U.S. patent application number 12/561018 was filed with the patent office on 2010-05-27 for accumulator.
This patent application is currently assigned to LI-TEC BATTERY GMBH. Invention is credited to Guenter EICHINGER, Andreas GUTSCH, Joerg KAISER, Holger MIKUS, Tim SCHAEFER, Martin SCHNEIDER.
Application Number | 20100129705 12/561018 |
Document ID | / |
Family ID | 41620924 |
Filed Date | 2010-05-27 |
United States Patent
Application |
20100129705 |
Kind Code |
A1 |
GUTSCH; Andreas ; et
al. |
May 27, 2010 |
ACCUMULATOR
Abstract
An accumulator comprises at least one galvanic cell and a
receiving device for supporting the galvanic cell(s) of the
accumulator. The receiving device comprises at least one protecting
wall for receiving energy by means of elastic and/or plastic
deformation. The protecting wall encases the at least one galvanic
cell at least partially and has a thickness which is at least
partially less than about 1/10 of the characteristic edge length of
the at least one galvanic cell. This Abstract is not intended to
define the invention disclosed in the specification, nor intended
to limit the scope of the invention in any way.
Inventors: |
GUTSCH; Andreas;
(Luedinghausen, DE) ; MIKUS; Holger; (Windeck,
DE) ; KAISER; Joerg; (Kamenz, DE) ; SCHNEIDER;
Martin; (Dresden, DE) ; EICHINGER; Guenter;
(Altenstadt, DE) ; SCHAEFER; Tim;
(Niedersachswerfen, DE) |
Correspondence
Address: |
GREENBLUM & BERNSTEIN, P.L.C.
1950 ROLAND CLARKE PLACE
RESTON
VA
20191
US
|
Assignee: |
LI-TEC BATTERY GMBH
Kamenz
DE
|
Family ID: |
41620924 |
Appl. No.: |
12/561018 |
Filed: |
September 16, 2009 |
Current U.S.
Class: |
429/163 ;
29/623.5 |
Current CPC
Class: |
Y10T 29/49115 20150115;
H01M 50/116 20210101; H01M 50/209 20210101; H01M 50/20 20210101;
Y02E 60/10 20130101; H01M 50/579 20210101 |
Class at
Publication: |
429/163 ;
29/623.5 |
International
Class: |
H01M 2/00 20060101
H01M002/00 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 17, 2008 |
DE |
10 2008 047 615.3 |
Claims
1. An accumulator, wherein the accumulator comprises at least one
galvanic cell and a receiving device for holding the at least one
galvanic cell, which receiving device comprises at least one
protecting wall for absorbing energy by means of at least one of
elastic and ductile deformation, the at least one protecting wall
surrounding the at least one galvanic cell which is held by the
receiving device at least partially and having a thickness which is
at least partially less than about 1/10 of a characteristic edge
length of the at least one galvanic cell.
2. The accumulator of claim 1, wherein the at least one protecting
wall surrounds the at least one galvanic cell which is held by the
receiving device at least partially and with positive locking.
3. The accumulator of claim 1, wherein that the at least one
galvanic cell comprises a gas-tight jacket and wherein the at least
one protecting wall is capable of absorbing more strain energy than
the gas-tight jacket.
4. The accumulator of claim 1, wherein the at least one protecting
wall at least one of (i) comprises at least one first material
which is electrically non-conducting at a voltage which is similar
to the nominal voltage of the accumulator and (ii) comprises at
least partially a covering layer.
5. The accumulator of claim 4, wherein the at least one first
material comprises at least one curable polymer.
6. The accumulator of claim 5, wherein the at least one first
material is capable of forming cavities during curing.
7. The accumulator of claim 1, wherein a density of the at least
one protecting wall is less than about 1,500 kg/m.sup.3.
8. The accumulator of claim 1, wherein a density of the at least
one protecting wall is less than about 150 kg/m.sup.3.
9. The accumulator of claim 1, wherein a density of the at least
one protecting wall is less than about 15 kg/m.sup.3.
