WO2010016771A1

WO2010016771A1 - Device for cooling or heating a battery module

Info

Publication number: WO2010016771A1
Application number: PCT/NO2009/000279
Authority: WO
Inventors: William George Clark; Jørgen VANGEN
Original assignee: Miljø Innovasjon As; VALØEN, Lars, Ole
Priority date: 2008-08-08
Filing date: 2009-08-07
Publication date: 2010-02-11
Also published as: NO20083466L

Abstract

The present invention relates to a system for cooling or heating a battery module, in order to uniformly lower the temperature of the battery module, reduce the overall weight and manufacturing costs and time. The system comprises a battery case having at least one cooling liquid inlet and outlet, at least one battery module arranged within the battery case, the battery module comprising a plurality of battery strings, the battery module (1) being fully immersed in the cooling fluid, a tension device (13) being connected to each battery string, the battery strings being arranged in such a way that cooling fluid flow spaces (5) are formed between two adjacent battery strings, a cooling liquid pipe connected to the inlet and outlet of the battery case, thereby forming a closed cooling fluid circuit. A circulating device and a reservoir are connected to the closed cooling fluid circuit, thereby circulating the cooling fluid continuously through the battery module, the closed cooling fluid circuit further being run through a heat exchanger.

Description

Device for cooling or heating a battery module

The present invention relates to a device for improving the safety and lengthening the lifetime of a battery module, first and foremost, used in electrically propelled cars, but is also applicable to other battery powered devices. The present invention also relates to a device for cooling or heating of battery modules.

A battery module comprises one or more series of individual battery cells that are connected in series, parallel or a combination of both to form a battery "string". One or more of these battery strings are then generally packed into a battery case or container to create the battery module. The battery cells may be manufactured as a rigid cell or as a soft package cell.

In recent years, with growing environmental concerns, development of electric and hybrid automobiles is actively being carried out. This has necessitated a need to also develop new and different kinds of batteries. These batteries must meet certain criteria; they are, for instance, required to have high output and high energy charac- teristics. For that reason lead-acid batteries and nickel-metal hydride batteries are less suitable to be utilized as a power source for electric automobiles. Such batteries have, among other factors, the problem that energy density per weight (kWh/kg) is low, and energy density per volume (kW/1) is low, which will result in a lower efficiency factor for the electric automobile. As Lithium-ion batteries are not burdened with the above mentioned drawbacks, they are used increasingly within the electrically propelled automobile segment: Lithium-ion batteries and their derivatives have high energy density per weight and high energy density per volume. In addition they do not suffer from memory effects and opportunistic charging can therefore be carried out without any adverse effect. Furthermore, they have a slow loss of charge when not in use and their re-cycling is not a problem either.

However, there are circumstances that can affect or even damage the performance of Lithium-ion batteries. The first problem is if the cells in a battery module are subjected either to a too high or a too low temperature: if the cells experience tem- peratures below -10 ⁰C, their capacity for charge and discharge diminish. If the cells experience temperatures above 70 ⁰C, physical damage can occur internally, where this can cause short circuit, fire and even explosion. However, already above 30 °C, the rate of irreversible capacity loss is usually notably greater than at 2O⁰C. This is usually climate related (winter or summer/tropical use etc.). The second problem is related to the temperature gradient: if the individual cells in a battery module are not all at the same temperature, their ability to accept charge and/or to discharge will vary accordingly and, in time, this will lead to cell voltage imbalance within the battery module and may result in much reduced capacity and possible failure. These temperature gradients within a battery module can be caused by: a) localized heating of one or more of the individual cells; cells in the middle of the battery module cannot dissipate internally generated heat as quickly as cells positioned near the outer areas of the battery module due to the insulating nature of the cells themselves, b) due to unavoidable manufacture imperfections, internal cell impedance can vary between the cells, which will give rise to differences in internal temperature from one cell to another. In this case a cell situated near the outer area of the battery module could get warmer than a lower impedance cell situated in the middle of the battery module and c) a combination of both a) and b). The third problem that can occur, is when the battery module is in use: the individual battery cells in a battery module are often "clamped" in order to hold the cells together (using a long threaded rod and nut or by "packing" the cell tightly together in a container), and due to temperature fluctuations within the battery module, the individual cells will expand and/or contract, which will result in an increase in sur- face and localized pressure points on the cells. If such a battery module is exposed to air, for instance if air is used to cool the battery module, the air may possibly affect the safety in a negative manner.

