WO2022137117A1 - Battery pack comprising one or more electrochemical cells and a plurality of electronic control boards - Google Patents

Battery pack comprising one or more electrochemical cells and a plurality of electronic control boards Download PDF

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Publication number
WO2022137117A1
WO2022137117A1 PCT/IB2021/062104 IB2021062104W WO2022137117A1 WO 2022137117 A1 WO2022137117 A1 WO 2022137117A1 IB 2021062104 W IB2021062104 W IB 2021062104W WO 2022137117 A1 WO2022137117 A1 WO 2022137117A1
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WIPO (PCT)
Prior art keywords
cell
battery pack
cells
pack according
control unit
Prior art date
Application number
PCT/IB2021/062104
Other languages
French (fr)
Inventor
Marco Venturini
Marco Calvini
Original Assignee
Phase Motion Control S.P.A.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Phase Motion Control S.P.A. filed Critical Phase Motion Control S.P.A.
Priority to EP21844059.2A priority Critical patent/EP4264726A1/en
Publication of WO2022137117A1 publication Critical patent/WO2022137117A1/en

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
    • H01M10/425—Structural combination with electronic components, e.g. electronic circuits integrated to the outside of the casing
    • H01M10/4257—Smart batteries, e.g. electronic circuits inside the housing of the cells or batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
    • H01M10/44—Methods for charging or discharging
    • H01M10/441—Methods for charging or discharging for several batteries or cells simultaneously or sequentially
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/60—Heating or cooling; Temperature control
    • H01M10/61—Types of temperature control
    • H01M10/613—Cooling or keeping cold
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/60—Heating or cooling; Temperature control
    • H01M10/64—Heating or cooling; Temperature control characterised by the shape of the cells
    • H01M10/647—Prismatic or flat cells, e.g. pouch cells
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/60—Heating or cooling; Temperature control
    • H01M10/65—Means for temperature control structurally associated with the cells
    • H01M10/655—Solid structures for heat exchange or heat conduction
    • H01M10/6556—Solid parts with flow channel passages or pipes for heat exchange
    • H01M10/6557—Solid parts with flow channel passages or pipes for heat exchange arranged between the cells
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/60—Heating or cooling; Temperature control
    • H01M10/65—Means for temperature control structurally associated with the cells
    • H01M10/656—Means for temperature control structurally associated with the cells characterised by the type of heat-exchange fluid
    • H01M10/6567—Liquids
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/10—Primary casings, jackets or wrappings of a single cell or a single battery
    • H01M50/102—Primary casings, jackets or wrappings of a single cell or a single battery characterised by their shape or physical structure
    • H01M50/103—Primary casings, jackets or wrappings of a single cell or a single battery characterised by their shape or physical structure prismatic or rectangular
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/10—Primary casings, jackets or wrappings of a single cell or a single battery
    • H01M50/116—Primary casings, jackets or wrappings of a single cell or a single battery characterised by the material
    • H01M50/121—Organic material
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/20—Mountings; Secondary casings or frames; Racks, modules or packs; Suspension devices; Shock absorbers; Transport or carrying devices; Holders
    • H01M50/204—Racks, modules or packs for multiple batteries or multiple cells
    • H01M50/207—Racks, modules or packs for multiple batteries or multiple cells characterised by their shape
    • H01M50/209—Racks, modules or packs for multiple batteries or multiple cells characterised by their shape adapted for prismatic or rectangular cells
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J7/00—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries
    • H02J7/0013—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries acting upon several batteries simultaneously or sequentially
    • H02J7/0014—Circuits for equalisation of charge between batteries
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J7/00—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries
    • H02J7/0013—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries acting upon several batteries simultaneously or sequentially
    • H02J7/0024—Parallel/serial switching of connection of batteries to charge or load circuit
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J7/00—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries
    • H02J7/0063—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries with circuits adapted for supplying loads from the battery
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
    • H01M10/48—Accumulators combined with arrangements for measuring, testing or indicating the condition of cells, e.g. the level or density of the electrolyte
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
    • H01M10/48—Accumulators combined with arrangements for measuring, testing or indicating the condition of cells, e.g. the level or density of the electrolyte
    • H01M10/486—Accumulators combined with arrangements for measuring, testing or indicating the condition of cells, e.g. the level or density of the electrolyte for measuring temperature
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/60—Heating or cooling; Temperature control
    • H01M10/61—Types of temperature control
    • H01M10/615—Heating or keeping warm
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/60—Heating or cooling; Temperature control
    • H01M10/62—Heating or cooling; Temperature control specially adapted for specific applications
    • H01M10/625—Vehicles
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/60—Heating or cooling; Temperature control
    • H01M10/65—Means for temperature control structurally associated with the cells
    • H01M10/657—Means for temperature control structurally associated with the cells by electric or electromagnetic means
    • H01M10/6571—Resistive heaters
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
    • H01M10/425—Structural combination with electronic components, e.g. electronic circuits integrated to the outside of the casing
    • H01M2010/4271—Battery management systems including electronic circuits, e.g. control of current or voltage to keep battery in healthy state, cell balancing
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
    • H01M10/425—Structural combination with electronic components, e.g. electronic circuits integrated to the outside of the casing
    • H01M2010/4278—Systems for data transfer from batteries, e.g. transfer of battery parameters to a controller, data transferred between battery controller and main controller
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M2220/00—Batteries for particular applications
    • H01M2220/20—Batteries in motive systems, e.g. vehicle, ship, plane
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/10—Primary casings, jackets or wrappings of a single cell or a single battery
    • H01M50/102—Primary casings, jackets or wrappings of a single cell or a single battery characterised by their shape or physical structure
    • H01M50/105—Pouches or flexible bags
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/20—Mountings; Secondary casings or frames; Racks, modules or packs; Suspension devices; Shock absorbers; Transport or carrying devices; Holders
    • H01M50/204—Racks, modules or packs for multiple batteries or multiple cells
    • H01M50/207—Racks, modules or packs for multiple batteries or multiple cells characterised by their shape
    • H01M50/211—Racks, modules or packs for multiple batteries or multiple cells characterised by their shape adapted for pouch cells
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/20—Mountings; Secondary casings or frames; Racks, modules or packs; Suspension devices; Shock absorbers; Transport or carrying devices; Holders
    • H01M50/249—Mountings; Secondary casings or frames; Racks, modules or packs; Suspension devices; Shock absorbers; Transport or carrying devices; Holders specially adapted for aircraft or vehicles, e.g. cars or trains
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/20—Mountings; Secondary casings or frames; Racks, modules or packs; Suspension devices; Shock absorbers; Transport or carrying devices; Holders
    • H01M50/262—Mountings; Secondary casings or frames; Racks, modules or packs; Suspension devices; Shock absorbers; Transport or carrying devices; Holders with fastening means, e.g. locks
    • H01M50/264—Mountings; Secondary casings or frames; Racks, modules or packs; Suspension devices; Shock absorbers; Transport or carrying devices; Holders with fastening means, e.g. locks for cells or batteries, e.g. straps, tie rods or peripheral frames
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/20—Mountings; Secondary casings or frames; Racks, modules or packs; Suspension devices; Shock absorbers; Transport or carrying devices; Holders
    • H01M50/289—Mountings; Secondary casings or frames; Racks, modules or packs; Suspension devices; Shock absorbers; Transport or carrying devices; Holders characterised by spacing elements or positioning means within frames, racks or packs
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J2207/00—Indexing scheme relating to details of circuit arrangements for charging or depolarising batteries or for supplying loads from batteries
    • H02J2207/20—Charging or discharging characterised by the power electronics converter

Definitions

  • the present invention relates to a battery pack comprising one or more electrochemical cells, a plurality of electronic control boards, and a central control unit connected to said control boards, each cell being associated with one relative said control board.
