Battery system and vehicle with such a system, as well as method for heating and / or cooling a battery

Abstract

A battery system comprising a battery, in particular a rechargeable battery (1), preferably a traction battery of an electric or hybrid vehicle, and a battery temperature control device with a thermochemical heat storage device (6) and at least one heat transfer element (11) that is in thermally conductive contact with the thermochemical heat storage device (6), wherein the heat transfer element (11) has at least one switching element by means of which a heat flow along the heat transfer element (11) can be interrupted, and wherein the heat transfer element (11) is designed such that it can be brought into thermally conductive contact with a battery (1) to be heated and / or cooled, wherein the battery (1) is in thermally conductive contact with the heat transfer element (11) or with the heat transfer elements (11) of the battery temperature control device,and two or more battery strings (2, 3, 4) connected electrically in parallel, wherein the thermochemical heat storage device (6) is in thermally conductive contact with exactly one of the battery strings (3) via a heat transfer element (11) or a plurality of heat transfer elements (11) connected in parallel, and the battery is designed such that the battery string in thermally conductive contact with the thermochemical heat storage device can be operated in isolation.

Description

The invention relates to a battery system and a vehicle comprising such a battery system. The invention furthermore relates to a method for heating and / or cooling a battery.It is known that batteries exhibit a temperature-dependent behavior. At too low temperatures, there is the problem that the usable energy content of the batteries is considerably sacrificed. Operation at too low external temperatures may also result in a shortened life of the batteries. Overheating can occur at too high temperatures, as a result of which operation is likewise disturbed and even defects can occur. In order to achieve the highest possible performance and the longest possible service life of batteries, these are ideally operated within a predefined temperature window. An optimum operating temperature is, for example, in the range from 20 to 30° C.Especially in traction batteries which are used for driving electric and hybrid vehicles, the problem arises that the batteries are exposed to the ambient temperatures which fluctuate over the year.In order to ensure optimum operation, the batteries should therefore be tempered, i.e. heated at too low ambient temperature and cooled at too high ambient temperatures. For regulating the temperature of such batteries, battery temperature control devices have been developed, with which they can be brought comparatively quickly to the temperature ideal for operation.For example, DE 10 2012 210 146 A1 discloses a battery temperature control device which comprises an electrical heating element, a temperature sensor, a voltage supply and a switching element which connects or disconnects the voltage source to the heating element. If it is registered via the temperature sensor of the battery temperature control device that the battery has a temperature which lies below a predefined value, the electrical heating element, which is a PTC resistor, is connected to the voltage source in order to heat the battery. The traction battery to be heated itself or an additional battery is used as a voltage source for the electric heating element.In the known battery tempering device, it is partly considered disadvantageous that the traction battery must also provide the electrical power for the heating element in addition to the electrical power which it is intended to provide in order to drive an electric or hybrid vehicle. This has the effect, among other things, that the aging process of the battery is further accelerated. If an additional battery is used for supplying the heating element, additional costs and additional weight are incurred and the additional battery then also has the problem of operating at an excessively low temperature.As for the cooling of traction batteries, it can be achieved using, for example, cooling air, refrigerants or refrigerants. If cooling air or coolant are used, overheating of the battery can nevertheless occur at high ambient temperatures. This problem is generally counteracted by reducing the power of the battery.Cooling the batteries using a refrigerant circuit can more reliably prevent overheating, but is again associated with an additional need for electrical energy. If a battery is to be cooled, which is used as a traction battery in an electric or hybrid vehicle, the range of the vehicle is thereby reduced.This problem is addressed in the prior art by using thermochemical heat storage devices for the temperature control of batteries. For example, DE 10 2012 012 820 A1 discloses a battery system which comprises a battery for an electric vehicle having a plurality of battery cells and a device for tempering the battery with a thermochemical heat storage device. The thermochemical heat storage device and the battery are thermally coupled to one another via lines of a heating circuit, and valves are arranged in the lines, by means of which valves a heat flow can be interrupted.US 2014 / 0224453 A1 discloses a heat recovery system having an ammonia buffer that can fix and desorb ammonia, and a chemical heat storage reactor having a chemical heat storage material that generates heat by a chemical reaction with ammonia.Document JPH09-326 263 A discloses a battery having a plurality of battery cells and a plurality of heat pipes for cooling the battery. Valves are provided with which the heat pipes can be switched on or off.The document DE 10 2013 225 582 A1 shows a battery pack with two battery modules and two thermochemical heat accumulators.The battery systems known from the prior art have proven themselves in principle. However, there is a need for further improved devices.Proceeding from the aforementioned prior art, it is an object of the present invention to specify an improved battery system, by means of which a battery can be reliably brought to a temperature suitable for operation.This object is achieved by a battery tempering system according to claim 1, a vehicle according to claim 17 and a method according to claim 19. The basic idea of the present invention is therefore to use a thermochemical heat storage device for the temperature regulation, i.e., the heating and / or cooling of a battery, in particular a rechargeable battery, preferably a traction battery of an electric or hybrid vehicle.The battery comprises two or more battery strings electrically connected in parallel and, according to the invention, the thermochemical heat storage device is in heat-conducting contact with exactly one of the battery strings via a heat transfer element or a plurality of heat transfer elements connected in parallel, and the battery is designed in such a way that the battery string which is in heat-conducting contact with the thermochemical heat storage device can be operated in an insulated manner.In particular, it can be provided that the battery comprises three or more battery strings lying next to one another and the thermochemical heat storage device is in heat-conducting contact only with the or a middle battery string via the heat transfer element or the plurality of heat transfer elements.According to the invention, it is achieved that in the case of a battery having a plurality of battery strings connected