Note: Descriptions are shown in the official language in which they were submitted.
BACKGROUND OF THE INVENTION
Secondary electric storage cells, operating at
hlgh rates of charge and discharge, require some method of
cooling to prevent overheating. This is especially true for
electrlc vehlcle applicatlons, where a large number of ln-
20 terconnected cells and a tlght packaglng arrangement may be
required. One solution is to clrculate electrolyte as a
heat exchange medlum through a cell and lnto a coollng
reservolr, and then to reclrculate the electrolyte back into
the cellO
Imschenetzky recognized this solutlon in UOS.
Patent 400,215, where an electrolyte supply plpe was arranged
at the bottom of a galvanic batteryO Thls forced fresh *
electrolyte up and around the electrodes in each cell stack-
-1- 13~
. ,: , , ~ , . , , : .
~, . . .: ~ . :~ . . . . .. . .
46,215
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up. Recently, Chiku, in U S. Patent 3,666,561, taught a
zinc-air battery, with clrculation of electrolyte through a
series of electric battery cellsO The circulation was ~-
accomplished by pumping electrolyte into the bottom of each
cellO Electrolyte, from an electrolyte chamber, flows up
through each cell and is removed from the top of each cell
through outlet pipesO The electrode stack-up is not sealed
against the container, so that electrolyte may flow around
one of the three plates of each cell, and oxygen gas is :-
introduced into the electrolyte circulation system to reduce
lnternal battery current~ ~
Necessarlly, a circulating electrolyte cooling ~-
system for a battery is complicated, and to date not all of
the problems associated with such systems have been solved.
Nearly all secondary electric storage cell cases are com-
posed of metal, glass, rubber, or plastlc boxesO ~ell
stack-ups are inserted into the boxes and then a cover is .
attachedO When it is desired to circulate electrolyte
through the cell stack-up for cooling purposes, standard
case and electrode stack-up construction has not proved
satisfactory
Associated wlth circulating electrolyte systems
are the problems of: coollng every cell on charge and/or .
discharge to permit high current rates to be used; hermetic
Joints between terminals, inlet and outlet tubes and case
walls; encapsulation and sealing o~ cell stack-ups, so that ~ -
electrolyte will be forced to go through them when going ~ :~
from an inlet to an outlet in the case; electrolyte level
maintenance; electrolyte specific gravity control and uni- : -
- 30 formity; collection and elimination of explosive hydrogen ~. .
-2-
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1070376 ~ ~
and oxygen gases at one location, where proper safety pre-
cautions can be taken; and maki~g the system simpler, so
that cell size changes can be readlly and inexpenslvely
accomplished O
To solve all o~ these problems the battery has to
have the following ~eatures: leakproof, since electrolyte ls
circulating under pressure, all the cell cases and plumblng
connections must be of the highest order of hermeticity; low
pressure drop, to keep the size of the circulation pump
small and for leakage and safety reasons; hi~h resistance in
the- electrolyte connections between cells, to minlmize self-
discharge; unlform pressure drop among all cells, to allow
the cells to be connected in parallel arrangement and stlll
achieve uniform flow through each cell; and most lmportantly,
uniform flow throughout the cell cross-sectlon, so that all
plates receive adequate electrolyte flow and assurance that
electrolyte flows through the stack-up of a cell, not around
them, so that the most effectlve coollng durlng charglng ls
achlevedO
SUMMARY OF THE INVENTION
The battery herein descrlbed solves all of the
listed problems and has the requlred features descrlbed
above. Electrolyte ls circulated through the battery and a
reservoir contalning a coollng mechanism by means of a pump.