  • the present disclosure relates to lithium-ion batteries, but it is clear to those skilled in the art that the invention can be applied to any suitable battery type.
  • Lithium-based batteries both primary and secondary, are characterized by a high stored energy density, which allows them to be used in countless applications of high energy and power, such as electric vehicles and aircraft, battery powered tools, and the like.
  • battery packs with a multiplicity of individual electrochemical cells are typically used, which are generally the same as each other and are connected in series until a useful overall voltage is reached.
  • Typical voltage values are in this case represented by 3.7 V batteries connected in series to each other up to an overall voltage of 450 V.
  • the output of the battery pack thus composed is connected to said inverter which, by operating transistor-based switching elements, performs pulse-width modulation (PWM) for the conversion of the output voltage to alternating current.
  • PWM pulse-width modulation
  • PWM is a technique for reducing the average voltage provided by an electrical signal, effectively dividing it into discrete parts.
  • the average voltage value supplied to the load is controlled by rapidly activating and deactivating the switching elements between positive and negative power supply and load for the creation of voltage pulses.
  • the duration of the pulses is proportional to the amplitude of the sinusoidal curve which is to be generated as an output voltage and an average is carried out by means of filters comprising inductors, which finally allows to obtain the desired voltage sinusoid.
  • PWM essentially does not bum energy and is therefore a very efficient process. In fact, the power is dissipated to a large extent only in the switching action of the switching elements of the inverter, which therefore tend to heat up and must therefore be substantially cooled.
  • DC/AC converters comprising a plurality of switching cells are currently known, described for example by document DE10103031. These converters connect to a direct voltage source and replace the classic phase modules comprising transistor switches and half bridge diodes with switching cells comprising capacitors as energy storage elements. Such switching cells are cascaded to form "phase legs". Thereby the stored energy is distributed in a plurality of small elements. This distributed energy storage configuration allows a finer graduation of the voltage produced by the converter with respect to apparatuses with a single common energy storage, thus reducing the complexity of levelling and filtering at the connection point of the apparatus.
  • the DC/AC conversion occurs at the overall level of the battery pack or converter which uses a plurality of batteries as power exchange elements for the AC system support.
  • the present invention instead obtains the AC conversion within the battery pack as described at the beginning, in which each control board is incorporated into the respective cell and comprises a switching cell provided with a set of semiconductor switches configured to arrange the cell in series, in anti-series or to bypass the cell, with respect to the set of the other cells of the pack.
  • said electronic board performs both the monitoring function, typical of the BMS, and said series or bypass connection function, with respect to the other cells of the system.
  • the switching cell is configured to alternatively arrange the respective cell in series, anti-series or bypass with respect to the set of the other cells of the pack.
  • the battery consisting of these cells is therefore able to make a variable voltage at intervals equal to the voltage of cells, positive or negative, and is therefore able to obtain an AC output or in any case at variable voltage without the need for a separate inverter.
  • control board to connect or disconnect the single cell from the battery pack also allows to perform the balancing function of the BMS without wasting energy and with great speed, unlike the normally used passive balancing systems, which are of a dissipative nature.
  • variable voltage can advantageously be a sinusoidal alternating voltage.
  • the battery natively has an AC output and must not be connected to an external inverter.
  • alternating voltage is not the only application of the present invention. It is possible, for example, to form a battery charging system, which must provide direct current but which is connected to an initially discharged battery, which must then receive a lower voltage, which voltage must rise as the battery recharges. By virtue of the present invention, it is possible to adjust the output voltage by acting on the individual cells and thus obtain an advantageously variable voltage, even if not necessarily alternating.
  • the output voltage of the supply batteries can vary significantly depending on the charge state.
  • the cells in the bypass condition are cycled, i.e. , the bypass condition is progressively assigned to different cells, so as to ensure a uniform discharge and at the same time a constant overall output voltage. Therefore, the term "variable voltage" means a voltage which can be controlled according to the charging needs.
  • the central control unit is configured to regulate the output voltage of the battery pack by periodically bypassing groups of cells, simultaneously obtaining the balancing thereof, with a BMS function, and the control, if even at discrete steps equal to the cell voltage, of the voltage across the battery.
  • the central control unit is configured so as to obtain a stepwise output voltage approximating a sinusoid at controllable frequency and amplitude.
  • the central control unit is configured to control the voltage of the battery pack so as to perform the charge control function even if interfaced with an uncontrolled direct voltage source.
  • the central control unit is configured to generate three offset sinusoidal voltages of 120 electrical degrees, of controlled amplitude and frequency, suitable for the direct control of electric motors.
  • the central control unit is configured to generate one or three sinusoidal voltages, of controlled amplitude and frequency, so as to control battery charging when interfaced with an uncontrolled single-phase or three-phase AC source.
  • the high energy density also makes the batteries susceptible to fire with flame release and chemically aggressive compounds in the event of battery failure or damage. This behaviour is to some extent intrinsic; in fact, if the energy contained in the battery is released suddenly, for example from an accident which physically damages the battery, the same high amount of energy necessarily produces heat to a significant extent.
  • lithium-ion batteries in the event of mechanical damage which short circuits positive and negative current carriers, release a large amount of energy which leads to a rapid overheating of the electrodes.
  • temperatures above 200 °C are reached, generally in fractions of a second.
  • the constituent elements gasify, causing the battery to explode and its metal parts to bum. Since the thermal degeneration of the battery produces oxygen, such a fire is particularly difficult to control.
  • hydrofluoric acid which is highly corrosive and toxic, is generally found among the combustion products.
  • the battery systems requested by the market are increasingly larger.
  • One example is the shipping industry, where there is a strong demand for ships with hybrid propulsion systems, such as to allow an electric propulsion when the ship moves near an urban environment.
  • the storage of between 10 and 15 MWh is requested.
  • the complexity of the connections grows. This is why the trend is to increase the size of the individual cells, but this makes the thermal regulation of the single cell increasingly problematic.
  • a hydraulic circuit is included for the circulation of a thermal regulation fluid, which hydraulic circuit is in thermal contact with the cell and the control board.
  • each cell and the respective control board are housed in a single casing immersed in said hydraulic circuit.
  • Such a configuration has an efficiency comparable to what occurs with a centralized inverter, but instead of providing a specific cooling circuit for the inverter, it uses the one already included for the batteries.
  • the casing is of thermoplastic material and the thermal regulation fluid is a non-polar, non-water-based liquid.
  • thermoplastic material allows to create a casing by means of a rigid and defined-shape moulding, in contrast to what occurs, for example, with current pouch-type batteries, which are covered by a soft case made of a layered sheet of plastic and aluminium, and thus forming a compact battery pack already provided with said hydraulic thermal regulation circuit.