electrically in parallel, not the entire battery is heated and / or has to be cooled by means of the thermochemical heat storage device, but only a part of the battery, specifically one of the battery strings, in particular the or a middle battery string. Since one of the battery strings also has only a part of the total heat capacity of the battery, a thermochemical heat storage device with a lower capacity is sufficient according to this embodiment.According to the invention, an adapted electrical circuit of the battery is thereby effected. Specifically, initially only that battery string which is heated by the thermochemical heat storage device is loaded. For this purpose, the battery is designed according to the invention such that the corresponding battery string can be operated in an insulated manner, i.e. independently of the remaining battery string or strings. This one phase can very rapidly and efficiently reach its ideal operating temperature by heating via the thermochemical heat storage device and can then be able to additionally emit current, by means of which in turn an in particular electrical heating of the remaining battery phases is possible, in order also to bring these to an ideal operating temperature. In this case, it is reliably prevented at all times that loading takes place from one or more battery strings which have a temperature outside an ideal range.The middle or middle, i.e. inner, battery string can be heated particularly efficiently, since possible heat losses are emitted to the outer battery strings and contribute there to preheating. In a particularly advantageous embodiment, therefore, the or a middle battery string is thermally conductively coupled according to the invention to the thermochemical heat storage device. At the same time, the thermochemical heat storage device provided according to the invention can be used to efficiently cool the or a middle battery string, which has proved difficult with the known device, in which case a further great advantage is present.The traction battery may be, for example, a lithium ion battery.In the thermochemical heat storage device used according to the invention, heat and / or cold can be stored almost loss-free over comparatively long periods of time, in particular even several weeks, and can be provided in a particularly simple manner and rapidly and with high power if necessary, for example during a cold start of an electric or hybrid vehicle.A heat source for raising the battery temperature and / or a heat sink for reducing the battery temperature can be obtained by means of the thermochemical heat storage device by starting a reaction. For this purpose, no or at least no appreciable additional electrical power has to be provided by the battery to be heated and / or cooled. In particular, it is not necessary to continuously supply energy for the maintenance of the reaction. As a result, the electric load of the battery at low external temperatures when heating is required can be significantly reduced compared to the prior art, thereby particularly extending the life of the battery.In the context of the present invention, in principle any arrangement which makes it possible to store heat via thermochemical processes and release it again, in particular by endothermic and exothermic reactions, can be used as thermochemical heat storage device. For this purpose, the thermochemical heat storage device has, for example, at least one, in particular solid, storage medium and at least one, in particular fluid, reaction medium, which is released from the storage medium with the supply of thermal energy and is absorbed by the storage medium with heating. An example of a thermochemical heat storage device that can be used in the battery tempering device according to the invention is a sorption storage device.According to the invention, the thermochemical heat storage device can be used in particular as a heat source for particularly rapid and efficient preheating of a battery and / or heating during a cold start. In addition, the thermochemical heat storage device can provide additional cooling capacity for the temperature control of a battery, which is of great use in particular in the case of load peaks and resultant temperature rises of batteries.In an advantageous embodiment, the thermochemical heat storage device is designed to be switchable. Means are then provided for starting a reaction in the thermochemical heat storage device and interrupting the reaction again.The exchange of thermal energy between the thermochemical heat storage device and a battery to be heated and / or cooled is made possible according to the invention by at least one heat transfer element which is in heat-conducting contact with the thermochemical heat storage device. The at least one heat transfer element is designed to enable the thermal coupling of the thermochemical heat storage device to the battery in such a way that it can be brought into heat-conducting contact therewith.The thermal coupling between the thermochemical heat storage device and the battery to be temperature-controlled can take place via a single heat transfer element. Alternatively, a plurality of heat transfer elements connected in parallel can also be provided, which are in heat-conducting contact with the thermochemical heat storage device and are designed such that they can be brought into heat-conducting contact with a battery to be heated and / or cooled.For the operation of a battery, the heat transfer element or the plurality of heat transfer elements connected in parallel is in heat-conducting contact with the battery to be heated and / or cooled. In this case, the heat transfer element or elements can be directly in physical contact with the battery, for example can contact the latter on the outside or form an integral part of the battery, wherein they can extend in particular through the battery. It can also be provided that the heat transfer element(s) is or are not in direct physical contact with the battery, but rather are in thermal contact with the battery via a further, readily thermally conductive component or, for example, a thermally conductive paste.The battery temperature control device can be installed from the beginning, on the one hand, as part of the production of new systems, for example, be installed together with the battery as part of the production of an electric or hybrid vehicle. Alternatively, the battery tempering device can also be retrofitted in existing systems, for example in electric or hybrid vehicles already in operation, by being installed subsequently in such a way that the heat transfer element or the heat transfer elements come into heat-conducting contact with the battery of the vehicle.The heat transfer element(s) can be tubular or line-shaped, for example. According to the invention, these may be, in particular, heat pipes (heat pipes).Heat pipes are known heat transfer elements of high effectiveness. They generally comprise a hermetically sealed, tubular container in which capillary structures are arranged. A fluid is provided in the container, which vaporizes from the capillary structures under the supply of heat in an end region of the heat pipe. The vapor flows through the heat pipe to the colder end region, condenses with the emission of vaporization heat and leads there to a temperature increase. By means of capillary forces, the liquefied fluid is returned to the region of the heat supply. Due to the combination of evaporation and condensation of the fluid and the associated high heat transfer coefficient and the