Any heat exchanglng means, such as cooling water clrculated
through colls ln the reservo~r, can be used to cool the
electrolyte~ Electrolyte ls clrculated at rates adequate to
remove the heat generated by varlous charge, dlscharge
rates. The reservoir and pump are attached to the battery
with quick disconnect couplings so the battery may be dls-
--3--
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~070376 -~ -
~ .
charge~ wlth or without them~ Electrolyte le~el and specific
~ ; ., ~ ..
gravity are maintained by adding water to the reservoir to
maintain a constant height levelO The battery system is
vented to the atmosphere at the reservoir through a barrier
venting means, which allows explosive hydro~en and oxygen to
escape. All of the listed necessary features for this
improved circulating electrolyte battéry are accomplished by
the foll-owing means:
a) The cell electrodes of each stack-up are sealed
and encapsulated in a molded case3 preferably by means of an
epoxy resin sealant filler, whlch adheres to the case
wall~, terminals, and electrolyte inlet and exhaust tubes, ;
providlng an effective hermetic seal ln all of these loca-
tionsO : ";
b) Low and uniform cell to cell pressure drops,
and uniform flow of electrolyte through the cell stack-ups
is accomplished by providlng channels in the plates, as by
cuttlng or pressing narrow slits in themO The channels are
spaced apart for effective cooling and constitute no more
than 10% of the plate surface area.
c) Electrolyte ls forced to flow through these
channels, and not around the perlphery of the cell stack-
ups, by the tight fit between the stack faces and the wide ;
front case walls, and by filling the space between the
stack-up edges and the narrow edge case walls with a suit-
able sealant filler. The filler can be any number of
materials, such as a liquid, curable, plastic resin or
rubber, foam in place materials, already foamed material cut
to fit, etc.
~30 d) High electrical resistance in the electrolyte
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plumbing network is accomplished by the use of long inlet
and exhaust tubes. The inlet tube preferably extends from
the top to the bottom of the cell, while the exhaust tube is
preferably formed in a coil at the top of the cellO The
manifolds connecting cells with each other are preferably
above the cells, which allows electrolyte to drain back into
the cells when circulation StopsD This latter feature re-
duces the electrical path between cells to the conductivity
of the electrolyte film which clings to the piping wallsO
.
Fl~w of electrolyte through the system can be
summarlzed as follows: Reservoir; Pump; Battery manifold
Cell inlet manifolds; Cell electrolyte lnlet tubes; Cell
reservoirs; Through channels in sealed cell stack-ups; Cell :
electrolyte outlet tubes; Cell exhaust manifold; Battery
manifold, and the~ on to the Reservolr for coollng.
This lmproved, cell stack-up electrolyte flow
system offers many advantages and benefits over other con-
ventlonal systems, some of which are:
a) Effective cooling of the stack-up enables
higher charge rates to be employed, thus reducing charge
tlmeO A typical cycle of charging/discharging, at the C/2
rate, malntains the temperature at between 30C and 35C
wlth circulationO Without circulation, temperatures would
exceed 70C, which severely hampers battery life.
b) The hermeticlty of the system elimlnates many
safety hazards such as spllls and mists which lead to short
circuit grounding paths and potential failures.
c) The parallel flow arrangement, with associated
plumbing, insures each cell of proper malntenance, and ell-
~30 minates failures due to over or under filling and improper
46,215
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10~70376 ~ ~
speclflc gravity~ ~ ~
.. .
d) The plumbing also prov-~des for safe gas handling ;~
and lends itself well for elimination of hydrogen and oxygen
formed during charg~ng. :
BRIEF DESCRIPTION OF THE DRAWINGS
For a better understandlng of the invention,
reference may be made to the preferred embodiment, exemplary
of the lnventlon, shown in the accompanying drawings, in
whlch:
Flgure 1 ls a three dimensional vlew of a circu-
latlng electrolyte battery module containlng flve series :
connected battery cells;
Flgure 2 ls a top view, partlally in sectlon, of
the battery module of Figure l; i
Figure 3 is a side view, partially in section, of
the battery module of Figure 2, along the line III;
Figure 4 is a cross-section of the battery module
of Figure 2, along llne IV, showlng an electrode plate,
having spaced apart channels, sealed into the container, :.:
20 cell inlet manifold, cell electrolyte inlet tube, cell ~ !:
reservolr, and the cell electrolyte outlet tube;
Figure 5 is a cross-section of the plate stack-up
of one embodiment of a cell, showlng the sealed electrode
plate sldes and edge~, and the channels ln the plate stack-
up prov~ding uniform fIow of electrolyte through the stack-
up rather than around the periphery of the stack-up; and
Figure 6 is a schematlc vlew of an assembly of
battery modules fed by a circulatlng electrolyte system,
with associated electrolyte cooling reservoir and pump.
