U.S. patent application number 09/878973 was filed with the patent office on 2001-11-22 for electrode plate for lead-acid battery and manufacturing method thereof.
This patent application is currently assigned to JAPAN STORAGE BATTERY CO., LTD.. Invention is credited to Kamada, Akira, Omae, Takao, Watanabe, Masashi.
Application Number | 20010042288 09/878973 |
Document ID | / |
Family ID | 27280321 |
Filed Date | 2001-11-22 |
United States Patent
Application |
20010042288 |
Kind Code |
A1 |
Omae, Takao ; et
al. |
November 22, 2001 |
Electrode plate for lead-acid battery and manufacturing method
thereof
Abstract
A lead-acid battery electrode plate is manufactured by
consecutively supplying a lead or lead alloy sheet; leaving a part
in the vicinity of the center of the sheet as a non-expansion
portion and expanding both sides like mesh to form a grid body;
filling active material paste into the grid body; and cutting the
grid body to predetermined dimensions. In the lead-acid battery
electrode plate, the non-expansion portion forms a current
collector part of the electrode plate along an expansion portion in
an up and down direction of the electrode plate. One or more
openings are made in a part of the non-expansion portion. A part of
the non-expansion portion is projected above the position of an
upper margin of the cut expansion portion as a current collector
lug part. When the current collector lug part is placed upside, the
expansion direction is the width direction of the electrode
plate.
Inventors: |
Omae, Takao; (Kyoto, JP)
; Kamada, Akira; (Kyoto, JP) ; Watanabe,
Masashi; (Kyoto, JP) |
Correspondence
Address: |
SUGHRUE MION ZINN MACPEAK & SEAS PLLC
2100 Pennsylvania Avenue, NW
Washington
DC
20037-3213
US
|
Assignee: |
JAPAN STORAGE BATTERY CO.,
LTD.
|
Family ID: |
27280321 |
Appl. No.: |
09/878973 |
Filed: |
June 13, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
09878973 |
Jun 13, 2001 |
|
|
|
09488639 |
Jan 21, 2000 |
|
|
|
Current U.S.
Class: |
29/2 ;
429/242 |
Current CPC
Class: |
H01M 4/745 20130101;
H01M 4/20 20130101; Y02E 60/10 20130101; Y10T 29/10 20150115; H01M
50/50 20210101; H01M 4/82 20130101 |
Class at
Publication: |
29/2 ;
429/242 |
International
Class: |
H01M 004/74; H01M
004/73; B23P 013/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 21, 1999 |
JP |
P.HEI. 11-013564 |
Apr 28, 1999 |
JP |
P.HEI. 11-121052 |
Jul 14, 1999 |
JP |
P.HEI. 11-199898 |
Claims
What is claimed is:
1. A lead-acid battery electrode plate manufactured by a process
comprising the steps of: (1) consecutively supplying a lead or lead
alloy sheet; (2) leaving a part in the vicinity of the center of
the sheet as a non-expansion portion and expanding both sides like
mesh to form a grid body; (3) filling active material paste into
the grid body; and (4) cutting the grid body to predetermined
dimensions; wherein the non-expansion portion forms a current
collector part of the electrode plate along an expansion portion in
an up and down direction of the electrode plate; one or more
openings are made in a part of the non-expansion portion; a part of
the non-expansion portion is projected above the position of an
upper margin of the cut expansion portion as a current collector
lug part; and when the current collector lug part is placed upside,
the expansion direction is the width direction of the electrode
plate.
2. The lead-acid battery electrode plate as claimed in claim 1,
wherein openings are not made in the current collector lug part or
the non-expansion portion in a given portion downward from the
position of the upper margin of the cut expansion portion, and the
dimensions of the given portion are equal to or greater than mesh
major axis dimensions of the expansion section.
