DE102016219624A1 - Method for controlling an electrical energy store - Google Patents

Abstract

The invention relates to a method for controlling an electrical energy store (2), in particular in a motor vehicle (1), in which the energy store (2) provides electrical energy for driving the motor vehicle (1), wherein the electrical energy store (2) is characterized by a first state of charge (SOC1), in which the energy store (2) provides a predetermined minimum power, and a second state of charge (SOC2), which is the fully charged state of the energy store (2) and decreases with its service life. The energy store (2) is controlled in a first operating phase (BP1) after its startup such that the charging of the energy store (2) via an external charging station at most up to a maximum charge state (MAX) is performed, a percentage value of 100% or is less of the second state of charge (SOC2). Furthermore, during operation of the electrical energy store (2) without charge via an external charging station, the electrical current and / or the electric power are measured, which are emitted and absorbed by the energy store (2), wherein by means of a temporal integration of the measured current and / or the measured power, the change in the state of charge (SOC) of the energy store (2) is detected and based on the detected change in the state of charge (SOC), a discharge of the energy store (2) from the maximum charge state (MAX) by a predetermined maximum charge amount (NH) allowed becomes. The maximum charge amount (NH) is set such that the maximum charge state (MAX) at startup of the energy store (2) minus the maximum charge amount (NH) corresponds to a charge state (MIN) that is above the first charge state (SOC1).

Description

The invention relates to a method for controlling an electrical energy store, in particular in a motor vehicle, as well as a corresponding motor vehicle.

In electrically powered vehicles, such as e.g. Electric vehicles or hybrid vehicles, electric energy storage are used, which provide electrical energy to drive the motor vehicle. There is the problem that the capacity of the energy storage is subject to fluctuations during its commissioning, the e.g. caused by manufacturing tolerances. Consequently, a fixed range of an electrically driven motor vehicle due to these fluctuations can not be specified exactly. In addition, there is an aging-related reduction in the capacity of the energy storage, resulting in an undesirable decrease in the range of the motor vehicle. Furthermore, the state of charge of the motor vehicle during its driving operation is conventionally estimated and the range determined on the basis of these estimated values. Due to estimation error corrections, there may be a sudden deviation in the range indicated to the driver, which is undesirable.

The object of the invention is to provide a method for operating an electrical energy storage, which compensates for fluctuations in the amount of energy provided by the energy storage in a predetermined period of time after the energy storage device is put into operation.

This object is achieved by the method according to claim 1. Further developments of the invention are defined in the dependent claims.

The method according to the invention serves to control an electrical energy store. The energy store is preferably provided in a motor vehicle, the energy store in this case providing electrical energy for driving the motor vehicle. Optionally, the electrical energy storage may also be provided for other applications. For example, it may be a buffer of energy from a regenerative energy source (e.g., wind or photovoltaic). The energy storage device may be configured differently and in a preferred embodiment comprises a plurality of battery cells, such as e.g. Lithium-ion batteries. The energy store is characterized by a first state of charge and a second state of charge. In the first state of charge, the energy store provides a predetermined minimum power. If the energy store is provided in a motor vehicle, the first state of charge is characterized by the fact that, when the first state of charge is not reached, the motor vehicle can no longer be driven by the energy store since it no longer supplies enough power. The first state of charge thus represents the physical power limit for driving the motor vehicle through the energy store. The second state of charge corresponds to the fully charged state of the energy store. This state of charge decreases with the operating time of the energy store. According to the invention, the energy store is controlled in a first operating phase after its (initial) startup as described below.

The charging of the energy storage is performed via an external charging station at most up to a maximum state of charge, which is a percentage value of 100% or less of the second state of charge. Achieving the maximum state of charge may e.g. be detected via a known state of charge estimate of the energy storage.

On the other hand, if the electrical energy store is operated without charge via an external charging station (which corresponds to the driving operation of the motor vehicle when using the energy store in a motor vehicle), the electric current is measured, which is output by the energy store and possibly also recorded (eg by recuperation). Alternatively or additionally, it is also possible to measure the electrical power which is output by the energy store and possibly also recorded. By means of a temporal integration of the measured current and / or the measured power, the change in the state of charge of the energy store is detected. Based on the detected change in the state of charge, a discharge of the energy store is permitted from the (current) maximum charge state by a predetermined maximum charge amount. In other words, the discharge of the energy storage device is measured and energy extraction from the energy storage device is then no longer permitted (i.e., the drive of the vehicle stopped) when the measured discharge corresponds to the predetermined maximum charge amount. The maximum charge amount is set such that the maximum charge state at startup of the energy storage minus the maximum charge amount corresponds to a charge state that is above the first charge state.