--6--
. ...... .. . . . . . - . -~ . .. . .. .
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DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring now to Figure 1 of the drawings, a
battery module 10 is shown with associated dimensions, which ~ -
may vary greatly depending on battery use. The battery ~
module, containing at least one cell, can comprise case 11, :
whlch may be, for example, a metal, rubber or plastic box.
Each cell 12 is in its own case or conta~ner havlng flat
~ront and edge wallsO The battery module case 11 is optional, `
however, as the separate cells may be held together solely
by the cell exhaust manifold 13 and cell inlet manifold 14,
shown disposed in a parallel arrangementO The cells may
also be held together by electrical connections between the
terminal studs 150 Of course, any other holding or clamping
means can be used to hold the separate cells together, such
as a bottom U plate, shown as 17 in the drawing, which would
be used without the battery module caseO
Figure 2 shows a top view of the battery module
with terminal studs 150 Also shown is the coiled cell
electrolyte outlet tube 21, which attaches to the cell
exhaust manifold 13 at opening 22. The cell electrolyte
lnlet tube is shown as 230 Figure 3 also shows the position
o~ these tubes within a cell, where the bottom of the cell
electrolyte inlet tube ls shown as 300
Flgure 4 shows a cross-section of a preferred cell
12 of thls inventionO Cell electrolyte circulation means,
tubular cell inlet manifold 14 and cell exhaust manlfold 13,
are preferably disposed in a parallel arrangementO These
electrolyte circulation means are preferably connected above
the cells to allow electrolyte to drain back into the cells
when clrculation stops~ This reduces the electrical path
--7--
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,.
between cells when electrolyte is not circulating, to the -:
conductivity of the electrolyte film which clings to the
manifold tube wallsO
The inlet and outlet manifold tubes will have a ~.
relatively large internal cross-sectionO This provldes low
,..
fluid flow resistance and minimum pressure drop across the
cell, which ls requlred to minimize the pressure necessary ~:
for adequate electrolyte flowO The cell inlet and outlet
manifold tubes have a long length for hig~ electrical re- .
10 sistance when filled with electrolyteg which is required to -`
minimize current leakage from cell to cellO
Preferably, electrolyte is pumped up through the
electrode stack-up, so that hydrogen and oxygen gases gene-
rated during charglng are easily exhausted to the cooling
reservoir without dangerous pressure build-up In the cell .
of Figure 4, electrolyte, from the manifold 14, flows from . .
the top of the cell case to the bottom of the cell stack-up, ~.
by means of the cell electrolyte inlet tube 23. Cell elec- ~. :
trolyte inlet tube 23 extends from the top of the electrode :
stack-up down along one edge of the battery cell between the
edge side of the stack-up and the edge wall of the cell -
caseO Then, the tube bends around the bottom Or the stack-
up and extends lnto the bottom cell reservoir 40 The cell
stack-up, comprising a series of alternate positive and
negatlve electrode plates, one of which is shown as 41, may
rest on plastic, rubber or foam blocks 42 to form the bottom
reservoir 40O
Thus, electrolyte flowing into the cell case will
fill up the bottom electrolyte reservoir formed by the
blocks or other suitable stack-up supporting means. The
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electrolyte will then be forced up the channels 43 in the -
electrode platesO
Referring now to Figure 5, a top cross-section
view of electrode plate 41, and other alternating positive
and negative plates maklng up one type of cell electrode
stack-up 50 is shownO The channels 43 can be formed by
cutting narrow slits in the electrode plates, by coining the
plates to form narrow channels in the plates, or by any
other suitable meansO
The cross-section of the channel can be clrcular
as shown, square, or any other configurationO The channels
can be on both sides of each plate lf desiredO The channels
need not be on both positive and negative plates as shown,
but may, for example, be pressed only into the positive or
negative plates, so that channels would appear on alternate
platesO
The channel should not extend through the electrode
plate becau~e thls would substantlally reduce the conduc-
tivity of the plateO The channel area can comprise from
about 0O5% to 10% of the plate face area. If the channels
constitute over 10% of the plate area, excessive active
material is lost with a reduction in battery performance.
