Patent Application
20220367960
This patent application claims priority from Italian patent application no. 102021000012623 filed on May 17, 2021, the entire disclosure of which is incorporated herein by reference.
The invention relates to power storage systems for the automotive industry and, in particular, it relates to a vehicle battery pack and to a relative assembling method.
Lithium batteries, thanks to their high energy density, allow electric drive systems to be more and more implemented in the automotive industry. Lithium polymers, in particular, currently represent, from a chemical point of view, the state of the art in the production of high-capacity batteries.
Solutions are known, which involve the interconnection—in series and in parallel—of different cells (generally, with 3.7 V each) in order to reach the desired total voltage and energy density for a vehicle battery pack.
The battery modules currently available in the market (not only in the automotive industry, but also in consumer electronics) often consist of planar pouch batteries, which have a much more limited thickness compared to the other dimensions. There are two very large opposite faces (through which heat is dissipated almost entirely) and four elongated narrow sides, wherein the positive and negative terminals of the cells are arranged on one side or on two opposite sides.
In detail, a known power storage system for an electric drive vehicle comprises a battery pack consisting of a plurality of battery modules electrically connected to one another. Each battery module comprises, in turn, a large support structure, which carries a plurality of electrochemical cells electrically connected to one another in series and/or in parallel.
A known power storage system further comprises an electrical connector to connect the power storage system to the drive system of the electric drive vehicle as well as a control unit (normally called BMS—“Battery Management System”), which interacts with all battery modules in order to control and manage each cell or sets of electrochemical cells of each battery module.
Alternatively, each battery module has a respective BMS connected to a further control unit in a centralised manner. In detail, each electrochemical cell has a positive pole at an end and a negative pole at an opposite end (or at the same end) and the control unit (namely, the BMS) is connected to each pole of the electrochemical cell to control the voltage values of each electrochemical cell.
Generally, the connection of the poles of the single electrochemical cells to the control unit takes place through a plurality of multicore electrical cables.
Each battery modules further comprises two temperature sensors, which are connected to the control unit through a corresponding electrical cable in order to transmit, to the control unit, a measure of the inner temperature of the modules (usually) in a couple of different zones.
Usually, in order to avoid inconvenient phenomena commonly known as “gassing”, namely formation of gas inside the single cells due, for example, to the oxidation of the electrolyte or to the chemical decomposition thereof (often increased by phenomena such as cell overheating or overload), the cell are maintained in a constant compression state. According to the prior art, this compression is provided by the support structure of each battery module, which is configured to compress the cells perpendicularly to the large opposite faces. This compression is provided, for example, by stiffening the support structure and by making sure that at least two lateral walls acts as tie rods in the compression. As a consequence, each battery module usually is pre-assembled and subsequently installed in a further support structure integral to a portion of the frame of the vehicle, so as to hold the different modules in position without jeopardizing the mutual connection thereof.
However, this does not lead, especially in high-performance vehicles such as sports car, to an increase in the mass and in the spaces needed for the storage system, namely for the battery pack. Furthermore, pre-assembling times for each battery module have to be added to the normal installation of the battery modules on board the vehicle.
Moreover, owing to the above, it is also clear that known power storage systems have a plurality of electrical cables connecting the single electrochemical cells to the control unit and extending inside the storage system. The presence of this plurality of electrical cables complicates the structure and the assembly of the power storage system, leads to an increase in volumes, dimensions and weights of the power storage system and risks jeopardizing the safety of the power storage system, especially if we think that between the cable connecting the initial electrochemical cells of the battery pack and the cables connecting the final electrochemical cells of the battery pack there can be a significant voltage difference, even in the range of several hundreds of Volts.
The object of the invention is to provide a vehicular battery pack and a relative assembly method, which are at least partially free from the drawbacks described above and, at the same time, are simple and economic to be manufactured and carried out.
According to the invention, there are provided a vehicular battery pack and a relative assembly method according to the appended claims.
