Thermoregulating system by immersion of a battery pack comprising cells which have terminals located along a side of the pack

Abstract

An electric battery unit, comprising an array of battery cells (2) immersed, within a container (4) of the battery unit (1), in a flow of a temperature-regulating fluid, for maintaining the battery unit within a determined temperature range. Each cell (2) has a positive pole (3P) and a negative pole (3N) arranged on a side surface (2C) of the cell, facing a side wall (4A) of the container (4). All the positive poles (3P) and all the negative poles (3N) of the cells (2) are contained in two respective side chambers (CP, CN) of the battery unit (1) that are insulated from each other and are insulated with respect to the gaps (7) between the cells (2). Each of the side chambers (CP, CN) is connected to the input collector chamber (5) and the output collector chamber (6). In the connection between each of the side chambers (CP, CN) and the inlet collector chamber (5) and / or in the connection between each of the side chambers (CP, CN) and the outlet collector chamber (6) at least one restricted passage (90A, 90B, 91A, 91B) is interposed, such that the temperature-regulating fluid does not tend to flow preferentially through the side chambers (CP, CN) rather than through the gaps (7) between the cells (2).

Description

[0001] THERMOREGULATING SYSTEM BY IMMERSION OF A BATTERY PACK COMPRISING CELLS WHICH HAVE TERMINALS LOCATED ALONG A SIDE OF THE PACK

[0002] ****

[0003] 5 TEXT OF THE DESCRIPTION

[0004] Field of the invention

[0005] The present invention relates to an electric battery unit with cells having poles arranged along one side of the unit and provided with an 10 immersion-type temperature-regulating system.

[0006] The invention relates in particular to an electric battery unit of the type comprising:

[0007] - an array of battery cells immersed within a container of the battery unit in a flow of a temperature-regulating fluid, for maintaining the battery

[0008] 15 unit within a determined temperature range,

[0009] - wherein said container includes an inlet opening for the temperature-regulating fluid, communicating with an inlet collector chamber, arranged below the array of battery cells, an outlet opening for the temperature-regulating fluid communicating with an outlet collector

[0010] 20 chamber, arranged above the array of battery cells,

[0011] - wherein the inlet collector chamber and the outlet collector chamber communicate with each other via a plurality of gaps defined by spacer walls between one battery cell and another.

[0012] 25 Prior art

[0013] Electric battery units having a temperature-regulating system of the type indicated above are known and have been used for some time.

[0014] Figure 1 of the attached drawings shows an example of an electric battery module 1 , comprising an aligned series of battery cells 2 of the 30 prismatic type illustrated in figure 2.

[0015] In the example of figure 2, the battery cell includes a casing with an upper wall 2A, from which the positive and negative poles 3P and 3N of the cell 2 protrude, two main walls 2B (only one of which is visible in figure 2), two side walls 2C (only one of which is visible in figure 2) and a lower wall 35 2D. As will be seen below, battery cells are also used which have the poles 3P and 3N on a side wall 2C.

[0016] According to the prior art described above, the battery cells 2 are arranged within a hermetic container 4 and are immersed in a flow of a dielectric temperature-regulating fluid (for example a dielectric oil). The container 4 defines within it an inlet collector chamber 5 (schematically illustrated in figure 3) arranged below the cells 2, and an outlet collector chamber 6 (also schematically illustrated in figure 3) arranged above the cells 2. The container 4 has an inlet 5A and an outlet 6A for the temperatureregulating fluid, communicating with the inlet collector chamber 5 and the outlet collector chamber 6, respectively. P and N indicate the positive pole and the negative pole of the battery module 1 of figure 1 , which are respectively electrically connected with all the poles 3P and 3N of the cells 2.