The method according to the invention is characterized in that the maximum charge amount permitted for removal from the energy store is fixed and the achievement of this charge quantity is detected directly via a current or power measurement. Due to the fixed predetermined maximum charge amount, which is also referred to below as Nutzhub, are fluctuations in the capacity of the energy storage for the user and in particular a driver in a motor vehicle no longer perceptible. When using the energy store in a motor vehicle, the range of the motor vehicle is determined based on the measured amount of charge taken in relation to the fixed Nutzhub and output via a user interface in the motor vehicle. In addition, the method has the advantage that the direct measurement of the charge quantity does not lead to any estimation errors, as is the case with charge state estimates. In particular, corrections of faulty estimates of the state of charge have no effect on the range of the motor vehicle. Furthermore, an aging-related decrease in the capacity of the energy storage for the driver is no longer perceptible and does not lead to a range change.

In a particularly preferred embodiment of the method according to the invention, in the first operating phase, the percentage value of the second state of charge, which defines the maximum charge state, is less than 100%. Preferably, it is between 95% and 99% of the second state of charge. In contrast to the conventional method, the energy storage is thus no longer charged to the fully charged state. In this way, loading in an area very close to the fully charged state is avoided. In this area occurs a degradation of the energy storage, which manifests itself in that the energy storage can be charged only with reduced power. By avoiding loading areas with degradation faster charging of the energy storage is guaranteed.

In a further particularly preferred embodiment, the maximum charge amount is between 80% and 90% of the difference between the second and the first charge state. A maximum charge amount of this magnitude leads to a slow capacity aging of the energy storage.

In a further preferred embodiment, the first operating phase is terminated when an estimated state of charge of the energy store when reaching a discharge around the maximum charge amount assumes a limit value at which the difference by which the limit value is greater than the first state of charge reaches a predetermined threshold. This ensures that the lower limit of the useful stroke does not reach the physical performance limit. The predetermined threshold is in a preferred variant between 2% and 3% of the maximum state of charge when starting the energy storage.

In a further variant of the method according to the invention, in a second operating phase, which directly follows the first operating phase, the percentage value of the second state of charge, which defines the maximum charge state, corresponds to the percentage value from the first operating phase. That is, in the second phase of operation is loaded via an external charging station at most to the same percentage value as in the first phase of operation. In contrast to the first operating phase, however, during operation of the energy store without charge via an external charging station (which corresponds to the driving operation of the motor vehicle when using the energy store in a motor vehicle) during the second operating phase, the state of charge of the energy store is estimated and based on this estimate a discharge of the energy store Energy storage permitted until the state of charge of the energy storage device reaches a threshold above the first state of charge, the threshold during the second phase of operation is constant. It is thus deviated in the second phase of operation of a current or power measurement for determining the discharge of the energy storage and estimated in a conventional manner, the state of charge. If the estimated state of charge reaches the above threshold, various actions can be taken. When using the electrical energy store in a motor vehicle, e.g. the drive of the motor vehicle can be stopped. Likewise, no remaining range can be displayed more or the motor vehicle can continue with reduced power until the electrical energy storage is completely empty.

In a preferred variant of the embodiment just described, the threshold value corresponds to the above limit value from the first operating phase, i. the limit when reaching the end of the first phase of operation is maintained in the second phase of operation.

In a further variant of the method according to the invention, the second operating phase is terminated when the difference between the maximum charge state and the threshold value reaches a predetermined charge amount. The predetermined amount of charge preferably corresponds to that amount of charge which, for a certain period of operation of the energy store, e.g. guaranteed by the vehicle manufacturer. In this way any warranty claims against the vehicle manufacturer can be avoided. Preferably, the above predetermined amount of charge is a predetermined percentage value of the maximum charge amount, the predetermined percentage value preferably being between 60% and 85%, and more preferably 70%.

In a further embodiment of the invention, in a third operating phase, which directly adjoins the second operating phase, the percentage value of the second state of charge, which defines the maximum state of charge, increased and / or the threshold value is reduced, so that a predetermined difference between the maximum state of charge and the threshold is maintained. In the third phase of operation is loaded analogous to the second phase of operation via an external charging station at most to the maximum state of charge and the operation of the energy storage without charge via an external charging station (which corresponds to the driving operation of the motor vehicle when using the energy storage in a motor vehicle), the state of charge of Energy storage estimated and based on this estimate, a discharge of the energy storage allowed until the state of charge of the energy storage reaches the threshold. The predetermined difference preferably corresponds to the predetermined amount of charge from the second operating phase. As described above, this amount of charge is preferably set to a value guaranteed for a certain period of operation of the energy storage. In this way it is achieved that the guaranteed amount of charge is provided as long as possible by the energy storage, whereby warranty claims are avoided.

In a further variant of the method according to the invention, in a fourth operating phase, which directly follows the third operating phase, the maximum state of charge is kept at 100% of the second state of charge and the threshold value on the first state of charge or the first state of charge plus a buffer. In analogy to the second and third operating phase is loaded in the fourth phase of operation via an external charging station at most to the maximum state of charge and during operation of the energy storage without charge via an external charging station (which corresponds to the driving operation of the motor vehicle when using the energy storage in a motor vehicle) estimated the state of charge of the energy storage and based on this estimate, a discharge of the energy storage allowed until the state of charge of the energy storage reaches the first state of charge or the first state of charge plus a buffer. In this phase of operation, the maximum available capacity of the energy storage is thus fully exploited.