10. The accumulator of claim 1, wherein a density of the at least
one protecting wall is higher than about 5 kg/m.sup.3.
11. The accumulator of claim 4, wherein the at least one first
material of the at least one protecting wall further comprises at
least one filler material which is able to at least partially join
with the cured first material by material engagement and the cured
first material at least partially surrounds the at least one filler
material, and wherein the cured first material with the filler
material shows at least one of a larger Young's modulus and a
larger tensile strength than the cured first material without the
filler material.
12. The accumulator of claim 4, wherein the at least one protecting
wall further comprises at least one second material which has a
larger thermal conductivity than the at least one first material
and is capable of passing through a phase change at predetermined
conditions, at least partially, which second material at least one
of (i) shows a larger absorptivity with respect to an electrolyte
of the galvanic cell than the at least one first material and (ii)
forms at least one channel which may be permeable.
13. The accumulator of claim 4, wherein the at least one protecting
wall further comprises filling particles, a density of which is
lower than a density of the at least one first material.
14. The accumulator of claim 12, wherein the at least one
protecting wall further comprises filling particles, a density of
which is lower than a density of the at least one first
material.
15. A method of manufacturing the accumulator of claim 1, wherein
the method comprises at least (a) arranging the at least one
galvanic cell in a mold corresponding to a shape of the
accumulator; and (b) filling the mold, at least partially, with a
material for forming the at least one protecting wall.
16. The method of claim 15, wherein at least one further substance
is added to the material for use in (b) for affecting a viscosity
of the uncured material for forming the at least one protecting
wall.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] The present application claims priority under 35 U.S.C.
.sctn. 119 of German Patent Application No. 10 2008 047 615.3,
filed Sep. 17, 2008, the entire disclosure of which is expressly
incorporated by reference herein.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention refers to an accumulator. The
invention is described with respect to lithium-ion accumulators to
supply the drivetrain of motor vehicles. The invention may be used
independent of the type of the accumulator or independent of the
type of the drive.
[0004] 2. Discussion of Background Information
[0005] Accumulators for supplying the drivetrain of motor vehicles
are known. Some of these types of accumulators share the feature
that their galvanic cells are not sufficiently protected against
damaging. Accordingly, it would be advantageous to be able to
protect an accumulator or its galvanic cells against mechanical
damaging with an adequate protecting device.
SUMMARY OF THE INVENTION
[0006] The present invention provides an accumulator which
comprises at least one galvanic cell and a receiving device for
holding the at least one galvanic cell. The receiving device
comprises at least one protecting wall for absorbing energy by
means of elastic and/or ductile deformation. The at least one
protecting wall surrounds the at least one galvanic cell which is
held by the receiving device at least partially and has a thickness
which is at least in parts less than about 1/10 of the
characteristic edge length of the at least one galvanic cell.
[0007] In one aspect, at least one protecting wall may surround the
at least one galvanic cell which is held by the receiving device at
least partially and with positive locking.
[0008] In another aspect, the at least one galvanic cell may
comprise a gas-tight jacket and the at least one protecting wall
may be capable of absorbing more strain energy than the gas-tight
jacket.
[0009] In another aspect, the at least one protecting wall may
comprise at least one first material which is electrically
non-conducting at a voltage which is similar to the nominal voltage
of the accumulator and/or may comprise at least partially a
covering layer. For example, the at least one first material may
comprise at least one curable polymer. Further, the at least one
first material may be capable of forming cavities during
curing.
[0010] In another aspect of the accumulator of the present
invention, the density of the at least one protecting wall may be
less than about 1,500 kg/m.sup.3, e.g., less than about 150
kg/m.sup.3, or less than about 15 kg/m.sup.3 and/or the density of
the at least one protecting wall may be higher than about 5
kg/m.sup.3.