[0017] Typically, the inlet 5A is always arranged below the cells 2, while the outlet 6A is arranged above the cells 2, to allow any air bubbles formed within the fluid to be collected in the upper collector chamber. However, this layout is not the only possible one. The inlet and outlet may be inverted when an inlet pressure suitable to avoid any form of evaporation of the liquid can be guaranteed. Furthermore, inlet 5A and outlet 6A may be arranged at opposite ends of the module 1 , instead of at the same end as illustrated in figures 1 and 3.

[0018] Battery modules of the type illustrated in figure 1 are used to make battery packs intended to power electric traction motors of electric and hybrid vehicles. In use, the temperature-regulating fluid enters the inlet collector chamber 5, arranged below the battery cells 2, and reaches the outlet collector chamber 6, arranged above the battery cells 2, flowing through a plurality of passages 7, arranged between the battery cells 2 (in figure 3, the dimensions of the passages 7 have been exaggerated for clarity).

[0019] In general, it is of primary importance to ensure that during the use of the electric vehicle, the battery cells are always at a temperature within a predetermined range, typically between a minimum threshold of 20°C and a maximum threshold of 55°C.

[0020] The battery cells used in electric vehicles are typically lithium-ion battery cells that tend to develop heat as a result of the chemical reaction that occurs inside the battery cell during operation, and also due to the Joule effect caused by the passage of current inside the battery. The term “battery operation” here refers to both the battery charging process and the discharging process, which typically occurs while the vehicle is in motion. It should be noted that the most critical battery operating conditions, which involve a risk of overheating of the cells, are those related to the fast charging process, i.e. charging the battery in less than an hour.

[0021] During normal operating conditions of the battery unit, the temperature-regulating fluid must perform a cooling action, to counteract the temperature increase due to the heat that develops in the cells for the reasons indicated above. To this end, the temperature-regulating system comprises a circuit external to the battery module (not shown in figure 1 ) including one or more heat exchangers configured to cool the hot fluid coming from the outlet 6A, before it is fed again, by a pump (not shown) to the inlet 5A. However, in extreme operating conditions, in particular in cold weather conditions, the temperature-regulating fluid must perform a heating function. To this end, the external circuit may comprise a heater exchanger and / or an electrical resistance heating device.

[0022] With reference to the configuration illustrated as an example in figure 3, the experiments conducted on batteries of this type show that the temperature inside the battery module varies considerably both from cell to cell, as the cells 2 that are further away from the input 5A of the temperatureregulating fluid are subjected to less cooling, and inside each cell, where the temperature distribution tends to be higher where the current lines are denser, for example near the poles.

[0023] Numerous studies have shown that:

[0024] - to reduce the aging process of the single battery cell it is advisable to reduce the temperature gradient inside the cell itself by 5°C

[0025] - to avoid a phenomenon of “thermal loss”, destructive for the battery, it is necessary to keep the maximum temperature of each single cell below 55°C

[0026] It is therefore desirable not only to keep the temperature of the battery cells within a preferred temperature range, but also to try to make the temperature of the different battery cells and the temperature inside each cell as uniform as possible. From this perspective, it is also important to try to obtain substantially equal fluid flow rates through the different passages that connect the inlet collector chamber with the outlet collector chamber.

[0027] In Italian patent applications IT 102023000022692, IT 1020230000 22698 and IT 10 2023 0000 22704, all filed on 10 / 30 / 2023 and still secret at the filing date of this application, the Applicant has proposed various solutions for a high-efficiency temperature-regulating system.

[0028] According to these previous proposals, in the battery unit the inlet collector chamber communicates with each of the said gaps defined between one cell and another through one or more restricted passages, sized so as to offer sufficient resistance to the flow of the temperatureregulating fluid to make the flow rates of the temperature-regulating fluid through the different gaps between the cells substantially equal, regardless of how far each gap is from the inlet opening and the outlet opening of the container. In this way uniform thermoregulation of the various cells of the module is ensured.

[0029] However, there is a need for further improvements in this field.

