Limp Home Mode for an electric vehicle

Abstract

Method (400) for increasing the range of a vehicle (100) driven by an electric motor, the method (400) comprising - determining (401) that a fill level reserve (206, 207) of an energy storage device (102) of the vehicle (100) is to be used for operating the electric motor; wherein the energy storage device (102) is configured to store electrical energy; wherein the fill level reserve (206, 207) lies outside a fill level range (205) provided for the energy storage device (102); - in response thereto, using (402) electrical energy from the fill level reserve (206, 207) of the energy storage device (102) to operate the electric motor of the vehicle (100); characterized in that - the fill level reserve (206, 207) comprises an upper fill level reserve (207), in which a fill level of the energy store (102) is brought above a maximum permissible fill level (203); and - during a charging process of the energy storage device (102) it is determined that the upper fill level reserve (207) is to be used.

Description

[0001] The invention relates to a method and a corresponding device for increasing the range of an electric vehicle.

[0002] Vehicles with an electric drive (i.e., with an electric motor used to propel the vehicle) typically include an energy storage device configured to store electrical energy for operating the electric motor. The electrical energy for propelling the vehicle (also referred to as traction energy) is typically stored electrochemically in the energy storage device. Example energy storage devices include one or more lithium-ion-based storage cells.

[0003] The electric energy storage system has a limited capacity for storing traction energy. However, the range achievable with this limited capacity is currently relatively small compared to that of a vehicle with a combustion engine. Furthermore, the number of public charging stations for electric vehicles is currently relatively limited. Therefore, there is an increased risk that an electric vehicle will not be able to reach its desired destination with the available electrical energy and may even break down.

[0004] For further information on the state of the art, please refer to DE 10 2008 009 568 A1 and DE 10 2010 034 444 A1.

[0005] This document addresses the technical challenge of efficiently reducing the risk of an electric vehicle not having sufficient electrical energy to reach a desired destination. In particular, it aims to efficiently enable an electric vehicle driver to increase the range of the electric vehicle when needed.

[0006] The object is achieved by the independent claims. Advantageous embodiments are described, inter alia, in the dependent claims.

[0007] According to one aspect, a method for increasing the range of a vehicle powered by an electric motor is described. The vehicle is, for example, a road vehicle, such as a passenger car or a truck. The method includes determining that a reserve charge level of an energy storage device of the vehicle should be used to operate the electric motor.

[0008] The energy storage device is configured to store electrical energy, wherein the amount of electrical energy in the energy storage device is typically indicated by a fill level (also referred to as state of charge, SOC) of the energy storage device. The energy storage device usually comprises one or more storage cells, e.g. one or more Li-ion based storage cells. The energy storage device is usually operated in a standard operating mode in which the energy storage device is not fully charged and / or not fully discharged in order to achieve the longest possible service life of the energy storage device (i.e. the highest possible number of storage cycles). The energy storage device can, for example, be discharged to a minimum permissible fill level (where the minimum permissible fill level is greater than 0%) and / or charged to a maximum permissible fill level (where the maximum permissible fill level is less than 100%) in the standard operating mode.In other words, in standard operating mode, the energy storage device can be operated within a fill level range intended (or permitted) for the energy storage device. The intended fill level range can be limited downwards by the minimum permissible fill level and / or upwards by the maximum permissible fill level.

[0009] The fill level reserve lies outside the fill level range intended for the energy storage device. The fill level reserve can, for example, comprise a lower fill level reserve, in which the fill level of the energy storage device is below the minimum permissible fill level (possibly down to a minimum possible fill level of, for example, 0%). Alternatively or additionally, the fill level reserve can comprise an upper fill level reserve, in which the fill level of the energy storage device is above the maximum permissible fill level (possibly up to a maximum possible fill level of, for example, 100%).

[0010] Typically, operating the energy storage device within the intended fill level range results in a statistically less reduction in its service life than operating it within the fill level reserve. Therefore, it is usually advantageous (for the service life of the energy storage device) to operate the energy storage device in standard operating mode, i.e., within the intended fill level range. On the other hand, the fill level reserve of the energy storage device should only be used in exceptional cases, since using the fill level reserve of the energy storage device typically statistically reduces the service life of the energy storage device (compared to using it exclusively within the intended fill level range).