Generally, battery modules for an electric or a hybrid automobile are mounted in a battery module holder in the vehicle. During charging and operation of the automo- bile, the battery modules may be heated up, where this may result in any of the above mentioned problems. If the battery modules keep at high temperature for a certain period of time, durability and functionality of the modules tend to deteriorate.

As an attempt to solve this problem, a cooling apparatus has been used to provide cold air into the battery module holder in a predetermined direction. The cooling apparatus is provided with at least one intake fan that draws air into the battery module holder or at least one exhaust fan that withdraws air from the battery module holder.

GB 2.295.264 discloses a cooling device for cooling a battery constructed from a plurality of cells. The cells are arranged in a thermally insulated battery case, and the battery case is filled with a cooling fluid to a specific level. The cooling fluid will have a boiling temperature that lies within the permissible operating temperature range of the battery cells. When the battery is "overheated", the cooling fluid will evaporate, thereby removing the excess heat from the battery. The cooling fluid vapor is then collected above the level mark and fed to a recondensing device outside the battery case, whereafter the recondensed cooling fluid is fed back into the battery case.

From DE 2.638.862 is known a cooling device for cooling a battery, where the battery is constructed from a plurality of cells. The cells are "stacked" in a battery housing, and are arranged in such a way that channels through which a coolant can be fed are provided between the walls of the housing and the cells, as well as between the walls of neighbouring cells. The coolant is fed to the battery via a feed line and is again removed via a manifold in order to dissipate the heat. The heated coolant is cooled in a heat exchanger, and the cooled coolant is fed back on the output side of the heat exchanger via the feed line to the battery. A pump is fitted at a suitable point in order to drive the coolant circuit.

Not all cooling devices with air or fluid as coolant investigated to date exhibit satisfactory results. The presented solutions either fail to produce the required cooling power or are accompanied by a non-uniform temperature distribution within the battery or else within the individual cells along their height direction. The result of this is that some cells or cell regions are operated at the upper edge of the permissible temperature window and others are operated at the lower edge. This influences the internal resistance of the battery and will lead to permanent deterioration in its life and performance. Because of the inadequate cooling power, it is furthermore necessary to start the cooling of the battery module very early as a preventative measure, in order to avoid an impermissible temperature rise, for instance in the case of heavy and prolonged power demand. On the other hand, this involves unnecessary energy losses if, because of only a low power demand, the critical temperature (up- per temperature limit) had never been reached at all and the cooling had therefore been started too early.

The present invention seeks therefore to develop a battery module in which the battery cells can be assembled and accommodated with uniform temperature control, the battery module having a high strength or flexural rigidity, but nevertheless, compared with total weight of the installed battery cells, having a low weight.

The above mentioned aims are achieved by a fluid cooled and heated battery module system according to the following independent claim, where alternative embodiments are given in the description and dependent claims.

The present invention regards a fluid cooled and heated battery module system, typ- ically for use in electrically propelled automobiles. The fluid cooled and heated battery module system may also be applicable for other battery powered devices, such as trucks, load leveling equipment etc. The fluid cooled and heated battery module system comprises a battery case, where the battery case is provided with at least one cooling fluid inlet and outlet. Within the battery case is arranged one or several bat- tery modules, where these battery modules may be connected to each other in series and/or parallel. Each battery module comprises series of individual battery cells that may be connected electrically in series, parallel or a combination of both, where each of the battery series form a battery string. This configuration will make it easy to adapt the battery module to specific use, for instance for the electric motor the battery module is to be used with, as the number of battery modules, battery strings and/or individual battery cells may be changed according to required voltage, power, accessible space etc.

