Abstract
An electrical energy storage unit for a motor vehicle, having at least one storage unit cell designed to store electrical energy, which storage unit cell has a cell housing in which an electrolyte and an electrode device are arranged, and having a temperature control device that has at least one temperature control channel arranged outside the cell housing, which temperature control channel is able to be flowed through by a temperature control fluid in order to control the temperature of the storage unit cell. At least one heating device is able to be supplied with the electrical energy stored in the storage unit cell and thereby able to be electrically operated. By way of the heating device, the storage unit cell is able to be heated, wherein the heating device is able to be operated without any damage only when the storage unit cell has a state of charge that is not more than 60% of the maximum state of charge of the storage unit cell.
Claims
1. An electrical energy storage unit for a motor vehicle, comprising: at least one storage unit cell configured to store electrical energy, which storage unit cell has a cell housing in which an electrolyte and an electrode device are arranged; a temperature control device that has a plurality of temperature control channels arranged outside the cell housing, which temperature control channels are flowed through by a temperature control fluid, wherein the temperature control device controls a temperature of the storage unit cell; and at least one heating device formed separately from the temperature control device and supplied with the electrical energy stored in the storage unit cell and thereby electrically operated, by way of which heating device the storage unit cell is heated, wherein the heating device is configured to be operated during a charging of the storage unit cell with an electric power that has a peak value of at least 100 kilowatts only when the storage unit cell has a state of charge that is not more than 60% of a maximum state of charge of the storage unit cell and only for at most an operating time of 30 minutes when the storage unit cell has the state of charge that is not more than 60% of the maximum state of charge of the storage unit cell.
2. The electrical energy storage unit according to claim 1, wherein the state of charge is not more than 50% of the maximum state of charge of the storage unit cell.
3. The electrical energy storage unit according to claim 1, wherein the state of charge is not more than 40% of the maximum state of charge of the storage unit cell.
4. The electrical energy storage unit according to claim 1, wherein the heating device has at least one electrical heating element arranged outside the cell housing.
5. The electrical energy storage unit according to claim 4, wherein the heating device has at least one electrical heating element arranged inside the cell housing.
6. The electrical energy storage unit according to claim 1, wherein the heating device has at least one electrical heating element arranged inside the cell housing.
7. The electrical energy storage unit according to claim 6, wherein the electrical heating element arranged inside the cell housing, the electrode device and the electrolyte are arranged at the same time in a reception space delimited by the cell housing.
8. The electrical energy storage unit according to claim 1, wherein a maximum temperature of the heating device is in a range from 60 degrees Celsius inclusive to 90 degrees Celsius inclusive.
9. The electrical energy storage unit according to claim 1, wherein the temperature control fluid is a liquid.
10. The electrical energy storage unit according to claim 1, wherein the storage unit cell is received in a storage unit housing of the electrical energy storage unit that is formed separately from the storage unit cell.
11. The electrical energy storage unit according to claim 10, wherein the temperature control channels, at least in a respective length region of the temperature control channels, are formed completely by a respective temperature control element formed separately from the storage unit housing and separately from the cell housing and received in the storage unit housing.
12. The electrical energy storage unit according to claim 10, wherein the temperature control channels are delimited at least partially directly by the storage unit housing.
13. A method for operating an electrical energy storage unit for a motor vehicle, having at least one storage unit cell configured to store electrical energy, which has a cell housing in which an electrolyte and an electrode device are arranged, and having a temperature control device, which has a plurality of temperature control channels arranged outside the cell housing, which temperature control channels are flowed through by a temperature control fluid, wherein the temperature control device controls a temperature of the storage unit cell, the method comprising: supplying at least one heating device with the electrical energy stored in the storage unit cell to thereby be electrically operated, by way of which heating device the storage unit cell is heated, wherein the heating device is configured to be operated during a charging of the storage unit cell with an electric power that has a peak value of at least 100 kilowatts only when the storage unit cell has a state of charge that is not more than 60% of a maximum state of charge of the storage unit cell and only for at most an operating time of 30 minutes when the storage unit cell has the state of charge that is not more than 60% of the maximum state of charge of the storage unit cell.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
(1) FIG. 1 shows a cutout of a schematic, side-on and sectional exploded view of an energy storage unit according to the invention, according to a first embodiment.