[0011] In yet another aspect, the at least one first material of
the at least one protecting wall may further comprise at least one
filler material which is able to at least partially join with the
cured first material by material engagement and the cured first
material may at least partially surround the at least one filler
material, and the cured first material with the filler material may
show a larger Young's modulus and/or a larger tensile strength than
the cured first material without the filler material.
[0012] In a still further aspect, the at least one protecting wall
may further comprise at least one second material which has a
larger thermal conductivity than the at least one first material
and is capable of passing through a phase change at predetermined
conditions, at least partially, which second material may show a
larger absorptivity with respect to the electrolyte of the galvanic
cell than the at least one first material and/or may form at least
one channel which may be permeable.
[0013] In another aspect, the at least one protecting wall may
further comprise filling particles, the density of which is lower
than the density of the at least one first material.
[0014] The present invention also provides a method of
manufacturing the accumulator of the present invention as set forth
above (including the various aspects thereof). The method comprises
at least [0015] (a) arranging the at least one galvanic cell in a
mold corresponding to the shape of the accumulator; and [0016] (b)
filling the mold, at least partially, with a material for forming
the at least one protecting wall.
[0017] In one aspect of the method, at least one further substance
may be added to the material for use in (b) for affecting a
viscosity of the uncured material for forming the at least one
protecting wall.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] The present invention is further described in the detailed
description which follows, in reference to the noted plurality of
drawings by way of non-limiting examples of exemplary embodiments
of the present invention, in which like reference numerals
represent similar parts throughout the several views of the
drawings, and wherein:
[0019] FIG. 1 shows a sectional view of an accumulator according to
the present invention; and
[0020] FIG. 2 shows an enlarged section of the protecting wall
3.
DETAILED DESCRIPTION OF THE PRESENT INVENTION
[0021] The particulars shown herein are by way of example and for
purposes of illustrative discussion of the embodiments of the
present invention only and are presented in the cause of providing
what is believed to be the most useful and readily understood
description of the principles and conceptual aspects of the present
invention. In this regard, no attempt is made to show structural
details of the present invention in more detail than is necessary
for the fundamental understanding of the present invention, the
description taken with the drawings making apparent to those
skilled in the art how the several forms of the present invention
may be embodied in practice.
[0022] An accumulator according to the present invention comprises
at least a galvanic cell and a receiving device. The receiving
device is intended to hold the galvanic cells of the accumulator.
The receiving device comprises at least a protecting wall. This
protecting wall is intended to absorb energy by means of elastic
and/or ductile deformation. At least partially, the protecting wall
surrounds the at least one galvanic cell which is held by the
receiving device. The thickness of the protecting wall is at least
partially less than about 1/10 of the characteristic edge length of
the at least one galvanic cell held by the receiving device.
[0023] The present accumulator is an apparatus intended to store
energy. The energy is stored as chemical energy in the at least one
galvanic cell of the accumulator. To supply an electrical drive,
chemical energy is at first converted to electrical energy. During
a charging process of the accumulator the conversion of electrical
energy to chemical energy is executed in the opposite
direction.
[0024] The present accumulator comprises at least one galvanic
cell. The construction of a galvanic cell is commonly known and
thus is not explained here. To explain the mode of action of the
invention it shall suffice to state that the galvanic cell also
includes an electrolyte. Also, a galvanic cell is usually
surrounded by a gas-tight jacket. This jacket serves to prevent the
galvanic cell from the influx of water or steam. To achieve this,
the jacket is usually designed to be a gas tight film, at least
partially, for instance to be a metal film.
[0025] The present accumulator comprises a receiving device. This
device is also intended to support the at least one galvanic cell
of the accumulator. Supporting shall be understood to mean that the
at least one galvanic cell of the accumulator remains within the
combination of the accumulator and its further components during
the intended use of the accumulator.