The battery strings are arranged within the battery case in such a way that one bat- tery string is not in physical or mechanical contact with an adjacent battery string or a wall of the battery case. This configuration will provide space between two adjacent battery strings or between the battery string and the wall of the battery case, where the spaces are used to allow circulation of a coolant fluid. In this embodiment at least one cooling fluid inlet is integrated in the top of the battery case, while at least one cooling fluid outlet is integrated in the bottom of the battery case. This will form a straight-lined flow pattern for the cooling liquid, as the cooling liquid is supplied through the inlet, whereafter it passes through the spaces between the battery strings and out through the outlet in the bottom of the battery case.

In another embodiment the outermost battery strings of the battery module are in contact with the inner walls of the battery case, this resulting in that spaces are not provided between the outermost battery strings and inner walls of the battery case.

Between two adjacent battery strings there is provided a space, through which space a cooling liquid can flow. At least one fluid cooling inlet is arranged on the top of and in the vicinity of the end of the battery case, while at least one fluid cooling outlet is arranged on the bottom and at the opposite end of the fluid cooling inlet.

The cooling fluid in this embodiment will have a meandering flow pattern through the battery case.

As the battery cells are tightly packed or stacked in order to form the battery strings, one or more battery cells in such a battery string may, due to temperature fluctuations and/or changes in state of charge, be exposed to expansion and contraction. These expansions and contractions may create an increase in surface and localized pressure points, where this may deteriorate or even destroy the battery cell. In order to prevent or at least reduce the effects of the thermal expansion and contraction, a tension device is connected to each battery string. The tension device is de- signed to impart a constant force on each battery string but also allowing the battery string to expand and contract. The tension device may be manufactured from any material that has flexible and/or resilient properties. In a preferred embodiment the tension device is manufactured from a carbon fiber composite plate, where the ends of the plate are bent towards the middle of the plate. The ends are given a convex form, which form will give the plate the resilient or flexible characteristics. From the bending area and towards the ends, each of the ends is provided with a plurality of holes and recesses. The holes are connected with the recesses, where the recesses extend from the holes and to the ends of the plate. This shaping will provide a plurality of independent sub-springs over the length of the tension device. When a ten- sion device is connected to a battery string, where this can be done by different me- chanical attachment or in another suitable ways, the convex ends will face away from the battery string, while a fiat portion of the tension device will be placed on the battery string. The tension device may be arranged on top of the battery strings, or it may also be arranged such that one battery string has the tension device on its top while the adjacent battery string has the tension device arranged on its bottom.

By designing the holes, recesses and/or shape of the ends in different ways, the spring tension may be adjusted for every battery module.

In another embodiment of the present invention the tension device may be consisted of a plate onto which plate a plurality of tube elements in appropriate ways are at- tached or fastened. The tubes may extend over both the length and width of the plate. In order to ensure the purpose of the tension device, i.e. the spring properties or characteristics, the tube elements are made of a resilient or elastic material. This could for instance be rubber, silicone rubber, neoprene or other materials exhibiting elastic properties. As the battery string over its length and/or width may be subjected to local expansion or contraction, the tension device may be consisted of tube elements with same or different spring properties. The tube elements will then be isolated elements forming same or different spring properties over the length and width of the plate.

As one skilled in the art would understand, the spring properties of the tube ele- ments are depending on the number of tubes, the diameter of the tubes, the material of the tubes, the ratio between the inner and outer diameter of the tubes etc. A person skilled in the art would also understand that the tubes could be replaced with other structures such as foams, gels, flexible spheres etc.

The plate can be made of any material rigid enough to exert an even pressure onto the battery string, for instance polypropylene, coated/painted aluminium or steel etc. The plate is preferably electrically non-conductive.