[0011] The method thus includes determining that (exceptionally) the fill level reserve of the energy storage device should be used to operate the vehicle's electric motor. This operating mode of the energy storage device can be referred to as a capacity-extending operating mode of the energy storage device. It can thus be determined that the capacity-extending operating mode of the energy storage device should be activated, in which not only the intended fill level range but also the fill level reserve of the energy storage device is used to operate the electric motor to drive the vehicle.

[0012] The method further comprises, in response to determining that the capacity-extending operating mode of the energy storage device is to be activated, using electrical energy from the fill level reserve of the energy storage device to operate the electric motor of the vehicle (i.e., to propel the vehicle). The use of the fill level reserve of the energy storage device can be limited to a predefined number of charging cycles of the energy storage device (e.g., to a single charging cycle). That is, the method can further comprise restricting the use of the fill level reserve of the energy storage device to a predefined, limited number of charging cycles. After the limited number of charging cycles, the energy storage device can automatically transition from the capacity-extending operating mode to the standard operating mode. The capacity-extending operating mode can then, if necessary, only be activated again by an explicit request / input from a user.

[0013] The method described in this document can efficiently expand the usable capacity of the energy storage system, thus increasing the range of a vehicle when needed. Furthermore, the selective provision of the energy storage system's fill level reserve can limit damage to the energy storage system.

[0014] Determining that the fill level reserve of the energy storage device should be used can comprise capturing an input from a user of the vehicle via an input / output unit of the vehicle. In particular, it may be necessary for the user of the vehicle (e.g. the driver of the vehicle or a passenger of the vehicle) to explicitly request the fill level reserve of the energy storage device via a human-machine interface of the vehicle. Furthermore, it can be determined whether the user of the vehicle accepts one or more conditions (e.g. changes to warranty conditions for the energy storage device and / or payment conditions for the use of the fill level reserve of the energy storage device) for the use of the fill level reserve. This can also be determined via the human-machine interface of the vehicle. The use of electrical energy from the fill level reserve can, if necessary,only be enabled if it is determined that the vehicle user has accepted the one or more conditions. In other words, the activation of the capacity-extending operating mode of the energy storage device may only occur if the user has accepted the one or more conditions. On the other hand, the energy storage device may remain in the standard operating mode.

[0015] By requiring explicit input from a vehicle user and by optionally linking the use of the energy storage's fill level reserve to one or more conditions, damage to the energy storage system caused by excessive use of the fill level reserve can be limited. Furthermore, the use of the fill level reserve can be offered to a user as a value-added feature of the vehicle (possibly for a fee).

[0016] The method may further comprise activating one or more measures by which the consumption of electrical energy by the vehicle is reduced, while electrical energy from the fill level reserve is used to operate the electric motor. It can be assumed that when a user activates the capacity-extending operating mode of the energy storage device, the user of the vehicle wishes to maximize the range of the vehicle. It may therefore be advantageous for one or more consumption-reducing measures (e.g., deactivating an air conditioning system and / or limiting the driving speed of the vehicle) to be carried out automatically if necessary when the capacity-extending operating mode of the energy storage device is activated. In this way, the range of the vehicle can be further increased.

[0017] As already explained above, the fill level reserve can include a lower fill level reserve, in which the fill level of the energy storage device falls below the minimum permissible fill level. The lower fill level reserve can be provided while the vehicle is driving to increase the vehicle's range (e.g., to reach a destination). In particular, it can be determined while the vehicle is driving that the lower fill level reserve should be used. This allows a so-called LIMP HOME function to be provided for the vehicle.

[0018] The fill level reserve includes an upper fill level reserve, which raises the energy storage level above the maximum permissible level. During a charging process of the energy storage system (e.g., at a charging station), it is determined that the upper fill level reserve should be used. This allows the amount of electrical energy available for an upcoming trip to be increased in advance.