comparatively rapid return transport, heat pipes represent particularly efficient heat transfer elements.The use of one or more heat pipe(s) as heat transfer elements enables a particularly low heat capacity of the heat transfer and thus a large part of the capacity stored in the thermochemical heat storage device to be available for heating up the battery. This is particularly advantageous above all in the case of preheating a battery.Furthermore, according to the invention, at least one switching element is provided in the heat transfer element or the plurality of heat transfer elements, by means of which switching element the thermal conductivity along the heat transfer element can be interrupted. This makes it possible for the thermal coupling between the thermochemical heat storage device and a battery to be heated and / or cooled to be produced and interrupted according to the invention as required.The use according to the invention of one or more switchable heat transfer elements makes it possible, on the one hand, for the amount of heat which is supplied to the battery or removed from the battery to be set very accurately. If the battery has reached a desired temperature, which can be detected, for example, by means of a temperature sensor, the thermal coupling between the thermochemical heat storage device and the battery can easily be canceled by actuating the switching element and thus interrupting a heat flow along the heat transfer element. A heat exchange between the thermochemical heat storage device and the battery is then no longer possible, or at most to a negligible extent possible.In addition, the switchability of the heat transfer element(s) enables the thermochemical heat storage device to be recharged without the amount of heat and / or cold fed in for the charging state being supplied to the battery. For this purpose, the thermochemical heat storage device and the battery are decoupled from one another during the charging process by actuating the switching element(s). Charging of the thermochemical heat storage device can thus take place at all times, in particular even when the battery is not intended to be heated or cooled further.If heat pipes are used as heat transfer elements, the switchability can be implemented, for example, structurally via at least one valve. The valve serving as a switching element is then expediently arranged between the heat source or heat sink and the battery to be heated or cooled in the heat pipe. When the valve position is closed, the fluid transport and thus heat flow between the heat source or heat sink and the battery is prevented.If both a heat source and a heat sink are provided via the thermochemical heat storage device, both can be coupled or couplable to the battery via the same heat transfer element, in particular heat pipe, or the same heat transfer elements, in particular heat pipes. The heat source and the heat sink are then each in thermally conductive contact with one end of the heat transfer element or with one end of the plurality of heat transfer elements or can be brought into thermally conductive contact with the end or ends. In this case, each heat transfer element expediently has two switching elements, in particular valves, provided in order that the heat source and the heat sink can be decoupled from a battery to be heated and / or cooled.Regeneration, i.e. charging of the thermochemical heat storage device, can take place in particular when excess heat energy, for example in the form of waste heat of the components of an electric or hybrid vehicle to be driven, is available. The waste heat can be transported, for example, in a manner known per se via a coolant to the thermochemical heat storage device. Alternatively or additionally, the thermochemical heat storage device can be charged if a heat sink is provided. A cooling circuit of a vehicle or the ambient air of the vehicle can serve as a heat sink, for example, especially at low external temperatures.According to one embodiment of the invention, it is provided that the thermochemical heat storage device comprises a cold-side reactor and a hot-side reactor, each of which has at least one container in which an in particular solid storage medium for accommodating a reaction medium is provided, wherein the storage media in the hot-side reactor and the cold-side reactor differ in terms of their temperature-dependent and pressure-dependent equilibrium states when accommodating the reaction medium, and wherein the hot-side reactor and the cold-side reactor are each in heat-conducting contact with a heat transfer element or with a plurality of heat transfer elements connected in parallel, and the container or containers of the hot-side reactor are connected to the container or containers of the cold-side reactor via a reactor connecting line, wherein the reactor connecting line is designed to be switchable between an open and a closed state.In an advantageous embodiment, the storage medium of the hot-side reactor and / or the storage medium of the cold-side reactor can comprise zeolite, silica gel, salts or a hydride-forming material or else be formed therefrom.In the hot-side reactor and the cold-side reactor, it is also possible to provide different storage media which differ in terms of their temperature-dependent and pressure-dependent equilibrium states during the uptake of the reaction medium.In addition, a reaction medium can be provided in the container or containers of the hot-side reactor and / or in the container or containers of the cold-side reactor, wherein in particular the reaction medium can comprise water or hydrogen or ammonia or can be formed therefrom.According to this embodiment, a closed thermochemical system with a hot-side reactor and a cold-side reactor is used, which can be or are coupled in a heat-conducting manner to the battery to be heated and / or cooled via one or more heat transfer elements connected in parallel. Such a thermochemical heat storage device has proven to be particularly suitable for easily allowing heating and / or cooling of the battery.The reactor connecting line, which can be switched, for example, via a valve and connects the hot-side and cold-side reactors to one another in terms of fluid technology, serves to be able to control, in particular to be started and interrupted, the reaction in the two reactors in a particularly simple and convenient manner. According to this embodiment, the provision of heat and / or cold can be switched in a particularly simple manner as a result.If a valve is provided in the reactor connecting line, this can also serve for controlling the amount of heat and / or cold provided by means of the thermochemical heat storage device, for example by means of clocked opening and closing of the valve.In order to be able to be used as a heat source and / or as a heat sink if required, the thermochemical heat storage device must first be loaded. Charging can be effected by heating the hot-side reactor and the storage medium provided therein with the reactor connecting line open, or cooling the cold-side reactor and the storage medium provided therein, or simultaneously heating the hot-side reactor and cooling the cold-side reactor. As a result of the heating and / or cooling, the capacities of the two storage media for the reaction medium arranged in the reactors are shifted. The reaction medium is therefore discharged from the storage medium of one reactor and taken up by the storage medium of the other reactor. As a result, a pressure difference is established between the two reactors and the