Phase Motion Control SpA

The present invention relates to a battery pack comprising one or more electrochemical cells and a battery management system for monitoring and controlling said cells.

The present disclosure relates to lithium-ion batteries, but it should be clear to a person skilled in the art that the invention can be applied to any suitable battery type.

Lithium-based batteries, both primary and secondary, are characterised by a high accumulated energy density, which allows them to be used in countless high energy and power applications, such as electric vehicles and aircraft, battery powered tools, and the like.

The high energy density, however, also makes the batteries susceptible to fire with the release of flames and chemically aggressive compounds in the event of battery failure or damage. This behaviour is to some extent intrinsic; if in fact the energy contained in the battery is released suddenly, for example from an accident that physically damages the battery, the same high amount of energy necessarily produces heat to a significant extent.

In fact, it is known that, in the event of mechanical damage that short-circuits positive and negative current carriers, lithium-ion batteries release a large amount of energy that leads to a rapid overheating of the electrodes. When this occurs, temperatures above 200°C are reached, generally in fractions of a second. Under these conditions, the constituent elements gasify, causing the battery to explode and its metal parts to bum. Since the thermal degeneration of the battery produces oxygen, a fire of this sort is particularly difficult to control. At the same time, hydrofluoric acid, which is highly corrosive and toxic, is generally found among combustion products.

Moreover, the battery systems demanded by the market are growing. One example is the shipping industry, where there is a strong demand for ships with hybrid propulsion systems, such as to allow electric propulsion when the ship moves in the vicinity of an urban environment. In such systems between 10 and 15 MWh need to be accumulated. However, as the accumulated energy increases, the complexity of the connections grows. This is why the trend is to increase the size of individual cells, though this makes the thermal regulation of the single cell increasingly problematic.

At the same time, in high power applications, and to avoid overheating due to a high current flow, it is often necessary to cool the battery when it is subjected to a rapid discharge. In the converse situation, it may be necessary to ensure rapid preheating of a battery stored at temperatures below 0°C, since at low temperatures the charging process is hazardous.

For the management of these thermal aspects of the batteries in use, state-of-the-art cooling/heating systems are known, comprising heat exchangers placed in contact with the outside of the batteries and provided with ducts for the circulation of a cooling/heating fluid. However, these systems have some disadvantages, in particular they significantly increase the weight of the battery pack, which goes against the demand from e-mobility for ever smaller weights.

A subject matter of the present invention is also a Battery Management System (BMS), i.e. , an electronic system that manages one or more rechargeable batteries, for example by protecting the batteries from operating outside the safe operating area, monitoring their status, calculating secondary data, reporting such data, controlling their environment, validating it and/or returning it to optimal conditions. In fact, if two or more cells have significant differences in state of charge, it is possible to trigger dangerous overheating that can also lead to fire. Among the primary purposes of the BMS are, therefore, the measurement of the cell voltage, the measurement of the cell temperature for safety reasons, and the selective discharge of the over-charged cells to bring them back to average with the other cells and thus maintain a homogeneity of state of charge between the cells. The BMS must therefore control cell by cell and this requires electrical connections, one or more electronic processing units and systems to dissipate the excess charge. The currently known BMSs include electronic boards placed outside the cells with a plurality of electrical resistors adapted to dissipate heat towards the surrounding air. The amount of energy that can be dissipated in these systems is limited, however, and this is confirmed by the fact that in current BMSs it sometimes takes up to several days to balance a new battery properly.

The systems currently known also face a further technical problem: the measurement of the voltage of many cells requires insulation systems in subgroups of cells to avoid prevent the electrical voltage to be managed by the BMS electronics from being too high. Currently, indeed, BMSs manage up to 12-14 elements in series, but the total voltage is summed and, therefore, in the presence of 10 elements of 3.7 V the electronics of the BMS must manage 37 V. As the number of elements increases, for a battery pack of, for example, 1000V, management of the entire voltage is not possible in a single integrated circuit. The cells are divided into subgroups, and subsequently electronic isolation systems are implemented between the subgroups to pass from one subgroup to another to a central control unit called a “master”.

In the same way, complexity increases with the increase in the size of the battery pack with regard to temperature detection, typically carried out with thermocouples connected by electrical wires. Moreover, if the dimensions of the single cell are also increased, the temperature is even more difficult to measure with precision, since even within the single cell there may be significant variations in temperature from area to area. This makes it necessary to increase the measuring stations on each cell.

Hence, there is currently a need unsatisfied by the state of the art for a battery pack equipped with BMS that overcomes the aforementioned drawbacks of the currently known systems, that therefore allows the number and complexity of the electrical connections required by the BMS to be reduced and that increases the efficiency of the energy dissipation during the balancing phase. The invention achieves the above purposes with a battery pack as described at the beginning, wherein further the battery management system comprises one or more local control units and at least one central control unit, each local control unit being associated with at least one cell, and the local control units being in connection with the central control unit via means of wireless communication.