3. A manufacturing method of a lead-acid battery electrode plate,
comprising the steps of: consecutively supplying a lead or lead
alloy sheet; leaving a part in the vicinity of the center of the
sheet as a non-expansion portion and expanding both sides like mesh
to form a grid body, so that the non-expansion portion forms a
current collector part of the electrode plate along an expansion
portion in an up and down direction of the electrode plate; making
one or more openings in a part of the non-expansion portion;
filling active material paste into the grid body; and cutting the
grid body to predetermined dimensions; wherein a part of the
non-expansion portion is projected above the position of an upper
margin of the cut expansion portion as a current collector lug
part; and when the current collector lug part is placed upside, the
expansion direction is the width direction of the electrode
plate.
4. The lead-acid battery electrode plate manufacturing method as
claimed in claim 3, further comprising the step of, after an active
material is pasted into the full face containing the non-expansion
portion of the grid body, partially removing the active material on
a portion corresponding to the current collector lug part for
exposing a metal surface.
5. The lead-acid battery electrode plate manufacturing method as
claimed in claim 4, wherein the step of partially removing the
active material on a portion corresponding to the current collector
lug part is performed after a surface of the electrode plate is
dried and before a curing step.
6. The lead-acid battery electrode plate manufacturing method as
claimed in claim 4, further comprising the steps of, after the
active material is consecutively pasted into the grid bodies
concatenated like a belt, separating electrode plates, and
subsequently rotating the electrode plate 90 degrees, then
partially removing the active material.
7. The lead-acid battery electrode plate manufacturing method as
claimed in claim 4, further comprising the step of: before pasting
the active material, applying a parting agent onto the portion on
which the active material is to be removed after pasting.
8. A manufacturing method of a lead-acid battery electrode plate as
claimed in claim 3, wherein after the grid body is cut to
predetermined dimensions, active material paste is pasted into the
full face containing the non-expansion portion.
Description
BACKGROUND OF THE TNVENTION
[0001] 1. Field of the Invention
[0002] This invention relates to an expanded grid body mainly used
with a large-sized lead-acid battery and a manufacturing method of
an electrode plate using the expanded grid body.
[0003] 2. Description of the Related Art
[0004] As a manufacturing method of pasted-type lead-acid battery
electrode plate, for example, there is the following manner as
shown in FIG. 1. That is, a lead or lead alloy sheet 1 is expanded
like mesh by an expanding machine 2. A current collector lug part
(simply referred lug part) is formed in a non-expansion portion 4.
A grid body which is an expansion portion 3 is filled with an
active material paste. Thereafter, the grid body is cut by a cutter
9 to separate electrode plates of a predetermined size. This method
is high in productivity and so-called expanded electrode plates
manufactured by the method are uniform and the mass of the grid
body relative to the active material can be decreased, so that
weight reduction is possible.
[0005] Hereinafter, the width and the height of the grid body or
electrode plate will refer to directions when the grid body or
electrode plate is placed with the lug part upside.
[0006] An electrode plate of a large-capacity lead-acid battery
used as a backup power source of telecommunication, etc., or an
emergency power source is sized about 150 mm in the width
direction, but about 250 to 500 mm in the height direction with a
lug part upside. If such a large-sized electrode plate is formed of
an expand plate expanded in the grid body height direction with a
non-expansion portion left as shown in FIG. 2, the expaned portion
grows and thus the following disadvantages are included:
[0007] Since the height of epanded portion becomes large, the
manufacturing devices are upsized;
[0008] handling at the assembling time becomes difficult to perform
(warpage, deformation of electrode plate because of insufficient
strength); and
[0009] voltage drop in the expansion portion becomes remarkably
large and poor discharge performance results.
[0010] As a method of overcoming these disadvantages, a method of
increasing a non-expansion portion 4 in the upper part of a grid
body and providing an opening 13 in the increased part
(JP-U-58-133271) as shown in FIG. 3, and a method of leaving a
non-expansion portion 4 both in margins and in the center and
providing an opening 13 in the center (JP-A-2-267864, FIG. 4) have
been proposed. However, improvement in the discharge performance is
insufficient for a large-sized electrode plate of which is large in
the height direction as compared with the width direction. Then,
several expanded electrode plates (grid bodies), each expanded in
the grid body width direction with a non-expansion portion left in
the grid body height direction were proposed in the past (for
example, JP-A-54-177525, JP-B-59-51107, JP-B-61-8540, and JP Patent
No. 2765020).