Usually 1 to 6 channels per plate are adequate for good
electrolyte circulation and battery coolingO
Channels on one side of the plate, as shown in
F~gure 5, are pre~erred, since this provides a strong elec-
trode structure requiring minimal machining or pressingO
Not shown are plate separators, which may be made of a con-
tlnuous or perforated film of cellulose, polypropylene,
nylon or other suitable insulating material between or
_g_
. 46,215
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1070376 ~; ~
wrapped in serpenti~e ~ashion around each plate~ ~he se- :~
parators of course should be compattble wlth the electro- .::~
lyteO For adequate cooling it i~ essential that electrolyte
flows only along the channels between the electro~e plates -~
in the stack-up, and not around the sides and edges of the
stack-up, although there may be minimal electrolyte seepage
through the platesO :
To provide a hermetic seal and to assure that no
electrolyte flows around the stack-up, the spaces 44 between
the edge s~de of the stack-up 45 and the edge wall of the
cell case 46, shown in Flgures 4 and 5, are filled with a
suitable sealantO The se~lant can be a curable 9 llquid,
epoxy resin, or any other plastic resln, rubber or other
materlal, such as polypropylene foam or polyethylene foam,
effective to hermetically seal the space 44 yet not be
chemlcally degraded by the electrolyte
Thls sealant ~lller will seal and encapsulate the
side edge o~ the stack-up and the middle portlon of the
electrolyte lnlet tubeO Preferably the sealant wlll be ;.
curable at about 25C~ Prevention of electrolyte flow
between the wide face slde of the cell stack-up and the
flat, front cell case walls can be accompllshed by a tlght
~lt and intimate contact between the two, as shown in Flgure
5 at 510 This arrangement seals the sides of the electrode
stack-ups, i~e the edge sldes and the wlde face sides but
not the top and bottom of the stack-upO
The electrode plates making up the stack-ups in
the cells are9 preferably~ flexible, porous plaques of about
75% to 95% porosity, made from dlf~usion bonded meta-l flbers,
such as nickel flbers, but preferably steel wool or nlckel
--10~
~ 46,215
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coated steel wool, as descrlbed in UO~O Patent 3,895,~600 ~ ~ :
Other type plates, such as porous slntered nickel powder or
cast porous nlckel can be used, but have not been found as
effective as the expanslble fiber metal platesO The fiber ~:
metal plates can expand and contract during "formation", to
provide superior active material loadingc
These plaques contaln active battery materlal
distributed upon and disposed within the ~ore volume of the
plaqueO When, for example, an iron-nickel cell is to be -:
10 made, the actlve material of the positive electrode plates . ~
may comprise Nl(OH)2, with small effective amounts o~ Co(OH)2 .
actlvating addltlveO The negative electrode plates may
comprise an iron oxide, such as FeO, Fe203, Fe304, Fe203 H20
or their mixtures, with small effective amounts of sulfur
contalnlng actlvating additives fused thereon or mixed
therewith, as described in UOSo Patent 3,853,624. Of course
other types of posltive and negative active materials and
other additlves can be used~
Each electrode plaque has an electrical lead tab :
spot welded or otherwise attached, generally to a colned top
areaO These lead tabs 47 provide means for making electrlcal
connectlons to the plates. Termlnal connection lugs 48 are
attached to the lead tabs to electrically connect the posi-
tive and negative plates to the terminal studs 150
Once the electrolyte flows up through the channels
43 of the stack up, in the preferred embodiment of this
invention, it exits from the cell through the cell electro-
lyte outlet tube 21 and cell exhaust manlfold 130 The
length of the cell electrolyte outlet tube 21 can preferably
be increased, to provide high electrical resistance in the
--11--
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1070376
electrolyte plumbing network., by making it in a coiled or ~:
similar configuration to that shown in Figures 2 and 4O
In all cases9 the plumbing in the cell and battery
module, such as inlet a.nd outlet tubes and manifolds should
be made of a non-conduct~ng tubular material such as poly~ ~ :
propylene, polyethylene, polyvinyl chloride, acrylonitrile .-~
butadiene styrene, nylon or other type plastic or rubber .:.
