Note: Descriptions are shown in the official language in which they were submitted.
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~A~I~RI~S
This invention relates to batteries, and in
particular to composite batteries comprising a plurality of
interconnected cells.
Various batteriQs according to this invention
will now be described by way of example with reference to
the drawings, in which:-
Figure 1 is a perspective view of a sodium-
sulphur cell with part broken away;
Figure 2 illustrates the series connection of two
cells as shown in Figure l;
15Figure 3 illustrates a battery comprising a
plurality of series arrangements of cells arranged between
a pair of bus plates;
Figure 4 illustrates a method of securing the bus
plates of the arrangement of Figure 3 together;
20Figure 5 is a plan view of a battery having
separators between adjacent cells:
Figure 6 is a plan view of a battery similar to
that of Figure 5 but with a different form of separator;
Figure 7 is a side view of a separator of the
25battery of Figure 6;
Figure 8 is an end view of the separator of
Figure 7; and
Figure 9 is a perspective view of a battery
comprising two arrays of series arrangements of cells.
Many forms of battery are known, from a single
cell, to arrangements comprising a plurality of intercon-
nected cells as necessary to give a required energy storage
capacity.
Batteries can also be divided into two main
types: primary batteries which have a relatively short life
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and which are discarded when exhausted, such batteries
often being a single cell and used for torches, radios and
toys: and secondary batteries which are rechargeable when
exhausted and thus have a relatively long life, such
batteries being used for starting automobiles, powering
fork lift trucks and electric vehicles, and providing
standby power for buildings and telephone exchange equip-
ment.
Both primary and secondary batteries of dry
alkaline type are known, as are secondary batteries of lead
acid type.
Recently secondary batteries of sodium sulphur
type have become known, such batteries having the advan-
tages of light weight, high storage capacity and relatively
quick recharging time. Further, such batteries use sodium
and sulphur both of which are cheap and abundant materials.
Unlike conventional lead acid batteries in which
a liquid electrolyte - dilute sulphuric acid - separates
two solid electrodes, in a sodium sulphur battery a solid
electrolyte - beta alumina - separates two liquid elec-
trodes, namely liquid sulphur and sodium electrodes.
Such a sodium sulphur cell is shown in Figure 1
of the drawings, which is a perspective view of the cell
with part broken away.
As shown the cell comprises a pressed steel case
1 in the form of a right circular cylinder containing a
solid ~lectrolyte cup 2 of beta alumina, the cup 2 contain-
ing a sodium electrode 3, while a space between the case 1
and the cup 2 contains a sulphur electrode 4. For use, the
cell is maintained at a temperature of about 350~C such
that the sodium and sulphur electrodes 3 and 4 are in
liquid form.
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The open end of the cup 2 is closed by an insu-
lating disc 5 of alpha alumina~ while the case 1 is closed
by an annular steel disc 6.
The case 1 serves as a terminal for the sulphur
electrode 4, while the sodium electrode 3 contains an
elongate metal current collector 8 which extends axially of
the case 1 out through the disc 5 where it is connected to
a centre terminal disc 7 mounted on the disc 5, the necess-
ary connections being made by welding.
The atomic structure of beta alumina is such that
it acts as a selective ion filter. When the cell is
discharging sodium ions pass from the sodium electrode 3
through the electrolyte 2 to react with the sulphur elec-
trode 4 to form sodium sulphide. The chemical energy of
this reaction i8 converted directly to electrical energy.
When the cell is charged, sodium and sulphur are
regenerated from the sodium sulphide, the input electrical
energy being converted into chemical energy.
To provide a battery capable of powering a
vehicle it may be necessary for about 3000 cells as
described above to be assembled together in arrays of
series-connected arrangements of cells, the arrangements in
each array being connected in parallel, and the arrays of
arrangements being connected in series.
According to one aspect this invention provides
a battery comprising a plurality of cells or series
arrangements of cells arranged between a pair of electri-
cally conductive bus plates each serving to interconnect
corresponding terminals of the cells or series arrangements
therebetween, each terminal of each cell, or the end
terminal of each series arrangement, being connected to the
adjacent bus plate by means of a conductive metal strip
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welded to the terminal and having free ends passing through
a hole in the bus plate and welded to the side of the bus
plate remote from the terminal.