[0011] Since an electric current flowing into an electrode plate
also becomes large in a large battery, it is necessary to widen the
lug part width to some extent. However, if the lug part and the
non-expansion portion following the lug part are set to the same
width, the grid body mass is increased and the active material
holding (filling) amount is decreased. Then, in the expand
electrode plates expanded in the grid body width direction, the
width of the non-expansion portion 4 following the lug part 11 is
made narrower than that of the lug part as shown in FIG. 5.
However, the lug part 11 of the grid body of this shape extends off
an active material fill part 12 to one side. Thus, as shown in FIG.
6, if an electrode plate using the grid body of this shape is
superposed on an electrode plate different in polarity to
manufacture a battery, a portion 14 not overlapping the adjacent
electrode plate occurs and the efficiency of active material
availability decreases, leading to capacity shortage of the
battery. Particularly, in a valve regulated sealed lead-acid
battery using a fine glass fiber separator, it is known that a
battery with a compression degree of the electrode plate and the
separator is inferior in life performance, and there is a
possibility that capacity lowering at an early stage will occur
because of shortage of the pressure degree in the portion not
overlapping the adjacent electrode plate. On the other hand, as
shown in FIG. 7, if the electrode plates are placed one upon
another so as to completely superpose the active material fill
portion 12, current collector lug parts 11 project to a side, thus
a battery container 15 must be designed large, resulting in
lowering of the volume energy density. Further, a grid body extends
in a gap 16 between the electrode plate and the battery container
15, whereby adhesion properties of grid members with active
material worsen, leading to lowering of the battery capacity.
[0012] To furthermore improve current collection performance and
decrease scrap loss, a mesh part is provided on both sides of a
non-expansion portion in JP-B-61-8545. However, if a decrease in
the scrap loss is given a high priority, an increase in the grid
body mass and battery capacity shortage caused by decrease of the
active material filling amount introduce a problem.
[0013] To provide an active material mass in the expanded grid body
expanded in the grid body width direction, an active material may
also be filled into a non-expansion portion. As shown in FIG. 1, to
fill an active material into the expanded grid body of the
conventional shape, the active material is prevented from being
deposited on current collection lug parts 8, because welding
becomes extremely difficult to perform if an active material is
deposited on electrode plate lug parts when the electrode plate of
the same polarity lug parts are welded at the battery assembling
process. However, as shown in FIG. 8, in the expanded electrode
plate expanded in the grid body width direction, to consecutively
fill an active material also into non-expansion portion 4 in a
concatenation state of grid body like a belt, the active material
is also deposited on the lug parts because the electrode plate lug
parts 8 are positioned on the same line as the fill part with
respect to the grid body travel direction To circumvent this
problem, it is also possible that the direction is changed after
cut to separate grid body forms and that the grid body is passed
through a pasting machine with the grid body set perpendicular to
the travel direction, but uniformity of filling and the
productivity of electrode plates are degraded.
[0014] In fact, the expanded grid bodies expanded in the width
direction are scarcely used because of the problems.
SUMMARY OF THE INVENTION
[0015] It is therefore an object of the invention to provide a grid
body form that can be intended for reducing the weight of an
electrode plate and enhancing the productivity of the electrode
plate and a manufacturing method of an electrode plate using the
grid body form without degrading battery performance to apply an
expanded electrode plate to a large-sized lead-acid battery.
[0016] According to the present invention, a lead-acid battery
electrode plate manufactured by a process comprises the steps of:
(1) consecutively supplying a lead or lead alloy sheet; (2) leaving
a part in the vicinity of the center of the sheet as a
non-expansion portion and expanding both sides like mesh to form a
grid body; (3) filling active material paste into the grid body;
and (4) cutting the grid body to predetermined dimensions; wherein
the non-expansion portion forms a current collector part of the
electrode plate along an expansion portion in an up and down
direction of the electrode plate; one or more openings are made in
a part of the non-expansion portion; a part of the non-expansion
portion is projected above the position of an upper margin of the
cut expansion portion as a current collector lug part; and when the
current collector lug part is placed upside, the expansion
direction is the width direction of the electrode plate.