[0019] According to a further aspect, a control unit (e.g., a control device) for a vehicle is described. The vehicle includes an electric motor for driving the vehicle. The control unit is configured to determine that a fill level reserve of an energy storage device of the vehicle is to be used to operate the electric motor. The energy storage device is configured to store electrical energy, and the fill level reserve of the energy storage device lies outside a fill level range permitted (or intended) for the energy storage device. This means that the energy storage device is typically operated within the fill level range by default. The control unit is further configured to cause electrical energy from the fill level reserve of the energy storage device to be used to operate the electric motor of the vehicle.

[0020] The energy storage device may comprise one or more storage cells whose service life decreases statistically significantly when they are charged to a level above a maximum permissible level and / or when they are discharged to a level below a minimum permissible level. In particular, the service life may decrease more sharply in the aforementioned cases than if the one or more storage cells are operated exclusively below the maximum permissible level and / or above the minimum permissible level.

[0021] The vehicle can be configured to operate the energy storage device exclusively within the permissible fill level range in the standard operating mode. Thus, in the standard operating mode, the fill level reserve of the vehicle's energy storage device is not used to operate the electric motor. On the other hand, in the capacity-extending operating mode, the fill level reserve can also be used in addition to the permissible fill level range.

[0022] According to a further aspect, a vehicle (e.g. a passenger car, a truck or a motorcycle) is described which comprises the control unit described in this document.

[0023] According to another aspect, a software (SW) program is described. The SW program can be configured to be executed on a processor (e.g., on a control unit) and thereby to carry out the method described in this document.

[0024] According to a further aspect, a storage medium is described. The storage medium may comprise a software program configured to be executed on a processor and thereby to carry out the method described in this document.

[0025] The invention will be described in more detail below with reference to exemplary embodiments. Fig. 1 exemplary components of a vehicle; Fig. 2 example filling levels of an energy storage device; Fig. 3 exemplary effects of a charging cycle on the lifetime of an energy storage device; and Fig. 4 a flowchart of an exemplary method for the selective provision of energy reserves for an electric vehicle.

[0026] As stated at the beginning, this document addresses the technical task of enabling the user of an electric vehicle to efficiently increase the range of the electric vehicle when necessary.

[0027] Fig. 1 shows a block diagram with exemplary components of a vehicle 100. In particular, the vehicle 100 includes an energy storage device 102 configured to provide electrical energy for operating an electric motor of the vehicle 100. The energy storage device 102 is configured to determine a charge level (also referred to as state of charge, SOC) of the energy storage device 102 and provide it to a control unit 101. The control unit 101 can be configured to determine a remaining range of the vehicle 100 based on the charge level of the energy storage device 102.

[0028] The vehicle 100 may further comprise a navigation unit 104 configured to determine a position of the vehicle 100 and / or a planned route for the vehicle 100. The control unit 101 may be configured to determine whether the vehicle 100 can travel the planned route given the remaining range. For example, it may be determined that the planned route is too long given the current charge level of the energy storage device 102, and thus the destination cannot be reached.

[0029] To increase the service life of an energy storage device 102 (in particular an electrochemical energy storage device, such as a Li-ion-based energy storage device), an energy storage device 102 is typically operated in a fill level range through which the effectively available capacity of the energy storage device 102 is reduced compared to a maximum capacity of the energy storage device 102. This is exemplified in Fig. 2. The energy storage device 102 has a maximum possible capacity, which is represented by the entire bar. The maximum possible capacity is reached at a maximum possible fill level 204 (of typically 100% SOC). To increase the service life of the energy storage device 102, the energy storage device 102 is typically only charged to a maximum permissible fill level 203 (of typically 80-90% SOC). The maximum permissible fill level 203 is below the maximum possible fill level 204, so that the energy storage device 102 has an effectively available capacity that is less than the maximum possible capacity of the energy storage device 102.