  • This is also particularly advantageous in combination with said non-polar and non-water-based liquid: in fact, a polymeric material in the presence of a water-based fluid could not ensure impermeability to water and moisture over time, putting the cell at risk of rapid degradation and potential damage such as explosion or fire.
  • a non-aqueous thermal regulation liquid to which the polymeric material is completely impermeable, the entry of water or moisture into the cell is completely prevented.
  • said cells are flat cells and the hydraulic circuit is configured in a coil such that the thermal regulation fluid laps each cell on both sides of the casing of the cell itself.
  • pressure setting means are provided for the thermal regulation fluid within said hydraulic circuit.
  • thermoplastic material is advantageously characterized by a liquefaction temperature which is lower than the thermal runaway temperature of the electrochemical cell. Since the cell is immersed in a pressurized, non-polar non-water-based liquid, such a liquid performs the dual function of thermal regulation of the cell and suppression of the thermal runaway if a degenerative phenomenon of the cell itself is accidentally triggered.
  • Battery packs typically need a battery management system (BMS), i.e. , an electronic system which manages the cell systems which together form the battery, for example 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.
  • BMS battery management system
  • the primary purposes of the BMS therefore include the measurement of the cell voltage, the measurement of the cell temperature for safety reasons, and the selective discharging of overly charged cells to bring them back to average with the other cells and thus maintain a homogeneity of charge status 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 comprise electronic boards placed outside the cells with a plurality of electrical resistors adapted to dissipate heat towards the surrounding air. The amount of energy which can be dissipated in these systems is limited, however, and this is confirmed by the fact that in the current BMSs it sometimes takes up to several days to properly balance a new battery.
  • control boards located in the cells communicate with each other and with the central control unit by wireless communication means.
  • each electronic board comprises said switching cell and a local BMS unit, both being controlled by the central control unit.
  • the presence of wireless communication means allows to avoid the presence of wired electrical connections both for the measurement of voltage and for the measurement of temperature, typical of the BMS, and for the control of the switching cells, reducing the complexity and weight of the battery pack.
  • the local BMS units are provided with thermal dissipation means for balancing the charge of the cells.
  • the thermal dissipation for the balancing does not occur in air, with the efficiency problems mentioned in the introduction, but exploits the same cooling circuit of the cell itself.
  • the fact that the local control unit is included inside the casing of the cell and that the latter is placed in the cooling circuit in fact allows the thermal dissipation means to be in thermal contact, by means of the casing, with the thermal regulation fluid.
  • a respective electronic board is associated with each cell which acts locally both for the conversion into alternating, or in any case variable, voltage output from the cell and as a BMS, wirelessly transmitting remotely. This allows to eliminate cable connections both for the BMS and to an external inverter and allows to cool the cell, the dissipation means of the BMS unit and the switching elements of the switching cell with the same hydraulic thermoregulation circuit.
  • the casing sealingly separates the cell and the electronic control board from the hydraulic circuit, but the thermal regulation fluid exerts its action through the casing on both the cell and on the electronic board.
  • the polymeric material advantageously does not create an impediment to the wireless communication between the local control units and with the central control unit.
  • said wireless communication means are of the NFC type.
  • said wireless communication means are of the electro-optical type.
  • Electro-optical communication between control boards is made possible by casings in at least partially transparent thermoplastic material as well as by a thermoregulation liquid in turn at least partially transparent.
  • the output electrodes of the cell are advantageously connected to the electronic control board, in particular to the switching cell.
  • the output poles of the control board form the new poles of the cell which can then be connected to the load. Bringing all the battery current on the electronic board is not a problem, since solid state switches have no difficulty switching even very intense currents, for example 200 A, but for low voltages, such as for example the 3.7 V typical of a battery.
  • fig. 1 shows a diagram of a single cell of the battery pack
  • figs. 2a, 2b and 2c show different connection configurations settable for a cell
  • fig. 3a and 3b show the variable output voltage of a single cell and the entire battery pack, respectively
  • fig. 4 shows a diagram of the battery pack
  • fig. 5 shows an exploded view of a cell with its casing and its electronic control board
  • fig. 6 shows a sectional view of the battery pack in assembled condition with a plurality of cells side by side
  • fig. 7 shows the complete battery pack in assembled condition
  • fig. 8 shows 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 one or more electronic control boards 8.
  • Each electronic control board 8 is connected to a respective cell 1 .
  • Each control board 8 is incorporated in the respective cell 1 and comprises a switching cell 7 provided with a set of semiconductor switches.
  • the switching cell 7 is configured to alternately arrange the respective cell 1 in series, in anti-series or in bypass condition with respect to the set of the other cells of the pack.
  • the output electrodes 11 of the cell 1 are advantageously connected with the electronic board 8 and in particular with the switching cell 7.
  • the output poles 71 of the electronic board 8, between which the variable voltage is generated, form the new poles of the cell 1 which can then be connected to the load.
  • the switching cell 7 comprises switching elements, preferably MOS-type transistors. In a preferred embodiment, four switching elements are included arranged in a full bridge configuration.
  • the battery pack can also comprise a single cell, or consist of any number of cells depending on the needs of the load.
  • Figure 2a shows a series connection of a cell T with respect to the other cells forming the battery pack.
  • the switching cell 7 can alternatively arrange the cell T in the bypass condition, i.e. , exclusion from the series connection of the set of batteries, as shown in figure 2b.
  • the battery pack according to the present invention further comprises a BMS for monitoring and controlling said cells 1.
  • the BMS consists of a plurality of local BMS units 51 and a central control unit 50.
  • Each local BMS unit 51 is associated with a respective cell 1 , so that each cell 1 of the battery pack is associated with its own local BMS unit 51.
  • the local BMS unit 51 and the switching cell 7 are included on the same electronic board 8 and the central control unit 50 controls both the BMS functions and the switching functions of all the cells 1.
  • the control boards 8 are connected to the central control unit 50 by wireless communication means.
  • the switching cell 7 uses the wireless communication means of the BMS system to communicate with the central control unit 50.
  • the control boards 8 are organized into an ordered series comprising a first control board 8’ and a last control board 8".
  • the wireless communication means are configured to form a chain, such that each control board 8 communicates only with the one immediately preceding it and the one immediately following it, if present.
  • the first control board 8’ is in communication with the central control unit 50 and with the respective next control board 8
  • the last control board 8” is in communication with the respective previous control board 8
  • the further control boards 8 are each in communication with the respective previous control board and with the respective next control board.
  • the communication means are of the NFC (Near Field Communication) type, but can use other technologies currently known to those skilled in the art adapted to obtain a chain configuration as described above.
  • NFC Near Field Communication
  • the wireless communication means implement a communication of the electro-optical type.
  • each electronic board 8 is provided with a photo-identifier, for example an LED or other light source, and a photo-receiver. Such elements are also included on the central control unit 50.
  • the data packets are therefore preferably generated by the central control unit 50 and pass from control board 8 to control board 8, imparting the commands to the local BMS units 51 and the switching cells 7 necessary for the management of the respective cells 1 . Once the last control board 8” is reached, the packets go back to the central unit 50, modified with the addition of information by each local BMS unit 51 .