[0017] According to the present invention, a manufacturing method
of a lead-acid battery electrode plate comprises the steps of:
consecutively supplying a lead or lead alloy sheet; leaving a part
in the vicinity of the center of the sheet as a non-expansion
portion and expanding both sides like mesh to form a grid body, so
that the non-expansion portion forms a current collector part of
the electrode plate along an expansion portion in an up and down
direction of the electrode plate; making one or more openings in a
part of the non-expansion portion; filling active material paste
into the grid body; and cutting the grid body to predetermined
dimensions; wherein a part of the non-expansion portion is
projected above the position of an upper margin of the cut
expansion portion as a current collector lug part; and when the
current collector lug part is placed upside, the expansion
direction is the width direction of the electrode plate.
[0018] According to the invention, the electrode plate using the
expanded grid body excellent in discharge performance and
productivity can be provided particularly as a large-sized
lead-acid battery electrode plate.
BRIEF DESCRIPTION OF THE DRAWINGS
[0019] In the accompanying drawings:
[0020] FIG. 1 is a schematic drawing to show a manufacturing method
of a conventional expanded grid body and an electrode plate using
the grid body;
[0021] FIGS. 2 to 5 are drawings to show conventional examples of
large-sized expanded grid bodies;
[0022] FIGS. 6 and 7 are drawings to show combination examples of
electrode plates using conventional large-sized expanded grid body
expanded in the grid body width direction;
[0023] FIG. 8 is a drawing to show an example of taking out a grid
body expanded in the width direction from an expanded sheet;
[0024] FIG. 9 is a drawing to show the form of a grid body of the
invention before filling and cutting;
[0025] FIG. 10 is a drawing to show the form of the grid body of
the invention after cutting;
[0026] FIG. 11 is an enlarged schematic drawing to show the grid
body of the invention;
[0027] FIG. 12 is a drawing to show an example of a conventional
large-sized expanded grid body;
[0028] FIG. 13 is a drawing to show a comparison example of an
expanded grid body of the invention;
[0029] FIGS. 14 to 16 are drawings to show the outlines of
large-sized expand electrode plates different in grid body
shape;
[0030] FIGS. 17A, 17B and 17C are enlarged schematic drawings to
show the comparison example of the expanded grid body of the
invention shown in FIG. 13;
[0031] FIG. 18 shows comparison of 0.2C.sub.10A discharge duration
of different types of batteries before and after overcharge
test;
[0032] FIG. 19 is a drawing to show the outline of a positive plate
of batteries A and G before and after overcharge test;
[0033] FIG. 20 is a drawing to show the outline of a positive plate
of batteries B, C and D before and after overcharge test;
[0034] FIG. 21 is a drawing to show the outline of a positive plate
of battery E before and after overcharge test;
[0035] FIG. 22 is a drawing to show the outline of a positive plate
of battery F before and after overcharge test;
[0036] FIG. 23 is a schematic drawing to show an electrode plate
using the grid body of the invention subjected to pasting the
active material and cutting steps;
[0037] FIG. 24 is a schematic drawing to show an example of a
manufacturing method of an electrode plate using the grid body of
the invention;
[0038] FIG. 25 is a schematic drawing to show the electrode plate
of the invention after a lug part is ground; and
[0039] FIG. 26 is a drawing to show an example of the grid body of
the invention.
PREFERRED EMBODTMENTS OF THE INVENTION
[0040] Preferred embodiments of the present invention will be
discussed, but it is understood that the present invention is not
limited to the embodiments.
[0041] First Embodiment:
[0042] A sheet 2.0 mm thick manufactured by rolling a
lead-calcium-tin alloy was consecutively expanded with a
non-expansion port 4 left in the center as shown in FIG. 9.