The appended claims describe preferred embodiments of the invention and form an integral part of the description.
The invention will now be described with reference to the accompanying drawings, which show some non-limiting embodiments thereof, wherein:
a are, respectively, two schematic exploded views of the battery pack of
In
The road vehicle 1 comprises a battery pack 3 supported by (mounted on) the frame 2. In particular, the battery pack 3 is arranged inside an engine compartment 4.
More in particular, the battery pack is arranged at the back of a passenger compartment 5, for example in the area of a vehicle floor, behind the seats contained inside the passenger compartment 5.
Advantageously, though not necessarily and according to
In particular, the battery pack 3 is suited to be connected to 1 a drive system (which is not shown herein) of the at least partially electric vehicle and is designed to store the power produced by an electric machine (which is not shown herein). The battery pack 3 is connected to the electric machine through the interposition of a power converter (commonly known as inverter), which, based on the different needs of the electric machine and of the battery pack 3, transforms the direct current outputted by the battery pack 3 into alternating current for the electric machine and vice versa.
According to the non-limiting embodiments of
Two connectors CN project out of the control system 8 and are configured to allow current to flow from and to the control system 8.
According to the non-limiting embodiments of
Advantageously and according, for example, to
In particular, in the non-limiting embodiments of
The battery pack 3 further comprises one or more bulkheads 17 arranged so as to divide the box portion BP by delimiting at least two housings, wherein the bulkheads 17 are arranged transversely to the two perimeter elements 16 and 18 facing one another. In other words, the frame 16 and the base 18 define two parallel planes, between which the bulkheads 17 extend crosswise (perpendicularly). In the non-limiting embodiment of
In particular, the battery pack 3 comprises a plurality of modules 12, which comprise, in turn, a plurality of planar electrochemical cells C, which are electrically connected and parallel both to one another and to the bulkheads 17 and are divided into at least two modules 12, in particular one module 12 for each housing. Therefore, in the non-limiting embodiment of
Advantageously, the modules 12 each comprise, furthermore, at least two insertion plates 32 arranged at the ends of each module 12, parallel to the bulkheads 17, and configured to facilitate the insertion of each module 12 in compression into the relative housing, so that the compression remains even after the insertion. In this way, the modules 12 of the cells C are compressed on the outside of the housing and inserted into the latter keeping the compression. By so doing, the cells C remain compressed between the two bulkheads 17 delimiting the respective housing.
In particular, the insertion plates 32, once the insertion of the module 12 into the respective housing is complete, act as compression plates (meaning “functional compression”, as discussed more in detail below) for the cells C of the relative module 12. In detail, the insertion plates 32 remain interposed between each bulkhead 17 and the first or last cell C of a module 12.
Advantageously, though not necessarily, each insertion plate 32 is in contact with a respective bulkhead 17. In particular, the coefficient of static sliding friction between each plate 32 and the respective bulkhead 17 is smaller than 0.3, preferably smaller than 0.1. In this way, the small friction between the insertion plate 32 and the bulkhead 17 allows each module 12 to slide into the respective housing, despite the compression reaction force exerted by the compressed cells (which, in other words, tend to re-expand).
The insertion plates 32 can be considered as “dispensable” elements, namely left inside the battery pack even though they are not made of active materials. However, advantageously though not necessarily, the insertion plates 32 are also configured to adjust the compression of the module 12 within the housing, compensating for any inaccuracies in the thickness of the plurality of cells C. In particular, the insertion plates 32 have different thicknesses. In this way, it is possible to ensure the achievement and the preservation of a desired compression of the batteries (depending on the number of cells and on their size) making up for possible production tolerances.
Advantageously, though not necessarily, the insertion plates 32 mainly comprise (namely, are made of) polytetrafluoroethylene.