  • the central control unit 50 performs the BMS functions, calculating the charge status of each cell 1 and commanding the safety actions for each local BMS unit 51.
  • the local BMS units 51 comprise a switch of the cell 1 whose opening can be controlled by the central unit 50 in case of anomalies.
  • the cells 1 are preferably flat lithium-ion cells such as the known pouch-type cells.
  • other types of cells such as cylindrical cells, can be provided without abandoning the object of the invention.
  • pouch cells of the currently known type which are typically covered by a case consisting of a layered sheet of plastic and aluminium, similar to a food package.
  • the primary purpose of the case is to absolutely avoid the penetration of moisture, which would inevitably lead to damaging the cell, with the consequent risk of fire and explosion.
  • the case is suitably shaped so as not to prevent communication between the control boards 8 and the central control unit 50.
  • the control board 8 can in this case be advantageously included inside the case.
  • each cell 1 comprises a plurality of overlapping laminated layers 10, a plurality of electrodes 11 and a casing 13 containing the layers 10.
  • the casing 13 is divided into two rigid, thermoformed half-shells 12 which can be assembled together by shape coupling.
  • Each rigid half-shell 12 has a flat peripheral edge 120 which completely surrounds it and a central tray-like recess 121 , of complementary shape to the set of layers forming the cell 1 .
  • the two peripheral edges 120 are brought into mutual contact and lie on a single plane, while the central recesses 121 extend symmetrically in opposite directions with respect to said plane.
  • the two central recesses 121 form a central housing seat of the constituent layers 10 of the cell 1 and the two peripheral edges 120 in mutual contact form a peripheral flange 122.
  • the two thermoformed half-shells 12 are made of polymeric material having a low melting temperature, preferably a melting temperature between 120 °C and 160 °C, such as polyethylene or polyethylene terephthalate.
  • the polymeric material forming the casing 13 is preferably transparent or semi-transparent, so as to allow for a possible electro-optical communication between electronic boards.
  • the two half-shells 12 are preferably heat-sealed together along the peripheral edges 120, but can also be glued or fixed to each other by any fastening means known in the state of the art capable of keeping the casing 13 sealed with respect to the outside.
  • the casing 13 formed by the assembly of the two half-shells 12 is provided with passage openings 124 of the electrodes 11 .
  • Such openings 124 are formed in the peripheral flange 122 by shaping one or both of the peripheral edges 120 such that, in the coupled condition of the two halfshells 12, the peripheral edges 120 are spaced apart from each other by the thickness of 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 .
  • peripheral edge 120 of each half-shell 12 has a plurality of through holes 126 such that in the assembled condition of the casing 13 the peripheral flange 122 has a perforated area.
  • the battery pack comprises a plurality of spacer frames 2 of substantially rectangular shape and dimensions corresponding to the peripheral flange 122.
  • the spacer frame 2 is adapted to be interposed between two cells 1 side by side, contacting the respective peripheral flanges 122.
  • the spacer frame 2 is provided with gasket elements 20 on opposite contact surfaces of two peripheral flanges 122 of two cells 1 side by side.
  • the thickness of the spacer frame 2, i.e., the distance between the two opposite contact surfaces, is such that, in the assembled condition of the battery pack, a watertight gap 30 is formed between the two cells 1 with respect to the outside of the battery pack, as shown in section in figure 4.
  • the two half-shells 12 are formed so as to also create a housing 127 for an electronic board 8 comprising a local BMS unit 51 and a switching cell 7, shown in figure 2.
  • the control board 8 is thus separated from the outside in a watertight manner by the casing 13.
  • the electronic board 8 is preferably physically separated from the cell 1 but is connected to the electrodes 11 thereof by means of conductors 511 .
  • the local BMS unit 51 is further provided with one or more temperature sensors 512 of the cell, preferably consisting of thermocouples.
  • the housings 127 of the electronic control boards 8 are obtained from an extension of the casing 13 outside its rectangular shape. In this case, such an extension is also present in the frame 2, so as to form the gap 30 also at the housing 127.
  • 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 there are two end cells 1 and a first and a second terminal cover 40 and 41 are included with gasket elements adapted to seal on the peripheral flanges 122 of such end cells 1 .
  • Both terminal covers are shaped so as to identify a first gap included between the first terminal cover 40 and the corresponding end cell 1 and a last gap included between the second terminal cover 42 and the corresponding further end cell 1 .
  • the first terminal cover 40 is provided with a housing seat of the central control unit 50.
  • the local units 51 and the central unit 50 are arranged stacked together as shown in figure 5.
  • the covers 40 and 41 are preferably provided with reinforcing ribs 401.
  • Retention means are further included in the assembled condition of the cells 1 , the spacer frames 2 and the terminal covers 40 and 41 .
  • such means consist of metal bars or bolts 42 fixed on special eyelets 43 included on both of the terminal covers 40 and 41.
  • the holes 126 present on each peripheral flange 122 put all the gaps 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 gap and an outlet 32 at the last gap, the inlet and the outlet being formed in the example of the figures by connection vents to an external circulation circuit of a thermal regulation fluid.
  • each cell 1 and the respective electronic board 8 comprising both the local control unit 51 and the PWM cell 7 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 consisting of vegetable oil.
  • the thermal regulation fluid is preferably transparent or semi-transparent, so as to allow for any electro-optical communication between electronic boards 8.
  • the external circuit is also provided with means for pressurizing the thermal regulation fluid, so that such a fluid flows pressurized 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, adding additional weight.
  • the local control units 51 are provided with thermal dissipation means 510 for balancing the load of the cells.
  • Such means 510 can be of any type known to those skilled in the art, preferably comprising electrical resistors. The heat generated by such resistors reaches the thermal regulation liquid through the casing 13, from which it is dissipated.
  • the balancing function can be exercised by the central unit simply by inserting or excluding elements from the series which delivers or receives current, thus carrying out a load imbalance opposite that detected until the perfect balancing without wasting energy.
  • the heat produced by the switching elements in the cell 7 reaches the thermal regulation liquid through the casing 13, from which it is dissipated.
  • the hydraulic circuit 3 has a coil shape such that the thermal regulation fluid laps each cell 1 on both sides of the casing 13 of the cell 1 itself.
  • the cells 1 are arranged in the stack such that two adjacent cells 1 have the respective peripheral flange areas 122 provided with holes 126 in positions opposite each other with respect to a longitudinal plane of the battery pack.
  • the housings 127 of the local control units 51 in positions such as to create a coil in the hydraulic circuit with a single pair of half-shells 12 which is simply tilted alternately, simultaneously ensuring a position aligned with the local control units 51 .
  • the cell 1 including its casing 13 has a thickness of 11 mm while the gap 30 measures 1 mm between the two recesses 121 of two adjacent cells 1 .
  • This size of the gaps 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.

Abstract

Battery pack comprising one or more electrochemical cells (1) each of which incorporates an electronic board (8) which shares the cooling of the cell, and which is configured for BMS functions and further comprises a switching cell (7) provided with semiconductor switches capable of connecting the cell to the other cells or bypassing it, so as to be able to obtain an overall variable voltage output, for example in alternating current.