(2) FIG. 2 shows graphs for illustrating a method according to the invention for operating the energy storage unit.
(3) FIG. 3 shows a schematic sectional view of a storage unit cell of the energy storage unit according to a second embodiment.
(4) FIG. 4 shows a schematic perspective view of a storage unit cell of the energy storage unit according to a third embodiment.
(5) FIG. 5 shows a schematic perspective view of the energy storage unit according to a fourth embodiment.
(6) FIG. 6 shows a cutout of a schematic plan view of the energy storage unit according to the fourth embodiment.
(7) FIG. 7 shows a further graph for further illustrating the method.
(8) In the figures, identical or functionally identical elements are provided with the same reference signs.
DETAILED DESCRIPTION OF THE DRAWINGS
(9) FIG. 1 shows a cutout of a schematic, side-on and sectional exploded view of an electrical energy storage unit 1 for a motor vehicle, in particular for a motor vehicle designed for example as a passenger motor vehicle. The electrical energy storage unit 1 is also referred to as energy storage unit or storage unit device and is designed to store electrical energy or electric current. The motor vehicle, in its fully manufactured state, has the energy storage unit 1 and at least one electric machine, by way of which the motor vehicle is able to be driven electrically, in particular fully electrically. In order to drive the motor vehicle electrically by way of the electric machine, the electric machine is operated in a motor mode and thus as an electric motor. To this end, the electric machine is supplied with electrical energy that is stored in the energy storage unit 1. The energy storage unit 1 has a plurality of, and thus at least two, storage unit cells 2a, b, wherein the above and below explanations regarding the storage unit cell 2a may also be readily transferred to the storage unit cell 2b, and vice versa. In this case, FIG. 1 illustrates a first embodiment of the energy storage unit 1. The energy storage unit 1 furthermore has a storage unit housing 3 that is formed separately from the storage unit cells 2a, b. The storage unit cells 2a, b are in this case arranged at least partially, in particular at least predominantly or completely, in the storage unit housing 3, that is to say in a housing space 4 that is formed or delimited, in particular directly, by the storage unit housing 3. The storage unit cells 2a, b are in particular arranged in a row, that is to say next to one another, along a direction illustrated in FIG. 1 by a double-headed arrow 5. The direction illustrated by the double-headed arrow 5 is for example a stacking direction, along which the storage unit cells 2a, b are arranged in a row. In this case, the storage unit cells 2a, b for example form a cell stack.
(10) The respective storage unit cell 2a, b has a cell housing 6 that in particular directly delimits a respective reception space 7. The respective storage unit cell 2a, b furthermore contains an electrolyte 8, illustrated particularly schematically in FIG. 1, that is arranged in the respective reception space 7 and thus in the cell housing 6. The respective storage unit cell 2a, b furthermore has an electrode device 9, illustrated particularly schematically in FIG. 1, that is arranged in the respective reception space 7 and thus in the respective cell housing 6. It is conceivable in this case for the respective electrode device 9 to be in at least partial contact with the electrolyte 8. The respective electrode device 9 has at least or precisely two electrodes 10 and 11. The electrode 10 has for example a first electrical polarity, wherein the electrode 11 has for example a second electrical polarity different from the first electrical polarity. The electrodes 10 and 11 are in particular for example electrically insulated from one another.
