing of Ma-AgCl Battery Components
(for 9 cells)
Number of Components
Item No.
Description
Presently New
Remarks
1
Battery Case
1
1
)
2
U-shaped spacers
9
0
)Permanent
3
Separators
9
0
)Parts
4
Ag/Mg - Anode, Cell No. 1
1
1 *
)
)Expendable
5
AgC1 - sheets, Cells 1-8
8
)
)
8**
)
6
Ag/Mg - sheets, Cells 2-9
8
)
)Refill
7
AgCl - Cathode, Cell No. 9
1
1***
)
I
F 37
11
TOTAL
See Figure 2, part A
See Figure 2, part B
See Figure 2, part C
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A first step towards a reduction of the required number of
components can be taken, by extending the technique described in Sec-
tion VA of Report No. 1 to include the silver chloride sheets. After
applying a small amount of Hysol 6101 B to one side of these sheets, a
satisfactory bond to the silver side of the leg/Ag-package is obtained
by applying about 300 lbs/inch2 pressure at 150?C. The curing cycle
is similar to the one described on pp. 13 and 14 of Report No. 1. This
step eliminates item No. 5 as separate entities.
Having now developed a Mg/Ag,AgCl package we can proceed to-
wards a second reduction in the number of battery components, by glueing
small textolite punchings to the silver chloride layer, thereby eliminating
the nine separators listed under Item No. 3. Figure 2 gives the cross
sectional view of the new components for a 2-cell battery. Actually 8
parts B are used, instead of 1, to obtain a 9-cell battery.
The capacity reducing effects of internal leakage, mentioned
already in Section IIIA, have been minimized by the use of U-shaped spacers.
Measurements made on small batteries indicate a substantial improvement in
battery capacity as a result of this. However, the relative importance of
such leakage effects deminishes with increasing battery size. Since the
power level has been increased by a factor 11, the use of spacers may nc
longer be required. Comparative tests with the large size battery show that
standard load conditions can be maintained for 75 minutes without spacers,
whereas a standard discharge can be maintained for 90 minutes with the
spacers in position. Since this corresponds to a sacrifice in capacity of
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0.258"
3.0"
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.012" Mg WITH
001" Ag BACKING
USING 6101-B WITH
SCREEN PRESS
METHOD
.080"
TEXTOLITE
SEPARATORS
.125" DIAMETER
ATTACHED -
WITH
GLYPTAL
Mg/Ag/AgCl
SCREEN PRESSED
WITH 6101-B
.062" X .032"
HOLES PUNCHED
IN THE AgCI
.015" AgCP WITH
.001" Ag BACKING
USING 6101-B RESIN
BUT NO SCREEN USED
NEW REFILL COMPONENTS FOR 2-CELL BATTERY
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only 17% it is felt that simpler operation, resulting from the elimination
of spacers, justifies this sacrifice. Consequently, item No. 2 in Table I
can also be omitted. As indicated in the column marked "New", the three-
step simplification project has resulted in a significant reduction of the
total number of battery components from 37 down to 11.
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Exploratory small scale load tests have been made and reported on
during all phases of this contract. In addition to this a certain number
of large scale tests have been performed during this period. Some of these
have already been discussed in the previous section in connection with the
omission of spacers. Wherever possible we have conducted such tests, using
only four cells instead of nine, to conserve our supply of silver chloride
and to accelerate the preparation of components required. Except for the
study of cooling problems it is felt that this is a permissable short-cut.
In order to simulate the high temperature regime usually encountered in a
9-cell run, we often preheat the 4-cell test battery and its electrolyte
to 70?C, prior to activation.
For direct comparison with No. 33*, which is representative of
the previous smaller size, the load characteristics of a large size 9-cell
run (No. 48) are shown in Figure 3. Except for the values of the load re-
sistors R1 and R2 the same test circuit has been used throughout. Spacers
# Annual Report, pp. 61, Figure 30
## Annual Report, pp. 56, Figure 26
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0 10 20 30 40 50 60 70 80 90
TIME (MINUTES)
RUN *48
9 CELL AgCI DIMEN. 9.0"
X 2.68? ?
24.1 2
PACK WIDTH ? 108 MILS
3% NoCt SOLN.