Description

BATTERY PACK COMPRISING ONE OR MORE ELECTROCHEMICAL CELLS AND A PLURALITY OF ELECTRONIC CONTROL BOARDS
The present invention relates to a battery pack comprising one or more electrochemical cells, a plurality of electronic control boards, and a central control unit connected to said control boards, each cell being associated with one relative said control board.
The present disclosure relates to lithium-ion batteries, but it is clear to those skilled in the art that the invention can be applied to any suitable battery type.
Lithium-based batteries, both primary and secondary, are characterized by a high stored energy density, which allows them to be used in countless applications of high energy and power, such as electric vehicles and aircraft, battery powered tools, and the like.
However, many applications require an alternating current supply and this requires the use of electronic circuits of the inverter type connected to the battery pack, which allow the conversion of the output voltage from direct, typical of electrochemical cells, to alternating.
In the state of the art, battery packs with a multiplicity of individual electrochemical cells are typically used, which are generally the same as each other and are connected in series until a useful overall voltage is reached. Typical voltage values are in this case represented by 3.7 V batteries connected in series to each other up to an overall voltage of 450 V. The output of the battery pack thus composed is connected to said inverter which, by operating transistor-based switching elements, performs pulse-width modulation (PWM) for the conversion of the output voltage to alternating current.
PWM is a technique for reducing the average voltage provided by an electrical signal, effectively dividing it into discrete parts. The average voltage value supplied to the load is controlled by rapidly activating and deactivating the switching elements between positive and negative power supply and load for the creation of voltage pulses. The duration of the pulses is proportional to the amplitude of the sinusoidal curve which is to be generated as an output voltage and an average is carried out by means of filters comprising inductors, which finally allows to obtain the desired voltage sinusoid. Unlike what would occur with a voltage modulation by means of potentiometers or other resistive solutions, PWM essentially does not bum energy and is therefore a very efficient process. In fact, the power is dissipated to a large extent only in the switching action of the switching elements of the inverter, which therefore tend to heat up and must therefore be substantially cooled.
DC/AC converters comprising a plurality of switching cells are currently known, described for example by document DE10103031. These converters connect to a direct voltage source and replace the classic phase modules comprising transistor switches and half bridge diodes with switching cells comprising capacitors as energy storage elements. Such switching cells are cascaded to form "phase legs". Thereby the stored energy is distributed in a plurality of small elements. This distributed energy storage configuration allows a finer graduation of the voltage produced by the converter with respect to apparatuses with a single common energy storage, thus reducing the complexity of levelling and filtering at the connection point of the apparatus.
This configuration is also taken up and implemented in the converter described by US8760122, in which the switching cells also comprise a battery placed parallel to the capacitor by means of switches. By controlling the switching elements of the cells, it is possible to have each cell provide its own voltage contribution. Thereby a phase leg provides a sinusoidal wave to the AC terminals of the converter. The selective activation of the battery of each individual cell makes the apparatus capable of providing or absorbing power based on the requests of the AC system connected in output, which AC system can thus be supported to increase its stability.
In all the above cases, the DC/AC conversion occurs at the overall level of the battery pack or converter which uses a plurality of batteries as power exchange elements for the AC system support. The present invention instead obtains the AC conversion within the battery pack as described at the beginning, in which each control board is incorporated into the respective cell and comprises a switching cell provided with a set of semiconductor switches configured to arrange the cell in series, in anti-series or to bypass the cell, with respect to the set of the other cells of the pack.
Preferably, said electronic board performs both the monitoring function, typical of the BMS, and said series or bypass connection function, with respect to the other cells of the system.
In an embodiment, the switching cell is configured to alternatively arrange the respective cell in series, anti-series or bypass with respect to the set of the other cells of the pack.
Suitably controlled, the battery consisting of these cells is therefore able to make a variable voltage at intervals equal to the voltage of cells, positive or negative, and is therefore able to obtain an AC output or in any case at variable voltage without the need for a separate inverter.
It is thereby possible to compose a battery pack consisting of any number of cells, based on the load supply needs, and obtain a variable voltage without the need to connect the batteries in series to an external inverter.
The ability of the control board to connect or disconnect the single cell from the battery pack also allows to perform the balancing function of the BMS without wasting energy and with great speed, unlike the normally used passive balancing systems, which are of a dissipative nature.
The variable voltage can advantageously be a sinusoidal alternating voltage. Thereby the battery natively has an AC output and must not be connected to an external inverter.
However, alternating voltage is not the only application of the present invention. It is possible, for example, to form a battery charging system, which must provide direct current but which is connected to an initially discharged battery, which must then receive a lower voltage, which voltage must rise as the battery recharges. By virtue of the present invention, it is possible to adjust the output voltage by acting on the individual cells and thus obtain an advantageously variable voltage, even if not necessarily alternating.
Similarly, in an electric propulsion system, the output voltage of the supply batteries can vary significantly depending on the charge state. By virtue of the present invention, it is possible to adjust the battery pack, stabilizing it at the lowest voltage corresponding to the discharged state, bypassing an initially high and then decreasing number of individual cells, as the current is supplied. Advantageously, the cells in the bypass condition are cycled, i.e. , the bypass condition is progressively assigned to different cells, so as to ensure a uniform discharge and at the same time a constant overall output voltage. Therefore, the term "variable voltage" means a voltage which can be controlled according to the charging needs.
In an embodiment, the central control unit is configured to regulate the output voltage of the battery pack by periodically bypassing groups of cells, simultaneously obtaining the balancing thereof, with a BMS function, and the control, if even at discrete steps equal to the cell voltage, of the voltage across the battery.
In a further embodiment, the central control unit is configured so as to obtain a stepwise output voltage approximating a sinusoid at controllable frequency and amplitude.
In a further embodiment, the central control unit is configured to control the voltage of the battery pack so as to perform the charge control function even if interfaced with an uncontrolled direct voltage source.
In a further exemplary embodiment, the central control unit is configured to generate three offset sinusoidal voltages of 120 electrical degrees, of controlled amplitude and frequency, suitable for the direct control of electric motors.
In a further embodiment, the central control unit is configured to generate one or three sinusoidal voltages, of controlled amplitude and frequency, so as to control battery charging when interfaced with an uncontrolled single-phase or three-phase AC source. Furthermore, the high energy density also makes the batteries susceptible to fire with flame release and chemically aggressive compounds in the event of battery failure or damage. This behaviour is to some extent intrinsic; in fact, if the energy contained in the battery is released suddenly, for example from an accident which physically damages the battery, the same high amount of energy necessarily produces heat to a significant extent.
In fact, it is known that lithium-ion batteries, in the event of mechanical damage which short circuits positive and negative current carriers, release a large amount of energy which 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, such a fire is particularly difficult to control. At the same time, hydrofluoric acid, which is highly corrosive and toxic, is generally found among the combustion products.
Moreover, the battery systems requested by the market are increasingly larger. One example is the shipping industry, where there is a strong demand for ships with hybrid propulsion systems, such as to allow an electric propulsion when the ship moves near an urban environment. In such systems, the storage of between 10 and 15 MWh is requested. However, as the stored energy increases, the complexity of the connections grows. This is why the trend is to increase the size of the individual cells, but this makes the thermal regulation of the single cell increasingly problematic.