Subsequently, the non-expansion portion 4 of the expanded sheet was
formed with openings 13 intermittently and a part of the expansion
portion was cut at a position indicated by a dotted line 7, whereby
a current collector lug part 8 was formed and an expanded grid body
of the present invention (grid height H except lug part=400 mm,
grid width W=140 mm) as shown in FIG. 10 was manufactured. The
openings were made by stamping about 45% of the non-expansion
portion when electrode plates were separated. Considering the
electrical conductivity, the strength, the active material mass,
and the mass of each electrode plate, a proper percentage of the
openings is 30% to 70% to the non-expansion portion per electrode
plate. This time, each opening was made rectangular, but the shape
may be changed as desired depending on a consideration similar to
the percentage of the openings described above.
[0043] As in the embodiment, the expansion portion is stamped,
whereby the stamp chippings can be minimized and the lug part width
can also be maximaized.
[0044] If high-rate discharge is executed with a battery using the
grid body, it is estimated that current will concentrate on the
part just below the lug part 11. Thus, as shown in FIG. 11, a
distance 17 from the lug part (grid body shoulder, expansion part
upper end) to the first opening was set to 1.1 times a mesh major
axis dimension 18 of the expansion portion and no opening existed
at the side of a top intersection point 19 of mesh intersection
points in contact with the non-expansion portion.
[0045] To make a comparison, expanded grid bodies having the same
grid body mass, the same grid body height except the lug part, and
the same (maximum) width as shown in FIGS. 2 to 5, 12 and 13 were
manufactured from the same rolled sheet. FIG. 2 shows a grid body
in the related art expanded in the grid body height direction; the
grid body is matched with the grid body of the invention in mass by
changing the cut width at the expanding process. FIG. 3 shows a
grid body expanded in the grid body height direction with a
non-expansion portion provided in an upper part of the grid body
and formed with openings. FIG. 4 shows a grid body expanded in the
grid body height direction with a non-expansion portion provided in
an intermediate part of the grid body and formed with openings.
FIG. 5 shows a grid body expanded in the grid body width direction
with the gradually lessened width of a non-expansion portion
following a lug part. FIG. 12 shows a grid body having the same
mass as the grid body of the invention with no openings made in a
non-expansion portion, a wide expansion portion, and the
non-expansion portion having a small width compared with the
invention grid body. FIG. 13 shows a grid body having the same
outside shape as the grid body of the invention with openings in a
non-expansion portion increased in the lug part direction (top) and
the non-expansion portion width slightly widened accordingly.
[0046] Next, pasting paper was applied to the grid bodies, a
positive active material was filled so as provide a thickness of
4.0 mm, and the active material was dried only on the surface in a
flash drying furnace. Subsequently, unformed positive plates were
manufactured through a normal curing and drying process. Since the
grid body types differ, after cutting to grid body shapes, filling
was performed so as not to fill active material 6 into the lug
parts 11; for the grid bodies in FIGS. 5 and 12, the active
material was not filled into the non-expansion portion (FIGS. 14
and 15) and for other grid bodies, the active material 6 was filled
into the full faces except the lug parts 11 (FIG. 16). Using a
lead-calcium-tin alloy rolled sheet 1.1 mm thick, similar working
to that of positive grid bodies was performed, whereby expanded
grid bodies having the same shapes as the positive grid bodies
different only in grid body thickness were manufactured, pasting
paper was applied to the expanded grid bodies, and active material
was filled so as to provide a thickness of 2.2 mm, then unformed
negative plates were manufactured through a similar process to that
of the positive plates. The positive and negative plates of the
same shape were combined through a fine glass fiber separator to
manufacture valve-regulated lead acid batteries of 2 V-150 Ah/10
hour rate. Table 1 lists the contents of the storage batteries.
1TABLE 1 Batteries used in test in First Embodiment Battery
Positive and Negative Electrode Plates and No. Content of Grid
Bodies corresponding thereto Remarks A Expansion Direction: Width
direction Inventive Grid body: An openings were provided in a non-
Product expansion portion at a predetermined distance below a lug
part. (FIG. 10) B Expansion Direction: Height direction
Conventional (FIG. 2) Product C Expansion Direction: Height
direction Conventional The upper part of a non-expansion portion
was Product widen, and openings were formed. (FIG. 3) D Expansion
Direction: Height direction Conventional A non-expansion portion
was provided in an Product intermediate part of a grid body and
openings were formed. (FIG. 4) E Expansion Direction: Width
direction Conventional The width of a non-expansion portion was
Product gradually lessened following a lug part. (FIG. 5) F
Expansion Direction: Width direction Conventional A non-expansion
portion was made small, and Product openings were not formed. (FIG.