The tension device may also in certain embodiments of the present invention be arranged between two adjacent battery cells or between groups of battery cells. In these embodiments the tension device may be provided to have or hold additional properties, for instance to prevent or slow down a fire in the battery module and/or to act as a heat transfer device between to adjacent battery cells or groups of battery cells in the battery module. The heat should then be transferred from middle of the battery cell surface and out to edge(s) of the battery cell surface, but prevented from propagating between battery cells. The tension device will then also comprise a first, thin outer layer adjacent to the cell of a material with very high thermal conductivity, and a second, thicker inside layer of a material providing fire propagation resistance. Optionally, a third layer may be provided between the second, inside layer and the tension device, where this third layer can be a highly conductive coating combined with a thin low conductivity layer.

The first, outer layer (conductivity coating) will then ensure a uniform temperature in the area facing the battery cell. This first, outer layer will in the case of a thermal event ensure some thermal dissipation, thereby lowering the maximum temperature in the battery module. This first, outer layer may also be divided in two sub layers, where the sub layer closest to the battery cell will provide good thermal conductivity but high electrical resistivity.

The function of the second, inside layer will be to prevent propagation of a fire be- tween two adjacent battery cells.

The optional, third layer has a similar purpose as the first, outer layer, as it also will dissipate heat developed in a battery string.

The layer(s) will be connected or fastened to the tension layer in appropriate ways, for instance by gluing, melting etc. The battery strings, associated electronics, connectors, connections are fully immersed in a high thermal conductivity, high electrical resistivity fluid. This can, for instance, be transformer oil, mineral oil, silicone oil plant oil, natural or synthetic ester, or other low viscosity fluid with similar properties. This immersion of all connections will also protect all terminals from oxidation. The associated electronics, connectors, connections, from now on called auxiliary battery module equipment, is in one embodiment of the invention arranged below or on the sides of the battery strings within the battery case, i.e. in the vicinity of the bottom or wall(s) of the battery case. The auxiliary battery module equipment is protected by a housing, where the housing is formed as a box with one open side. As the auxiliary battery module equipment during use may become warm, the housing is perforated in order to allow the cooling fluid to flow through the housing, thereby cooling (or heating) the auxiliary battery module equipment as well as the battery cells.

The auxiliary battery module equipment could also be arranged fully immersed out- side the battery module, and could then be cooled down or warmed up by an additional cooling circuit.

The battery module is further connected to a closed cooling and heating circuit, where the cooling and heating circuit comprises a recirculation pump and a reservoir or expansion tank. In order to cool or heat the battery module, the cooling and heating circuit is run through a heat exchanger, from which heat exchanger generated heat from the battery module is extracted. In one embodiment devices like resistance heating elements, refrigerant air conditioning units or Peltier diodes may be connected with the heat exchanger. The devices can then remove excess heat from the heat exchanger, or add heat to the heat exchanger in the event of extreme cold operating conditions of the battery module. As an addition, a temperature control and monitoring device may be used to control the temperature of the cooling liquid.

A battery module according to the present invention therefore consists of at least one battery string, the battery string further comprising a plurality of individual cells. For a better understanding of the nature and objects of the present invention, reference should be made to the following detailed description with the accompanying drawings, in which:

Figure 1 is a cross-sectional view of a battery module according to a preferred embodiment of the present invention, Figure 2 is a cross-sectional view of a battery module according to another preferred embodiment of the present invention,

Figure 3 is showing a tension device in form of a spring plate arranged on a battery string,

Figure 4 is showing a tension device according to another embodiment of the pre- sent invention,

Figure 5 is showing a tension device according to another embodiment of the present invention, and