At the same time, in high power applications, it is often necessary to cool the battery when it is subjected to a rapid discharge, to avoid the overheating thereof due to a high current flow. In the opposite situation, it may be necessary to quickly preheat a battery conserved at temperatures below 0 °C, because at low temperatures the charging process is dangerous. 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 therein. However, such systems have some disadvantages, in particular they significantly increase the weight of the battery pack, contrary to the demand by electric mobility for ever lower weights.
In an embodiment of the present invention, a hydraulic circuit is included for the circulation of a thermal regulation fluid, which hydraulic circuit is in thermal contact with the cell and the control board.
According to an improvement, each cell and the respective control board are housed in a single casing immersed in said hydraulic circuit.
This allows to thermally regulate the cell and at the same time dissipate the heat produced by the control board with the same hydraulic circuit.
Such a configuration has an efficiency comparable to what occurs with a centralized inverter, but instead of providing a specific cooling circuit for the inverter, it uses the one already included for the batteries.
In an embodiment, the casing is of thermoplastic material and the thermal regulation fluid is a non-polar, non-water-based liquid.
The use of thermoplastic material allows to create a casing by means of a rigid and defined-shape moulding, in contrast to what occurs, for example, with current pouch-type batteries, which are covered by a soft case made of a layered sheet of plastic and aluminium, and thus forming a compact battery pack already provided with said hydraulic thermal regulation circuit. This is also particularly advantageous in combination with said non-polar and non-water-based liquid: in fact, a polymeric material in the presence of a water-based fluid could not ensure impermeability to water and moisture over time, putting the cell at risk of rapid degradation and potential damage such as explosion or fire. By virtue of the use of a non-aqueous thermal regulation liquid, to which the polymeric material is completely impermeable, the entry of water or moisture into the cell is completely prevented. In an embodiment said cells are flat cells and the hydraulic circuit is configured in a coil such that the thermal regulation fluid laps each cell on both sides of the casing of the cell itself.
This imposes an obligatory path to the thermal regulation fluid, which must flow along the opposite faces of each cell and thereby lap all the areas of the battery pack exercising its thermal regulation function.
In an embodiment, pressure setting means are provided for the thermal regulation fluid within said hydraulic circuit.
The thermoplastic material is advantageously characterized by a liquefaction temperature which is lower than the thermal runaway temperature of the electrochemical cell. Since the cell is immersed in a pressurized, non-polar non-water-based liquid, such a liquid performs the dual function of thermal regulation of the cell and suppression of the thermal runaway if a degenerative phenomenon of the cell itself is accidentally triggered.
Battery packs typically need a battery management system (BMS), i.e. , an electronic system which manages the cell systems which together form the battery, for example 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 charge status inhomogeneities, it is possible to trigger dangerous overheating which can also lead to fire. The primary purposes of the BMS therefore include the measurement of the cell voltage, the measurement of the cell temperature for safety reasons, and the selective discharging of overly charged cells to bring them back to average with the other cells and thus maintain a homogeneity of charge status 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 comprise electronic boards placed outside the cells with a plurality of electrical resistors adapted to dissipate heat towards the surrounding air. The amount of energy which can be dissipated in these systems is limited, however, and this is confirmed by the fact that in the current BMSs it sometimes takes up to several days to properly balance a new battery.
According to a further embodiment of the present invention, the control boards located in the cells communicate with each other and with the central control unit by wireless communication means.
Thereby, the electronic control boards and the central control unit to which they are connected form the BMS of the battery pack. Each electronic board comprises said switching cell and a local BMS unit, both being controlled by the central control unit.
The presence of wireless communication means allows to avoid the presence of wired electrical connections both for the measurement of voltage and for the measurement of temperature, typical of the BMS, and for the control of the switching cells, reducing the complexity and weight of the battery pack.
In an embodiment, the local BMS units are provided with thermal dissipation means for balancing the charge of the cells.
Thereby, since the casing is immersed in the thermoregulation circuit, the thermal dissipation for the balancing does not occur in air, with the efficiency problems mentioned in the introduction, but exploits the same cooling circuit of the cell itself. The fact that the local control unit is included inside the casing of the cell and that the latter is placed in the cooling circuit, in fact allows the thermal dissipation means to be in thermal contact, by means of the casing, with the thermal regulation fluid.
Thereby, a respective electronic board is associated with each cell which acts locally both for the conversion into alternating, or in any case variable, voltage output from the cell and as a BMS, wirelessly transmitting remotely. This allows to eliminate cable connections both for the BMS and to an external inverter and allows to cool the cell, the dissipation means of the BMS unit and the switching elements of the switching cell with the same hydraulic thermoregulation circuit.
In fact, the casing sealingly separates the cell and the electronic control board from the hydraulic circuit, but the thermal regulation fluid exerts its action through the casing on both the cell and on the electronic board.
The polymeric material advantageously does not create an impediment to the wireless communication between the local control units and with the central control unit.
In a first embodiment, said wireless communication means are of the NFC type.
In a second embodiment, said wireless communication means are of the electro-optical type.
Electro-optical communication between control boards is made possible by casings in at least partially transparent thermoplastic material as well as by a thermoregulation liquid in turn at least partially transparent.
However, the possibility of selectively connecting each individual element makes it possible, in a preferred implementation of the invention, to perform the balancing simply by selectively and temporarily disconnecting the less charged elements so as to bring the more charged elements back to the level of the less charged ones, thus making it possible to use all the energy available in all the cells, without dissipating any of them.
This creates a battery with an AC output, or in any case variable voltage, and internally incorporates an electronic management unit already prepared to be connected wirelessly in a distributed BMS which is easy to compose and configure with any number of batteries.
The output electrodes of the cell are advantageously connected to the electronic control board, in particular to the switching cell. The output poles of the control board form the new poles of the cell which can then be connected to the load. Bringing all the battery current on the electronic board is not a problem, since solid state switches have no difficulty switching even very intense currents, for example 200 A, but for low voltages, such as for example the 3.7 V typical of a battery.
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 diagram of a single cell of the battery pack; figs. 2a, 2b and 2c show different connection configurations settable for a cell; fig. 3a and 3b show the variable output voltage of a single cell and the entire battery pack, respectively; fig. 4 shows a diagram of the battery pack; fig. 5 shows an exploded view of a cell with its casing and its electronic control board; fig. 6 shows a sectional view of the battery pack in assembled condition with a plurality of cells side by side; fig. 7 shows the complete battery pack in assembled condition; fig. 8 shows 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 one or more electronic control boards 8. Each electronic control board 8 is connected to a respective cell 1 . Each control board 8 is incorporated in the respective cell 1 and comprises a switching cell 7 provided with a set of semiconductor switches. The switching cell 7 is configured to alternately arrange the respective cell 1 in series, in anti-series or in bypass condition with respect to the set of the other cells of the pack.
As shown in figure 1 , the output electrodes 11 of the cell 1 are advantageously connected with the electronic board 8 and in particular with the switching cell 7. The output poles 71 of the electronic board 8, between which the variable voltage is generated, form the new poles of the cell 1 which can then be connected to the load.
