WO2012032272A1

WO2012032272A1 - Battery comprising a temperature balancing plate

Info

Publication number: WO2012032272A1
Application number: PCT/FR2011/052062
Authority: WO
Inventors: Bernard Bavoux; Franck Guillemard
Original assignee: Peugeot Citroën Automobiles SA
Priority date: 2010-09-09
Filing date: 2011-09-08
Publication date: 2012-03-15
Also published as: FR2964799B1; FR2964799A1

Abstract

The invention balances the temperature of the cells of a vehicle battery, particularly a motor vehicle battery, comprising a plurality of cells (1, 2,..., 12) each including two electric terminals (13, 14), positive and negative respectively, electric connections (15-27) connected to the electric terminals in order to connect the cells to one another and to the exterior of the battery, and battery cooling means comprising a plate (30) which is made from a thermally conductive and electrically insulating material and which includes said electric connections (15, 16, 17, 18,..., 27).

Description

BATTERY COMPRISING A BALANCING PLATE OF

TEMPERATURE

The invention relates to a vehicle battery, particularly a motor vehicle, comprising a plurality of cells each comprising two internal or external electrical connection terminals.

More specifically, the invention relates to temperature balancing within the battery.

Generally, the batteries are formed of a set of cells interconnected in series and / or in parallel. In order to optimize the operation of the battery, a need is felt to ensure the most uniform temperature possible between the cells and within each cell, during all operating conditions. A need is also felt to be able to cool or heat the cells by maintaining a distributed temperature as uniformly as possible between the different cells and within each cell. There is a need to be able to cool or heat cells as efficiently as possible.

To warm or cool the cells of the battery, there are many devices that implement air ventilation or circulation of liquid fluid, outside the battery or between the cells. The disadvantage of these devices is that the air or the fluid is generally in contact with only a portion of the cells of the battery.

The low thermal conductivity and low heat capacity of the air are not conducive to extensive cooling. In its path through a battery in contact with cells hotter than air, the temperature of the air increases gradually. This results in uneven cooling of the cells.

A solution consisting simply in circulating a coolant through a circuit hollow, for example a polymer envelope disposed between the cells of the battery, is not completely satisfactory because, the thermal contact being made on a part of the outer surface of certain cells, in particular on the widest face of these cells. it is difficult to ensure an equal temperature.

The existing cooling devices do not generally take into account the fact that the cells, regardless of their shape, for example cylindrical or prismatic, always have a positive terminal and a negative terminal, these terminals being very good electrical conductors which are also very good thermal conductors.

In order to obtain a sufficiently high total potential difference with respect to the need for a given application, the cells are usually connected in series forming a chain. The series connection makes it possible to obtain globally at the input and output of the battery, a potential difference which cumulates the potential differences of each cell.

Now the two end cells are cooled by the electrical cables to which they are connected. These cables consist of electrical conductors of large section, are also very good thermal conductors. The cell terminals themselves are connected directly to the sheets of the anodes and cathodes which are made of electrically conductive materials, for example copper or aluminum, and therefore are also very good thermal conductors. Thus, the cells connected to the terminals of the battery are cooled directly at their center, on each sheet through the terminals and cables to which they are connected. As a result, the end cells are cooler than the cells in the center of the battery.

Knowing that the temperature of a cell considerably influences the losses during charging and discharge of a cell, it is understood that the systematic temperature difference between the cells, for the reasons mentioned above, can introduce an imbalance between the voltages of each cell, that is to say their state of electric charge. If it is not treated regularly, this imbalance has the effect of reducing the capacity of the entire battery.

On the other hand, the difference in temperature between the cells induces a differentiated aging of these cells. In this case, the hottest cells will have a shorter life while the colder ones will have a longer life. With different temperatures between cells, the battery life will ultimately be shorter than with identical cell temperatures since the life of a battery consisting of cells placed in series is essentially related to the duration. of life of the hottest cell.

Finally, a cooler cell can have a lower voltage and provide lower power than if it were warmer. This can be critical, for example for starting a vehicle in winter.