[0030] Analogously, it is typically advantageous not to completely empty the energy storage device 102 (to the minimum possible fill level 201, e.g., 0% SOC). Instead, the energy storage device 102 is discharged during normal operation (i.e., in a standard operating mode) to a minimum permissible fill level 202 (e.g., 10-20% SOC) in order to increase the service life of the energy storage device 102.

[0031] During normal operation of an electric vehicle (i.e., in the standard operating mode), the energy storage device 102 is thus operated between a minimum permissible fill level 202 and a maximum permissible fill level 203. The effectively available (i.e., directly usable) capacity of the energy storage device 102 is thus determined from the capacity lying between the minimum permissible fill level 202 and the maximum permissible fill level 203. By limiting the fill levels, the longest possible service life of the energy storage device 102 can be achieved. On the other hand, it is to be expected that operating the energy storage device 102 outside the permissible fill level range 205 between the fill levels 202 and 203 will result in a relatively significant reduction in the service life of the energy storage device 102.

[0032] Fig. 3 illustrates, by way of example, the reduction in the service life of an energy storage device 102 caused by a charging cycle. The minimum or maximum actual fill level 301 that occurred during the charging cycle of the energy storage device 102 is plotted on the x-axis, and the reduction 302 in the service life of the energy storage device 102 (in the number of charging cycles still available) is shown on the y-axis. It can be seen that the service life of the energy storage device 102 decreases more sharply when operated outside the permissible fill level range 205 than when operated within the permissible fill level range 205. For example, the service life of the energy storage device 102 is statistically reduced by exactly one charging cycle if the energy storage device 102 is operated exclusively within the permissible fill level range 205 in a current charging cycle.On the other hand, use of the energy storage device 102 in the current charging cycle outside of the permissible fill level range 205 leads to a statistical reduction 302 of the service life by more than one charging cycle.

[0033] The vehicle 100 may include an input / output unit 103 configured to output information (in acoustic and / or optical form) to a user of the vehicle 100 and / or to capture inputs from the user of the vehicle 100. In particular, the input / output unit 103 may provide a human-machine interface (i.e., human-machine interface, HMI). A user may be enabled to initiate, via the input / output unit 103 of the vehicle 100, the provision of energy reserves resulting from the operation of the energy storage device 102 outside the permissible fill level range 205.

[0034] For example, the user of the vehicle 100 can use the input / output unit 103 to cause a lower fuel level reserve 206 (below the minimum permissible fuel level 202) to be provided at least partially for operating the electric motor of the vehicle 100 while driving the vehicle 100. This allows the occupant of the vehicle 100 to use the lower fuel level reserve 206 to increase the range of the vehicle 100 in order to reach a desired destination.

[0035] Furthermore, the control unit 101 can be configured to cause one or more control units 105 of the vehicle 100 to switch to energy-saving mode if it has been detected that the user of the vehicle 100 intends to use the lower fuel level reserve 206. For example, an air conditioning system of the vehicle 100 can be deactivated and / or a driving speed and / or acceleration of the vehicle 100 can be limited. In other words, the control unit 101 can be configured to take measures to reduce energy consumption of the vehicle 100 in order to further increase the range of the vehicle 100 achievable with the lower fuel level reserve 206.

[0036] Alternatively or additionally, the user of the vehicle 100 can use the input / output unit 103 to cause an upper fill level reserve 207 (above the maximum permissible fill level 203) to be made available at least partially for the operation of the electric motor of the vehicle 100 during a charging process of the vehicle 100. The energy storage device 102 can then be charged, if necessary, up to the maximum possible fill level 204 during the charging process. This allows the occupant of the vehicle 100 to prepare the vehicle 100 for a particularly long journey. In particular, the range of the vehicle 100 can be increased in advance of a journey. Even when the upper fill level reserve 207 is used, the control unit 101 can initiate consumption-reducing measures if necessary.