The switching cell 7 comprises switching elements, preferably MOS-type transistors. In a preferred embodiment, four switching elements are included arranged in a full bridge configuration.
The battery pack can also comprise a single cell, or consist of any number of cells depending on the needs of the load.
Figure 2a shows a series connection of a cell T with respect to the other cells forming the battery pack. The switching cell 7 can alternatively arrange the cell T in the bypass condition, i.e. , exclusion from the series connection of the set of batteries, as shown in figure 2b.
If it is already possible to obtain a variable voltage by modulating the series and bypass states of the individual cells 1 , an even more complete control of the output voltage can be obtained with the possibility of arranging each cell T in an anti-series condition with respect to the set of cells 1 , as shown in figure 2c. In the anti-series condition, the single cell T is placed at inverted polarity in the chain of cells 1 forming the battery pack.
By controlling the switching cell 7 it is possible to modulate the voltage contribution of the cell 1 in the battery pack over time, which can go from a positive voltage value, to a corresponding but negative value, to a null value, as indicated in figure 3a.
By adding the contribution of each individual cell, it is possible to modulate the overall voltage output of the battery pack with a stepwise trend as shown in figure 3b.
The battery pack according to the present invention further comprises a BMS for monitoring and controlling said cells 1. The BMS consists of a plurality of local BMS units 51 and a central control unit 50. Each local BMS unit 51 is associated with a respective cell 1 , so that each cell 1 of the battery pack is associated with its own local BMS unit 51. Advantageously, the local BMS unit 51 and the switching cell 7 are included on the same electronic board 8 and the central control unit 50 controls both the BMS functions and the switching functions of all the cells 1.
It is possible to include more than one central control unit 50, and it is possible to envisage a local BMS unit 51 associated with multiple cells 1.
The control boards 8 are connected to the central control unit 50 by wireless communication means.
The switching cell 7 uses the wireless communication means of the BMS system to communicate with the central control unit 50. The control boards 8 are organized into an ordered series comprising a first control board 8’ and a last control board 8". The wireless communication means are configured to form a chain, such that each control board 8 communicates only with the one immediately preceding it and the one immediately following it, if present. In other words, the first control board 8’ is in communication with the central control unit 50 and with the respective next control board 8, the last control board 8” is in communication with the respective previous control board 8, and the further control boards 8 are each in communication with the respective previous control board and with the respective next control board.
Preferably, the communication means are of the NFC (Near Field Communication) type, but can use other technologies currently known to those skilled in the art adapted to obtain a chain configuration as described above.
Alternatively or in combination, the wireless communication means implement a communication of the electro-optical type. In this case, each electronic board 8 is provided with a photo-identifier, for example an LED or other light source, and a photo-receiver. Such elements are also included on the central control unit 50.
The data packets are therefore preferably generated by the central control unit 50 and pass from control board 8 to control board 8, imparting the commands to the local BMS units 51 and the switching cells 7 necessary for the management of the respective cells 1 . Once the last control board 8” is reached, the packets go back to the central unit 50, modified with the addition of information by each local BMS unit 51 .
The central control unit 50 performs the BMS functions, calculating the charge status of each cell 1 and commanding the safety actions for each local BMS unit 51. In an embodiment, the local BMS units 51 comprise a switch of the cell 1 whose opening can be controlled by the central unit 50 in case of anomalies.
The cells 1 are preferably flat lithium-ion cells such as the known pouch-type cells. However, other types of cells, such as cylindrical cells, can be provided without abandoning the object of the invention. It is possible to use pouch cells of the currently known type, which are typically covered by a case consisting of a layered sheet of plastic and aluminium, similar to a food package. The primary purpose of the case is to absolutely avoid the penetration of moisture, which would inevitably lead to damaging the cell, with the consequent risk of fire and explosion. In this case, the case is suitably shaped so as not to prevent communication between the control boards 8 and the central control unit 50. The control board 8 can in this case be advantageously included inside the case.
A further particularly advantageous embodiment is shown in the figures. According to such an example, each cell 1 comprises a plurality of overlapping laminated layers 10, a plurality of electrodes 11 and a casing 13 containing the layers 10. The casing 13 is divided into two rigid, thermoformed half-shells 12 which can be assembled together by shape coupling. Each rigid half-shell 12 has a flat peripheral edge 120 which completely surrounds it and a central tray-like recess 121 , of complementary shape to the set of layers forming the cell 1 . In the coupled condition of the two half-shells 12 the two peripheral edges 120 are brought into mutual contact and lie on a single plane, while the central recesses 121 extend symmetrically in opposite directions with respect to said plane. Thereby the two central recesses 121 form a central housing seat of the constituent layers 10 of the cell 1 and the two peripheral edges 120 in mutual contact form a peripheral flange 122.
The two thermoformed half-shells 12 are made of polymeric material having a low melting temperature, preferably a melting temperature between 120 °C and 160 °C, such as polyethylene or polyethylene terephthalate. The polymeric material forming the casing 13 is preferably transparent or semi-transparent, so as to allow for a possible electro-optical communication between electronic boards. Alternatively, it is possible to include transparent inserts in the half-shells at the communication means so as to form optical communication windows between the control boards (8). The two half-shells 12 are preferably heat-sealed together along the peripheral edges 120, but can also be glued or fixed to each other by any fastening means known in the state of the art capable of keeping the casing 13 sealed with respect to the outside.
The casing 13 formed by the assembly of the two half-shells 12 is provided with passage openings 124 of the electrodes 11 . Such openings 124 are formed in the peripheral flange 122 by shaping one or both of the peripheral edges 120 such that, in the coupled condition of the two halfshells 12, the peripheral edges 120 are spaced apart from each other by the thickness of the electrodes 11 . To ensure the watertight seal 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 peripheral edge 120 of each half-shell 12 has a plurality of through holes 126 such that in the assembled condition of the casing 13 the peripheral flange 122 has a perforated area.
The battery pack comprises a plurality of spacer frames 2 of substantially rectangular shape and dimensions corresponding to the peripheral flange 122. The spacer frame 2 is adapted to be interposed between two cells 1 side by side, contacting the respective peripheral flanges 122. The spacer frame 2 is provided with gasket elements 20 on opposite contact surfaces of two peripheral flanges 122 of two cells 1 side by side.
The thickness of the spacer frame 2, i.e., the distance between the two opposite contact surfaces, is such that, in the assembled condition of the battery pack, a watertight gap 30 is formed between the two cells 1 with respect to the outside of the battery pack, as shown in section in figure 4.
The two half-shells 12 are formed so as to also create a housing 127 for an electronic board 8 comprising a local BMS unit 51 and a switching cell 7, shown in figure 2. The control board 8 is thus separated from the outside in a watertight manner by the casing 13. The electronic board 8 is preferably physically separated from the cell 1 but is connected to the electrodes 11 thereof by means of conductors 511 . The local BMS unit 51 is further provided with one or more temperature sensors 512 of the cell, preferably consisting of thermocouples. In the embodiment of figures 2 and 5, the housings 127 of the electronic control boards 8 are obtained from an extension of the casing 13 outside its rectangular shape. In this case, such an extension is also present in the frame 2, so as to form the gap 30 also at the housing 127.