According to another aspect this invention
provides a battery comprising a plurality of parallel cells
or parallel series arrangements of cells, including elec-
trically insulating separators between adjacent cells or
series arrangements, the separators being in the form of
metal sheets covered with an electrically insulating
coating.
According to yet another aspect this invention
provides a battery comprising a plurality of parallel cells
or parallel series arrangements of cells, including elec-
trically insulating separators between adjacent cells or
series arrangements, each separator comprising an elongate
member formed with peripherally spaced concave surfaces
which engage respective cells or cells in respective series
arrangements.
According to a further aspect this invention
provides a battery comprising one or more arrays of cells
or series arrangements of cells, arranged between a pair of
bus plates, including a heat sink in thermal connection
with one of the bus plates of the or each array with an
interposed electrically insulating layer interposed between
the heat sink and the bus plate or plates.
According to a still further aspect this inven-
tion provides a battery enclosed in a thermally insulating
housing which helps to maintain the battery at a required
temperature, in which terminals of the battery are con-
nected to leads which extend out of the housing, the length
of each lead within the housing wall being greater than the
thickness of that housing wall.
Figure 2 of the drawings is a side view, partly
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in section, of a two-cell battery comprising a pair
of cells separated by an interposed spacer member, a
terminal of one cell being connected to a terminal of
the other cell by a conductive member secured to the
terminals of the t~o cells and extending through an
aperture in the spacer member.
With cells as described above with reference to
Figure 1, the conductive member can be welded to the
centre terminal disc of the one cell and to the case
of the other cell, thereby to connect the cells
together in series.
The spacer member can be of any suitable
insulating material, such as a ceramic or porcelain
material, and can either be preformed, for example in
the shape of an annulus, or otherwise formed in situ,
for example by injection of a cement material between
the cells.
The spacer member serves to prevent contact
between the cases of the t~o cells while permitting
the necessary connection between the centre terminal
of one cell and the case of the other.
More specifically the battery of Figure 2
comprises two cells 20, 21, each having a cylindrical
case 22 constituting one terminal and a centre
terminal disc 23 at one end of the case 22
constitu,ing the other terminal. The cells 20, 21
are arranged end-to-end with the centre terminal disc
23 of the lower (as shown) cell 20 adjacent the
bottom surface 24 of the other upper (as shown) cell
'0 21, with an annular spacer member 25 of insulating
ceramic or porcelain material interposed between
them. The spacer member 25 serves to prevent contact
between the cases 22 of the two cells 20, 21. A
strip 26 of conductive metal extends across the
bottom surface 24 of the upper cell 21 and is welded
thereto at the free ends of the strip 26. At its
1 31 62 1 1
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centre the strip is formed to extend downwardly
through the aperture 27 in the spacer member 25 to
engage over the current collector 28 of the lower
cell 20 and be welded to the centre terminal disc 23
of the lower cell 20. The strip 26 thus provides the
necessary connection between the centre terminal disc
23 of the lower cell 20 and the case 22 of the upper
cell 21, while the spacer member 25 prevents direct
contact between the cases 22 of the two cells 20, 21.
Clearly larger batteries can be provided by
arranging the required number of cells in end-to-end
arrangement with an annular spacer member interposed
between each pair of adjacent cells and with adjacent
cells connected by a welded strip conductor as
described.
To achieve a battery having the required
storage capacity and voltage, it may be necessary to
connect a plurality of cells or series arrangements
of cells, for example as described with reference to
Figure 1 or Figure 2, in parallel, that is with ends
of the cells or series arrangements connected
together, and such a battery will now be described
with reference to Figure 3 of the drawings which is a
sectional side elevational view of part of the
battery.
The battery comprise a plurality of series
arrangements of cells arranged between a pair of
electrically conductive bus plate~ each serving to
interconnect corresponding terminals of the series
arrangements therebetween.