12) G Expansion Direction: Width direction Comparative An openings
formed non-expansion portions were Product increased in the lug
part direction (top) and a non-expansion portion width slightly
widened. (FIG. 13)
[0047] A dilute sulfuric acid was poured into the storage batteries
and container formation was performed, then discharge tests at some
discharge rates wer carried out. Table 2 lists the test
results.
2TABLE 2 Discharge Test Results of Each Rate 1C.sub.10A (150A)
3C.sub.10A (450A) 3C.sub.10A (450A) Condition of 0.1C.sub.10A (15A)
Discharge Discharge voltage at Electrode Battery Discharge Duration
Duration fifth sec. of Plate after No. Duration (h) (min) (min)
discharge Test A 10.37 33.63 5.58 1.78 No abnormal B 10.53 20.62
1.23 1.56 *1 C 10.42 25.67 3.58 1.64 *1 D 10.43 26.22 1.46 1.58 *1
E 9.53 28.85 5.08 1.76 No abnormal F 10.25 32.57 4.68 1.71 *1 G
10.33 33.12 3.93 1.74 *1 *1: Negative grid body was melted and
diminished.
[0048] *1: Negative grid body was melted and diminished.
[0049] In low-rate (0.1 C.sub.10A) discharge, any batteries except
battery E having a small active material mass showed the
substantially same discharge duration. In high-rate (1C.sub.10A,
3C.sub.10A) discharge, storage batteries A, F and G using a grid
body expanded in the width direction as a positive electrode showed
a longer discharge duration than storage batteries B, C and D using
a grid body expanded in the electrode plate height direction. The
3C.sub.10A discharge duration of the storage batteries F and G
showing the same discharge duration to that of the battery A in the
1C.sub.10A discharge was shorter than that of the battery A. After
the test, the batteries were disassembled. The negative electrode
lug part of the battery F, the mesh intersection point in contact
with the upper margin of each of the batteries B, C, and D, and a
part 20 (see, FIG. 17A) at the side of the opening just below the
negative electrode lug part of the battery G were melted and
diminished. Even in the 3C.sub.10A discharge, the grid body of the
storage battery E was not melted and diminished, but the storage
battery E has a smaller active material mass than the battery A
using the grid body of the invention, thus showed a small discharge
capacity (discharge duration) at each rate.
[0050] To reveal the difference between the grid body used with the
battery G having the grid body melted and diminished and the grid
body of the present invention, a grid body having openings shifted
lower than an intersection point 19 nearest to a lug part 8 among
mesh intersection points in contact with a non-expansion portion as
shown in FIG. 17B, and a grid body having openings shifted exactly
as the grid body in FIG. 17B and a mesh intersection point
positioned at the side of the opening nearest to a lug part as
shown in FIG. 17C were manufactured. These batteries were
manufactured in a similar manner to that described above, and
3C.sub.10A discharge was executed. The negative electrode grid body
of the shape in FIG. 17B was not melted and diminished, but the
part 20 at the side of the opening nearest to the lug part of the
grid body in FIG. 17C was melted and diminished.
[0051] Considering the magnitude of current flowing per
cross-sectional area of the grid body, there is a possibility that
the mesh intersection point 19 nearest to the lug part may be
melted and diminished. However, considering an electrical path with
the lower part than the melted and diminished point, it is
considered that the effect on the discharge characteristic is small
particularly in a battery large in the height direction as compared
with the case where the part 20 in the non-expansion portion is
melted and diminished. Then, the grid body of the invention was
used as a positive electrode, and the grid body of the invention
(FIG. 11) wherein the intersection point 19 nearest to the lug part
8 among the mesh intersection points in contact with the
non-expansion portion was previously cut and the comparison grid
body (FIG. 17C) wherein the part 20 on the expansion portion side
at the side of the opening nearest to the lug part was previously
cut were used as negative electrodes to manufacture two types of
batteries, and 1C.sub.10A discharge test was carried out. Table 3
lists discharge duration. The test result indicates that if the
mesh intersection point 19 near to the lug part is melted and
diminished in high-rate discharge, discharge performance is less
degraded if the grid body of the invention is used.