Figure 6 is a schematic view of a cooling/heating circuit according to a preferred embodiment of the present invention. Figure 1 shows a battery module 1 according to the present invention, where the battery module 1 comprises a plurality of individual battery cells 2 arranged within a battery case 3. For insulation reasons the battery case 3 is advantageously made of plastic, and it is hermetically sealed from outside. The (individual) battery cells 2 that are accommodated in the battery case 3 are electrically connected together in series and/or parallel (not shown), in order to form a battery string 4. In the exemplary embodiment the battery case 3 is intended to accommodate several battery strings 4. Furthermore, the battery strings 4 are coupled in series to provide a higher voltage, but they can also be coupled in parallel in order to provide a redundancy in the system. Each of the battery strings 4 is arranged within the battery case 3 in such a way that the battery string 4 is not in physical or mechanical contact with an adjacent battery string 4 or inner walls of the battery case 3. This can for instance be done by providing the inner walls of the battery case 3 with inwardly directed protrusions (not shown), on which protrusions the battery strings 4 can rest. This arrangement will provide a space 5 between two adjacent battery strings 4 and between a battery string 4 and the inner walls of the battery case 3. These spaces 5 are then utilized to allow circulation of a coolant fluid with which the battery case 3 is filled.

The cooling fluid is selected from a group of fluids having a high thermal conduc- tivity and high electrical resistivity. In the shown embodiment the cooling fluid is transformer oil.

Auxiliary battery module equipment 7, such as associated electronics, connectors, connections etc. is placed on the bottom of the battery case 3. The auxiliary equipment 7 is then protected by a housing 8. The housing 8 is perforated, in order to al- low a circulation of the cooling fluid and is further covered with non-conductive protective plates on its side facing the battery strings 4.

The auxiliary battery module equipment 7 can also be placed outside the battery case in an attached auxiliary battery module equipment case (not shown). In this case the auxiliary battery module equipment case will be in fluid connection with the battery case 3, as it is arranged corresponding openings or recesses between the battery case 3 and the auxiliary battery module equipment case.

The battery strings 4 and the auxiliary equipment 7 are fully immersed in the cooling fluid.

The battery case 3 has an inlet 9 arranged on a long side 10 of the battery case 3, and an outlet 12 arranged on an opposite side of the other long side 11 of the battery case 3. The inlet 9 and outlet 12 are connected with a heat exchange system that will be described further below. By arranging the inlet 9 and outlet 12 opposite each other the cooling fluid will have a meandering flow pattern through the battery case 3 by means of the spaces 5, where this will provide a uniform cooling (or heating) for each of the battery strings 4.

The battery strings 4 may during use of the battery module 1 be subjected to expansion and contraction (i.e. state of charge effects in individual battery cells 2), where this will result in surface and local pressure points on the battery string 4. In order to avoid or at least to diminish these pressure points, each of the battery strings 4 are bound to a spring plate element 13, where the spring plate element 13 due to its characteristics will allow the battery string to expand and contract. As shown in figure 1, the spring plate elements 13 are arranged on opposite sides of two adjacent battery cells 4, i.e. one battery string 4 will have the spring plate element 13 ar- ranged on its "top", while the neighbouring battery string 4 will have the spring plate element 13 arranged on its "bottom". The top and bottom of a battery string 4 is defined relative to the long side 12 of the battery case 3.

In figure 2 is shown another embodiment of the present invention, where this bat- tery module 1 also comprises several battery strings 4 which are arranged within the battery case 3. In this embodiment the battery strings 4 are connected in series, whereby a parallel flowing pattern is used to cool or to heat the battery string 4. The inlet 9 arranged on the long side 10 and the outlet 12 arranged on the opposite long side 11 are then placed directly opposite each other. The cooling fluid is then via spaces 5 allowed to flow through the battery case 3.

The tension devices (spring plate elements) 13 in this embodiment are all arranged on the top of the battery strings 4.

The battery strings 4 and the auxiliary equipment 7 are, also in this embodiment, fully immersed in the cooling fluid. The battery case 3 in the two described embodiments can be manufactured in one piece or can be made from several individual parts.