The end terminal of each series arrangement is
connected to the adjacent bus plate by means of
conductive metal strip welded to the terminal and
having free ends passing through a hole in the bus
plate and welded to the side of the bus plate remote
from the terminal.
1 31 621 1
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one bus plate (the lower one in the drawing)
serves to interconnect the cases of the cells at one
end of the arrangements. If eoualisation of voltage
is requi,ed, then other corresponding cells in the
series arrangements can be interconnected by means of
electrically conductive members arranged between
their cases, the battery thus comprising a plurality
of series arrangements of parallel connected cells.
More specifically, as shown in Figure 3 a
plurality of series arrangements each of three cells
30, as described above with reference to Figures 1
and 2, with adjacent cells in each arrangement
separated by spacer members 31 and connected by
conductive metal strips 32, are arranged in parallel
between a pair of mild steel bus plates 33.
Each bus plate 33 is formed with a matri~ of
holes 34 aligned with the central axes of the series
arrangements of cells 30, and the case 35 of the
lower (as shown) cell 30 in each arrangement, and the
centre terminal disc 36 of the upper (as shown) cell
30 in each arrzngement, is electrically connected to
the adjacent bus plate 33 by means of a conduc~ive
metal st,ip 37 welded at its centre to the case 35 or
terminal disc 36, and having its free ends passing
through the aligned hole 34 and welded to the side of
the bus plate 33 remote from the cells 30.
Thus, the cells 30 are connected in series
within each serles arrangement while the series
arrangements are connected in parallel by the bus
plates 33. As shown, the cases 35 of corresponding
cells 30 in the series arrangements are
interconnected by electrically conductive members 38
arranged between them whereby equalisation of voltage
is achieved at each cell level in the battery.
As a modification of the battery described
above with reference to Figure 3, the lower cell 30
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in each series arrangement can be connected to the
adjacent bus plate 33 by a conductive metal strip 37
having its free ends welded to the case 35 of the
cell 30 with an initial central loop portion
extending through the aligned hole 34 in the bus
plate 33. The loop portion is then cut to provide
two free end portions which are then folded back over
the surface of the bus plate 33 remote from the cells
30, and welded thereto.
Batteries as described above have the advantage
of low resistance in the connections between adjacent
cells and between the series arrangements of cells.
With a battery as shown in Figure 3, the pair
of bus plates can be clamped together by means of a
plurality of tie rods, for example one adjacent each
corner of the battery, each tie rod either having a
head at one end and a screw thread at the other, or
screw threads at both ends. The ends of the tie rods
can be located in pockets formed in the bus plates in
any convenient manner in order to maintain a flush
arrangement, nuts being applied to the threads on the
rods and tightened to clamp the bus plates together.
An insulating washer of, for example, ceramic
material, is provided at at least one end of each tie
rod in order to prevent the tie rod providing a short
cirucuit between the bus plates.
Such an arrangement is shown in Figure 4 of the
drawings, which shows bus plates 33 each formed with
a pocket 40. A tie rod 41 extends between the
pockets 40. The pocket 40 in the lower plate 33
receives a nut 42 engaged on a thread on the tie rod
41, while the pocket in the upper plate 33 receives a
ceramic insulating washer 43 which is engaged by a
head 44 on the rod 41. 8y tightening the nut 42 the
plates 33 can be clamped together about the series
arrangements of cells therebetween.
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With a battery as described above comprising a
plurality of series arrangements of cells clamped
between a pair of bus plates, it must be ensured that
the cases of cells in adjacent seri_s arrangements do
not touch and thus produce unwanted short-circuit
paths. Further, it is preferable for the series
arrangements to be as close as possible to each other
in order to keep the battery as small as possible.
Thus, a battery comprising a plurality of cells
;0 clamped between a pair of bus plates preferably
includes electrically insulating separators between
adjacent cells.
Preferably the separators extend the full
distance between the bus plates.
The cells can be in series-arrangements as
described above, in which case the separators
preferably each extend the length of the series
arrangements between the bus plates.