3TABLE 3 1C.sub.10A discharge test result Battery using negative
Battery using negative electrode with previously cut electrode with
previously cut part 19 of grid body of the part 20 of comparison
grid invention (FIG. 11) cut body (FIG. 17C) cut Discharge 27.33
19.83 duration (min)
[0052] To cut grid bodies consecutively from an expanded sheet to
form lug parts, the position of the mesh intersection point 19
nearest to the lug part changes depending on the cut position of
the upper end of the expansion portion as in FIGS. 17B and 17C.
Thus, to prevent the grid body from being melted and diminished in
high-rage discharge, it is desirable that an opening does not exist
at the side of mesh intersection point nearest to the lug part. For
this purpose, it is advisable to place no openings at least within
the mesh major axis dimension 18 from the upper end of the
expansion portion.
[0053] Thus, it was found that the storage battery A using the grid
body of the present invention has excellent discharge performance
at both low rate and high rate.
[0054] Batteries (A to G) provided aside from the above-described
each discharge rate test were subjected to 0.2C.sub.10A discharge
test, then 0.1C.sub.10A constant-current overcharge test was
carried out. The overcharge test was carried out at test
temperature 60.degree. C. for 60 days, then 0.2C.sub.10A discharge
test was carried out. Subsequently, the storage batteries were
disassembled and the corrosion state of each positive electrode
grid body was examined. FIG. 18 shows the capacity test results
before and after the overcharge test and FIGS. 19 to 22 show the
outlines of the positive plates. FIG. 19 is a drawing to show the
outline of a positive plate of batteries A and G before and after
overcharge test. FIG. 20 is a drawing to show the outline of a
positive plate of batteries B, C and D before and after overcharge
test. FIG. 21 is a drawing to show the outline of a positive plate
of battery E before and after overcharge test. FIG. 22 is a drawing
to show the outline of a positive plate of battery F before and
after overcharge test.
[0055] The capacities of the batteries B, C, and D after the
overcharge test lowered large and the capacity of the battery F
lowered large next to those of the batteries B, C, and D. The
capacities of the batteries A, E and G lowered small as compared
with those before the overcharge test; the capacities of the
storage batteries A and G each having a large amount of active
material mass were also larger than the battery E after the test.
As shown in FIGS. 19 to 22, comparing positive plate outlines 21
before the overcharge test with outlines 22 after the test, the
deformation degree of the positive plate of each of the storage
batteries B, C, D and F (FIGS. 20 and 22) is larger than that of
each of the storage batteries A, E and G (FIGS. 19 and 21) and it
is considered that the deformation degree is involved in capacity
lowering. That is, it is considered that the capacity is maintained
because the positive plate becomes less deformed if the grid body
of the invention is used as the positive plate.
[0056] Therefore, it was found that the grid body of the invention
is a grid body excellent in both discharge performance and life
performance.
[0057] Second Embodiment:
[0058] In the first embodiment, it was found that the grid body of
the invention has excellent discharge performance and life
performance. An example of a method of actually manufacturing
electrode plates consecutively will be discussed. FIG. 24 shows a
sequence of steps.
[0059] To manufacture the expanded electrode plate shown in FIG.
10, a lead-calcium-tin alloy rolled sheet 2 mm thick and 130 mm
wide was expanded to both sides with a non-expansion portion left
in the center by a reciprocation-type expanding machine. Next,
openings were stamped to provide the shape shown in FIG. 9. If the
expanded sheet is cut in the length direction, electrode plates can
be taken out two at a time; paraffin as a parting agent of an
active material was applied only to a part 8' corresponding to
electrode plate lug part of one series of electrode plates. The
sheet was passed through a pasting machine 5 for filling active
material paste 6 into the full face of the sheet. At the pasting
process, pasting paper was applied to the rear and surface of the
expanded sheet and roll press was performed for bringing the
pasting paper into intimate contact with the active material. After
the pasting, the expanded sheet was cut to predetermined dimensions
to form the state shown in FIG. 23. The electrode plate dimensions
were 140 mm wide, 400 mm high, 15 mm in lug part width, and 30 mm
in lug part height. The cut electrode plate was passed through a
flash drying furnace 23 (FIG. 24) and was dried at 200.degree. C.