(11) The respective storage unit cell 2a, b furthermore has two connection elements, also referred to as terminals, of which one connection element, denoted 12, may be seen in FIG. 1. As may be seen from the example of the connection element 12, the terminals are arranged outside the cell housing 6 and thus in surroundings 13 of the respective storage unit cell 2a, b, wherein the terminals of the respective storage unit cell 2a, b are preferably arranged in the housing space 4. One of the electrodes 10 and 11 is for example electrically connected to a first of the terminals, wherein the respective other electrode 11 or 10 is electrically connected to the respective other terminal. A first of the terminals thereby forms for example a positive electrical pole of the respective storage unit cell 2a, b, wherein for example the second terminal forms a negative electrical pole of the respective storage unit cell 2a, b. It is in particular conceivable for the storage unit cells 2a, b to be electrically connected to one another via their terminals and thereby connected to one another in parallel and/or in series. By way of their terminals, the storage unit cells 2a, b are able to provide electrical energy that is stored, in particular electrochemically stored, in the storage unit cells 2a, b.
(12) The energy storage unit 1 furthermore has a temperature control device 14 associated with the storage unit cells 2a, b, which temperature control device is arranged at least partially, in particular at least predominantly or completely, along the direction between the storage unit cells 2a, b and in this case in particular between the cell housings 6 and is thus designed as a cell intermediate temperature controller. In the first embodiment shown in FIG. 1, the temperature control device 14 has a plurality of temperature control channels 15 that are each arranged outside the storage unit cells 2a, b, that is to say outside the cell housing 6. In this case, the temperature control channels 15 are arranged along the direction between the storage unit cells 2a, b and in this case between the cell housings 6. The temperature control channels 15 are furthermore able to be flowed through by a temperature control fluid, preferably in the form of a liquid, by way of which the temperature of the storage unit cells 2a, b is able to be controlled, that is to say they are able to be heated and/or cooled.
(13) In the first embodiment shown in FIG. 1, the temperature control device 14 comprises a temperature control element 16 formed separately from the cell housings 6 and separately from the storage unit housing 3, which temperature control element is designed here as a temperature control plate, in particular as a cooling or heating plate. The feature whereby the temperature control element 16 or the temperature control device 14 is arranged along the direction between the storage unit cells 2a, b, also referred to simply as cells, or between the cell housings 6 should in particular be understood to mean that the cell housing 6 of the storage unit cell 2a, in the direction of the cell housing 6 of the storage unit cell 2b, is covered or overlapped at least partially, in particular at least predominantly or completely, by the temperature control device 14, in particular by the temperature control element 16, wherein the storage unit cell 2b or the cell housing 6 of the storage unit cell 2b, in the direction of the cell housing 6 of the storage unit cell 2a, is overlapped or covered at least partially, in particular at least predominantly or completely, by the temperature control device 14, in particular by the temperature control element 16. Accordingly, the cell housing 6 of the storage unit cell 2a in the direction of the cell housing 6 of the storage unit cell 2b and the cell housing 6 of the storage unit cell 2b in the direction of the cell housing 6 of the storage unit cell 2a is in each case overlapped or covered at least partially by the temperature control channels 15. For example, when the temperature control fluid is colder than the storage unit cells 2a, b or the cell housing 6, heat may be transferred from the cell housings 6 to the temperature control fluid, as a result of which the storage unit cells 2a, b are cooled. If the temperature control fluid is for example hotter than the cell housing 6, then heat may be transferred from the temperature control fluid to the cell housing 6, as a result of which the storage unit cells 2a, b are heated.