The separators can be in the form of corrugated
sheets each having a plurality of corrugations shaped
to engage about part of the periphery of a plurality
of cells or series arrangements of cells,
respectively, thereby to ~aintain adjacent cells or
series arrangements in the required spaced ar_ay.
The separators can be made of aluminium sheets
of say 1.6 mm thickness, covered with an elec~.ically
insulating coating of, for example, flame sprayed
ceramic material, alumina, chromium carbide, or
magnesia. The sheets can otherwise be anodised or
coated with a heat resistent vitreous enamel.
The separators not only serve to insulate
adjacent cells from one another while also serving to
locate the cells in the complete cell array, but also
serve to conduct heat within the array of cells and
between the bus plates to maintain a substantially
uniform temperature throughout the battery.
1 31 621 1
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Figure 5 of the drawings in a plan view of a
battery including separators as described above, the
upper bus plate of the battery being partly broken
away.
As shown, a plurality of series arrangements of
cells 50 are arranged between two bus plates 51, with
the end cells 50 in each arrangement being
electrically connected to the adjacent bus plate 51
by metal strips 52, as shown in Figure 3. The cell
arrangements are arranged in mutually staggered rows
with corrugated insulating separators 53 arranged
between the rows, the separators 53 serving to
electrically insulate the cells in adjacent rows from
each other while maintaining the cells 50 in their
positions in the complete array. If necessary or
desirable adjacent cells 50 in the rows defined by
the separators 53 can be separated by electrically
insulating chock members 54 which can either extend
the full height of the series arrangements of cells
or be individual to pairs of adjacent cells 50.
Figure 6 of the drawings shows a battery
including a different form of separator, each
comprising an elongate member extending between the
bus plates 51 and formed with three peripherally
spaced concave surfaces 61 which engage respective
cells 50 or the cells in respect series
arrangements. Figures 7 and 8 of the drawings are a
side elevation view and an end view, respectively, of
such a separator 60.
Such separators can be made of porcelain
material such as cordierite, for example by
extrusion, and can be of any length, the appropriate
number being used as required.
Although in the battery shown in Figure 6 all
the space between the cells 50 is filed with spacer
members 61, it will be appreciated that alternate
l~11621l
rows of spacer members 61 can be omitted to leave air
spaces, the remaining spacer members 61 being
sufficient to locate the cells 50 as necessary.
Further, as shown, the spacer members can each
have a longitudinally extending hole therethrough for
the passage of a cooling fluid through the battery.
A complete battery can be constituted by one or
more arrays of cells or series arrangements of cells,
arranged between a pair of bus plates, as described
above.
Such a battery can include a heat sink in
thermal connection with one of the bus plates of the
or each array with an interposed electrically
insulating layer interposed between the heat sink and
the bus plate or plates, heat from the array or
arrays being conducted to the heat sink for
dissipation as necessary.
The heat sink can be of aluminium with the
insulating layer being in the form of a suitable
coating thereon.
The heat sink can be formed of two layers of
aluminium with an electrical heating element
sandwiched between them, the heating element serving
for at least initial heating of the battery from
cold. Otherwise the heating element can be located
in a slot in a one piece heat sink.
The heat sink can otherwise be constructed from
a relatively thin aluminium sheet carrying a foil of
pyrolitic graphite. Such a foil has a very
anisotropic heat conductivity, being high in the
plane of the foil and low transverse to the plane of
the foil. The aluminium sheet would be formed with a
plurality of studs which are received in respective
holes in the foil thereby to transmit heat between
the sheet and foil. With such a heat sink the heat
from the battery would be conducted to the edges of
1 31 621 1
the heat sink for dissipation. As a modification of
such a heat sin~ the pyrolitic graphite foil can be
cut into strips and reassembled to give a layer with
high conductivity through the thickness of the heat
S sink and in only one direction in the plane of the
:~eat sink whereby heat to be dissipated is conducted
to one edge only of the heat sink for dissipation.