[0026] The present receiving device comprises at least one
protecting wall. The protecting wall serves the purpose to prevent
the at least one galvanic cell of the accumulator from mechanical
damaging, too. So the protecting wall or its material are intended
to absorb impacting mechanical energy through elastic and/or
ductile deformation and to hold mechanical energy off the at least
one galvanic cell, for example. An elastic deformation is
preferably inverted after consuming the impacting mechanical
energy. Depending on the sort and amount of mechanical energy or
the sort of the body carrying said energy, the elastic
deformability of the protecting wall may not suffice. The
protecting wall is designed to also absorb mechanical energy
through ductile deformation. So, a body carrying energy or being
loaded with a force will intrude into the protecting wall by a
certain distance and will displace its material. This may result in
a breaking of the protecting wall. The energy absorbed in such a
way is not available to further damaging the accumulator or its
galvanic cells. Also, the impacting mechanical energy is spread
onto a larger surface by the protecting wall.
[0027] Kinetic or potential energy presently acts on the
accumulator through a thrust or blow or through a force. This will
act on the accumulator or a galvanic cell through an arbitrary body
over a time interval and/or a certain distance.
[0028] At least partially, the protecting wall surrounds the at
least one galvanic cell. Economical considerations of material
usage and cost of manufacturing, available space, design of the
accumulator, number or arrangement of several galvanic cells, if
applicable, site of operation of the accumulator, kind and extent
of the expected damaging effects and other conditions will define
the extent by which the protecting wall surrounds the at least one
galvanic cell. Only one of several boundary surfaces of an
accumulator may feature a protecting wall.
[0029] The thickness of the protecting wall is chosen depending on
the expected peril, the weight of the accumulator or the material
used for the protecting wall. To maintain a desired specific power
or energy with respect to volume or weight of the accumulator, the
protecting wall is chosen to be as thin as possible. The protecting
wall is chosen to be as thick as necessary to provide the
protection required. The thickness of the protecting wall is chosen
depending on the load and need not be uniform. The thickness of the
protecting wall is to be chosen in relation to the characteristic
edge length. Preferably, the thickness of the protecting wall is at
least partially less than about 1/10 of the characteristic edge
length of the at least one galvanic cell held by the receiving
device, preferably less than about 1/25 of this characteristic edge
length. Alternatively, the thickness of the protecting wall is
dimensioned in mm. Preferably, the thickness of the protecting wall
is at least partially from about 0.01 mm to about 100 mm,
preferably from about 0.1 mm to about 20 mm, most preferred from
about 0.5 mm to about 10 mm.
[0030] The characteristic edge length of a galvanic cell is a
reference size. It is calculated as the mean average of the lengths
of the edges of the galvanic cell and accounts for the geometry of
the galvanic cell. For instance, in case of a block-shaped galvanic
cell, the three different lengths of edges of the rectangular block
are used. In case of a cylindrical cell or a rotationally symmetric
cell, the lengths along the rotational axis and the radius of the
base area are used. In case of a prismatic cell with arbitrary base
area, a substitute body with the same volume is defined, at first.
Its circular base area has the same surface area as the base area
of the prism. Then the length of the rotational axis and the radius
of the substitute base area are used, similar to the case of the
cylindrical cell. Usually, several uniform galvanic cells are
processed to an accumulator. Otherwise, the mean average of the
characteristic edge lengths of the different galvanic cells is to
be defined and to be used. Presently, the dimension defined in this
manner is to be understood as the "mean characteristic edge
length". In this case, the mean characteristic edge length is to be
used in lieu of the characteristic edge length.
[0031] By design of an accumulator or its receiving device
according to the invention with a protecting wall, occurring
damaging mechanical loads may be held off the galvanic cells of the
accumulator. So, the accumulator is prevented from damaging and the
underlying aim is met. Further advantages of the invention can be
taken from the following non-limiting embodiments.