(14) In order then to be able to control the temperature of the energy storage unit 1, in particular to heat it, in a particularly advantageous manner and as required, such that for example particularly advantageous fast charging of the energy storage unit 1 is able to be achieved, the energy storage unit 1 comprises at least or precisely one heating device 17a, b, in particular per storage unit cell 2a, b. The respective heating device 17a, b may have a respective electrical or electrically operable heating element 18, which may be designed as a heating structure or else be referred to as a heating structure. The heating device 17a, b or the respective heating element 18 is formed separately from the temperature control device 14 and separately from the cell housings 6. The respective heating device 17a, b, that is to say the respective heating element 18, is able to be supplied with electrical energy stored in the respective storage unit cell 2a, b and thereby able to be electrically operated, as a result of which heat for heating the respective storage unit cell 2a, b is able to be provided by way of the respective heating device 17a, b. It may be seen from FIG. 1 that the heating device 17a or its heating element 18 is arranged along the direction between the temperature control element 16 and the cell housing 6 of the storage unit cell 2a, such that for example the cell housing 6 of the storage unit cell 2a is overlapped or covered at least partially, in particular at least predominantly or completely, by the heating device 17a, in particular by the heating element 18 of the heating device 17a, in the direction of the temperature control element 16. The heating device 17b, in particular the heating element 18 of the heating device 17b, is accordingly arranged along the direction between the cell housings 6 of the storage unit cell 2b and the temperature control element 16, such that the cell housing 6 of the storage unit cell 2b is overlapped or covered at least partially, in particular at least predominantly or completely, by the heating device 17b, in particular by the heating element 18 of the heating device 17b, in the direction of the temperature control element 16. The above and below explanations regarding the heating device 17a or regarding the heating element 18 of the heating device 17a may also readily be transferred to the heating device 17b or to the heating element 18 of the heating device 17b, and vice versa.
(15) In order to be able to supply the heating devices 17a, b with the electrical energy stored in the storage unit cells 2a, b and thereby to be able to operate them, the heating devices 17a, b are for example connected or able to be connected electrically to the storage unit cells 2a, b, in particular via their terminals.
(16) There is furthermore provision for the heating devices 17a, b to be able to be operated without any damage, in particular without any interruption and without any damage over an operating time, only when the storage unit cells 2a, b each have a state of charge that is not more than 60 percent of the maximum state of charge of the respective storage unit cell 2a, b, that is to say that is less than or equal to 60 percent of the maximum state of charge of the respective storage unit cell 2a, b. The maximum state of charge of the respective storage unit cell 2a, b denotes a maximum amount of electrical energy able to be stored in the respective storage unit cell 2a, b, such that, when the respective storage unit cell 2a, b has its maximum state of charge, no further electrical energy is able to be stored in the respective storage unit cell 2a, b, that is to say no further electrical energy is able to be fed into the respective storage unit cell 2a, b for storage. Expressed in yet other words, the respective storage unit cell 2a, b, when it has its respective maximum state of charge, is fully charged. The abovementioned operating time is preferably five minutes, 15 minutes or 30 minutes. The operating time, in particular when the heating devices 17a, b are designed as cell intermediate heaters, is preferably at most five minutes, in particular at most or precisely three minutes and very preferably at most or precisely two minutes. It has proven to be particularly advantageous, in particular when the heating devices 17a, b are designed as cell-internal heaters, for the operating time to be at most or precisely 60 seconds, in particular at most or precisely 30 seconds. The feature whereby the respective heating device 17a, b is only able to be supplied with electrical energy stored in the storage unit cells 2a, b and thereby able to be operated without any damage, in particular only able to be supplied with electrical energy stored in the storage unit cells 2a, 2b and thereby able to be operated without any interruption and without any damage over a predefined operating time, should in particular be understood to mean that, if a current state of charge of the storage unit cells 2a, b is greater than 60 percent of the maximum state of charge of the storage unit cells 2a, b and in this case the heating devices 17a, b were to be supplied with electrical energy stored in the storage unit cells 2a, b and thereby operated, in particular without the temperature of the storage unit cells 2a, b or of the heating devices 17a, b being controlled by the temperature control device 14, before expiry, that is to say before the end of the operating time that begins in particular when the heating devices 17a, b begin to be supplied with electrical energy stored in the storage unit cells 2a, b and thereby operated, the respective heating devices 17a, b would be damaged or destroyed, in particular burnt out. The heating devices 17a, b may possibly be supplied with electrical energy from the storage unit cells 2a, b and thereby operated at a state of charge of the storage unit cells 2a, b greater than 60 percent of the maximum state of charge of the respective storage unit cell 2a, b, but not over the entire operating time, since the heating devices 17a, b would be damaged or destroyed, in particular burnt out, before expiry of the operating time.