materlals not degradable by the elect~olyteO These non~
conducting tubes and mani~olds can be attached by a suitable
adhesive such as epoxy or polyvinyl chloride adhesiveO
To insure electrolyte exit through the electrolyte
exhaust tube 21, the space 49 between the top of the cell
case and the top of the exhaust tube entrance may be filled
with a suitable sealant similar to that described herein-
above~ This would also provide a top for the cell caseO In
order to provide such a top, a barrier can be placed over
the top of the bottom opening of the cell electrolyte outlet
tube, and sealant in~ected or poured on top of the barrier
to encapsulate the top of the outlet tube, the top of the ~ .
lnlet tube and the terminalsO
Referring now to Figure 6; a battery is built by
conneeting cell inlet manifolds 14 and outlet manifolds 13
preferably in parallelO To facilitate constructing a hlgh
power battery, several sets of cells, iOeO sets of battery
modules 10, are fa~tened in place with all the fluld flow ln
parallel to minlmize the pressure required for the syætem
and to provide uniform cell to cell coollngO The battery
modules can then be positioned to build a complete high
power battery ~ystem for the voltage and space requirements
of each individual application Figure 6 shows a high power
-12-
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1070376
battery consisting of three banks of three battery modules.
Each battery module contains five cells.
The modules are connected by common battery mani- ;
fold electrolyte circulation means 60, the length and posi-
tion of which are dependent on the battery layoutO The
battery manifolds can be detached from the heat exchanger
means 61 and the electrolyte pumping means 62 by quick
dlsconnect couplings 63, so that the high power battery can -
be discharged wlthout the heat exchanger and pumpO The heat
exchanger or cooling means can comprise an electrolyte
cooling reservoir 64 contaln ng cold water cooling coils 65.
A radiator or other cooling apparatus could be added to the
system for air cooling to replace or supplement the cooling
colls. Electrolyte will be circulated by the pump at rates
effective to remove the heat generated by the various charge,
discharge ratesO
Electrolyte level and specific gravity are con-
trolled by adding water to the electrolyte cooling reservoir
64 through inlet 66, to maintain a constant height level in
the cellsO The battery system is vented to the atmosphere,
preferably at the reservoir, by any suitable means, such as,
for example, a barrler venting means 67, which can be a
slntered ceramic barrler, whlch allows hydrogen and oxygen
to escape whlle acting as a flame and explosion barrler A
bubble tube extending from the openlng in the reservoir lnto
the bottom of an open container of water can also be used to
allow gas to escapeO The alkaline electrolyte generally
used will be a 10 wto% to 35 wt.% KOH or NaOH aqueous solu-
tion wlth preferably about 2 to 20 grams/liter of Li(OH)2.
No gase~ are added to the electrolyte.
-13-
4 6 ~ 2 15
~070376 -`~
" '' ~,
Example 1
An iron-nickel hlgh power battery system sililar ~ -
to that shoNn in Figures 1 through 6 was constructedO The
battery plates were made .~rom nickel plated steel fibers :,.
~ormed into plaquesO Fibers approximately 0 001 x 00 002 x
0025 inch long were used in the flexible, expansible, fiber
metal plaquesO They were then heated, in a protective : ~ :
,.,
environment, causing metal to metal diffusion bonds to form
at fiber contact pointsO There was no melting of fibers so
10 as to assure maximum pore volumeO ~ '`~"`
The "nickel" plaques were then colned to about 8
percent- o~ theoretlcal densityg 92 percent porous, and the
"iron" plaque bodie~ were coined to 17 percent of theoretical ~ ~.