[0032] Advantageously, the protecting wall surrounds at least
partially the at least one galvanic cell held by the receiving
device by positive locking. The degrees of freedom of motion of a
galvanic cell are significantly reduced by surrounding with
positive locking. Thereby, the protecting wall abuts tightly on the
at least one galvanic cell. If the accumulator comprises a
plurality of galvanic cells, which are arranged side by side and in
a row in close contact similar to rows and columns of a table, the
degrees of freedom of motion of the galvanic cells arranged inside
are limited by their neighbors. Thereby, the protecting wall
imposes elastic restoring forces on to the galvanic cells
surrounded with positive locking, preferably. Preferably, the at
least one galvanic cell is at least partially encapsulated by this
protecting wall. So, good positive locking is achieved between the
protecting wall and the at least one galvanic cell of the
accumulator. This is done to save space, to hold the at least one
galvanic cell within the receiving device and to prevent the
accumulator from damaging through vibrations. This is achieved by
choosing an appropriate material for the protecting wall and the
design of the protecting wall. So, the protecting wall preferably
shows high internal friction. This helps to absorb impacting energy
from vibrations, too. The protecting wall surrounds the at least
one galvanic cell to protect against moisture, corrosion and other
damaging substances. After a failure of a galvanic cell, it may be
removed from this receiving device and may be replaced,
advantageously.
[0033] Advantageously, a galvanic cell comprises a gas tight
jacket. This is true in case of using an electrolyte with lithium
ions. To aid this, the gas tight jacket may be manufactured from a
metal film, for instance. The protecting wall is able to absorb
more strain energy than the gas tight jacket by choosing an
appropriate wall thickness and material. To this end, the
protecting wall preferably comprises stays and/or reinforcing
ridges. The term `strain energy` as well as methods for its
calculation are defined in the literature concerning engineering
mechanics.
[0034] Advantageously, the protecting wall also acts to isolate
electrically. To this end the protecting wall comprises a first
material. The protecting wall acts to isolate electrically at
voltages similar to the nominal voltage of the accumulator. Most
preferred, the protecting wall acts to isolate electrically at
voltages which are equal to several times the nominal voltage of
the accumulator. This is achieved by choosing an appropriate first
material for the protecting wall. To this end, expected voltages
need to be considered. Preferably, the first material isolates
electrically at a voltage which is equal to about 10 times the
nominal voltage of the accumulator, most preferred equal to about
100 times the nominal voltage of the accumulator.
[0035] Preferably, the protecting wall is equipped with at least
one covering layer, at least partially. The at least one covering
layer is arranged on an outside surface of the protecting wall. For
instance, a covering layer is arranged on an inside surface of the
protecting wall, wherein the inside surface faces the galvanic
cell(s) of the accumulator. Optionally, the outer surface of the
protecting wall is equipped with a covering layer. Preferably, the
protecting wall comprises a covering layer in regions which are
exposed to particular wear, to avoid grit, for instance. Depending
on the selection, the covering layer will act against chemical
and/or thermal exposure, preferably. The covering layer acts in a
flame-retarding manner, for instance. In case of a fire, such a
covering layer may expand and/or produce foam, carbonize or become
a ceramic. Preferably, a protecting wall comprises several
different covering layers at the same time.
[0036] Advantageously, the first material of the protecting wall is
a curable polymer. Preferably, polymers are chosen which can be
manipulated easily, show low density, high ability to absorb
energy, high ability to isolate electrically. Optionally, the first
material may be a mixture of materials depending on what the
protecting wall is subjected to. Preferably, a copolymer is chosen
to form the first material to adapt the material properties to the
expected exposures. The first material may be pretreated depending
on the requirements of processing, if needed. For instance, the
polymer may be chosen from a group including unsaturated polyester
(UP), epoxy (EP), polyamides, polystyrenes.
[0037] Advantageously, the first material comprises cavities after
curing. Preferably, the cavities are filled with a gas. The
cavities are surrounded by a joisting of the first material.
Compared to the solid first material, the first material with
cavities shows higher values of moment of inertia, of bending
stiffness, of density, of ability to absorb energy and/or of
reversible deformation or of elastic strain. Preferably, the
diameter of a substitute body of a cavity with similar volume is
less than about 1/5 of the thickness of the protecting wall.