(17) FIG. 2 shows a graph 19 on the ordinate 20 of which an electric charge current, which is fed into the storage unit cells 2a, b for storage, is plotted. The time is plotted on the abscissa 21 of the graph 19. The charge current is denoted I, and the time is denoted t. FIG. 2 furthermore shows a graph 22, on the ordinate 23 of which a temperature T of the storage unit cell 2a, b is plotted. The time t is likewise plotted on the abscissa 24. A curve 25 illustrates a temporal profile of the charge current, wherein curves 26 and 27 illustrate temporal profiles of the temperature T. The charge current I is fed into the storage unit cells 2a, b or into the energy storage unit 1 for storage for example during fast charging of the energy storage unit 1. The fast charging, also referred to as charging process, begins at a first time t.sub.1. At the start of the charging process, the respective storage unit cell 2a, b has a starting temperature T.sub.start. The greatest temperature of the storage unit cell 2a, b during the charging process is denoted T.sub.max. The charging process ends at a second time t.sub.2, at which the respective storage unit cell 2a, b has an end temperature T.sub.end. The end temperature T.sub.end is lower than the greatest temperature T.sub.max and greater than the starting temperature T.sub.start. A first phase P1 of the charging process extends from the first time t.sub.1 to a time t.sub.3 that is between the times t.sub.1 and t.sub.2. The first phase P1 is a heating phase and may have two sub-phases T1 and T2. During the sub-phase T1, which extends for example from the time t.sub.1 to a time t.sub.4 that is between the times t.sub.1 and t.sub.3, the storage unit cells 2a, b are heated for example by way of the electrical heating devices 17a, b. There may in particular be provision for the storage unit cells 2a, b to be heated only by way of the heating device 17a, b during the sub-phase T1, with regard to the heating devices 17a, b and the temperature control device 14. It is furthermore conceivable, in the phase P1, in particular in the first sub-phase T1, for the temperature control fluid to be heated to a supply temperature, also referred to as target supply temperature, that is for example in a range from 30 degrees Celsius to 35 degrees Celsius. This may be achieved for example by way of a heating device that is provided in addition to the heating devices 17a, b and is in particular electrically operable, and may be designed as a flow heater and/or arranged in the surroundings 13 and in this case in the storage unit housing 3 or outside the storage unit housing 3. There may thus be provision, during the sub-phase T1, for the storage unit cells 2a, b to be heated by way of the temperature control fluid and thus by way of the temperature control device 14, in particular by virtue of the supply temperature being greater than the temperature of the storage unit cells 2a, b. During the phase P1, in particular during the sub-phase T1, the temperature control fluid is for example circulated, as a result of which it is possible to avoid overheating of the heating devices 17a, b. This may allow a particularly high and in particular full heating time of for example 90 to 120 seconds. The target supply temperature of the temperature control fluid is in particular thereby able to be reached quickly. In parallel, it is possible to set a small charging current that is able to be raised in accordance with the temperature T of the storage unit cells 2a, b, in particular in accordance with a rise in the temperature T. After the target supply temperature has been exceeded, that is to say when the storage unit cells 2a, b are hotter than the temperature control fluid, a cooling effect brought about by the temperature control fluid may arise, as a result of which the storage unit cells 2a, b are cooled, in particular during the sub-phase T2. The sub-phase T2 ends at the time t.sub.3. The end of the sub-phase T2 is the end of the phase P1, at the end of which a target starting temperature, advantageous for the actual fast charging, of the respective storage unit cell 2a, b is reached. The actual fast charging thus begins at the time t.sub.3. A second phase P2, which is a cooling phase, starts with the actual fast charging and thus at the time t.sub.3. The maximum charge current I is also present during the phase P2. During the cooling phase, heating, brought about by the heating device 17a, b and by the temperature control device 14, of the storage unit cells 2a, b is omitted, wherein the storage unit cells 2a, b during the phase P2 are cooled by way of the temperature control fluid and thus by way of the temperature control device 14, specifically to the full extent. As may be seen from FIG. 2, the charge current I has for example a stepped profile.