According to the non-limiting embodiment of
In the non-limiting embodiment of the accompanying figures, each bulkhead comprises, for each surface in contact with a respective insertion plate 32, three parallel seats 35, which house three corresponding parallel sakes 34 obtained on the respective insertion plate 32.
According to the non-limiting embodiment of
In particular, each dissipating element 20 comprises at least one projecting portion 21, which, together with the ones of the other dissipating elements 20, defines the lateral surface LS. In detail, according to the non-limiting embodiment of the accompanying figures, each dissipating element 20 comprises two opposite projecting portions 21, in particular parallel to one another, which, together with the ones of the other dissipating elements 20, define the two opposite lateral surface LS.
Advantageously, though not necessarily and according to the non-limiting embodiment of
In the non-limiting embodiment of
Each cell C′, C″ comprises a pair or terminal poles TT′, TT″ (positive and negative poles, namely cathode and anode) extending on the same side of the cells C′, C″.
In other non-limiting cases, the terminal poles TT′, TT″ are arranged on opposite sides of the cells C′, C″.
In particular, the dissipating element 20 comprises a main (metal) plate parallel to the main surfaces of the cells C′ and C″ and the projecting portions 21 on opposite sides of the unit 19, in detail on opposite sides where there are not the terminal poles TT′, TT″.
Preferably, the projecting portions 21 comprise a surface perpendicular to the main plate. In other words, the cross section of the dissipating element 20 is H-shaped.
Advantageously, the cells C′ and C″ of a same unit 19 are connected in series, the units 19 of a same module 12 are connected in series and the different modules 12 are also connected in series.
According to the non-limiting embodiment of
Advantageously, though not necessarily, according to the non-limiting embodiment of
Preferably, the main plate of the dissipating element 20 has two flat faces, against which a protective film layer 26 (in detail, made of isofoil) rests. In addition, the unit 19 further comprises a further protective layer between two adjacent units 19, namely a separation film 26 (also made of isofoil).
Advantageously, though not necessarily, the unit 19 further comprises a plastic material support 27 configured to support the terminal poles TT′, TT″ and on which they are connected in series. In particular, in case of the first cell C′, both terminal poles TT′, TT″, are bent in the same direction, whereas, in case of intermediate cells C″, the terminal poles TT′, TT″ are bent with an S shape, so as to connect each intermediate cell C″ both to the preceding and to the following cell. In case a connection series has to be created, the support 27 has a passage 28, which permits an interconnection between the cells C′, C″. On the contrary, the support 27 has a separation 29, which prevents the poles of the two adjacent cells C′, C″ from coming into contact.
Preferably, the support 27 has fixing means 30, which allow said support to be fixed to channels 22 obtained on the dissipating element 20.
In particular, the unit 19 further comprises one or more connection plates 31 configured to connect and protect the connection between two terminal poles TT′, TT″
In the non-limiting embodiment of
According to the non-limiting embodiment of the accompanying figures, the battery pack 3 comprises at least one cooling panel 11 arranged in the area of said at least one lateral surface LS and configured to be fixed to the support structure 15 so as to dissipate the heat transmitted by the dissipating elements 20.
In particular, the battery pack 3 comprises two cooling panels 11 arranged on the two opposite lateral surfaces LS. More in particular, the cooling panels 11 are mounted on board the support structure 15, in particular on board the bulkheads 17, by means of fixing elements 10, 10′. The cooling panels 11 being configured to dissipate the heat provided by the dissipating elements 20.
In the non-limiting embodiment of the accompanying figures, the battery pack 3 comprises one single cooling panel 11 for several modules 12, in particular for each lateral surface LS.
Advantageously, though not necessarily, a thermo-convective paste is present between each cooling panel 11 and the respective lateral surface. In this way, the transmission of heat between the projecting portions 21 of the dissipating elements 20 and the cooling panels 11 is further increased.