The state of the art has proposed solutions that are unsatisfactory.

DE10003740 proposes to put the connection elements between cells in contact with an electrically insulating cooling plate and thermally good conductor. The disadvantage of this solution is to complicate the production of the battery by adding to the usual assembly operations which consist in connecting the connection elements to the cells, additional operations which consist in putting the cooling plate in thermal contact with the elements of the battery. connection.

The object of the invention is to propose a battery equipped with a high-performance balancing plate temperature in the cells and easy to assemble and, if necessary to disassemble.

To achieve the object, an object of the invention is a vehicle battery, particularly a motor vehicle, comprising a plurality of cells each comprising two positive and negative electrical terminals respectively, electrical connections connected to the electrical terminals so as to connecting the cells together and outside the battery and cooling means of the battery, characterized in that the means comprise a plate made of a thermally conductive material and electrically insulating, which comprises said electrical connections so as to balance the temperature of said cells ..

In particular, the material comprises a thermally conductive and electrically insulating resin.

More particularly, the resin is an epoxide resin loaded with alumina.

Advantageously, the plate comprises said electrical connections by overmoulding so as to be removable.

Preferably, the electrical connections are formed of metal bars.

Specifically, at least one electrical terminal is tapped and the plate has at least one hole passing through the metal bar above the electrical terminal to accommodate a plate fastening element on the electrical terminal ensuring electrical conductivity between the electrical terminal and the metal bar.

In other words, the plate is deposited on the electrical terminals so that the electrical bars interconnect the corresponding electrical terminals and so as to fix the plate on the terminals by fixing means passing through the bars and engaging in the electrical terminals. Advantageously also, the plate comprises a heat exchange circuit for regulating the temperature of the plate.

In particular, the circuit is metallic.

In particular, the circuit is hollow for conveying a fluid.

In a particular mode of implementation, the plate is disposed in the upper part of the battery and the battery comprises in the lower part, a second plate-like plate disposed in the upper part.

Other characteristics and advantages of the invention will emerge clearly from the description which is given hereinafter, by way of indication and in no way limitative, with reference to the appended drawings, in which:

- Figure 1 is a top view of the battery before internal connection of the cells;

FIG. 2 is a view from above of the battery after internal connection of the cells in the absence of

The invention;

- Figure 3 is a top view of a plate according to the invention;

Figure 4 is a side view of the plate of Figure 3;

- Figure 5 is a sectional view of the plate of Figure 3 according to the invention;

Figure 6 is a system diagram that implements the invention.

As represented in FIGS. 1 and 2, a vehicle battery, in particular a motor vehicle, generally comprises several cells 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12 which each comprise two electrical terminals 13, 14.

As indicated above, the object of the invention is to effectively solve the problem of balancing the cell temperatures of a battery by means of a plate and facilitate the mounting of the battery so equipped.

FIG. 1 is a view from above of cells of a conventional battery in which the cells 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12 are cylindrical and comprise terminals 13, 14 of positive and negative connections on the same side. The battery is here represented in a mounting state before interconnection of the cells. The illustrated cell assembly comprises twelve 3.6V lithium-ion cells placed side by side, forming a 43.2-volt battery after serial interconnection.

The cells are interconnected in accordance with the following explanations with reference to FIG. 2. Metal connecting bars 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27 are each screwed to the terminal 14, forming a cathode, of a cell 1 to 11 and on the terminal 13, forming anode, of the next cell 2 to 12 so as to connect the cells in series. A metal electrical connection bar 15 is screwed on the terminal 13 of the cell 1 and a metal electrical connection bar 16 is screwed on the terminal 14 of the cell 12.

In order to balance the temperature of the different cells of a battery, the invention essentially consists in connecting their anodes and cathodes by a device, in particular a plate, which is removable and thermally conductive. This device or plate comprises the electrical connections between anodes and cathodes necessary for the operation of the battery, at least one positive and negative contact for the external connection of the battery. Optionally, the device may further comprise electrically and / or thermally conductive elements connectable to another system for heating or cooling the battery.