reaction medium flows, in particular in the gaseous state, through the open reactor connecting line from one reactor into the other reactor, in particular from the warm-side reactor into the cold-side reactor. After the reaction medium has expediently flowed at least to a large extent into the container or containers of the other reactor, in particular of the cold-side reactor, the reactor connecting line is closed, that is to say the fluidic connection between the hot-side reactor and the cold-side reactor is interrupted, and the heat supply to the hot-side reactor and / or the heat removal from the cold-side reactor is ended. The hot-side reactor and the cold-side reactor are then brought to the same temperature, which can expediently be effected by waiting until both reactors have adapted to the ambient temperature, that is to say the hot-side reactor has been cooled passively to the ambient temperature and / or the cold-side reactor has been heated passively to the latter. This results in a pressure difference between the container or containers of the hot-side reactor on the one hand and the container or containers of the cold-side reactor on the other hand. The thermochemical heat storage device is loaded in this state.If the charged thermochemical heat storage device is to be used to heat and / or cool a battery, only the reactor connecting line has to be opened and thus the fluidic connection between the hot-side reactor and the cold-side reactor has to be established, which is associated only with a very low energy consumption. Due to the existing pressure difference, the reaction medium flows from the container or containers of the cold side reactor into the container or containers of the hot side reactor. This in turn leads to the storage medium in the hot-side reactor absorbing the reaction medium and heating up in the process. At the same time, the storage medium in the cold side reactor releases reaction medium, which results in the temperature of the storage medium in the cold side reactor being reduced.The thermal energy released in the warm-side reactor can be supplied to the battery via the heat transfer element(s) which connect the warm-side reactor and the battery in a heat-conducting manner. In an analogous manner, the battery can be cooled by means of the cold-side reactor if required by heat energy being dissipated from the battery to the cold-side reactor via the heat transfer element(s) which couples the cold-side reactor to the battery in a heat-conducting manner.Both for the hot-side reactor and for the cold-side reactor, a heat transfer element or a plurality of heat transfer elements can be provided in each case, via which the hot-side reactor and the cold-side reactor are in heat-conducting contact or can be brought into heat-conducting contact with the battery to be heated and / or cooled in each case.Alternatively, both reactors are in heat-conducting contact with the battery via the same heat transfer element or the same plurality of heat transfer elements or can be brought into heat-conducting contact therewith. In this case, in particular the warm-side reactor and the cold-side reactor are connected to one another via a heat transfer element, in particular a heat pipe, or a plurality of heat transfer elements, in particular heat pipes, connected in parallel, in such a way that each of the reactors is in heat-conducting contact with in each case one end region of the heat transfer element(s). In this embodiment, the heat transfer element(s) expediently each have at least two switching elements, via which, on the one hand, a heat flow between the hot-side reactor and a central region of the heat transfer element, which can be brought into heat-conducting contact with a battery to be heated and / or cooled or is in heat-conducting contact with the battery, and, on the other hand, between the cold-side reactor and the central region of the heat transfer element can be prevented.If heat pipes are used as heat transfer elements, two valves are provided in particular in each heat pipe, by means of which the flow cross section of the fluid through the closed, tubular container of the heat pipe can be interrupted. One of the valves is then expediently arranged in such a way that a flow of the fluid from an end region of the heat pipe which is in thermally conductive contact with the warm side reactor to the central region of the heat pipe can be prevented, and the second valve is positioned in such a way that a heat transport between the cold side reactor which is in thermally conductive contact with the other end region of the heat pipe and the central region of the heat pipe can be prevented.It can be provided, for example, that a heat transfer element, in particular a heat pipe or a plurality of heat transfer elements connected in parallel, in particular heat pipes, extend through a battery to be heated and / or cooled, wherein the heat transfer element(s), in particular heat pipe(s), protrude from the battery on both sides and the two ends of the heat pipe(s) are each in heat-conducting contact with one of the reactors of the thermochemical heat storage device. Then, a switching element, preferably a valve, is expediently arranged in each of the end regions of the heat transfer element or elements protruding from the battery on both sides between the battery and the respective reactor.This arrangement makes it possible in a simple structural manner for the or each of the heat transfer element(s) to be able on the one hand to serve a heat exchange between the hot-side reactor and the battery and on the other hand to serve a heat exchange between the cold-side reactor and the battery, wherein for the corresponding heat exchange the respective switching element, in particular valve, is to be brought into the open position, which enables a heat flow, in particular a flow of a fluid provided in a heat pipe, between the respective reactor-side end region and the central region of the heat pipe which is in heat-conducting contact with the battery.According to a further advantageous embodiment of the invention, it is provided that the thermochemical heat storage device is or can be coupled to a heat source and / or a heat sink in a heat-conducting manner.In this case, in particular the warm side reactor of the thermochemical heat storage device can be coupled or can be coupled to a heat source in a heat-conducting manner and / or the cold side reactor of the thermochemical heat storage device can be coupled or can be coupled to a heat sink in a heat-conducting manner.In particular, for charging the thermochemical heat storage device, the hot-side reactor may be heated by means of a heat source and / or the cold-side reactor may be cooled by means of a heat sink. A vehicle component can serve as a heat source, for example, which heats up during operation. For example, the ambient air of the vehicle can be used as a heat sink, in particular at low external temperatures. Alternatively, a vehicle air conditioner may be used as a heat sink.The thermal coupling of the heat source and / or heat sink to the thermochemical heat storage device can be effected, for example, by means of a circuit for a heat transfer medium. Alternatively, heat pipes can be used for this purpose.In a further development of the invention, it is further proposed that the heating and / or cooling of a battery according to the invention using a thermochemical heat storage device is combined with the heating and / or cooling of the battery using one or more conventional heat exchangers.For this purpose, the battery