[0037] The control unit 101 can be configured to output information regarding the activation of the fill level reserves 206, 207 to the user of the vehicle 100 via the input / output unit 103 and / or to obtain confirmations from the user of the vehicle 100. For example, the user of the vehicle 100 can be informed that the activation of the fill level reserves 206, 207 can lead to a reduction in the service life of the energy storage device 102 and that the activation of the fill level reserves 206, 207 may potentially impair a warranty for the energy storage device 102. Furthermore, the user of the vehicle 100 can be requested to confirm certain conditions for the activation of the fill level reserves 206, 207. For example, the user of the vehicle 100 may be asked to accept changed warranty conditions for the energy storage device 102 and / or to make a payment for the use of the fill level reserves 206, 207.A payment transaction can be processed via the input / output unit 103 if necessary.

[0038] Through a human-machine interface provided via the input / output unit 103, the user of the vehicle 100 can thus activate a LIMP HOME mode of the vehicle 100. In this LIMP HOME mode, the vehicle 100 can use the energy reserves 206, which are typically stored in the energy storage device 102 for service life considerations, for the traction of the vehicle 100. At the same time, the vehicle 100 can be placed in a particularly energy-efficient mode. For example, the driving speed and / or the acceleration of the vehicle 100 can be limited, and / or auxiliary consumers, such as the air conditioning system, can be switched off.

[0039] In order to resolve a conflict of objectives resulting from the activation of the LIMP HOME mode with a warranty for the energy storage device 102, the activation of the LIMP HOME mode can be made dependent on the payment of a fee by the user of the vehicle 100. The amount thus collected can then be used to cover increased warranty claims that may arise from the activation of the LIMP HOME mode.

[0040] As already explained above, an upper and / or a lower fill level reserve 206, 207 can be made available. Thus, an extended range can be provided both for short distances (i.e., for a so-called LIMP HOME) and for long distances. The method described in this document thus makes it possible to increase the range of an electric-powered vehicle 100 in a flexible and simple manner, if necessary.

[0041] Fig.4 shows a flowchart of an exemplary method 400 for increasing the range of a vehicle 100 powered by an electric motor. The method 400 includes determining 401 that a fill level reserve 206, 207 of an energy storage device 102 of the vehicle 100 should be used to operate the electric motor. The energy storage device 102 is configured to store electrical energy for operating the electric motor. In a standard operating mode, the energy storage device is operated within a designated or permissible fill level range 205. In this way, a reduction in the service life of the energy storage device 102 in the standard operating mode can be kept as low as possible, while still maintaining sufficient storage capacity for operating the electric motor.

[0042] On the other hand, it can be determined that the energy storage device (typically as an exception) should be operated in a capacity-expanding operating mode. This means that it can be determined that, in addition to the intended fill level range 205, a fill level reserve 206, 207 of the energy storage device 102 should be used for the operation of the electric motor. The fill level reserve 206, 207 lies outside the fill level range 205 intended for the energy storage device 102 and thus expands the available (i.e., usable) storage capacity of the energy storage device 102. On the other hand, by operating the energy storage device 102 with the fill level reserve 206, 207, the service life of the energy storage device 102 is typically statistically reduced (compared to exclusive operation within the intended fill level range 205). The determination 401 that the fill level reserve 206, 207 should be used (i.e.,that the capacity-expanding operating mode is to be activated) can be done via a human-machine interface of the vehicle 100.

[0043] The method 400 further comprises, in response to determining 401 that the fill level reserve 206, 207 is to be used, using 402 electrical energy from the fill level reserve 206, 207 of the energy storage device 102 to operate the electric motor of the vehicle 100. Typically, the fill level reserve 206, 207 is only used in a single charging cycle of the energy storage device 102 (or only a certain number of charging cycles). This means that the energy storage device 102 typically automatically transitions back from the capacity-extending operating mode to the standard operating mode. In particular, it may be necessary for the capacity-extending operating mode to be explicitly reactivated via a human-machine interface of the vehicle 100 for each charging cycle of the energy storage device 102 (or for each group of charging cycles).

[0044] The selective provision of a capacity-extending operating mode for the energy storage device 102 of the vehicle 100 makes it possible to flexibly increase the range of the vehicle 100. On the other hand, an automatic return to the standard operating mode prevents the energy storage device 102 from being damaged by regular activation of the capacity-extending operating mode (i.e., by regular use of the fill level reserve 206, 207).