for one minute, whereby only the surface of the electrode plate was
dried. After the electrode plate was passed through the flash
drying furnace, the lug part of the electrode plate was parallel to
the travel direction. Then, the electrode plate whose surface was
dried was rotated 90 degrees by a rotating machine 24, making the
electrode plate lug part perpendicular to the travel direction of
the electrode plate. Subsequently, the lug part was ground by a
rotating brush (grinding machine 25) for removing the deposited
active material. The grinding time of the lug part by the grinding
machine was changed for testing. The active material on an
electrode plate lug part 8' to which paraffin was applied before
pasting can be completely removed in about a third the time
required for removing the active material on an electrode plate lug
part 8 to which no treatment was applied, and a metal shine was
observed. In addition to paraffin, grease and Vaseline were also
used for testing, and similar results were provided. Before
pasting, a parting agent is thus applied to the lug part, whereby
the active material removal time can be shortened and the risk of
thinning the lug part by grinding it can be lessened.
[0060] The purpose of rotating the electrode plate 90 degrees
before passing it through the grinding machine 25 is to align the
electrode plate lug parts relative to the grinding machine and
grind only the lug parts consecutively so that the active material
in other portions is not removed. In doing so, the active material
on the lug parts can be removed easily and completely.
[0061] FIG. 25 shows a state in which the active material on the
lug part was removed. Then, the electrode plate was cured at
50.degree. C. for two days. The post-cured electrode plate and a
separator were combined to assemble a 2V-1000 Ah battery by a
normal method. At the assembling process, lug part weldability did
not introduce a problem and workability similar to that of
conventional articles was observed.
[0062] Third Embodiment:
[0063] In the sequence of the electrode plate manufacturing steps
described in the second embodiment, the timing of removing the
active material on the electrode plate lug part using the grid body
of the invention was studied. The active material removal timings
listed below are possible and thus an experiment was conducted at
the timings. Before an active material was pasted into an expansion
sheet, paraffin was applied to the part which becomes a lug part as
a parting agent.
[0064] 1) Just after filling, 2) after passing through flash drying
furnace, 3) after completion of curing, and 4) just before
assembling.
[0065] The Results Are as Follows:
[0066] 1) Just after pasting: The active material was soft, a
rotating brush of a grinding machine was clogged with the active
material, and it became hard to remove the active material with
time.
[0067] 2) After passing through flash drying furnace: The active
material became hard as compared with that just after pasting, and
can be easily removed without being caught in the rotating brush of
the grinding machine.
[0068] 3) After completion of curing: The active material was hard
and it took about twice the time in removing the active material;
in addition, unintended parts other than the lug part also peeled
off together.
[0069] 4) Just before assembling: Similar result to that in 3)
after completion of curing.
[0070] From the results, it was found that the appropriate timing
of removing the active material on the electrode plate lug part is
before curing after passing through flash drying furnace in which
only the surface of the electrode plate is dried.
[0071] In the description of the embodiments, the lug part placed
in the margin of the grid body is taken as an example. However, it
was found that the discharge performance of a battery using a grid
body comprising an expansion portion on both sides of a
non-expansion portion formed with a lug part and openings (FIG. 26)
is further enhanced (for example, 1C.sub.10A discharge duration is
increased about 10%) although the grid body can be taken out only
one at a time when an expanded sheet is cut in the length direction
to provide grid bodies.
[0072] As described throughout the specification, to use an
expanded grid body for a lead-acid battery, particularly for a
large-sized battery using an electrode plate having a large height
dimension, the invention provides an expanded grid body excellent
in productivity, voltage characteristic, and life characteristic
and a method of efficiently manufacturing an electrode plate from
the grid body.
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