density, 83 percent porousO Each nickel plaque had two
vertical 1/8" wide pressed channelsO The plaque was about
6.5" wide and ~bout 0O09ll thicko The channels were about
0O08ll deepO The channels comprised about 4% of the plaque
surface areaO A steel sheet was then spot welded onto the
top coined port.ion of the plaques to form electrical lead
20 tab connections, shown as 47 in Figure 4O ' :
The tron active material comprised sulfurized :~
magnetlc iron oxlde particlesO The magnetic iron oxide, had
a compo~ition of about 79 percent Fe2O3, 22 percent FeO and
1 percent impuritiesO Enough sulfur was used to provide a
ratio o~ sulfur to iron oxide of about Oo l to 10 percent of
the sulfurized iron oxideO This additive helped keep the
iron active material surface in the active state
The "iron" plaques were loaded with the sulfurized .
magnetic iron oxide by a wet pasting techniqueO These iron .
electrode plates were then sized and driedO They contained
-14-
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~ 07037~ `
about 1.5 to about 1.9 grams/cm3 plaque volume of sulfurized
iron active material.
The nickel active material comprised nickel h~-
droxide doped with a small amount of cobalt h~droxide. The
nickel plaques were loaded b~ an impregnation "formation"
impregnation technique. The~ contained about 0.9 to about
1.3 grams/cm3 of active material. The "iron" and "nickel"
plates were then read~ for the cell stack-up operation.
A batter~ module having dimensions about 7" wide x
10" deep x 10" high, as shown in Figure 1 was used and
consisted of five cells. The cell cases, made of high
density pol~eth~lene and having an open top, were about 7"
wide x 2" deep x 10" high. The~ would contain the electrode
stack-ups.
In the stack-up operation, iron and nickel plates
were alternatel~ stacked, insulated from each other with a
sexpentine wound polyprop~lene separator, and then the
terminal connection lugs, shown as 48 in Figure 4, were
iner~ gas welded to the tabs to pro~ide means for making
electrical connections to the plates. The cell stack-up,
along with a 3/16" inside diameter pol~prop~lene cell elec-
trolyte inlet tube, was then inserted into the cell case on
top of two pol~eth~lene foam blocks, about 1' wide x 2"
deep x 5/8" high, shown as 42 in Figure 4.
The inlet tube ran down the edge side of the
stack-up and next to the narrow edge wall of the cell con-
tainer, curving at the bottom to run underneath the cell
stack-up. The inlet tube stopped at about the middle of the
bottom reservoir, shown as 40 in Figure 4, formed b~ the
cell stack-up and foam blocks 42. A groove had been formed
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ln the foam block whlch the inlet tube ran through so that
the inle~ tube would fit around the bottom of the stack~up
This provided cells having Lnserted electrode
stack-ups supported on the bottom with foam blocks9 having
an electrolyte inlet tube running into a reservoir at the
bottom of the cellO The space, shown as 44 in Figure 4, be-
tween edge sides of the stack-up and the 2" edge walls of
the cell contai.ners was unfilledO ~ -
A viscous9 room temperature curable epoxy resin
was then dispensed, ~rom an in~ection gun, ~nto thls space
44 between each edge side of the stack-ups and each edge
wall of the cell case, to act as a hermetic sealant and to
encapsulate the stack-up between the foam blocks and the top
of the electrode stack-upO The top and bottom of the stack-
up remained unsealedO This would force the pumped electro-
lyte, from the bottom reservoir, to run through the plate
channels 43 to the top of the cell rather than around the
plates.
The top of the cell was fitted with a 5/16" inside
diameter polypropylene cell electrolyte outlet tubeO This
tube, shown as 21 in the drawlngs, is ln a coiled conflgur-
ation. It starts Just above the electrode stack-ups, under
the cell exhaust manifold and runs across the cell width,
coiling around the cell electrolyte lnlet tube, running back
across the cell, and fitting into the cell exhaust manifold,
as shown in Figures 2, 3 and 4O
In order to ~orm a top on the cell, the cell .
electrolyte outlet tube was held in place, with the outlet
opening Just at the top of the cell stack-up, with polyvinyl .. ;
chloride adheslve tapeO The tape had holes for the Dottom
-16-
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-,~
portion of the electrolyte outlet tube, the positive and
negative interconnection lugs and the top of the electrolyte
inlet tube to fit throughO A top reservoir volume was thus
formed bekween the tape and the top of the stack-upsO
A vigcous, room temperature curable epoxy resin
was then dispensed, from an in~ection gun, on top of the .