temperature control device can comprise at least one heat exchanger which is in heat-conducting contact with a heat transfer element or with a plurality of heat transfer elements connected in parallel, wherein the at least one heat exchanger is coupled or can be coupled in a heat-conducting manner to a heat source and / or a heat sink.The combination of thermochemical heat storage device and conventional heat exchangers makes it possible, for example, for a battery to be temperature-regulated, in particular heated, by means of the thermochemical heat storage device only during a startup phase, in particular during a cold start, and for the battery to be temperature-regulated by means of the conventional heat exchangers after the startup phase.The heat exchanger or exchangers can be designed in a manner known per se in such a way that a heat transfer medium can flow through them. In the heat exchanger(s), an exchange of heat can then take place between the heat transfer medium and the heat transfer element(s), so that a battery can be heated and / or cooled by means of the heat transfer medium.In a particularly expedient embodiment, the battery temperature control device comprises a plurality of heat exchangers, in particular at least one warm-side heat exchanger and / or at least one cold-side heat exchanger, which are each in heat-conducting contact with a heat transfer element or with a plurality of heat transfer elements connected in parallel, wherein the at least one warm-side heat exchanger is or can be coupled to a heat source in a heat-conducting manner and the at least one cold-side heat exchanger is or can be coupled to a heat sink in a heat-conducting manner.The at least one warm-side heat exchanger can then be designed such that a warm-side heat transfer medium can flow through it for supplying heat to a battery, and the cold-side heat exchanger can be designed such that a cold-side heat transfer medium can flow through it for removing heat from the battery.A further embodiment of the invention is characterized in that the battery temperature control device comprises an electrical heating device serving as a heat source. This heat exchanger can serve in a manner known per se to heat a heat transfer medium which flows through, for example, one or more conventional heat exchangers. The thermal energy then transfers in the heat exchangers to the heat transfer element(s) thermally coupled to the heat exchanger(s) and is supplied to the battery for heating it.It can furthermore be provided that at least one heat transfer element is designed as a heat pipe, in particular all heat transfer elements are designed as heat pipes.It can furthermore be provided that all heat transfer elements each have at least one switching element, by means of which a heat flow along the respective heat transfer element can be interrupted, and all heat transfer elements are designed such that they can be brought into heat-conducting contact with a battery to be heated and / or cooled.If the battery temperature-control device comprises at least one warm-side heat exchanger and / or at least one cold-side heat exchanger, it is provided in particular that the at least one warm-side heat exchanger and / or the at least one cold-side heat exchanger is in heat-conducting contact with the battery via a heat transfer element or via a plurality of heat transfer elements connected in parallel.The remaining battery string or the remaining battery strings which are not in heat-conducting contact with the thermochemical heat storage device can then each be in heat-conducting contact with the warm-side heat exchanger and / or the cold-side heat exchanger via a heat transfer element or via a plurality of heat transfer elements connected in parallel.A heat transfer medium heated using electrical energy can flow through the warm-side heat exchanger or exchangers, for example, in order to electrically heat the battery strings in thermally conductive contact with the heat exchangers.The invention further relates to a vehicle, in particular a motor vehicle, preferably an electric vehicle, having a battery system according to the present invention.According to one embodiment of the vehicle according to the invention, a heat transfer medium circuit is provided, in particular for cooling the vehicle engine and / or other vehicle components which heat up during operation of the vehicle, and the thermochemical heat storage device comprises a cold side reactor and a warm side reactor, wherein the warm side reactor is in heat-conducting contact with the heat transfer medium circuit.The invention further relates to a method according to claim 19, wherein in particular the battery is heated during the cold start phase by means of the thermochemical heat storage device and in the case of a cold start only that battery string which is heated by means of the thermochemical heat storage device is initially loaded.In an advantageous embodiment, electrical energy from the battery string heated by means of the thermochemical heat storage device can then be used to electrically heat the remaining battery string or the remaining battery strings.According to a further embodiment of the method according to the invention, a battery of an electric or hybrid vehicle, in particular a traction battery of the electric or hybrid vehicle, is operated, and waste heat of the electric or hybrid vehicle is used to recharge the thermochemical heat storage device by heating, and / or a refrigerant circuit of the electric or hybrid vehicle is used to recharge the thermochemical heat storage device by cooling.The invention is illustrated in more detail in the drawing by means of an exemplary embodiment. The single FIG. 1 shows a battery system according to the invention in schematic illustration.The battery system illustrated in FIG. 1 comprises a rechargeable traction battery 1 for an electric vehicle having a total of three battery strings 2, 3, 4 connected electrically in parallel, specifically a left battery string 2, a middle battery string 3 and a right battery string 4, and a battery temperature control device 5.The battery system is installed in an electric vehicle not shown in FIG. 1, wherein the rechargeable traction battery 1 serves in a manner known per se to supply an electric motor of the electric vehicle with electrical energy for driving the vehicle.The traction battery 1 is designed in such a way that the middle battery line 3 can be operated in an insulated manner, i.e. independently of the two remaining battery lines 2, 4.The battery tempering device 5 comprises a thermochemical heat storage device 6, which has a warm-side reactor with a container 7 and a cold-side reactor with a container 8 for a storage medium. The two containers 7, 8 are fluidically connected to one another via a reactor connecting line 9, wherein a valve 10 is provided in the reactor connecting line 9, via which valve the reactor connecting line 9 can be switched over between an open and a closed state.In each of the two containers 7, 8, a solid storage medium, not shown in the figure, for receiving a reaction medium is arranged. Furthermore, a reaction medium, in the present case hydrogen, is provided in the two containers 7, 8. The two solid storage media, which are each hydride-forming materials, differ in terms of their temperature-dependent and pressure-dependent equilibrium states during the uptake of the hydrogen.For the thermal coupling between the thermochemical heat storage device 6 and the middle battery string 3 of the traction battery 1, four heat transfer elements 