[0045] The present invention is not limited to the embodiments shown. In particular, it should be noted that the description and figures are intended only to illustrate the principle of the proposed methods, devices, and systems.

Claims

[1] Method (400) for increasing the range of a vehicle (100) driven by an electric motor, the method (400) comprising - determining (401) that a fill level reserve (206, 207) of an energy storage device (102) of the vehicle (100) is to be used for operating the electric motor; wherein the energy storage device (102) is configured to store electrical energy; wherein the fill level reserve (206, 207) lies outside a fill level range (205) provided for the energy storage device (102); - in response thereto, using (402) electrical energy from the level reserve (206, 207) of the energy storage device (102) to operate the electric motor of the vehicle (100); characterized by , that - the fill level reserve (206, 207) comprises an upper fill level reserve (207), in which a fill level of the energy storage device (102) is brought above a maximum permissible fill level (203); and - during a charging process of the energy storage device (102) it is determined that the upper fill level reserve (207) is to be used. [2] Method (400) according to claim 1, wherein during operation of the energy storage device (102) within the intended fill level range (205) a service life of the energy storage device (102) is statistically reduced less than during operation of the energy storage device (102) within the fill level reserve (206, 207). [3] Method (400) according to one of the preceding claims, wherein - the intended fill level range (205) extends from a minimum permissible fill level (202) to a maximum permissible fill level (203) of the energy storage device (102); and - the fill level reserve (206, 207) - comprises a lower fill level reserve (206), in which a fill level of the energy storage device (102) is below the minimum permissible fill level (202); and / or - an upper fill level reserve (207) in which the fill level of the energy store (102) is above the maximum permissible fill level (203). [4] Method (400) according to one of the preceding claims, wherein the determining (401) comprises detecting an input from a user of the vehicle (100) via an input / output unit (103) of the vehicle (100). [5] Method (400) according to one of the preceding claims, wherein - the method (400) further comprises determining whether a user of the vehicle (100) accepts one or more conditions for using the fill level reserve (206, 207); and - electrical energy from the fill level reserve (206, 207) is only used to operate the electric motor if it is determined that the user of the vehicle (100) accepts the one or more conditions. [6] Method (400) according to one of the preceding claims, further comprising activating one or more measures by which consumption of electrical energy by the vehicle (100) is reduced while electrical energy from the fill level reserve (206, 207) is used for the operation of the electric motor. [7] Method (400) according to one of the preceding claims, wherein - the fill level reserve (206, 207) comprises a lower fill level reserve (206), in which a fill level of the energy storage device (102) falls below a minimum permissible fill level (202); and - during a journey of the vehicle (100) it is determined that the lower fill level reserve (206) should be used. [8] Control unit (101) for a vehicle (100), wherein the vehicle (100) comprises an electric motor for driving the vehicle (100), wherein the control unit (101) is arranged - to determine that a fill level reserve (206, 207) of an energy storage device (102) of the vehicle (100) is to be used for the operation of the electric motor; wherein the energy storage device (102) is configured to store electrical energy; wherein the fill level reserve (206, 207) lies outside a fill level range (205) provided for the energy storage device (102); - to then cause electrical energy from the fill level reserve (206, 207) of the energy storage device (102) to be used to operate the electric motor of the vehicle (100) characterized by , that - the fill level reserve (206, 207) comprises an upper fill level reserve (207), in which a fill level of the energy storage device (102) is brought above a maximum permissible fill level (203); and - to determine during a charging process of the energy storage device (102) that the upper fill level reserve (207) is to be used. [9] Control unit (101) according to claim 8, wherein - the energy storage device (102) comprises one or more storage cells whose service life decreases statistically when they are charged to a fill level that is above a maximum permissible fill level (203) and / or when they are discharged to a fill level that falls below a minimum permissible fill level (202); and / or - the vehicle (100) is configured to operate the energy storage device (102) in a standard operating mode exclusively in the intended fill level range (205).

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