Referring now to figure 3, the spring plate element 13 will be explained further. The spring plate element 13 is designed to impart a constant force on the battery string 4 thus allowing for expansion and retraction whilst still maintaining a relatively con- stant force. In one embodiment the spring plate element 13 is manufactured from a carbon fiber composite plate 14, where ends 15 of the carbon fiber composite plate 14 are bent towards the middle of the carbon fiber composite plate 14. The ends 15 have a convex form, which will give the spring plate element 13 a resilient or flexible characteristic. Along their lengths towards the bending area, each end 15 is pro- vided with a plurality of holes 16 and recesses 17. The holes 16 are connected with recesses 17, where these recesses 17 extend from the holes 16 and to the ends 15 of the carbon fiber composite plate 14. This shaping will provide a plurality of independent sub-springs 18 over the length of the spring plate element 13. The spring plate element 13 is bound to a battery string 4 in such a way that the convex ends 15 will face away from the battery string 4, i.e. that the flat part of the carbon fiber composite plate 14 is placed on the top (or bottom) of the battery string 4. The flat part of the carbon fiber composite plate 14 is, on the side facing the battery string 4, machined to give a very even surface against the battery string 4. A (non- conductive) coating may also be applied on the flat side that is facing the battery string 4.

By designing the holes 16, recesses 17 and or the form of the ends 15 in different ways, the spring tension can be adjusted for each battery string 4. Furthermore, the holes 16 and recesses 17 will also allow the cooling fluid to flow "correctly" through the battery module 1, thereby obtaining a uniform cooling (or heating) of the battery strings 4.

The spring plate element 13 will also impart a constant force on each battery string 4, thus allowing for expansion and contraction whilst still maintaining a relatively constant load. This will prevent buildup of local and/or surface pressure points.

One another embodiment of the tension device 13 is shown in figure 4 (from above and side), where the tension device 13 comprises a plate element 24 and a plurality of tubular elements 25 attached to the plate element 24. The plate element 24 is preferably electrically non-conductive and is made of a material that is rigid enough to exert an even pressure onto the battery string 4, for instance polypropylene, coated/painted aluminum or steel etc. As described above, the battery strings 4 (groups of adjacent battery cells) may during the use of the battery module 1 be subjected to expansion and contraction, due to changes in state of charge, where this will result in surface and local pressure points on one or more of the battery cells in a battery string 4. In order to compensate for the different expansion and contraction, the tubular elements 25 are made to have or hold different spring or resilient properties. The spring or resilient properties of the tubular elements can be controlled by the number of tubular elements used, the diameter of the tubular elements, the material of which the tubular elements are made, the ratio between inner and outer diameter of the tubular elements etc.

The tubular elements 25 can be attached to the plate element 24 in appropriate ways, for instance by gluing, melting etc.

In figure 5 is shown another embodiment of the tension device 13 according to the present invention, where at least one tension device 13 is to be arranged between two adjacent battery cells 2 or between groups of battery cells 2 within a battery string 4. In this case the tension device 13 comprises additional layers 26 - 28 in order to prevent or slow down a fire and/or to act as a heat transfer device in the battery module 1. The first, outermost layer 26, facing a surface of the battery cell 2, is comprised of a material with a very high thermal conductivity. The second layer 27 is comprised of a material that provides a fire propagation resistance, while the third layer 28 is comprised of a material having a high thermal conductivity.

If the tension device 13 has a low thermal resistance, the third layer 28 can be split into two layers (not shown), where the layer closest to the second (fire propagation prevention) layer 27 have a high thermal conductivity to ensure adequate thermal transfer, whereas the layer closest to the tension layer 13 acts as a thermal barrier.

The tension device 13, being of a low conductivity material, will act as a thermal barrier between two adjacent battery cells 2 or groups of battery cells 2. Thus, the tension device 13 will ensure that heat is transferred from the middle of a battery cell 2 and outwards to the ends of the battery cell 2, while at same time preventing (or slowing down) a fire to propagate between two adjacent battery cells 2 or groups of battery cells 2. In figure 6 is shown a cooling and heating system for two battery modules 1 that are connected in series. Each of the battery cases 3 is provided on its short sides 18 with an inlet 9 and an outlet 12, where the inlet 9 and outlet 12 is arranged on opposite short sides 19 of the battery case 3. A pipe 20 connects the two battery modules 1 in a closed circuit, where the outlet 12 of the first battery module 1 is connected to the inlet 9 of the second battery module land the outlet of the second battery module 1 is connected to the inlet 9 of the first battery module 1. This closed circuit contains the cooling fluid. A reservoir or expansion tank 21 for the cooling fluid is connected to the closed circuit as well as a recirculation pump 22. Furthermore, the closed circuit is also run through a heat exchanger 23, where generated heat from the battery module 1 is extracted. Suitable devices (not shown) are connected to the heat exchanger 23, where these devices can remove excess heat from the heat exchanger 23, or add heat to the heat exchanger 23 in the event of extreme cold operating conditions. Such devices could be resistance heating elements, refrigerant air conditioning units or Peltier diodes etc. As an addition, a temperature control and monitoring device (not shown) can be used to control the temperature of the cooling liquid.