11 arranged in parallel are provided in the exemplary embodiment shown. The heat transfer elements 11 are heat pipes 11 which extend through the middle battery string 3, the ends of each heat pipe 11 protruding from the battery string 11 on both sides. The heat pipes 11 are in direct contact with the middle battery string 3, thereby enabling efficient heat transfer between the heat pipes 11 and the battery string 3.The ends of the four heat pipes 11 pointing downward in FIG. 1 are each in direct contact with the container 7 of the hot-side reactor of the thermochemical heat storage device 6, and the ends of the four heat pipes 11 pointing upward in FIG. 1 are each in heat-conducting contact with the container 8 of the cold-side reactor of the thermochemical heat storage device 6.In each of the heat pipes 11, two valves 12 are provided, by means of which a flow of a fluid provided for heat conduction in the heat pipes 11 can be prevented in a manner known per se. In order to completely thermally decouple the battery string 3 from the container 7 of the warm-side reactor, the four valves 12, which are arranged in the four heat pipes 11 between the container 7 of the warm-side reactor and the battery string 3, are switched into the closed state. A flow of fluid and thus a exchange of heat between the end regions of the heat pipes 11 in contact with the container 7 and the central regions of the heat pipes 11 in contact with the battery string 3 is then not possible.In order to thermally decouple the container 8 of the cold side reactor from the middle battery bank 3, the four valves 12, which are arranged between the container 8 and the middle battery bank 3, are switched into the closed state in the same way.The battery temperature control device 5 further comprises two warm-side heat exchangers 13 and two cold-side heat exchangers 14.For the thermal coupling between the warm-side heat exchangers 13 and the cold-side heat exchangers 14 and the traction battery 1, a plurality of heat pipes 11 are provided-just as for the thermal coupling between the thermochemical heat storage device 6 and the traction battery 1. Specifically, there are eight heat pipes 11 arranged in parallel, of which four serve for the heat-conducting connection between one of the two warm-side heat exchangers 13 and one of the two cold-side heat exchangers 14 and the left battery bank 2, and a further four heat pipes 11 serve for the heat-conducting connection between the second warm-side heat exchanger 13 and the second cold-side heat exchanger 14 and the right battery bank 4. For this purpose, four of the eight heat pipes 11 extend through the left battery string 2 and a further four through the right battery string 4.The ends of each of the eight heat pipes 11 protrude--just like the four heat pipes 11 which extend through the middle battery string 3--from the left and right battery strings 2, 4 on both sides. The ends of the eight heat pipes 11 pointing downward in FIG. 1 are in heat-conducting contact with the warm-side heat exchangers 13. In the same way, the ends of the eight heat pipes 11 pointing upward in FIG. 1 are in direct contact with the cold-side heat exchangers 14.The vehicle has a circuit, not shown in the figure, with a line for a warm-side heat transfer medium, which is in heat-conducting contact with the two warm-side heat exchangers 13, so that thermal energy can be transferred in the heat exchangers from the warm-side heat transfer medium to the heat pipes 11 in contact with the warm-side heat exchangers 13 and thus to the left and right battery strings 2, 4 when the valves 12 arranged between the two warm-side heat exchangers 13 and the respective battery string 2, 4 are in the open position. The heat-side heat transfer medium then serves as a heat source for heating the left and right battery strings 2, 4.The line of the circuit for the heat transfer medium is furthermore in heat-conducting contact with the container 7 of the warm-side reactor of the thermochemical heat storage device 6, so that heat energy can be transferred from the warm-side heat transfer medium flowing through the line to the container 7, in particular in order to be able to regenerate the thermochemical heat storage device 6, i.e. to be able to recharge it again.The flow direction of the heat-side heat transfer medium is indicated schematically in FIG. 1 by corresponding arrows.The battery tempering device 5 further comprises an electrical heating device 15 with a PTC element, not shown in the figure, which is electrically connected to the middle battery string 2 so that it can be supplied with electrical energy from the middle battery string 2.The line of the circuit for the warm-side heat transfer medium is in heat-conducting contact with the electric heating device 15, so that the warm-side heat transfer medium flowing through the line can be heated by means of the latter. The electric heating device 15 is furthermore connected upstream of the hot-side heat exchangers 13 and the container 7 of the hot-side reactor in the flow direction of the hot-side heat transfer medium.The vehicle furthermore has a further circuit, not shown in FIG. 1, for a cold-side heat transfer medium, in the present case an air conditioning system of the vehicle. A line through which the cold-side heat transfer medium can flow is in heat-conducting contact with the cold-side heat exchangers 14 and the container 8 of the cold-side reactor of the thermochemical heat storage device 6.The cold-side heat transfer medium serves as a heat sink in order to transport heat energy away from the cold-side heat exchangers 14 and thus to be able to cool the left and right battery strings 2, 4 when the valves 12 arranged between the cold-side heat exchangers 14 and the respective battery string 2, 4 are in the open position.The line for the cold-side heat transfer medium is furthermore in heat-conducting contact with the container 8 of the cold-side reactor of the thermochemical heat storage device 6, so that the cold-side heat transfer medium can serve as a heat sink in order to remove heat energy from the container 8, i.e. to cool it, in particular in order to recharge the thermochemical heat storage device 6.The flow direction of the cold-side heat transfer medium is schematically indicated in FIG. 1 by corresponding arrows.To monitor the temperature of the three battery strings 2, 3, 4, a temperature detection device, not shown in FIG. 1, is provided.For a (cold) start of the electric vehicle, electrical energy must be provided by the traction battery 1 for driving the electric motor, specifically even if the ambient temperature lies outside the ideal operating temperature range from 20° C. to 30° C.In order to bring the traction battery 1 to the ideal operating temperature and maintain it at it particularly rapidly and reliably, the battery tempering device 5 according to the invention is used.After the electric motor has been started at an external temperature of 5° C., initially only the middle battery string 3 of the traction battery 1 is loaded and the thermochemical heat storage device 6 is activated by the valve 10 in the reactor connecting line 9, which was in the closed position since the end of the last charging process of the thermochemical heat storage device 6 during a preceding operation of the electric vehicle, being opened.Simultaneously with or shortly after the opening of the valve 10 in the reactor connecting line 9, the valves 12 in those heat pipes 11 via which the containers 7, 8 of the hot-side and cold-side reactors are in heat-conducting