Preferably, the cavities are distributed within the first material
as evenly as possible. So, the protecting wall with a cured first
material with cavities gains thickness and protective effect, too,
while the specific power or energy with respect to volume and
weight diminishes insignificantly.
[0038] The structure of the protecting wall may be compared to a
frozen foam. This frozen foam of low density is able to bear a high
bending load or a high impact loading in comparison. Depending on
the material used and the curing conditions, the frozen foam may
comprise various Young's moduli or permitted values of elastic
strain. So the protecting wall will absorb energy through elastic
or ductile strain while showing a low weight. This is also known
from foamed plastic or metal foam.
[0039] Optionally, an auxiliary substance may be added to the first
material. This auxiliary substance may expand at predetermined
conditions, preferably before or while curing of the first
material. Preferably, the auxiliary substance acts to improve
foaming of the first material, for example as a propellant, acts to
improve cohesion of the solid phase of the protecting wall, to
improve curing of the participating polymers and/or to increase
long term stability of the cured first material. Preferably, the at
least one auxiliary substance is able to form a gaseous phase at
predetermined conditions. In doing so, the gaseous phase is created
as a result of a phase change of the auxiliary substance and/or as
a result of a chemical reaction of the auxiliary substance while
creating a gas, preferably. Preferably, the gaseous phase remains
contained within the cavities of the cured material.
[0040] Preferably, the protecting wall is designed to be
lightweight. Its density is less than about 1,500 kg/m.sup.3,
preferably less than about 150 kg/m.sup.3, most preferred less than
about 15 kg/m.sup.3, and more than about 5 kg/m.sup.3. So, the high
specific power of the accumulator is maintained with respect to
volume or weight. To this end, cavities are useful which are
preferably filled with gas and are enclosed within the protecting
wall.
[0041] Preferably, the first material (4) of the protecting wall
(3) further comprises at least one filler material. It is capable
of material engagement with the cured polymer of the first material
(4), at least partially. Thereby the cured polymer surrounds this
filler material, at least partially. This filler material acts such
that the first material (4) after curing with the filler material
features a higher Young's modulus and/or higher permitted values of
elastic strain. Preferably, the filler material comprises a
plurality of short rods or fibers, though other geometries are
possible. These rods or fibers may be either arranged without order
and distributed or are arranged as a woven fabric or a laid layer
within the cured first material. Thereby, several layers of woven
fabrics or laid layers may be put one upon the other with different
directions of the fibers. The presence of the filler material
alters the properties of the first material (4). When compared with
the polymer of the first material (4), the fibers show increased
Young's modulus and/or permitted values of elastic strain in their
axial direction. Depending on the arrangement of the fibers, the
cured first material can be set up to have different material
properties with respect to the axes of a Cartesian coordinate
system. The rods or fibers may be made from glass, carbon or an
aramide, for instance.
[0042] Preferably, the protecting wall further comprises a second
material. The second material shows a larger thermal conductivity
than the first material, preferably. For instance, aggregations
show predetermined shapes, such as wire sections, films, a net,
woven fabrics, non-woven fabrics, rounded geometries like beads,
films or strips of film. Preferably, such aggregations are arranged
within the protecting wall in an aligned manner and are inserted
during the manufacturing of the protecting wall. So, thermal energy
may be added or removed. Preferably, the second material passes
through a phase change at predetermined conditions to absorb or
release thermal energy. These predetermined conditions are chosen
depending on the operating conditions of the accumulator.
Preferably, the second material is arranged in rounded, distributed
aggregations. The diameter of a ball shaped substitute body with a
volume similar to the volume of an aggregation is less than half
thickness of the protecting wall, preferably less than about 1/10
of its thickness.
[0043] There is a variation of the volumes of several aggregations
of the second material within a range, which offers advantages with
respect to their application and the cost of manufacturing.
Preferably, the second material shows a higher absorptivity with
respect to the electrolyte than the first material. Emerging
electrolyte may be absorbed particularly by the second material
after damage to the jacket of a galvanic cell. In doing so, the
proximity is protected from the electrolyte.