[0030] In particular, further problems arise when said concepts are applied to a battery unit of the type illustrated schematically in the end view of figure 10 and in the plan view of figure 11 . Figures 10, 11 illustrate a battery unit 1 in which the cells 2 arranged within the container 4 each have the positive pole 3P and the negative pole 3N on a side wall 2C facing a side wall 4A of the container 4. The gap 20 between the side wall 4A and the side walls 2C of the cells 2 bearing the poles 3P, 3C constitutes a passage for the temperature-regulating fluid that is much larger than the sum of the passage areas of the restrictions 9 of each of the gaps 7 between the cells 2, which would create a considerable non-uniform ity of the temperature-regulating action within the unit 1 .

[0031] There is therefore a need to solve this problem.

[0032] Object of the invention

[0033] It is therefore a object of the invention to provide an electric battery unit, in particular an electric battery unit for powering an electric traction motor of an electric or hybrid vehicle, provided with a temperature-regulating system configured to promote maintenance of the temperature of the battery unit within a predetermined temperature range and to promote substantial uniformity of temperature within the battery unit, from cell to cell and within each cell, even in the case in which the battery unit is of the type with cells having the poles on one side of the battery unit.

[0034] A further aim of the invention is to achieve said object with relatively simple and low-cost means.

[0035] Summary of the invention

[0036] In order to achieve one or more of said aims, the invention has as its object an electric battery unit, comprising:

[0037] - an array of battery cells immersed, within a container of the battery unit, in a flow of a temperature-regulating fluid, for maintaining the battery unit within a determined temperature range, wherein said container includes:

[0038] - an inlet opening for the temperature-regulating fluid, communicating with an inlet collector chamber, arranged below the array of battery cells,

[0039] - an outlet opening for the temperature-regulating fluid, communicating with an outlet collector chamber, arranged above the array of battery cells,

[0040] - wherein the inlet collector chamber and the outlet collector chamber communicate with each other via a plurality of gaps defined by spacer walls between one battery cell and another,

[0041] - wherein the battery cells each comprise an upper surface, a lower surface, two opposite main surfaces, orthogonal to the direction of cell alignment, and two side surfaces,

[0042] - wherein at least some cells each have a positive pole and a negative pole that are arranged on a side surface of the cell, facing a side wall of the container, or on opposite side surfaces of the cell, respectively, said battery unit being characterized in that:

[0043] - the inlet collector chamber communicates with each of said gaps defined between one cell and another, through one or more restricted passages, so that the flow rates of the temperature-regulating fluid through the different gaps are essentially equal,

[0044] - all the positive poles and all the negative poles of the cells are contained in two respective side chambers of the battery unit that are insulated from each other and are insulated from the gaps between the cells,

[0045] - each of said side chambers containing the positive poles and the negative poles of the cells communicate with the inlet collector chamber and the outlet collector chamber, so that the temperature-regulating fluid can flow from said inlet collector chamber to said outlet collector chamber also flowing through said side chambers containing the poles of the cells,

[0046] - in the connection between each of said side chambers and said inlet collector chamber and / or in the connection between each of said side chambers and said outlet collector chamber, at least one restricted passage is interposed, such that the temperature-regulating fluid does not preferentially flow through said side chambers rather than through said gaps between the cells.

[0047] Thanks to said features, the temperature-regulating action is substantially the same in all parts of the battery unit, so that the temperature of the cells is maintained within the determined range in a substantially uniform manner from cell to cell and in the various parts of each cell.