Alternatively or in addition, advantageously, though not in a limiting manner, the panels 11 are mounted to the support structure 15, in particular to the perimeter elements 16, 17, so as to hermetically seal the lateral surface or surfaces LS. In particular, in order to obtain the aforesaid hermetic seal, a sealing fluid is applied onto the lateral perimeter of the section 7 or onto the perimeter of the panels 11.
In some non-limiting cases, like the one shown in
In this way, through the closing element 9, the base 18 and the cooling panels 11, a hermetic seal of the battery pack 3 is ensured, in particular an IP67 seal, protecting the cells C from liquids, dusts, fumes present inside the engine compartment 4. Furthermore, advantageously, said hermetic seal allows the air flows inside the battery pack 3 to be adjusted with utmost precision, through the venting valve CC, which becomes an obligated passage. In particular, the bulkheads 17 comprise channels 36 configured to lighten the support structure 15.
In some non-limiting cases, the support structure 15 and/or the bulkheads are made of aluminium or of a composite material (for example, carbon fibre).
Preferably, the bulkheads 17 are configured to connect the frame 16 and the base 17.
Advantageously, though not necessarily, the busbar BB has an elongated shape and runs, under the cover element 9, along the entire length of the section 7, so as to connect the series of cells C to the terminals T of the control system 8. Preferably, the busbar BB comprises, for example at half its length, a current sensor so as to monitor more accurately the flow of current through it and free space inside the section 6.
According to a further aspect of the invention, a control unit 13 is provided, which can be installed in a battery pack 3 comprising at least one module 12 provided with a plurality of electrochemical cells C carried on board a support structure 15 of the vehicle battery pack 3. In particular, the unit 13 can be installed in the battery pack 3 according to the description above.
Advantageously, though not necessarily, the control unit 13 can be installed on board the support structure 15 (in particular, above the terminal poles TT′, TT″).
In the non-limiting embodiment of
Advantageously, though not necessarily, at least part of the sensors elements 14 are arranged, on the support substrate 37, in single rows so as to be each positioned, once the unit 13 is installed on board the vehicle battery pack 3, in the area of a respective terminal pole TT′, TT″ of each electrochemical cell C′, C″.
In some non-limiting cases, like the one shown in
Advantageously, though not necessarily, the contact elements 39 are (entirely) interposed and compressed (squashed) between the planar support substrate 37 and the respective terminal pole TT′, TT″ (
Hence, in particular, the contact elements 39 extend from the planar substrate 37 (in detail, from a lower face thereof) downwards, contacting the terminal poles TT′, TT″ and holding the contact through compression.
Advantageously, though not necessarily, the contact elements 39 are V-shaped with two contiguous segments, a first segment being parallel and fixed to the planar substrate 37, whereas a second segment diverges from the planar substrate 37 itself, in particular towards the outside of the terminal pole TT′, TT″ (
Advantageously, though not necessarily, each sensor element 14 further comprises a temperature sensor TS configured to detect the temperature in the area of the respective terminal pole TT′, TT″.
Preferably, the temperature sensors TS are arranged in two single rows.
In some non-limiting cases, the temperature sensor is a wired (and remote) thermistor of the NTC type.
Preferably, the temperature sensor comprises a remote NTC connector 38, to which probes are wired, which are arranged as close as possible to the cell C′, C″.
Alternatively or in addition, the temperature sensor is a thermistor 42 of the NTC SMD type with a thermal gap, configured to detect the thermal conduction of the respective terminal pole TT′, TT″.
Advantageously, though not necessarily, the temperature sensor TS is an infrared sensor 40 arranged on board the planar substrate 37 on the same (lower) face as the contact elements (39) and configured to face the respective terminal pole TT′, TT″, so as to point a respective infrared light beam 41 at it in order to measure the temperature thereof. In particular, the light beam 41 is a beam with a conical shape (
Advantageously, though not necessarily, the battery pack 3 comprises at least one unit 13 for each module 12.