[0044] Preferably, the second material is designed to be at least
one solid body, forming a channel. The channel of this solid body
may accept a cooling agent or may be passed through by a cooling
agent. So, thermal energy may be delivered or dissipated.
Preferably, the second material acts flame-retarding. For instance,
the second material may expand and/or produce a foam during a fire,
carbonize or convert to a ceramic. The damaging effects of a fire
upon the proximity of the accumulator may at least be reduced in
this manner.
[0045] An advantageous embodiment of the protecting wall (3)
further comprises several filling particles. The shape of a filling
particle mainly results from the outcome of the manufacturing of
the filling particle. It is not compulsory that the filling
particles have the same shape. For instance, the filling particles
may show a ball-shaped, an ellipsoidic, a drop shaped or any other
geometry which is mainly rotationally symmetric. The mean diameter
of a filling particle, which is alternatively determined by
measuring a ball of similar volume (substitute body), is within a
range of from about 0.01 to about 5,000 microns, preferably from
about 0.1 to about 1,000 microns, most preferably from about 1 to
about 400 microns. The mean diameters of the filling particles
scatter about an averaged mean diameter of a multitude of filling
particles. Preferably, the filling particles are predominantly
hollow and/or show closed surfaces. The density of a filling
particle preferably is less than the density of the cured first
material. Preferably, the filling particles comprise at least one
solid material such as glass or plastic, for instance.
[0046] A mold and at least one material are required to manufacture
a receiving device of the accumulator according to the present
invention. The at least one galvanic cell of the accumulator is
arranged within the mold. Usually, the accumulator comprises a
multitude of galvanic cells which are electrically connected by
serial connection/parallel connection. In this case, all galvanic
cells of the accumulator are arranged within the mold. Within the
mold, the galvanic cells are prevented from unintended displacement
against each other with spacers or with the help of an auxiliary
device from outside the mold, for instance. Extra necessary devices
of the accumulator may be arranged within the mold. Next, the
designated chambers in the mold are at least partially filled with
the material for forming the protecting wall. If the protecting
wall has to include further materials or parts, they are added to
designated chambers of the mold.
[0047] Optionally, the galvanic cells and the produced protecting
wall remain in the mold. Then the mold becomes the casing of the
accumulator. In this case, the shape of the mold, i.e. its material
or its geometry, is adapted to the requirements of the operation of
the accumulator, too. In this case, the mold may have one or more
parts, may be made from metal and/or plastic, may be equipped with
devices to connect to the motor vehicle, and may be designed with
openings to lead in electric cables and/or other supply lines.
[0048] Optionally, a further substance may be added to the material
for forming the protecting wall, whereby the viscosity of the
mixture is altered with respect to the uncured material. In doing
so, the flowability of the first material is affected during its
processing to become the protecting wall. Preferably, the further
substance is a powdery solid matter, most preferably Aerosil.RTM..
Also, a different solid matter may be used as further substance, if
the viscosity of the pourable mixture of the further substance and
said material is to be different from the viscosity of said
material.
[0049] FIG. 1 shows a sectional view of an accumulator according to
the present invention. This accumulator comprises four galvanic
cells 1 in serial connection plus a receiving device 2. The serial
connection of the galvanic cells 1 is symbolized by three bridges
and two pins on the upper ends of the galvanic cells 1. The
receiving device 2 is provided with a protecting wall 3. The cross
section of this protecting wall 3 is depicted to the left and to
the right of the galvanic cells 1. The thickness of the protecting
wall 3 is dimensioned to be less than a tenth of the mean
characteristic edge length of the galvanic cells 1 held. Pre-foamed
and aeriferous beads 4 made of polystyrene serve as first material
of the protecting wall 3. The beads 4 are expanded with the help of
hot steam. Thereby, the air contained by the beads expands, the
beads increase to become balls. The present balls 4 of polystyrene
connect to each other. The polystyrene 4 expanded in this manner
has a density of about 70 kg/m.sup.3, for instance. The design of
the protecting wall 3 is depicted in FIG. 1 schematically, only. In
fact, the polystyrene forms the walls of the balls 4 and their
inner bars. The voids between the bars of a ball 4 are filled with
air. The mass fraction of the polystyrene is negligible. By
choosing polystyrene as first material 4, the protecting wall 3 is
not electrically conductive with respect to the nominal voltage of
the accumulator, i.e., 12V. The small density of the protecting
wall 3 causes the specific power or energy of the accumulator with
respect to volume of weight not to decrease significantly.