[0048] Detailed description of the invention

[0049] Further features and advantages of the invention will be apparent from the following description with reference to the attached drawings, provided purely by way of non-limiting example, in which:

[0050] - figure 1 is a perspective view of an embodiment of an electric battery module, comprising the plurality of prismatic type battery cells,

[0051] - figure 2 is a schematic perspective view of a battery cell of the type used in the battery module of figure 1 ,

[0052] - figure 3 is a schematic view of a temperature-regulating system provided in the battery module of figure 1 ,

[0053] - figure 4 is a prismatic type battery cell in an embodiment of the invention,

[0054] - figures 5, 6 are a perspective view and a front view of a spacer wall, arranged between one battery cell and another in an embodiment of the invention,

[0055] - figure 7 is a perspective view of the battery cell of figure 4 illustrating the flows of temperature-regulating fluid at the inlet of the passages defined by the spacer wall visible in figure 4,

[0056] - figure 8 is a front view of a battery cell of said embodiment of the invention, where the flow field of the temperature-regulating fluid is displayed, that passes through the passage defined between one battery cell and another,

[0057] - figure 9 is a variant of figure 8, which refers to the flow field of the temperature-regulating fluid in the case of a second embodiment of the invention,

[0058] - figures 10, 11 are schematic views, already discussed above, of a battery unit of the type with cells having the poles on a side surface facing a side wall of the container of the battery unit, and

[0059] - figure 12 is a schematic end view of a battery unit according to the invention.

[0060] Figures 1-3 relating to the prior art have already been described above.

[0061] Figures 4-9 illustrate some features of an exemplary implementation of the invention, with reference to a battery module of the type illustrated in figure 1 , with battery cells 2 of the prismatic type illustrated in figure 2.

[0062] As illustrated in detail below, the present invention refers in particular to the case in which the battery cells 2 have their poles 3P, 3N (which are not visible in figures 4-9) arranged on a side surface, as schematized in figures 10-12. The following description of figures 4-9 must therefore be understood as referring to a battery unit of this type, with lateral poles.

[0063] With reference to the example of figures 4-9, the passages 7 for the temperature-regulating fluid between each battery cell and another are defined by a plurality of lower spacer walls 8.

[0064] The attached drawings do not show the construction details relating to the way in which the battery cells 2 are held in position one to the other and the way in which the spacer walls 8 are mounted and secured between the battery cells 2. Such details can in fact be made in any known way. In particular, each spacer wall 8 can for example be secured by simple pressure between the facing surfaces of adjacent cells, in the assembled condition of the array of cells 2 in the container 4. Furthermore, in particular to avoid the effects of the swelling problem typical of electrochemical cells, rigid spacer elements are normally introduced inside the gaps 7. These elements, although altering the hydraulic circuit through the gaps 7, do not have an influence on the problem of the preferential path due to the positioning of the poles on the side of the cells.

[0065] According to the example illustrated here, each spacer wall 8 occupies only a lower part of the gap between one cell and another, adjacent to the inlet collector chamber 5.

[0066] As shown in figures 4-6, the spacer wall 8 defines a plurality of passage slits 9 (five in the example) for the temperature-regulating fluid, distributed along the X direction of the cell 2, i.e. along a horizontal direction transversal to the longitudinal direction of the battery module 1.

[0067] Each passage slit 9, defined by the spacer wall 8 interposed between each battery cell and another, constitutes a restricted passage that connects the inlet collector chamber 5, arranged below the battery cells 2, to the gap between two adjacent cells, defined above each spacer wall 8. A particular case is represented by the spacer walls 8 that are connected to the first and last cell of the module 1 represented in figure 1 that are not interposed between two cells but between a cell and the container 4.

[0068] With reference in particular to figures 5, 6, the inlet 9 has a lower inlet port 9A, an upper outlet port 9B having a passage cross-section significantly larger than that of the inlet 9A, and a passage connecting the inlet 9A to the outlet 9B, defined by two side walls 9C diverging towards the outlet 9B.