Figure 9 of the drawings shows a complete
battery comprising two arrays of series arrangements
of cells 90 arranged between respective pairs of bus
plates 91 as described above, with the lower bus
plates 91 of the arrays resting on a common aluminium
heat sink 92 having an electrical heating element 93
sandwiched therein, there being an electrical
insulating layer 94 between the bus plates 91 and the
heat sink 92.
As shown in Figure 9, the upper bus plate 91 of
one array of cells is connected to the lower bus
?late 91 of the other array of cells, thereby to
connect the two arrays in series, by means of a
.-umber (only one shown) of rods 95. The rods 95 can
_e of aluminium but with stainless steel end
?ortions. Thus, the end portions of the rods 95 can
be readily welded to the mild steel bus plates,
.ielded interconnections being desirable in order to
:~eep the internal resistance of the battery as low as
~ossible. The stainless steel end portions can
-eadily be frict~on welded to the aluminium rods,
.ihereas aluminium can not be welded to mild steel.
otherwise a single plate can be bent to serve
as the upper bus plate of one array and the lower bus
-late of the adjacent array, the intermediate portion
^f the plate extending between the arrays and in
effect replacing the rods 95. Further, if an array
can be used upside down in relation to an adjacent
array, a single "double size" bus plate can be used
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to span the two arrays.
The current distribution in a bus plate 91 can
be improved by providing an edge plate 96 along one
edge of the bus plate 91, for example by welding a
strip of aluminium to the bus plate 91 as shown in
Figure 9. Such an edge plate can be provided with
one or more tab portions 97 for establishing
electrical connections thereto.
If required the heat sink 92 can be used as one
terminal of the complete battery by being connected
to the lower bus plate 91 of one of the arrays.
Although the battery shown in Figure 9 consists
of only two cell arrays, it will be appreciated that
any required number of arrays can be similarly
connected to give a complete battery having the
required parameters.
For use, batteries as described above are
generally enclosed in a thermally insulating housing
which helps to maintain the battery at the reauired
temperature. Such a housing can be constructed from
two spaced layers of steel, with the space bet.;een
the layers evacuated to give good thermal insulation
properties. One end of such a housing can initially
be left open for insertion of the battery, and can
2~ then be closed, for example by a wall of insulating
material or by a wall constructed similarly to the
remainder of the housing, but having a portion or
portions formed of electrically insulating material
for passage therethrough of leads for establishing
connections to the terminals of the battery.
Batteries as under consideration are capable of
giving high power output, and thus the leads
connected thereto must be of substantial diameter,
say 6mm. Such leads can be connected to the
3S terminals of the battery and led out of the housing
through the insulating wall or the insulating
1 31 62 1 1
material in the finally applied wall.
A difficulty which arises with such provision
of leads is that due to the necessary size, that is
cross-section, of the leads for them to serve their
electrical function, they also provide a good path
for heat to be conducted out of the battery, and
steps should be taken to minimise this heat loss.
Thus, in such a battery assembly comprising a
battery contained in a thermally insulating housing,
0 with ter~inals of the battery being connected to
leads which extend out of the housing, the length of
each lead within the housing wall is preferably
greater than the thickness of that housing wall.
Such an arrangement enables leads of sufficient
power handling capability to be used while
restricting heat loss from the battery along the
leads to a minimum.
The greater the length of lead used the greater
the electrical resistance, and thus care must be
taken to ensure that the length used does not result
in creation of a hot spot in the lead.
As an example, with a lead diameter of 6 mm, a
length of lead of 120 mm in a housing wall thickness
of 50 mm has been found to be acceptable.
The temperature across the wall of the housing
of a battery assembly as discussed above changes
gradually, and thus the leads should extend gradually
through the wall thickness. This can be achieved by
winding the portion of each lead in the wall into a
helical path which progresses gradually across the
wall thickness.
Otherwise the lead can follow a zig-zag path or
any planar path of suitable length. The dimensions
of the lead can vary along the path in order to give
3s the lead the required thermal conductivity at all
positions along the path.
--` 131621 1
Although the batteries specifically described
above comprise sodium sulphur cells it will be
appreciated that batteries as described can otherwise
incorporate cells of a different type.
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lS