contact with the middle battery string 3 are adjusted in such a way that the container 7 of the hot-side reactor is thermally coupled to the middle battery string 3 and the container 8 of the cold-side reactor is not thermally coupled to the middle battery string 3. That is, the four valves 12 disposed in the heat pipes 11 between the tank 7 and the middle battery string 3 are opened, and the four valves 12 disposed between the tank 8 and the middle battery string 3 are closed.As a result of the pressure difference existing between the container 7 of the hot-side reactor and the container 8 of the cold-side reactor of the thermochemical heat storage device 6 in the loaded state, hydrogen flows through the open reactor connecting line 9 from the container 8 of the cold-side reactor into the container 7 of the hot-side reactor. The solid storage medium arranged in the container 7 of the hot side reactor absorbs the hydrogen and is thereby heated. Meanwhile, the storage medium in the cold side reactor releases hydrogen, which causes the temperature of the storage medium in the container 8 to decrease.Heat energy is transferred particularly efficiently and rapidly from the container 7 of the hot-side reactor to the middle battery bank 3 via the four heat pipes 11 extending through the middle battery bank 3, so that the latter is heated very quickly and reliably. After it has reached a defined operating temperature range, the middle battery bank 3 can additionally emit electrical energy in order to electrically heat the two remaining battery banks 2, 4.For this purpose, the electric heating device 15 is actuated and supplied with electric energy by the middle battery string 3. The warm-side heat transfer medium, which during operation of the electric vehicle flows through the circuit with that line which is in heat-conducting contact with the electric heating device 15, is consequently heated.Simultaneously with or shortly after the actuation of the electric heating device 15, in the eight heat pipes 11 which extend through the left and right battery strings 2, 4, those valves 12 which are arranged between the respective warm-side heat exchanger 13 and the left and right battery strings 2, 4 are opened, so that a heat transport from the warm-side heat exchangers 13 to the two battery strings 2, 4 is possible. In the warm-side heat exchangers 13, thermal energy is transferred from the heat transfer medium heated in the electric heating device 15 to the heat pipes 11 and by means of these particularly efficiently to the left and right battery strings 2, 4.After the temperature of the left and right battery strings 2, 4 has also reached the ideal range, the left and right battery strings 2, 4 are also operated in order to drive the electric motor of the vehicle.The heating of the middle battery bank 3 via the thermochemical heat storage device and the heating of the left and right battery banks 2, 4 can be ended.For this purpose, the valve 10 in the reactor connecting line 9 is closed in order to stop the reaction in the thermochemical heat storage device 6, and the valves 12 in the heat pipes 11 extending through the middle battery bank 3, which are arranged between the container 7 and the middle battery bank 3, are closed again.At the same time, the operation of the electric heater 15 is stopped by stopping the supply of electric power thereto. The valves 12 in the heat pipes 11 of the left and right battery strings 2, 4 which are arranged between the respective warm-side heat exchanger 13 and the respective battery string 2, 4 are likewise closed.If cooling of the traction battery 1 is required at a later operating time, this can be effected on the one hand via the cold-side heat exchangers 14, through which the cold-side heat transfer medium of the air conditioning system of the electric vehicle flows.Alternatively or additionally, the traction battery 1, specifically the middle battery string 3, can be cooled via the container 8 of the cold side reactor of the thermochemical heat storage device 6. For this purpose, the valve 10 in the reactor connecting line 9 is opened again in order to restart the reaction described above. The container 7 of the hot side reactor is thus heated and the container 8 of the cold side reactor generates cold. Since the valves 12 in the heat pipes 11 of the middle battery string 3, which are arranged between the container 7 of the warm-side reactor and the middle battery string 3, are closed, no heat transfer takes place from the container 7 to the battery string 3.In order that heat can be dissipated from the middle battery string 3 to the container 8 of the cold side reactor in order to cool the latter, the valves 12 arranged between the container 8 and the middle battery string 3 are opened in the heat pipes 11 extending through the middle battery string 3.Once the traction battery 1 has been sufficiently cooled, all the cold-side valves 12 in the heat pipes, i.e. the twelve valves 12 arranged between the cold-side heat exchangers 14 or the container 8 of the cold-side reactor and the traction battery 1, can be closed. In order to stop the reaction in the thermochemical heat storage device 6, the valve 10 in the reactor connecting line 9 is also switched back to the closed position.Regeneration, i.e. charging of the thermochemical heat storage device 6, is expediently carried out as soon as waste heat from one or more component(s) of the electric vehicle is available, which is not supplied any other way of use, so that no additional energy consumption is required for charging the thermochemical heat storage device 6. The waste heat which is otherwise discharged unused to the environment can be fed to the container 7 of the warm-side reactor for regeneration. In the thermochemical heat storage device 6, this thermal energy can be stored almost without losses even over long periods of time, in particular even several weeks, in order to then be called up again in a simple and reliable manner if necessary, in particular for the next cold start of the electric vehicle.The thermochemical heat storage device 6 can also be charged using the electric heating device 15 by heating the warm-side heat transfer medium by means of the electric heating device 15 and transferring heat from the warm-side heat transfer medium to the container 7 of the warm-side reactor. The electric heating device 15 can be supplied with electric energy, for example, during a charging process of the battery 1 in order to heat the heat-side heat transfer medium.In addition, the thermochemical heat storage device 6 can be recharged by cooling the container 8 of the cold-side reactor. For this purpose, the vehicle air conditioning system can serve as a heat sink. Specifically, the container 8 of the cold-side reactor can be cooled by means of the cold-side heat transfer medium.Alternatively or additionally, at low external temperatures, the ambient air can also serve as a heat sink in order to cool the container 8 of the cold side reactor.For the charging process of the thermochemical heat storage device 6, the valve 10 in the reactor connecting line 9 is opened and heat is supplied to the container 7 of the hot-side reactor and, alternatively or simultaneously, the container 8 of the cold-side reactor is cooled.All valves 12 in the heat pipes 11 extending through the middle battery bank 3 are expediently closed during the charging process, so that the thermal energy supplied or discharged serves exclusively for charging and no undesired heating and / or cooling of the middle battery bank 3 takes place.