[0069] In the illustrated example, the lower spacer wall 8 is in the form of a strap with an upper longitudinal edge 80, a lower longitudinal edge 81 and two end edges 82. Again in the case of the illustrated example, the passage slits 9 are defined by recesses configured substantially in a V shape, with the sides of the V defining said diverging side walls 9C and with the vertex of each V-shaped recess defining the inlet 9A. The vertex of each V-shaped recess defining the inlet 9A protrudes below the level 50 (figure 6) of the temperature-regulating fluid within the inlet collector chamber 5, so that the inlet 9A of each opening 9 is in fluid communication with the inlet collector chamber 5, as exemplified in figure 7, where the arrows 51 indicate the flows of temperature-regulating fluid entering the inlet ports 9 of the passage slits 9 defined by each spacer wall 8. Essentially, figure 7 shows how the fluid enters the passage slit 9, with a direction normal to the spacer wall 8.

[0070] As visible in figures 5, 6, in the preferred embodiments, the two side walls 9C of each passage slit 9, defined by the spacer wall 8, have curved profiles diverging from each other in the direction of the outlet port 9B. Thanks to this feature, the flow of temperature-regulating fluid that flows adjacent to each of said curved side walls 9C tends, by Coanda effect, to flow out of the outlet port 9B, following a trajectory corresponding to a theoretical extension of said curved wall 9C. If one wishes to increase the Coanda effect, a connection could be provided between the end part of the curved wall 9C and the upper horizontal section of the spacer wall.

[0071] Said phenomenon is illustrated in figure 8, which shows a front view of the main wall 2C of a battery cell 2, with the spacer wall 8 in the lower part of the cell, defining the passage slits 9 for the temperature-regulating fluid. In figure 8, the flows of the temperature-regulating fluid have been displayed with areas having different hatching corresponding to different fluid speeds and correspond to what emerged in tests carried out by the Applicant.

[0072] As can be seen, thanks to the provision of a relatively high number (preferably greater than 3 and even more preferably equal to at least 5) of openings 9 distributed along the direction X of each spacer wall 8, and thanks to the configuration of the openings 9, the result is obtained of causing the temperature-regulating fluid to uniformly touch substantially the entire surface of the wall of the battery cell facing the passage for the temperature-regulating fluid.

[0073] Figure 9 is similar to figure 8 and shows the results of tests conducted by the Applicant in the case of a further embodiment, in which, between each battery cell and another, in addition to the lower spacer wall 8 described above, there is an auxiliary spacer wall 10 arranged above and at a distance from the lower spacer wall 8 and defining a plurality of restricted passages 11 , each defined by two walls parallel to each other. The auxiliary spacer wall 10 is arranged substantially at least at a vertical level above half the height of the cell 2 and has the dual purpose of obtaining an increase in the speed of the temperature-regulating fluid exiting from each of the passages 11 as well as making the flow field more uniform in the upper part of the auxiliary spacer wall 10. Preferably, the passages 11 , also distributed along the direction X, are relatively high in number, preferably greater than 10. The studies and experiments conducted by the Applicant have shown that the features provided in the battery unit described above allow a drastic increase in the temperature-regulating efficiency of the entire battery unit and above all drastically better results in uniform izing the temperature of the various areas of each battery cell. Of course, the same advantages are also obtained in operating conditions in which the fluid performs a heating function of the battery module, when it is operating in a cold climate.

[0074] According to a further teaching forming part of the present invention, each of the inlet ports 9A of the passage slits 9 defines a restricted passage configured and sized so as to create a certain pressure drop, preferably of at least 35 mbar, in the flow of the temperature-regulating fluid.

[0075] The sum Atot of the passage areas of the restricted sections defined by the inlet ports 9A of all the passage slits 9 is preferably chosen to be less than 1 / 6 of the passage area A1 in the inlet collector chamber 5, in a plane normal to the direction of alignment of the cells 2 (where A1 is considered equal to the product D x H, where D is the largest horizontal dimension of each cell 2 and H is the height of the inlet collector chamber 5). However, for a given configuration of n cells separated by n+1 gaps 7: if Gi is the flow rate through the i-th gap, if Gmax is the maximum flow rate of all the Gi, if Gmedia is the average value of the flow rates and if Gmin is the minimum flow rate among all the Gi, accepting a maximum deviation of 10% between Gmax and the average value and of 10% between Gmin and the average value, it is possible to reduce to 1 / 4 the value of the ratio previously described between the areas of all the restrictions and the passage areas A1.