(18) The phase P2 may be followed by a phase P3. The phase P3 begins at the time t.sub.2, at which the phase P2 ends. After the highest current stage ends, this ending for example at a time t.sub.5 between the times t.sub.3 and t.sub.2, the highest temperature T.sub.max is reached. After the highest current stage, an in particular step-shaped reduction of the charge current I takes place, and the storage unit cells 2a, b are cooled down to the end temperature T.sub.end. The end temperature T.sub.end is then the temperature of the storage unit cells 2a, b at which the phase P3 and thus for example onward travel following the fast charging begins. It may be seen from FIG. 1 that an electrically insulating and thermally conductive layer 28 may be arranged between the respective heating element 18 and the respective cell housing 6, in particular along the direction. It is furthermore conceivable that an adhesive layer 29 may be arranged along the direction between the respective layer 28 and the respective cell housing 6.
(19) FIG. 3 shows, for example, the storage unit cell 2a according to a second embodiment of the energy storage unit 1. FIG. 3 shows the connection element 12 and the second connection element, denoted 12′ in FIG. 3, of the storage unit cell 2a. FIG. 3 furthermore shows that the heating element 18 may run at least substantially in meandering form and/or be electrically connected to the terminals (connection elements 12, 12′), as a result of which the heating element 18 or the heating device 17a is able to be supplied with electrical energy stored in the storage unit cell 2a and thereby able to be operated. In FIG. 3, a surface available for effectively cooling the storage unit cell 2a is denoted F. As an alternative or in addition, cooling may take place via the terminals, in particular when the surface F is not large enough.
(20) FIG. 4 shows the storage unit cell 2a for a third embodiment of the energy storage unit 1. It may be seen from FIG. 4 that the storage unit cell 2a or the cell housing 6 may have a prismatic outer circumference and in this case in particular have a cuboidal design.
(21) FIGS. 5 and 6 show the storage unit cell 2a for a fourth embodiment of the energy storage unit 1. In the fourth embodiment, the storage unit cell 2a, in particular its cell housing 6, is designed with a round, in particular circular outer circumference. The heating device 17a in the fourth embodiment is furthermore designed as a cell-internal heater that is arranged inside the cell housing 6 and in this case in particular in the reception space 7. Particularly fast and effective heating of the storage unit cell 2a is thereby able to be achieved.
(22) FIG. 7 finally shows a further graph, in the form of a flowchart, for further illustrating the method. In a block B1, a possible driving scenario is analyzed. In a block B2, starting conditions and target variables are determined for all sections of a journey, in particular journey sections and charging processes. The determination performed in block B2 takes place for example on the basis of an initial state of charge of the storage unit cells 2a, b, of an initial temperature of the storage unit cells 2a, b, of a journey distance and of a route selection, of a desired setpoint state of charge or a setpoint range, a target time, or a target temperature at the end of the charging process. Starting from block B2, a distinction is drawn between travel of the motor vehicle and charging of the energy storage unit 1. In the case of travel, the method is continued with block B3. In the case of charging the energy storage unit 1, the method is continued with a block B4. In block B3, the driving route is analyzed, in particular with regard to a speed and acceleration profile. A required driving power and recuperation power are furthermore calculated over time and heating requirements and cooling requirements are derived. It may for example be determined that there is no cooling requirement. If there is a cooling requirement, then advantageous supply temperatures and volume flows are determined and set, in particular for temperature control fluids, whereupon cooling takes place with advantageous parameters. With regard to any heating requirements for the driving route, no heating requirement, a low heating requirement or a large heating requirement may be determined. When a low heating requirement is determined, it is determined for example whether the current state of charge of the storage unit cells 2a, b is greater or less than 60 percent of the maximum state of charge. If the current state of charge is less than 60 percent of the maximum state of charge, then maximum heating is performed by way of the heating devices 17a, b, for example, wherein heating is possibly also additionally performed by way of the temperature control device 14. If the current state of charge is for example greater than 60 percent of the maximum state of charge, then heating is performed by way of the temperature control device 14, and heating may likewise be performed for a short time interval by way of the heating device 17a, b, wherein the time interval is however shorter than the operating time, such that the heating device 17a, b is not damaged or destroyed—since the current state of charge is greater than 60% of the maximum state of charge. When it is determined that there is a large heating requirement, if the current state of charge is less than 60 percent of the maximum state of charge, maximum heating is performed for example by way of the heating device 17a, b and by way of the temperature control device 14. If, when a large heating requirement is determined, the current state of charge is greater than 60 percent of the maximum state of charge, then heating is performed by way of the temperature control device 14. Heating may be performed by way of the heating devices 17a, b, but only during a time interval that is shorter than the operating time.