In particular, the units 13 are arranged on a same plane between the terminal poles TT′, TT″ of the cells C′, C″ of the units 19 and the closing element 9 (or the busbar BB).
According to a further aspect of the invention, there is provided a road vehicle 1 comprising a battery pack 3 of the type described so far.
According to a further aspect of the invention, there is provided a method to assemble a battery pack 3. The method comprises the steps of:
In particular, the insertion is accomplished with the aid of the two insertion plates 32 arranged at the ends of the module 12 under compression, parallel to the bulkheads 17, wherein the insertion plates 32 facilitate the insertion of the module 12 under compression into the relative housing, so that compression remains even after insertion. More in particular, the insertion plates 32 are inserted into the relative housing together with the module 12 and remain inside the battery pack 3 even after the insertion.
In detail, it is known, for new-generation batteries, that maintaining a correct pressure of compression of the cells C is crucial to exploit the performances of the cells C and to preserve the functionalities thereof during the charging/discharging cycles. The compression (force CF), which remains after the insertion of the module 12, is a so-called “functional compression”, which maintains the cells C of the module 12 within a superficial pressure range and, as it is known, is necessary in order to ensure the correct electrochemical operation of the module 12.
Preferably, the compression remaining after the insertion depends on the type of cells C (for example, lithium-ion, lithium metal, solid-state, etc.) and ranges from 0.5 to 25 bar. In particular, from 0.5 bar to 5 bar for cells C with liquid electrolytes and from 2.5 to 25 bar for solid-state cells C.
Advantageously, though not necessarily, the compression force CF is applied to the insertion plates 32 and/or to portions of the supports 27 arranged in the area of the plurality of cells C (and of the units 19), on the opposite side relative to the housing. In particular, the aforesaid portions are arranged between the terminal poles TT′, TT″ of the plurality of cells C, which are arranged in the two parallel rows.
Advantageously, though not necessarily, the method comprises the further step of applying a sealing fluid along the elongated perimeter elements so as to surround the two opposite lateral surfaces LS of the box portion BP and hermetically seal said lateral surfaces LS with the same number of cooling panels 11 arranged in the area of the lateral surfaces.
In some non-limiting cases, alternatively or in addition, the method comprises the further step of applying a sealing fluid along the elongated perimeter elements in the area of at least one upper opening of the box portion BP and hermetically closing said upper opening with the cover element 9.
According to some preferred non-limiting embodiment, the method further entails installing one or more units 13 according to the description above, so that each sensor element 14 is in the area of a respective terminal pole TT′, TT″ and so that said at least two conductor and elastically deformable contact elements 39 are elastically compressed between the planar support substrate 37 and the respective terminal pole TT′, TT″, contacting the latter in two different points.
Even though the invention described above specifically relates to some precise embodiments, it should not be considered as limited to said embodiments, for its scope of protection also includes all those variants, changes or simplifications covered by the appended claims, such as for example a different shape of the battery pack, a different location thereof, a different conformation of the units 19, a different type of materials, etc.
The invention offers many advantages.
First of all, it reduces the overall dimensions and lightens the normal structure of a traditional battery pack, which comprises several concentric housings, one for each module and one for the interconnection between the modules and their positioning inside the frame.
Furthermore, the invention facilitates the assembly of the battery pack, anyway ensuring a sufficient heat dissipation.
A further advantage of the invention lies in the possibility of adjusting the compression inside the housing by changing the thickness of the insertion plates.
In addition, the invention offers a battery pack with an easier maintenance, since the risk of current discharges is reduced, facilitating the removal of the busbar.
Furthermore, the invention allows manufacturers to quickly and easily install the control units 13, eliminating useless wirings and further lightening the structure.
Finally, the invention allows the temperature of the terminal poles of the cells to be monitored without necessarily having to contact them, thus preserving them.
| Number | Date | Country | Kind |
|---|---|---|---|
| 102021000012623 | May 2021 | IT | national |