[0076] Preferably, the same conditions indicated above, i.e. a preferable ratio of 1 / 6, or a ratio of 1 / 4 in the case of accepting flow rate variations of 10% (with respect to the average value) in the different gaps between the cells, also apply to the passage area B1 in the outlet collector chamber 6 (where B1 is considered equal to the product D x H1 , where D is the largest horizontal dimension of each cell 2 and H1 is the height of the inlet collector chamber 5). Therefore, the area B1 must be at least six times the value of the area Atot of all the restricted sections 9A.

[0077] In the case where the auxiliary spacer wall 10 is present, then the condition is preferably verified that the sum of the passage areas of all the restricted sections of the wall 8 and of the additional wall 10 must be less than 1 / 6 of the passage area A1 in the inlet collector chamber 5 and preferably must also be less than 1 / 6 of the passage area B1 in the outlet collector chamber 6.

[0078] Thanks to this feature, each of the passage slits 9 associated with the different cells 2 offers a resistance to the flow of the temperatureregulating fluid sufficiently high to discourage a tendency of the temperature-regulating fluid to flow with greater flow rate in the passages 7 that are closer to the inlet opening 5A.

[0079] Figures 10, 11 , already discussed above, show the specific problem that the present invention aims to solve. These figures are a schematic end view and a schematic plan view of a battery unit in which the cells 2 have their respective poles 3P, 3N, arranged on a side surface 2C of each cell facing a side wall 4A of the container 4. In this case, the side wall 4A must necessarily be placed at a distance from the side surfaces 2C of the cells 2, which gives rise to a large gap 20 where the temperature-regulating fluid tends to flow, thus altering the uniformity of the cooling action inside the container 4.

[0080] Figure 2 shows in section, in a plane orthogonal to the longitudinal direction of the battery unit, an example of a solution according to the invention that allows said problem to be solved. In figure 12, the parts common to those of figures 1 -11 are indicated with the same references.

[0081] Also in the example of figure 12, between each cell 2 and another there is at least one spacer element 8 defining restricted passages 9 (schematically indicated in figure 12) that connect the inlet collector chamber 5 to the gap defined between each cell 2 and another by the spacer element 8. In the example of figure 12, between each cell 2 and another there are also interposed partitions 80 that tend to horizontally divide the various areas of each cell 2, so as to channel a plurality of parallel flows of the temperature-regulating fluid along the main face of each cell. Similarly to the examples described above, the flows of the temperature-regulating fluid that travel through the gaps between the cells 2 then flow through openings 81 into the outlet collector chamber 6. Figure 12 shows an example in which each cell 2 has its poles 3P, 3N, arranged on a side surface 2C of the cell. In the example illustrated in figure 12, the container 4 is configured to define two separate longitudinal chambers CP and CN, in which all the positive poles 3P and all the negative poles 3N of all the cells 2 of the battery unit are arranged, respectively. Furthermore, between each cell 2 and another, at the ends facing the chambers CP, CN, there are partitions and dividers D which separate the gaps between the cells 2 from the chambers CP, CN, in which the poles 3P, 3N of the cells are arranged. The dividers D may also be part of a single wall, placed in contact with the side surfaces 2C of all the cells 2 and having openings for the passage of the poles 3P, 3N.

[0082] The chamber CP containing the positive poles 3P of the lower cells in the battery unit communicates with both the input collector chamber 5 and the output collector chamber 6, so that the temperature-regulating fluid can also flow through this chamber. The connection to the chamber CP and the input collector chamber 5 is achieved by one or more restricted passages 90A formed in the container body 4. The restricted passages 90A may be equal in number to the number of cells and be distributed along the longitudinal direction of the battery unit. Similarly, in the container body 4 there are additional passages 91 A that connect the upper part of the chamber CP with the output collector chamber 6.