This makes it possible to avoid the presence of wired electrical connections for both voltage measurement and temperature measurement, reducing the complexity and weight of the battery pack. Consequently, moreover, the system is inherently insulated and solves the above-mentioned problem of increased voltage as the number of cells increases without any need for dedicated electronic isolation systems.

In an exemplary embodiment, a plurality of said local control units are provided, the local control units being organised in an ordered series comprising a first local control unit and a last local control unit, the means of wireless communication being configured such that the first local control unit is in communication with the central control unit and with the respective next local control unit, the last local control unit is in communication with the respective preceding local control unit, and the further local control units are in communication each with the respective preceding local control unit and with the respective following local control unit.

In this way, a chain network architecture is formed in which data containing the commands is sent from the central control unit and passed from local unit to local unit until the last in the series, and then back along the same path to bring the information to the central unit.

In a preferred exemplary embodiment, the communication means are of the NFC (Near Field Communication) type.

Such transceiver technology provides short-range bidirectional radio frequency wireless connectivity, currently up to a maximum of about 10 cm, and thus allows the chain architecture described above to be implemented without complex arrangements. In a further exemplary embodiment, said means of wireless communication are of the electro-optical type.

Electro-optical communication between control boards is possible through enclosures made of at least partially transparent thermoplastic material as well as by a temperature control liquid which is also at least partially transparent.

According to one embodiment, each cell is provided with a respective said local control unit.

The battery pack is thus managed entirely by the BMS and the ordered set of cells is replicated by the ordered set of local control units placed to form the chain architecture described above.

In one embodiment, each cell is provided with a watertight peripheral enclosure, in which enclosure the respective local control unit is housed.

In this way, a battery is created that incorporates an electronic management unit already prepared to be connected wirelessly in a distributed battery management system that is easy to set up and configure with any number of batteries.

According to one improvement, the packaging is made of thermoplastic polymeric material.

The polymeric material advantageously does not impede wireless communication between the local control units and with the central control unit.

In an exemplary embodiment, each cell and its local control unit are immersed at least partially in a hydraulic circulation circuit of a thermal regulation fluid.

In this way, the enclosure separates the cell and the local control unit from the hydraulic circuit in a watertight manner, but the thermal regulation fluid exerts its action through the packaging on both the cell and the local control unit.

In a preferred embodiment, said thermal regulation fluid is nonpolar and non-water-based. This proves particularly advantageous in combination with the polymeric material packaging described above, said material being characterised by a liquefaction temperature lower than the temperature of the thermal runaway or thermal leakage of the electrochemical cell. Since the cell is immersed in a non-polar, non-water-based liquid under pressure, this liquid performs the dual function of thermal regulation of the cell and suppression of the thermal runaway in the event that a degenerative phenomenon of the cell itself is accidentally triggered.

In one embodiment, said cells are flat and the hydraulic circuit is configured as a coil, such that the thermal regulation fluid laps each cell on both sides of the packaging of the cell itself.

This imposes an obligatory path on the thermal regulation fluid, which must flow along the opposite faces of each cell and in this way lap all the areas of the battery pack exercising its thermal regulation function.

According to a further exemplary embodiment, the local control units are provided with thermal dissipation means for balancing the charge of the cells.

In this way, the thermal dissipation for balancing does not take place in air, with the consequent efficiency problems mentioned in the introduction, but exploits the same cooling circuit of the cell itself. The fact that the local control unit is provided inside the packaging of the cell and that the latter is placed in the cooling circuit, in fact allows the means of thermal dissipation to be in thermal contact with the thermal regulation fluid by means of the packaging.

These and other features and advantages of the present invention will become clearer from the following description of some non-limiting exemplary embodiments illustrated in the attached drawings in which:

Fig. 1 shows a design of the battery pack;

Fig. 2 illustrates an exploded view of a cell with its packaging and its local control unit;

Fig. 3 illustrates an embodiment of the system;

Fig. 4 illustrates a sectional view of the battery pack in assembled condition with a plurality of cells side by side; Fig. 5 illustrates the battery pack in the assembled condition;

Fig. 6 illustrates a sectional view of the hydraulic circuit formed by the complete battery pack in assembled condition.

The present invention relates to a battery pack comprising one or more electrochemical cells 1 and a BMS for monitoring and controlling said cells 1 .

The BMS includes a plurality of local control units 51 and a central control unit 50. Each local control unit 51 is associated with a respective cell 1 , such that each cell 1 of the battery pack is associated with its own local control unit 51.

It is possible to provide for more than one central control unit 50, and it is possible to provide for a local control unit 51 to be associated with multiple cells 1 . It is also possible to provide for a configuration with only one central unit 50 and only one local unit 51 .