[0050] The protecting wall is produced by using pre-foamed
aeriferous beads 4 from polystyrene and a mold. At first, the
galvanic cells 1 of the accumulator are arranged within the mold
and are jammed against each other to avoid undesired displacements.
Next, the beads 4 are added to designated chambers within the mold.
During the following step, the mold with its content is exposed to
the conditions required to expand the beads. The beads 4 are
exposed to hot steam, thereby. The beads 4 will expand and fill the
designated chambers to fix the galvanic cells 1. Thereby, the
galvanic cells 1 are surrounded by foam only by as much as to leave
the electrical contact surfaces of the galvanic cells to protrude
from the protecting wall 3. In a further step the accumulator may
be removed from the mold and the mold may be reused. After their
failure, individual galvanic cells 1 may be removed from the
receiving device 2 and may be replaced.
[0051] The mold of this embodiment also forms the casing of the
accumulator. The casing is provided with corresponding means for
connection and openings. Also the casing is adapted to being
installed in the motor vehicle with respect to its shape. The
casing also offers extra protection of the accumulator. The casing
is made from steel plate, which is folded and welded. The casing
may also be manufactured entirely/partially from plastic or may be
manufactured with other manufacturing methods, too.
[0052] Alternatively, the designated mold is first filled with a
first material 4. The galvanic cells 1 are connected to a
supporting unit, which is an auxiliary production means, which
supports the galvanic cells 1 against one another immovably. Then
the galvanic cells 1 are dipped into the first material 4. The
supporting unit is connected to the mold. The processes of
expanding and curing of the first materials 4 follow. Afterwards
the galvanic cells 1 are not entirely surrounded by the protecting
wall 3.
[0053] FIG. 2 shows an enlarged detail of the protecting wall 3 of
a further embodiment. The protecting wall 3 shows an expandable
polymer 4 and a second material 7 with high thermal conductivity,
both serving as first material. The second material 7 features a
significantly larger thermal conductivity than the first material
4. The second material 7 is designed to have oblong, irregular
strips. By its shape and design, the second material 7 contributes
to remove thermal energy from a galvanic cell 1 contacting the
protecting wall 3.
[0054] Another second material 7a passes through a phase change at
predetermined conditions. The second material 7a forms solid matter
at a predetermined temperature of the accumulator. The second
material 7a is chosen such that its melting temperature exceeds the
predetermined operating temperature of the accumulator only by a
small margin. If the temperature of a galvanic cell 1 in contact
exceeds the melting temperature of the second material 7a, it
passes through a phase change and becomes a liquid, partially. The
aggregation of the second material 7a will keep the melting
temperature until it has been entirely converted to a liquid. In
doing so, the aggregation of the second material 7a absorbs thermal
energy and contributes to cooling a galvanic cell 1 in contact.
[0055] It is noted that the foregoing examples have been provided
merely for the purpose of explanation and are in no way to be
construed as limiting of the present invention. While the present
invention has been described with reference to exemplary
embodiments, it is understood that the words which have been used
herein are words of description and illustration, rather than words
of limitation. Changes may be made, within the purview of the
appended claims, as presently stated and as amended, without
departing from the scope and spirit of the present invention in its
aspects. Although the present invention has been described herein
with reference to particular means, materials and embodiments, the
present invention is not intended to be limited to the particulars
disclosed herein; rather, the present invention extends to all
functionally equivalent structures, methods and uses, such as are
within the scope of the appended claims.
* * * * *