[0083] Similarly, in the container body there are multiple restricted passages 90B that connect the input collector chamber 5 to the chamber CN containing the negative poles 3N of all the cells 2 (which in the example is in the upper position in the battery unit). The chamber CN also communicates directly to the outlet collector chamber 6 by restricted passages 91 B. The passages 90B and 91 B can also be made, for example, in a number equal to the number of cells 2 and be distributed along the longitudinal direction of the battery unit.

[0084] In the case in which all the poles P are contained in a single chamber CP, a single passage 90A could be sufficient to guarantee the correct flow rate of temperature-regulating fluid; this also applies to the poles N if contained in a single chamber CN. As an extreme case, it could happen that all the poles P and the poles N are contained in a single chamber CX and therefore a single restricted passage could be sufficient to solve the problem. If the dimensions of the restricted section 90A and the restricted section 90B were to be quantified, it is possible to state that they must be sized so that the flow rate of fluid that feeds the chambers CP and CN, overall, is less than 15% of the flow rate entering the inlet 5A

[0085] Thanks to the arrangement described above, the circulation of the temperature-regulating fluid through the chambers 3P, 3N, also requires overcoming the restricted passages 90A, 90B, formed in the side wall 4A of the container 4. These passages are configured to offer a sufficiently high resistance to the flow to ensure that the flow does not find a preferential path to reach the outlet collector chamber 6. Therefore, the flow rate of the temperature-regulating fluid through the different passages 9 for access to the gaps between the cells 2 and through the restricted passages 90A and 90B for access to the chambers CP, CN, associated with the poles of the cells, is substantially uniform.

[0086] Of course, notwithstanding the principle of the invention, the construction details and the embodiments may vary widely from what is described and illustrated purely by way of example, without thereby departing from the scope of the present invention, as defined in the attached claims.

[0087] For example, it is possible that not all cells have the poles on one side. Furthermore, the cells may have the positive pole and the negative pole on two opposite sides of the cell: in this case, however, nothing changes. Simply, the chamber CP and CN are on two opposite sides.

Claims

CLAIMS1. An electric battery unit, comprising an array of battery cells (2) immersed, within a container (4) of the battery unit (1 ), in a flow of a temperature-regulating fluid, for maintaining the battery unit within a determined temperature range, wherein said container (4) includes:- an inlet opening (5A) for the temperature-regulating fluid, communicating with an inlet collector chamber (5) arranged below the array of battery cells (2),- an outlet opening (6A) for the temperature-regulating fluid communicating with an outlet collector chamber (6), arranged above the array of battery cells (2),- wherein the inlet collector chamber (5) and the outlet collector chamber (6) communicate with each other via a plurality of gaps (7) defined by spacer walls (8) between one battery cell (2) and another,- wherein the battery cells (2) each comprise an upper surface (2A), a lower surface (2D), two opposite main surfaces (2P), orthogonal to the direction of alignment of the cells (2) and two side surfaces (2C), said electric battery unit being characterized in that:- the inlet collector chamber (5) communicates with each of the gaps defined between one cell and another by one or more restricted passages (9), so that the flow rates of the temperature-regulating fluid through the gaps (7) between the cells (2) are essentially equal,- at least some cells (2) each have a positive pole (3P) and a negative pole (3N) that are arranged on a side surface (2C) of the cell, facing a side wall (4A) of the container (4), or on opposite side surfaces of the cell, respectively,- all the positive poles (3P) and all the negative poles (3N) of the cells are contained in two respective side chambers (CP, CN) of the battery unit (1 ) that are insulated from each other and are insulated with respect to the gaps (7) between the cells (2),- each of said side chambers (CP, CN) containing the positive poles (3P) and the negative poles (3N) of the cells (2) communicate with the inlet collector chamber (5) and the outlet collector chamber (6), so that thetemperature-regulating fluid can flow from said inlet collector chamber (5) and said outlet collector chamber (6) also flowing through said side chambers (CP, CN), containing the poles (3P, 3N) of the cells (2), and- in the connection between each of said side chambers (CP, CN) and said inlet collector chamber (5) and / or in the connection between each of said side chambers (CP, CN) and said outlet collector chamber (6) there is interposed at least one restricted passage (90A, 90B, 91 A, 91 B), such that the temperature-regulating fluid does not preferentially flow through said side chambers (CP, CN) rather than through the gaps (7) between the cells.

