Chemistry: electrical current producing apparatus – product – and – Current producing cell – elements – subcombinations and... – Plural cells
Reexamination Certificate
2000-10-06
2003-05-27
Maples, John S. (Department: 1745)
Chemistry: electrical current producing apparatus, product, and
Current producing cell, elements, subcombinations and...
Plural cells
C429S120000, C429S136000, C429S153000, C429S176000
Reexamination Certificate
active
06569561
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Technical Field of the Invention
The present invention relates to a battery pack constructed with a plurality of battery modules that are respectively constituted by unitizing a plurality of cells.
2. Description of Related Art
It has been the practice to constitute a battery pack, in order to achieve a necessary output power, when employing rechargeable batteries. In a battery pack, generally, a plurality of battery modules, each being constituted by connecting a plurality of cells in series and bonding them into a unitized body, are arranged in parallel and mutually connected in series.
FIG. 11
shows a conventional battery module made by connecting a plurality of cells and coupling them together as one. In this battery module, a plurality of cells
41
(
41
a
to
41
j
) are arranged side by side, with the long lateral walls of their cell cases opposite each other. End plates
52
are arranged against the outside of the cells
41
a
and
41
j
at both ends, and the group of cells and the two end plates
52
are bound together with binding bands
53
so as to couple the cells together as one piece.
For the cells
41
, as shown in
FIG. 12
, an electrode plate group
47
, comprising positive electrode plates and negative electrode plates layered with intervening separators, thereby constituting elements for electromotive force, is accommodated in a cell case
42
together with a liquid electrolyte, and the open end of the cell case
42
is closed with a lid
46
provided with a safety vent
45
. From the upper end at one side of the positive electrode plates forming the electrode plate group
47
, leads
49
extend upward and are connected to a positive electrode terminal
43
above them, and similarly, from the upper end of the other side of the negative electrode plates, leads
49
extend upward and are connected to an negative electrode terminal
44
above them. The positive electrode terminal
43
and the negative electrode terminal
44
are attached to the lid
46
.
The positive electrode terminals
43
and negative electrode terminals
44
of coupled neighboring cells
41
are connected by connection plates
51
, thereby connecting all cells
41
in series. When the cell cases
42
are coupled, ribs
48
, which protrude vertically from the long lateral walls of the cell cases
42
, are abutted against each other, forming coolant passages running in the vertical direction along the long lateral walls of the cell cases
42
in the space between ribs
48
, so that the cells
41
a
to
41
j
are cooled by flowing air through these coolant passages.
In the battery pack employing such battery module as described above, because the plurality of cells
41
(
41
a
-
41
j
) are tightly bound together, if the internal pressure rises in some of the cells
41
due to generation of gas induced by, for example, overcharging, whereupon the cell cases
42
of these cells
41
expand, then the other cells adjacent the expanding cells become depressed in order to accommodate the expansion. Thus the internal pressures in each of the cells
41
are maintained substantially uniform in each of the battery modules. Therefore, as far as one battery module is concerned, even if there is an imbalance in the internal pressure between various cells
41
whereupon the output characteristics and the life of some cells deteriorate, the output characteristics and the service life of the battery module as a whole are relatively unaffected.
However, when a plurality of the battery modules as shown in
FIG. 11
are bound together to constitute a battery pack, the cells
41
of one battery module will not be bound in tight contact with the cells
41
of adjacent battery module, and there will be variations in the internal pressure between the cells
41
of different battery modules. Therefore, it can happen that the internal pressure in the cells
41
of some battery modules become higher than that in the cells
41
of the other battery modules, and when this battery pack is taken as a whole, the output characteristics and service life of the battery pack may deteriorate because of degradation in the output characteristics or service life of some of the battery modules.
Moreover, the battery module shown in
FIG. 11
is constituted by unitizing a plurality of cells, and in order to constitute a battery pack, a plurality of such battery modules are coupled together. Accordingly, the battery pack becomes relatively bulky with a complex structure and heavy weight. There is thus the problem that the battery pack as a whole has relatively low percentages of output by volume and by weight.
The higher the power output of each cell is, the higher the heat generation in the cell becomes. When the temperature in the cell rises, the internal pressure rises accordingly due to expansion of electrode plates or generation of gas, which adversely affects the output characteristics and service life of the cell. The battery pack therefore needs to meet the requirements for high cooling performance. However, with the construction of the prior art battery pack constituted with battery modules shown in
FIG. 11
, it is hardly possible to further improve the cooling performance, because the cell cases
42
of each cell
41
are made of synthetic resin having low thermal conductivity, and the cells are cooled by passing air through the coolant passages between the cells.
SUMMARY OF THE INVENTION
In view of the problems in the prior art described above, it is an object of the present invention to provide a battery pack wherein variations in the internal pressure between various cells of various battery modules are eliminated, so that the output characteristics and service life of the battery pack are not affected by unbalanced internal pressure in some cells or battery modules. A further object of the present invention is to provide a battery pack having higher percentages of power output by volume and by weight and excellent cooling performance.
A battery pack according to the present invention comprises:
a plurality of battery modules, each being constructed of an integral battery case which is constituted by forming a plurality of prismatic cell cases into a unitized body, wherein positive electrode plates and negative electrode plates laminated alternately upon one another with intervening separators are respectively accommodated in each of the cell cases, thereby constituting a plurality of cells, the plurality of cells being electrically connected in series,
the plurality of battery modules being arranged in a direction in which the electrode plates are laminated within each cell, in a condition with coolant passages formed between the battery modules;
end plates arranged at both ends in the direction of adjacent arrangement of the battery modules; and
means for binding the plurality of battery modules and the end plates together.
In the battery pack of the present invention, all of the cells that constitute the battery pack are bound together in tight contact with each other, and thereby, variations in the internal pressure of all of the cells can be eliminated. Therefore, there is no risk that some of the cells or battery modules deteriorate because of the expansion of electrode plates or increased internal pressure, resulting in degradation of the output characteristics or service life of the battery pack as a whole. Thereby, the output characteristics and service life of the battery pack can be improved and, when taken as a whole, the volume density and weight density of power output of the battery pack are increased.
Other and further objects, features and advantages of the invention will be apparent more fully from the following description.
REFERENCES:
patent: 1152247 (1915-08-01), Walker
patent: 4107402 (1978-08-01), Dougherty et al.
patent: 5456994 (1995-10-01), Mita
patent: 5639571 (1997-06-01), Waters et al.
patent: 5641589 (1997-06-01), Grive et al.
patent: 5985483 (1999-11-01), Verhoog et al.
patent: 6004693 (1999-12-01), Fukuda et al.
patent: 6352793 (2002-03-01), Kitoh et al.
Hamada Shinji
Kimura Tadao
Ogata Yoshiaki
Sekimori Toshiyuki
Yamauchi Tomokazu
Jordan and Hamburg LLP
Maples John S.
Matsushita Electric - Industrial Co., Ltd.
LandOfFree
Battery pack does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Battery pack, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Battery pack will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3062109