The local control units 51 are connected to the central control unit 50 via means of wireless communication.

The local control units 51 are organised in an ordered series comprising a first local control unit 5T and a last local control unit 51". The means of wireless communication are configured to form a chain such that each local control unit communicates only with the one immediately preceding and the one immediately after, if any. In other words, the first local control unit 5T is in communication with the central control unit 50 and with the respective next local control unit 51 , the last local control unit 51” is in communication with the respective previous local control unit 51 , and the additional local control units 51 are in communication each with the respective previous local control unit and with the respective subsequent local control unit.

Preferably, the communication means are of the Near Field Communication (NFC) type, but other technologies currently known to a person skilled in the art may be used, having been adapted to make a chain configuration as described above.

Alternatively or in combination, the means of wireless communication activate communication of the electro-optical type. Each local unit 51 in this case is provided with a photo-signal, e.g., a LED or other light source, and a photo-receiver. These elements are also provided on the central control unit 50.

The data packets are then preferably generated by the central control unit 50 and passed from the local unit to the local unit, giving the commands necessary for the management of the respective cells. Once they reach the last local control unit 51” the packets go back to the central unit 50, modified with the addition of information by each local unit 51.

The central control unit 50 calculates the state of charge of each cell 1 and controls the safety actions for each local control unit 51 . In one exemplary embodiment, the local control units 51 comprise a switch of the cell 1 the opening of which can be controlled by the central unit 50 in the event of anomalies.

Cells 1 are preferably lithium-ion flat cells such as the known pouch cells. However, other types of cells, such as cylindrical cells, may be adopted without abandoning the purpose of the invention.

It is possible to use pouch cells of the currently known type, which are typically enveloped in packaging consisting of a layered sheet of plastic and aluminium, similar to food packaging. The primary purpose of the packaging is to avoid at all costs the penetration of moisture, which would inevitably damage the cell with the consequent risk of fire and explosion. In this case, the packaging is suitably shaped so as not to impede communication between the local control units 51 and the central control unit 50.

A further particularly advantageous exemplary embodiment is illustrated in the Figures. According to this exemplary embodiment, each cell 1 comprises a plurality of overlapping laminated layers 10, a plurality of electrodes 11 and a packaging containing the layers 10. The packaging is divided into two rigid thermoformed half-shells 12 that can be joined to one another by means of coupling. Each rigid half-shell 12 has a flat perimeter edge 120 that completely surrounds it and a central recess 121 as a tray, complementary to the set of layers that make up the cell 1 . In the coupled condition of the two half-shells 12, the two perimeter edges 120 are brought into mutual contact and rest on a single plane, while the central recesses 121 extend symmetrically in opposite directions with respect to said plane. In this way, the two central recesses 121 form a central housing seat for the constituent layers 10 of the cell 1 and the two perimeter edges 120 in mutual contact form a perimeter flange 122.

The two thermoformed half-shells 12 are of polymeric material having a low melting temperature (preferably ranging from 120°C to 160°C), such as polyethylene or polyethylene terephthalate.

The polymeric material constituting the packaging 13 is preferably transparent or semi-transparent, so as to allow for possible electro-optical communication between local units 51. Alternatively, it is possible to provide transparent inserts in the half-shells 12 in immediate proximity to the communication means in such a way as to form optical communication windows between the local units 51.

The two half-shells 12 are preferably heat-welded together along the perimeter edges 120, but can also be glued or secured by any known state of the art fixing method capable of keeping the packaging sealed from the outside.

The packaging formed by the assembly of the two half-shells 12 is provided with electrode 11 passage openings 124. These openings 124 are formed in the perimeter flange 122 by shaping one or both of the perimeter edges 120 such that, in the coupled condition of the two halfshells 12, the perimeter edges 120 are spaced apart by the thickness of the electrodes 11. To ensure a watertight sealing on the electrodes 11 , each passage opening 124 is internally provided with a gasket element 125 adapted to interpose between the walls of the passage opening 124 and the electrode 11 .

One side of the perimeter edge 120 of each half-shell 12 has a plurality of holes 126 such that in the assembled condition of the packaging the perimeter flange 122 has a perforated zone.

The battery pack comprises a plurality of spacer frames 2 having a substantially rectangular shape and dimensions corresponding to the perimeter flange 122. The spacer frame 2 is adapted to be interposed between two cells 1 side by side, coming into contact with their respective perimeter flanges 122. The spacer frame 2 is provided with gasket elements 20 on opposite contact surfaces of two perimeter flanges 122 of two cells 1 side by side.

The thickness of the spacer frame 2, i.e., the distance between the two opposite said contact surfaces, is such that, in the assembled condition of the battery pack, a watertight cavity 30 is formed between the two cells 1 with respect to the outside of the battery pack, as illustrated in the sectional view in Figure 4.