2. The electric battery unit according to claim 1 , characterized in that each of said side chambers (CP, CN) containing the poles (3P, 3N) of the cells (2) extends along the entire length of the battery unit in the direction of alignment of the cells (2) and communicates with the inlet collector chamber (5) and the outlet collector chamber (6) through a plurality of passages (90A, 90B, 91 A, 91 B) distributed along said longitudinal direction of the battery unit.

3. The electric battery unit according to claim 1 , characterized in that said at least one restricted passage (90A, 90B, 91 A, 91 B) has a passage cross-section sized such that the total flow rate of the temperatureregulating fluid flowing through said side chambers (CP, CN) is not more than 15% of the total flow rate of the temperature-regulating fluid entering through said inlet (5A)4. The electric battery unit according to claim 1 , characterized in that said spacer walls (8) arranged between the cells (2) occupy only a lower part of the gap (7) between each cell and the other, adjacent to the inlet collector chamber (5) and each spacer each has a plurality of passage slits (9) for the temperature-regulating fluid, which are parallel to each other and spaced apart from each other, to connect the inlet collector chamber (5) with the gap (7) between two adjacent cells (2) above the spacer wall (8).

5. The electric battery unit according to claim 4, characterized in that each of the passage slits (9) of each spacer wall (8) is configured to define:- a lower inlet port (9A),- an upper outlet port (9B), and- a passage connecting the inlet port (9A) with the outlet port (9B),and wherein:- the upper outlet port (9B) of each passage slit (9) has a passage cross-section significantly larger than that of the respective inlet port (9A),- the passage connecting the inlet port (9A) with the outlet port (9B) of each passage slit (9) has two side walls (9C) diverging towards the outlet port (9B).

6. The electric battery unit according to claim 5, characterized in that said two side walls (9C) of each passage slit (9) are curved walls diverging from each other in the direction of the outlet (9B), so that the flow of the temperature-regulating fluid flowing adjacent to each of said diverging curved side walls (9C) tends, by Coanda effect, to flow out of the outlet port (9B) following a trajectory corresponding to a theoretical extension of said curved side wall (9C).

7. The battery unit according to claim 5, characterized in that the inlet port (9A) of each of said passage slits (9) defines a restricted section, configured and sized so as to create a pressure drop, preferably of at least 35 mbar, in the flow of the temperature-regulating fluid, the sum A TOT of the passage areas of the restricted sections defined by the inlet ports (9A) of all said passage slits (9) being less than 1 / 6 of the passage area A1 in the inlet collector chamber (5) in a plane normal to the direction of alignment of the cells (2) and preferably is also less than 1 / 6 of the passage area B1 in the outlet collector chamber (6) in a plane normal to the direction of cell alignment.

8. The battery unit according to claim 5, characterized in that the inlet port (9A) of each of said passage slits (9) defines a restricted section, configured and sized so as to create a pressure drop, preferably of at least 35 mbar, in the flow of the temperature-regulating fluid, the sum A TOT of the passage areas of the restricted sections defined by the inlet ports (9A) of all said passage slits (9) being less than 1 / 4 of the passage area A1 in the inlet collector chamber (5) in a plane normal to the direction of alignment of the cells (2), such that the flow rate of the temperature-regulating fluid in the gaps (7) between the cells (2) varies from cell to cell not more than 10% from the average value between the flow rate values in the different gaps (7) between the cells.

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