EXTRA COOLING
TORETICAL AMP-MIN = 361
ACTUAL FROM RUN ? 272 = 75.5 %
TEMP DURING RUN 25?C --- 95?C
OPEN CIRCUIT VOLTAGE
VOLTAGE AT 20 OHMS
I
VOLTAGE AT 2.1 OHMS
THICKNESS OF MATERIALS USED:
SILVER CHLORIDE = 0.015 MILS
MAGNESIUM a 0.012 MILS
SILVER 0.001 MILS
LOAD
CURRENT
AT 20 OHMS
LOAD CURVES OF LARGE BATTERY
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similarity in their voltage regulation features, some striking differ-
ences are also noticeable. As expected, current levels are about
eleven times higher in run No. 48. This is the direct result of the
increase in battery size. However, in contrast to No. 33, these high
current levels can be extended to a 90 minute period rather than the
required 60 minutes, with load voltages remaining above 12 V. Thus
the large size battery performance reveals the existence of a substan-
tial reserve in capacity. The break in the curves at about 65 minutes
is due to the accidental and temporary shorting of a single cell.
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While the electrical characteristics of run 48 are very
encouraging, its thermal behavior reveals somewhat inadequate cooling.
With the battery case cooled by the surrounding air at 25?C and with the
entire system at room temperature at the time of activation, the follow-
ing approximate battery temperatures were recorded.
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Minutes after Battery
activation Temperature
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50?C
70?C
80?C
93?C
At this point "boiling" of the electrolyte became quite notice-
able. Only by means of artificial cooling of the two side panels with
small amounts of ice was it possible to stabilize the battery temperature
between 80 and 93?C for the last part of the run. Other types of heat
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removal such as partial submersion in a liquid bath or forced air cooling
would have been equally effective. With an expected heat generation,
equivalent to approximately 200 Watt (Section III, Report No. 1), such
behavior is not too surprising. Since ice, liquid bath or forced air
cooling cannot be considered to be desirable solutions to this cooling
problem, the dissipation of excess heat will require further attention,
particularly in connection with the ? 40?C temperature tests of Phase 2.
D. Heat Transfer Measurements
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Since battery cooling is a problem determined essentially by
"external" parameters, it can be studied independently of the actual
heat generating processes. In the interest of efficiency and flexibility
it was therefore decided to perform exploratory heat transfer measurements
of this type by generating such heat by means of a resistance heater, sub-
merged in the water filled battery case, in lieu of 9-cell battery runs.
The resistance heater is placed inside a U-shaped quartzglass tube for
protection, which fits inside the battery case. The amount of heat gen-
erated can be adjusted to the desired value with a Variac and it is mea-
sured directly by a wattmeter.
By means of this calibrated heat supply to the battery it was
found that at the calculated rate of 180 Watt equivalent (Report No. 1,
page 3) and normal air cooling, the battery never reached the boiling
stage. Only at a heating level of 250 W could the thermal behavior of
run No. 48 be reproduced. This corresponds to a H/W ratio of about 7,
instead of the value 5 calculated in Report No. 1. This experimental
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result is consistent with the known occurrence of an internal leakage
process, the existence of which has been neglected in our calculations.
The effect of heating on the equilibrium temperature of the water filled
battery case is given in Figure 4. The boiling point of 100?C is reached
at a heating level somewhere between 200 W and 250 W.
Other types of battery cooling have been investigated at a
heating level of 250 W. Placing the hot battery case in 1 1,2" of cold
water, provides excellent cooling. For our particular geometry and start-
ing at the boiling point, the battery temperature dropped rapidly to 72?C,
rising slowly thereafter up to 82?C. Cooling by means of wet sand in
contact with the side-panels is also suitable, although it is not as
effective as water. The cooling effect of dry sand, on the other hand,
is very disappointing.
All our tests indicate very good heat transfer from the center
of the battery to the outer surfaces of the two panels. On the other hand
the transport processes, carrying the heat away from these surfaces, are
the ones requiring improvement. The search for a more suitable cooling
method cor.tinues.
IV. CONCLUSIONS
During this reporting period the design and fabrication of the
large battery, including all the components for chemical recharge, have
been completed. Its electrical performance at room temperature exceeds
the requirements by a substantial margin.
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40 60
WATER TEMPERATURE
EFFECT OF HEATING ON BATTERY TEMPERATURE
FIGURE 4
14
40
00
cONFIDEnTIAL ?
ROOM TEMP. 230C
AIR COOLING
60
20
so
40
0 2
0
a
o
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Further application of the bonding technology, developed during
the previous period, combined with some sacrifice in excess capacity, has
led to a reduction in the number of battery components from 37 down to 11.
This leads to a substantial simplification in operating procedures, an
achievement not included in the objectives called for in the contract.
The heat dissipated by the battery under load is larger tran
expected (H/W:--7 instead of 5) and the means for dissipating this heat,
developed so far, are not entirely satisfactory.
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V. FUTURE PLANS
During the next period our efforts will be devoted mainly to
Phase 2, with special emphasis on the development of a new cooling
method, permitting satisfactory operation at +40 0 C without the need
for additional accessories and/or increases in size or weight.
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