(23) The same may take place in block B4. In block B4, for example, a charging profile is calculated, and an advantageous starting temperature, an advantageous maximum temperature T.sub.max and an advantageous end temperature T.sub.end are determined. A solution is optimized for example with regard to a minimum risk, minimum temperature, best efficiency, in a time-optimized manner, matching a desire specified by the driver of the motor vehicle, for example with regard to a shortest charging time or a desired pause time of for example 20 minutes. Starting from block B4, a heating requirement and a cooling requirement are for example determined over time for the respective charging process. It may be determined that there is no cooling requirement. If it is determined for example that there is a cooling requirement, then advantageous supply temperatures, a volume flow of the temperature control fluid, etc. may be determined and set. Cooling may therefore be performed with advantageous parameters at an advantageous time.
(24) With regard to the heating requirement, it may be determined that there is no heating requirement, a low heating requirement or a large heating requirement. If for example there is a low heating requirement, then it is determined whether the current state of charge of the storage unit cells 2a, b is less than or greater than 60 percent of the maximum state of charge of the storage unit cells 2a, b. If the state of charge is less than 60 percent of the maximum state of charge, then maximum heating is performed by way of the heating devices 17a, b, wherein heating is possibly also performed by way of the temperature control device 14. If the current state of charge is greater than 60 percent of the maximum state of charge, heating is performed for example by way of the temperature control device 14. Heating may be performed by way of the heating device 17a, b during a time interval, wherein the time interval is however shorter than the operating time and in particular short enough that damage or destruction of the heating devices 17a, b is avoided. If, in the course of determining a large heating requirement, it is determined that the current state of charge is less than 60 percent of the maximum state of charge, then heating is performed for example by way of the heating devices 17a, b and by way of the temperature control device 14. If the current state of charge is however greater than 60 percent of the maximum state of charge, then heating is performed for example by way of the temperature control device 14. Heating may be performed by way of the heating devices 17a, b, but only during a time interval that is shorter than the operating time and is in particular short enough that damage or destruction of the heating devices 17a, b is avoided.
(25) The foregoing disclosure has been set forth merely to illustrate the invention and is not intended to be limiting. Since modifications of the disclosed embodiments incorporating the spirit and substance of the invention may occur to persons skilled in the art, the invention should be construed to include everything within the scope of the appended claims and equivalents thereof.
LIST OF REFERENCE SIGNS
(26) 1 energy storage unit 2a, b storage unit cell 3 storage unit housing 4 housing space 5 double-headed arrow 6 cell housing 7 reception space 8 electrolyte 9 electrode device 10 electrode 11 electrode 12, 12′ connection element 13 surroundings 14 temperature control device 15 temperature control channel 16 temperature control element 17a, b heating device 18 heating element 19 graph 20 ordinate 21 abscissa 22 graph 23 ordinate 24 abscissa 25 curve 26 curve 27 curve 28 layer 29 layer B1 block B2 block B3 block B4 block F surface I charge current p1 phase p2 phase t time T1 sub-phase T2 sub-phase t.sub.1 time t.sub.2 time t.sub.3 time t.sub.4 time t.sub.5 time T.sub.start starting temperature T.sub.end end temperature T.sub.max greatest temperature