tape to encapsulate the top portion of the cell electrolyte
outlet and inlet tubes and the intercell connection lugs. `
Thus epoxy resin formed the top of the cellO
The iron plaque in the stack-up was still in un-
formed conditionO An electrolyte solution containing 25
wt.% KOH and 15 grams/liter of Li(OH)2 was po~red lnto the
cell and "formation" of the iron plaques was accomplsihed by
a series of charge-discharge cyclesO ~
Cells were then matched and electrically connected ~-
to form a five cell battery moduleO Four modules were
placed in series and 1/2" inside diameter polyvinyl chloride
cell inlet manlfolds and 3/4" inside diameter cell exhaust
manlfolds were connected to the cell electrolyte inlet tubes
and cell electrolyte outlet tubes respectively with room
temper~ture curable epoxy resin glueO Each module was
slmilar to that shown in Figure 1, ~ith the manifolds 13 and
14 in parallel on top of the cellsO The modules were assem- ~
bled as shown in Figure 6, only there were four banks of - ::
modules, each bank contain four connected battery modules,
each module containing five cellsO Thusg there were a total
of 16 modules or 80 cells to form the high power batteryO
Referring to Figure 6, the cell inlet manifolds 14
and exhaust manifolds 13 were connected to common 1" inside
diameter polyvinyl chloride battery manifolds with flexible
-17- :,
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.,,i
polyvinyl chlorlde hose and hose clamps The pump manifolds
were connected to a 1/4 HoPo pump and a 25 gallon electro-
lyte reservolr 61 made of polyvinyl chlorideO
The reser~oir had a closed top and a cer~mic flame : ~
arrestor barrier vent 66, to exhaust hydrogen or oxygen ~ ~ `
present in the electrolyte due to charglng, and an inlet 67
for adding water or electrolyteO The cooling coils 65 were
made: from 20' of coiled 1/2" lnside diameter stainless
steelO Cold water was circulated through the colls to cool
10 the circulating electrolyteO `~.
The electrolyte solutton used. in the system con~
tained 25 wt % KOH and 15 grams/liter of Li(OH)2o No gases
were added to the electrolyteO The pump and reservoir were
connected to the battery modules through dlsconnect valves
in the common pump manlfolds so that the high power battery -
could be discharged without themO
The assembled hlgh power battery was then bench :~
tested through several 3 hour charge9 2 hour discharge test
cycles to establish a capacity ratingO Best results yielded
about 17 KWH, or 20 Wh/pounds of cellO The battery was then
operated in several electrical vehicles in excess of 100
cycles O
The 80 cell (96 volt) circulatlng electrolyte
battery was charged uslng a C/2 (100 AmpO ) charge rate for 3
hoursO Total electrolyte flow was 9 galO per m~nO, at an
average pressure drop across the cell lnlet-exhaust mani-
folds of 5 psio The in~tial reservoir electrolyte tempera-
ture was 25Co The temperature of the battery after a full
charge was 32Co If no electrolyte circulation was pro~ided
30 during charging, the battery temperature after a full charge :
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46,215
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. ~070376
would have been in excess of 70C, which would be very
detrimental to the operating life of the electrodes and
separators.
In operation, the epoxy resin sealing system at
the edge sides of the plates in the stack-up and the top of
each cell proved to be leakproofO Uniform and very efficient
and ef~ectlve cooling of the cells during charging was
accomplished~ No deleterious self-discharge was observed by ~- .
electrlcal conductivity of the electrolyte circulation
10 plumbing systemO There was no excessive increase in pres- ~.
sure drop in a cell after 2,000 charge-discharge cyclesO
This shows evldence of no plugging of the plate channels due
to plate swelling or loose active material. The use of 2
channels per nickel plate, constltutlng 4% of one side of ~:~
the nlckel plate surface area, provided adequate cooling ~or
thls system. More channel~, up to 10% of plate surface
area, could be added where more cooling and le~s active
material volume is required~
-19- ' .
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