In the exemplary embodiment the cooling liquid is continuously recirculated through the battery module 1 in a clock-wise direction.

Although the present invention has been described and illustrated in detail, it is to be clearly understood that the same is by way of illustration and example only, and is not to be taken by way of limitation. The spirit and the scope of the present invention are to be limited only by the terms of the appended claims.

Claims

1. A fluid cooled and heated battery module system comprising a battery case (3) having at least one cooling fluid inlet (9) and at least one cooling fluid outlet (12), a cooling fluid pipe (20) connected to the cooling fluid inlet (9) and outlet (12), thereby forming a closed cooling fluid circuit, to which closed cooling fluid circuit a recirculation device (22) and a reservoir (21) are connected, the closed cooling fluid circuit further being run through a heat exchanger (23), at least one battery module (1) arranged within the bat- tery case comprising a plurality of battery strings (4) connected electrically in series or in parallel, each battery string (4) including at least one battery cell (2), the battery module (1) being fully immersed in the cooling fluid, cooling fluid flow spaces (5) formed for each battery string (4) between adjacent battery strings (4) and between the battery string (4) and inner walls of the battery case (3), the cooling fluid flow spaces (5) allowing a cooling fluid to pass from the cooling fluid inlet (9) to the cooling fluid outlet (12), characterized in that at least one tension device (13) is connected to each battery string (4), the tension device (13) allowing the battery string (4) to expand and contract, whilst still imparting a constant force on the battery string (4).

2. A fluid cooled and heated battery system according to claim 1, characterized in that the tension device (13) is provided with a plurality of holes and recesses.

3. A fluid cooled and heated battery system according to claim 1, characterized in that the tension device (13) is provided with a plurality of tubes arranged over the length of the tension device (13).

4. A fluid cooled and heated battery system according to claim 1, characterized in that the tension device (13) comprises at least one additional layer (26, 27, 28).

5. A fluid cooled and heated battery system according to claim 4, characterized in that at least one tension device (13) is arranged between two adjacent battery cells (2) or groups of battery cells (2) in a battery string (4).

6. A fluid cooled and heated battery module system according to claim 1, characterized in that the cooling fluid flow spaces (5) form a meandering flow pattern through the battery case (3).

7. A fluid cooled and heated battery module system according to claim 1, characterized in that auxiliary battery module equipment (7) is arranged within the battery case (3).

8. A fluid cooled and heated battery module system according to claim 1 or 3, characterized in that the auxiliary battery module equipment (7) is arranged within a protecting housing (8).

9. A fluid cooled and heated battery module system according to claim 1, characterized in that the heat exchanger (23) is connected to heat removable devices.

10. A fluid cooled and heated battery module system according to claim 4- 5, characterized in that the heat removable devices can be resistance heating elements, refrigerant air conditioning units, Peltier elements etc.

11. A fluid cooled and heated battery module system according to claim 1 , characterized in that the cooling liquid is a high thermal conductivity and high electrical resistivity fluid.

12. A fluid cooled and heated battery module system according to claim 1, characterized in that the cooling fluid is continuously circulated through the battery case (3).

13. A fluid cooled and heated battery module system according to claim 1, characterized in that the battery cell (2) is a soft cell.

14. A fluid cooled and heated battery module system according to claim 1, char- acterized in that the tension device (13) is a spring plate element