In order to obtain the device which is the subject of the invention, a heat-conducting plate 20 is produced. by overmoulding the metal connecting bars of the cells. In the example of Figure 3, a hollow zone 40 of square shape is left around the fixing holes of the plate 20 on the cells, but it may have another shape, round for example.

The overmold resin is a thermo resin ^¬ conductive and electrically insulating, for example an epoxy resin filled with alumina two components, having good adhesion to metals such as E708 resin Epotecny the company, or even the Durapot resin 865 of the final company.

In this diagram of Figure 3, there is shown in dotted only some interior elements, including the bars 17 to 27 which connect the cells.

Figure 5 is a sectional view of the plate shown in profile in Figure 4. The inclusion of the connection bars in the plate provides a compact assembly that provides two remarkable technical effects.

The first technical effect is that of optimizing the heat exchange between the connecting bars and the material of the plate in intimate contact with the connecting bars.

The second technical effect is that of considerably facilitating assembly operations. The block positioning of the plate on the cell assembly avoids having to position the many connection bars one by one on each pair of cells. Pre-established contacting of the material of the plate with the connection bars, avoids having to inject at the end of assembly, an additional material such as thermally conductive foam to fill the gaps between connecting bars and plate resulting from a assembly in several stages.

In a first method of connecting the plate 30 to the cells 1 to 12, the electrical terminals 13 and / or 14 are tapped and the plate 30 has holes passing through the metal bar for the establishment of fasteners of the plate 30 on the electrical terminal 13 and / or 14 ensuring electrical conductivity between the electrical terminal and the metal bar. The elements are in particular screws.

In a screwed fastener, the positioning of the cells must be able to adjust slightly to the position of the holes in height and laterally to ensure a good contact by screwing. To facilitate this positioning, the holes of the plate 30 may be a little wider in order to have a margin that takes into account the positioning dispersions of the cells. It is also possible to optionally use spring washers to improve contact by allowing better vertical adjustment of the cells.

In another embodiment, the plate may be welded to the terminals of the cells, or else bonded, or riveted or any other method of attachment.

FIG. 5 shows an exemplary embodiment of the device that is the subject of the invention, seen in horizontal section at the level of the electrical connection elements 15, 16 of external connection.

In the diagram of FIG. 5, there are the internal connections 17, 18, 27 of internal connection constituted by the series connection bars of the cells of a battery on which the plate 30 will be mounted. The electrical connections 15, 16, respectively realize a negative input pad and a positive output pad to the outside after mounting the plate directly on the cells.

A hatch is distinguished by a cooling circuit, which in the illustrated example has two paths 31, 32 of inputs and outputs 33, 34. The cooling circuit is formed by a thermal conductor, for example, a metal mass and or a circuit for a liquid or gaseous coolant. There are also two pads 35, 36 of a heating circuit 37, made by a resistive wire which travels from the pad 35 to the plane 36 between the connection bars. The wire allows a self warming of the battery, especially when the battery is too cold to be able to provide sufficient energy to the need of the vehicle. In this case, a control circuit with a control logic 41, shown in the diagram of FIG. 6, makes it possible to temporarily connect the pads 35, 36 of the battery 100 to the circuit of the battery during the period necessary to warm the battery. heater. Thus, not only will the battery be heated by supplying current, knowing that the internal resistance of the cold battery is higher than when the battery is hot, but moreover, the current flowing in the circuit 37 goes through joule heat the plate 30 so that a good part of the heat thus produced will be directly fed back into the battery through the terminals 13, 14 of its cells 1 to 12.

The heating circuit 37 and the cooling circuit 31, 32 may have different shapes so as to have as high a heat exchange surface as possible with the connection bars of the terminals, while remaining electrically isolated therefrom. For example they can walk above or below connecting bars.

The bars and the heating and cooling circuits may also have a serrated shape, for example with fractal-shaped patterns to have a greater heat exchange surface within the plate 30.

The metal cooling conductors may be oriented and / or physically connected to a cold source 42, in contact with the outside air and / or the cooling system of the car.