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 there are two end cells 1 and a first and a second terminal cover 40 and 41 are included with gasket elements adapted to seal on the peripheral flanges 122 of such end cells 1 . Both terminal covers are shaped so as to identify a first gap included between the first terminal cover 40 and the corresponding end cell 1 and a last gap included between the second terminal cover 42 and the corresponding further end cell 1 .
The first terminal cover 40 is provided with a housing seat of the central control unit 50. When the entire battery pack is assembled, the local units 51 and the central unit 50 are arranged stacked together as shown in figure 5.
The covers 40 and 41 are preferably provided with reinforcing ribs 401.
Retention means are further included in the assembled condition of the cells 1 , the spacer frames 2 and the terminal covers 40 and 41 . In the example in the figure, such means consist of metal bars or bolts 42 fixed on special eyelets 43 included on both of the terminal covers 40 and 41. In the stack thus formed, the holes 126 present on each peripheral flange 122 put all the gaps 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 gap and an outlet 32 at the last gap, the inlet and the outlet being formed in the example of the figures by connection vents to an external circulation circuit of a thermal regulation fluid.
Thereby, each cell 1 and the respective electronic board 8 comprising both the local control unit 51 and the PWM cell 7 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 consisting of vegetable oil. The thermal regulation fluid is preferably transparent or semi-transparent, so as to allow for any electro-optical communication between electronic boards 8.
The external circuit is also provided with means for pressurizing the thermal regulation fluid, so that such a fluid flows pressurized 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, adding additional weight.
The local control units 51 are provided with thermal dissipation means 510 for balancing the load of the cells. Such means 510 can be of any type known to those skilled in the art, preferably comprising electrical resistors. The heat generated by such resistors reaches the thermal regulation liquid through the casing 13, from which it is dissipated.
Alternatively, and preferably, if the required output voltage allows it, being less than the series of all the elements, the balancing function can be exercised by the central unit simply by inserting or excluding elements from the series which delivers or receives current, thus carrying out a load imbalance opposite that detected until the perfect balancing without wasting energy. Similarly, the heat produced by the switching elements in the cell 7 reaches the thermal regulation liquid through the casing 13, from which it is dissipated.
As shown in figure 6, the hydraulic circuit 3 has a coil shape such that the thermal regulation fluid laps each cell 1 on both sides of the casing 13 of the cell 1 itself.
To obtain this configuration, the cells 1 are arranged in the stack such that two adjacent cells 1 have the respective peripheral flange areas 122 provided with holes 126 in positions opposite each other with respect to a longitudinal plane of the battery pack.
In the configurations shown in the figures, two distinct forms of pairs of half-shells 12 are necessary, in order to present the respective peripheral flange areas 122 provided with holes 126 in opposite positions to each other but the housings 127 of the local control units 51 in the same position, in order to be aligned in the assembled condition of the battery pack.
However, it is possible to provide the housings 127 of the local control units 51 in positions such as to create a coil in the hydraulic circuit with a single pair of half-shells 12 which is simply tilted alternately, simultaneously ensuring a position aligned with the local control units 51 .
In a preferred embodiment, the cell 1 including its casing 13 has a thickness of 11 mm while the gap 30 measures 1 mm between the two recesses 121 of two adjacent cells 1 . This size of the gaps 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.

Claims

1. Battery pack comprising electrochemical cells (1 ), a plurality of electronic control boards (8), and a central control unit (50) connected to said control boards (8), each cell (1 ) being associated with one relative said control board (8), characterized in that each control board (8) is incorporated in the respective cell (1 ) and comprises a switching cell (7) provided with a set of semiconductor switches, which switching cell (7) is configured to alternately arrange the respective cell (1 ) in series, or to bypass said cell (1 ), with respect to the set of the other cells (1 ) of the pack.
2. Battery pack according to claim 1 , wherein said switching cell (7) is configured to alternatively arrange the respective cell (1 ) also in antiseries with respect to the set of the other cells (1 ) of the pack.
3. Battery pack according to claims 1 or 2, wherein the central control unit (50) is configured so as to regulate the output voltage of the battery pack by bypassing groups of cells periodically, obtaining at the same time the balancing thereof, with a BMS function, and the control, even if at discrete steps equal to the cell voltage, of the voltage across the battery.
4. Battery pack according to claim 3, wherein the central control unit (50) is configured to obtain a stepwise output voltage approximating a sinusoid at controllable frequency and amplitude.
5. Battery pack according to claim 3, wherein the central control unit (50) is configured to control the voltage of the battery pack so as to perform the load control function even if interfaced with an uncontrolled direct voltage source.
6. Battery pack according to claim 3, wherein the central control unit (50) is configured to generate three offset sinusoidal voltages of 120 electrical degrees, of controlled amplitude and frequency, suitable for the direct control of electric motors.
7. Battery pack according to claim 3, wherein the central control unit (50) is configured to generate one or three offset sinusoidal voltages of 120 electrical degrees, of controlled amplitude and frequency, so as to control the battery load when interfaced with an uncontrolled single-phase or three-phase AC source.
8. Battery pack according to one or more of the preceding claims, wherein a hydraulic circuit (3) is provided for the circulation of a thermal regulation fluid, which hydraulic circuit (3) is in thermal contact with each cell (1 ) and the respective control board (8).
9. Battery pack according to one or more of the preceding claims, wherein each cell (1 ) and the respective control board (8) are housed in a single casing (13) immersed in said hydraulic circuit (3).
10. Battery pack according to claim 4, wherein the casing (13) is of thermoplastic material and the thermal regulation fluid is a non-polar and non-water-based liquid.
11 . Battery pack according to one or more of the preceding claims, wherein the control boards (8) located in the cells (1 ) communicate with each other and with the central control unit (50) by wireless communication means.
12. Battery pack according to claim 6, wherein said wireless communication means are of the NFC or electro-optical type.
PCT/IB2021/062104 2020-12-21 2021-12-21 Battery pack comprising one or more electrochemical cells and a plurality of electronic control boards WO2022137117A1 (en)

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Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2011025029A1 (en) * 2009-08-31 2011-03-03 三洋電機株式会社 Inverter and power converter having inverter mounted therein
FR2972308A1 (en) * 2011-03-02 2012-09-07 Commissariat Energie Atomique BATTERY WITH INDIVIDUAL MANAGEMENT OF CELLS
US20140347014A1 (en) * 2010-11-02 2014-11-27 Navitas Solutions Fault tolerant wireless battery area network for a smart battery management system
EP3322015A1 (en) * 2015-08-14 2018-05-16 Microvast Power Systems Co., Ltd. Battery

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2011025029A1 (en) * 2009-08-31 2011-03-03 三洋電機株式会社 Inverter and power converter having inverter mounted therein
US20140347014A1 (en) * 2010-11-02 2014-11-27 Navitas Solutions Fault tolerant wireless battery area network for a smart battery management system
FR2972308A1 (en) * 2011-03-02 2012-09-07 Commissariat Energie Atomique BATTERY WITH INDIVIDUAL MANAGEMENT OF CELLS
EP3322015A1 (en) * 2015-08-14 2018-05-16 Microvast Power Systems Co., Ltd. Battery

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