Claims

Battery system comprising a battery, in particular a rechargeable battery (1), preferably a traction battery of an electric or hybrid vehicle, and a battery tempering device having a thermochemical heat storage device (6) and at least one heat transfer element (11) which is in thermally conductive contact with the thermochemical heat storage device (6), wherein the heat transfer element (11) has at least one switching element by means of which a heat flow along the heat transfer element (11) can be interrupted, and wherein the heat transfer element (11) is designed such that it can be brought into thermally conductive contact with a battery (1) to be heated and / or cooled, wherein the battery (1) is in thermally conductive contact with the heat transfer element (11) or with the heat transfer elements (11) of the battery tempering device, and comprises two or more battery strings (2, 3, 4) connected electrically in parallel, wherein the thermochemical heat storage device (6) is in heat-conducting contact with exactly one of the battery strings (3) via a heat transfer element (11) or a plurality of heat transfer elements (11) connected in parallel, and the battery is designed such that the battery string which is in heat-conducting contact with the thermochemical heat storage device can be operated in an insulated manner.Battery system according to Claim 1, characterized in that the battery (1) comprises three or more battery strings (2, 3, 4) lying next to one another, and the thermochemical heat storage device (6) is in heat-conducting contact only with the middle or a middle battery string (3) via the heat transfer element (11) or the plurality of heat transfer elements (11).Battery system according to Claim 1 or 2, characterized in that the battery temperature-control device comprises at least one warm-side heat exchanger (13) and / or at least one cold-side heat exchanger (14), wherein the at least one warm-side heat exchanger (13) and / or the at least one cold-side heat exchanger (14) is in thermally conductive contact with the battery (1) in each case via a heat transfer element (11) or via a plurality of heat transfer elements (11) connected in parallel.Battery system according to Claim 3, characterized in that the remaining battery string or the remaining battery strings (2, 4) which are not in heat-conducting contact with the thermochemical heat storage device (6) are each in heat-conducting contact with the warm-side heat exchanger (13) and / or the cold-side heat exchanger (14) via at least one heat transfer element (11) or via a plurality of heat transfer elements (11) connected in parallel.Battery system according to one of the preceding claims, characterized in that the battery tempering device comprises a plurality of heat transfer elements (11) connected in parallel, which are in heat-conducting contact with the thermochemical heat storage device (6).Battery system according to Claim 5, characterized in that the thermochemical heat storage device (6) comprises a cold-side reactor and a hot-side reactor, each of which has at least one container (7, 8), in which an in particular solid storage medium for accommodating a reaction medium is provided, and wherein the hot-side reactor and the cold-side reactor are in thermally conductive contact in each case with a heat transfer element (11) or with a plurality of heat transfer elements (11) connected in parallel, and the container or containers (7) of the hot-side reactor are connected in fluidic terms to the container (8) or the containers (8) of the cold-side reactor via a reactor connecting line (9), wherein the reactor connecting line (9) is designed such that it can be switched over between an open and a closed state.Battery system according to Claim 6, characterized in that the storage medium of the hot-side reactor and / or the storage medium of the cold-side reactor comprises zeolite or silica gel or salts or a hydride-forming material or is formed therefrom.Battery system according to Claim 6 or 7, characterized in that the hot-side reactor and the cold-side reactor are provided with different storage media which differ with regard to their temperature-dependent and pressure-dependent equilibrium states when the reaction medium is absorbed.Battery system according to one of Claims 6 to 8, characterized in that a reaction medium is provided in the container or containers (7) of the hot-side reactor and / or in the container or containers (8) of the cold-side reactor, wherein in particular the reaction medium comprises water or hydrogen or ammonia or is formed therefrom.Battery system according to one of the preceding claims, characterized in that the thermochemical heat storage device (6) is or can be coupled to a heat source and / or a heat sink in a heat-conducting manner.Battery system according to one of Claims 6 to 9 and Claim 10, characterized in that the warm-side reactor of the thermochemical heat storage device (6) is or can be coupled to a heat source in a heat-conducting manner and / or the cold-side reactor of the thermochemical heat storage device (6) is or can be coupled to a heat sink in a heat-conducting manner.Battery system according to one of the preceding claims, characterized in that the battery temperature control device comprises at least one heat exchanger (13, 14) which is in heat-conducting contact with a heat transfer element (11) or with a plurality of heat transfer elements (11) connected in parallel, wherein the at least one heat exchanger (13, 14) is or can be coupled to a heat source and / or a heat sink in a heat-conducting manner.Battery system according to Claim 12, characterized in that the battery tempering device comprises a plurality of heat exchangers, in particular at least one warm-side heat exchanger (13) and / or at least one cold-side heat exchanger (14), which are each in heat-conducting contact with a heat transfer element (11) or with a plurality of heat transfer elements (11) connected in parallel, wherein the at least one warm-side heat exchanger (13) is or can be coupled to a heat source in a heat-conducting manner and the at least one cold-side heat exchanger (14) is or can be coupled to a heat sink in a heat-conducting manner.Battery system according to one of the preceding claims, characterized in that the battery temperature control device comprises an electrical heating device (15) serving as a heat source.Battery system according to one of the preceding claims, characterized in that at least one heat transfer element (11) is designed as a heat pipe, in particular all heat transfer elements (11) are designed as heat pipes.Battery system according to one of the preceding claims, characterized in that all heat transfer elements (11) each have at least one switching element (12), by means of which a heat flow along the respective heat transfer element (11) can be interrupted, and all heat transfer elements (11) are designed in such a way that they can be brought into heat-conducting contact with a battery (1) to be heated and / or cooled.Vehicle, in particular motor vehicle, preferably electric vehicle, having a battery system according to one of Claims 1 to 16.Vehicle according to claim 17, characterised in that a heat transfer medium circuit is provided, in particular for cooling the vehicle engine and / or other vehicle components which heat up during operation of the vehicle, and the thermochemical heat storage device (6) comprises a cold side reactor and a warm side reactor, wherein the warm side reactor is in heat-conducting contact with the heat transfer medium circuit.Method for heating and / or cooling a battery (1), in particular a rechargeable battery, preferably a traction battery of an electric vehicle, in particular using a battery system according to one of Claims 1 to 16, in which the battery (1) is heated by means of a thermochemical heat storage device (6), wherein a battery (1) is operated with two or more battery strings (2, 3, 4) connected electrically in parallel, and wherein only one of the battery strings (3) is heated by means of the thermochemical heat storage device (6), and initially only that battery string (3) which is heated by means of the thermochemical heat storage device (6) is loaded.Method according to Claim 19, characterized in that the battery (1) is heated by means of the thermochemical heat storage device (6) during the cold start phase and, in the case of a cold start, only that battery string which is heated by means of the thermochemical heat storage device (6) is initially charged.Method according to claim 19 or 20, wherein electrical energy from the battery string (3) heated by means of the thermochemical heat storage device (6) is used to electrically heat the remaining battery string or strings (2, 4).Method according to one of Claims 19 to 21, wherein a battery (1) of an electric or hybrid vehicle, in particular a traction battery of the electric or hybrid vehicle, is operated, and waste heat of the electric or hybrid vehicle is used to recharge the thermochemical heat storage device (6) by heating and / or an electric heating device is used to recharge the thermochemical heat storage device (6) by heating and / or a refrigerant circuit of the electric or hybrid vehicle is used to recharge the thermochemical heat storage device (6) by cooling.

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