The two half-shells 12 are shaped so as also to create a housing 127 for a local control unit 51 , shown in Figure 2. The local control unit 51 is then separated from the outside in a watertight manner by the packaging.

The local control unit 51 is preferably physically separated from the cell 1 but is connected to the electrodes 11 thereof by conductors 511. The local control unit 51 is further provided with one or more temperature sensors 512 of the cell, preferably consisting of thermocouples. In the exemplary embodiment of Figures 2 and 5, the housings 127 of the local control units 51 are obtained from an extension of the packaging outside its rectangular shape. In this case, such an extension is also present in the frame 2, so as to form the cavity 30 also at the housing 127.

Figure 3 illustrates an alternative embodiment, wherein the housing 127 for the local control unit 51 is triangular and formed in a corner of the rectangle substantially defining the central housing location of the layers 10 constituting the cell 1 , and separated therefrom.

In this case, the spacer frame 2 between different cells 1 can be entirely rectangular in shape.

To assemble the battery pack, the cells 1 are stacked together as shown in Figure 5, i.e., placed on planes parallel to each other and aligned along a longitudinal axis. A spacer frame 2 is placed between two adjacent cells 1 throughout the stack, so as to form an alternating series of cells 1 and frames 2. At the opposite ends of the stack are two end cells 1 , and a first and second end cap 40, 41 are provided with gasket elements adapted for sealing the perimeter flanges 122 of said end cells 1. Both end caps are shaped so as to identify a first cavity provided between the first end cap 40 and the corresponding end cell 1 and a last cavity provided between the second end cap 42 and the corresponding further end cell 1.

The first end cap 40 is provided with a central control unit housing seat 50. When the entire battery pack is assembled, the local units 51 and the central unit 50 are stacked together as shown in Figure 5.

The caps 40 and 41 are preferably provided with reinforcing ribs 401.

Means for holding are also provided in the assembled condition of the cells 1 , the spacer frames 2 and the end caps 40 and 41 . In the example given in the Figure, these means consist of metal bars or bolts 42 fixed on special eyelets 43 provided on both end caps 40 and 41 .

In the stack thus formed, the holes 126 present on each perimeter flange 122 put all the cavities 30 in hydraulic communication with each other to form a single hydraulic circuit 3.

The hydraulic circuit 3 comprises an inlet 31 at the first cavity and an outlet 32 at the last cavity, the inlet and the outlet being connections to an external circulation circuit of a thermal regulation fluid, as shown in the example in the Figures.

In this way, each cell 1 and the respective local control unit 51 are placed in the hydraulic circuit 3 for the circulation of a thermal regulation fluid.

The thermal regulation fluid is preferably a non-polar and non- water-based liquid, for example vegetable oil. The thermal regulation fluid is preferably transparent or semi-transparent, so as to allow for any electro-optical communication between circuit boards 8.

The external circuit is also provided with means for pressurising the thermal regulation fluid, so that this fluid flows under pressure in the hydraulic circuit 3 of the battery pack, in particular with a pressure between 1 and 3 Bar, preferably 2 Bar. This also ensures the correct pressure between the electrodes of the cell, which would otherwise be obtained with springs, or other means, adding additional weight.

The local control units 51 are provided with thermal dissipation means 510 for balancing the charge of the cells. Such means 510 can be of any type known to a person skilled in the art and preferably comprise electrical resistors. The heat generated by these resistors reaches the thermal regulation liquid through the packaging, from which it is dissipated.

As illustrated in Figure 5, the hydraulic circuit 3 has a coil configuration such that the thermal regulation fluid laps each cell 1 on both sides of the packaging of the cell 1 itself.

To obtain this configuration, the cells 1 are arranged in the stack such that two adjacent cells 1 have their respective perimeter flange zones 122 equipped with holes 126 in opposite positions to each other with respect to a longitudinal plane of the battery pack.

In the configurations illustrated in the Figures, two distinct shapes of pairs of half-shells 12 are necessary, in order to present the respective perimeter flange zones 122 provided with holes 126 in opposite positions to each other, but the housings 127 of the local control units 51 are in the same position, so that they are aligned in the battery pack in an assembled condition.

However, it is possible to have the housings 127 of the local control units 51 in positions such as to create a coil in the hydraulic circuit with only one pair of half-shells 12 which is simply tilted alternately, while ensuring an aligned position for the local control units 51 .

In a preferred embodiment, the cell 1 including its packaging has a thickness of 11 mm while the cavity 30 measures 1 mm between the two recesses 121 of two adjacent cells 1 . This size of the cavities 30 has been shown to be sufficient for effective thermal regulation and at the same time allows for a minimum weight of thermal regulation fluid and reduced volumes.