The heating or cooling circuits of the plate 30 may be hollow circuits which convey a gas or a liquid. These fluids may be those already provided for cooling the rest of the battery and the periphery of the cells. Circulation of gases and liquids may in some cases replace other means of cooling the battery. The heating and / or cooling circuits may be controlled by a valve system and / or use the vehicle heating and / or cooling circuits.

Cooling circuits, whatever their nature, can give rise to the production of thermoelectricity, for example by using a well known device based on the Seebeck effect not shown in the figure and a cold source in contact with the outside air and or the cooling system of the car. The electricity thus generated can be used to operate a coolant circulation pump. In a variant, this pump can operate according to an already known principle of Magneto-Hydro-Dynamics (MHD).

The explanations which have just been given apply to cells which comprise anode and cathode on one and the same face. The invention also applies to cells that have an anode and a cathode placed at both ends. These cells are usually mounted upside down to facilitate their series connection. In this case a variant of the invention comprises two plates on the same principle above and below the battery.

We have seen that a device according to the invention comprises at least the plate 30 in which are embedded the cells connecting rods, by overmoulding in a thermo ^¬ conductive resin. In this case the function provided is limited to a better balancing of the temperature of the cells.

Optionally, the plate comprises an electrical circuit for implementing a self-heating of the battery 100. In this case the plate 30 comprises two terminals which are connected by an external connection, one to a terminal of the battery on the plate and the other to an electrical switching circuit 43 or to a switch external to the plate, the other terminal of the switch being connected to the other terminal of the battery. Outside the plate it is necessary to implement a control logic using at least one sensor or a temperature estimator of the battery to drive the switch to implement the self-heating circuit at the moment required and for the duration required.

Optionally the plate comprises one or more cooling devices which can be solid conductors for example metal cables or plates, or tubes for circulating a fluid. These plate cooling devices are connected by means external to the plate to a cold source 42 external to the plate 30. The connection means are similar in nature to those included in the plate, that is to say either solid conductors of heat, for example cables or metal plates permanently connected to the plate, or a switching device and / or circulation fluid driven by control logic 41. Optionally the battery system comprises a switching device 44 of fluid in the form of a Magneto-Hydro-Dynamic device (MHD).

The system shown in FIG. 6 also optionally comprises a device 45 for electrical generation by thermoelectricity outside the plate 30.

Claims

A vehicle battery, in particular a motor vehicle, comprising a plurality of cells (1, 2, 12) each comprising two electrical terminals

(13, 14) respectively positive and negative, electrical connections (15-27) connected to the electrical terminals so as to connect the cells together and outside the battery and cooling means of the battery, characterized in the means comprise a plate (30) of a thermally conductive and electrically insulating material, which comprises said electrical connections (15, 16, 17, 18, 27) so as to balance the temperature of said cells (1, 2, 12 ), in that the material of the plate (30) comprises a thermally conductive and electrically insulating resin and in that said resin is an epoxy resin filled with alumina.

2. Battery according to claim 1, characterized in that the plate (30) comprises said electrical connections by overmoulding so as to be removable.

3. Battery according to one of the preceding claims, characterized in that the electrical connections are formed of metal bars.

4. Battery according to claim 3, characterized in that at least one electrical terminal (13, 14) is tapped and in that the plate (30) has at least one hole through the metal bar above the electrical terminal for housing a plate fastener (30) on said electrical terminal providing electrical conductivity between the electrical terminal and the metal bar.

5. Battery according to one of the preceding claims, characterized in that the plate (30) comprises a heat exchange circuit (31, 32, 37) for regulating the temperature of the plate (30).

6. Battery according to claim 5, characterized in that said circuit is metallic.

7. Battery according to claim 5 or 6, characterized in that said circuit is hollow for conveying a fluid.

8. Battery according to one of the preceding claims, characterized in that the plate (30) is disposed in the upper part of the battery and in that it comprises a second plate similar to the plate (30) in the lower part of the battery. drums.