In addition to the method described above, the invention relates to a motor vehicle, comprising an electrical energy storage, wherein the energy storage provides electrical energy for driving the motor vehicle and is characterized by a first state of charge, under which the motor vehicle is no longer drivable by the energy storage, and a second state of charge , which is the fully charged state of the energy storage and decreases with its service life. The motor vehicle is configured to control the energy store based on the method according to the invention or one or more preferred variants of the method according to the invention. In other words, the motor vehicle includes a control unit, which causes such control of the energy storage.

Embodiments of the invention are described below in detail with reference to the accompanying drawings.

Show it:

1 a schematic representation of a motor vehicle with an electrical energy storage, which is operated based on an embodiment of the method according to the invention;

2 a diagram showing the operation of an electrical energy storage in a motor vehicle according to the prior art, and

3 a diagram illustrating the operation of the electrical energy storage for the motor vehicle 1 according to one embodiment of the invention.

Hereinafter, an embodiment of the method according to the invention will be explained with reference to a motor vehicle in the form of an electric vehicle. Such an electric vehicle is in 1 shown and with the reference numeral 1 designated. For this electric vehicle is schematically a high-voltage energy storage 2 shown from a variety of battery cells. This energy storage 2 serves for the electric drive of the vehicle 1 via an electric motor (not shown). The motor vehicle has a charging connection (not shown), to which the energy store can be charged via an external charging station. The charging of the energy storage and its discharge during operation of the motor vehicle is via a schematically indicated control unit 3 regulated. The car 1 of the 1 does not need to be a pure electric vehicle, but it can also be a hybrid vehicle with the possibility of external charge (so-called plug-in hybrid vehicle).

Before on the inventive control of the energy storage 2 in the motor vehicle 1 is first received, a control according to the prior art with reference to 2 explained. 2 shows a diagram along the abscissa shows the aging or capacity aging A of a high-voltage energy storage in an electric vehicle. The capacity aging correlates with the duration or operating hours of the Energy storage since its first use, but also depends on many other factors. Along the ordinate of 2 and also the one described below 3 For example, the state of charge SOC is plotted based on a scale in which each percentage step corresponds to the same amount of charge at each time point. In other words, the state of charge SOC corresponds to the currently usable charge of the energy store divided by its rated capacity. By the dotted line K of 2 the capacity of the energy storage device is represented as a function of its aging A. The dashed line SOC2, the fully charged state of the energy storage is indicated, which correlates with the capacity K, but slightly less than the capacity, since current and voltage limits must be met during the charging process, so that a charge up to the capacity K is not possible is. The fully charged state SOC2 corresponds to the second state of charge within the meaning of the claims.

In addition to this fully charged state SOC2 there is also the state of charge SOC1, which represents the lower physical power limit and is indicated by a dashed line. Below this power limit, the motor vehicle can not be operated with the energy storage. The power limit SOC1 corresponds to the first state of charge in the sense of the claims and is constant over the operating time of the energy store - in contrast to the fully charged state SOC2.

In 2 is in the upper part of a distribution V reproduced, which indicates that respective energy storage are subject to fluctuations in terms of their capacity when used in the motor vehicle. Such fluctuations have different causes. Among other things, manufacturing tolerances lead to such fluctuations. By the vertical line L1, the commissioning of a corresponding energy storage in the motor vehicle is indicated. The initial capacity according to this line corresponds to an average capacity corresponding to the indicated distribution V. Due to capacity fluctuations according to the distribution V, other capacities can be present when commissioning the energy storage device, which can be larger or smaller. For the energy storage, however, a nominal capacity is specified, which is guaranteed by the manufacturer of the energy storage.

In the diagram of 2 is represented by the solid line MAX of the maximum state of charge, to which the energy storage is maximally charged by means of an external charging station. In contrast, indicated by the solid line MIN of the minimal charge state, to which the energy storage is maximally discharged when driving the motor vehicle. In 2 Furthermore, three operating phases P1, P2 and P3 are indicated, which are separated by the vertical line L2 and L3.

According to the in 2 In the case of the conventional control of the energy accumulator, the maximum charge state MAX is always chosen such that it substantially reaches fully charged state SOC2 of the energy store, whereby this fully charged state decreases with the duration of operation due to the aging of the energy store. In contrast to this, the minimum charge state is selected differently in different operating phases. In the first operating phase P1 is taken into account that the aging of the energy storage can be reduced by the Nutzhub, ie the difference between the maximum charge state MAX and the minimum charge state MIN is not chosen excessively large. As a result, in the operation phase P1, the minimum load state MIN is set to be much larger than the physical power limit SOC1.

Since, due to the decrease in the maximum state of charge, the useful stroke decreases markedly over time, the transition finally takes place into the operating phase P2. The transition to the operating phase P2 takes place when the guaranteed for the energy storage Nutzhub, for example, is 70% of the initial Nutzhubs reached. Subsequently, the minimum charge state MIN is changed in accordance with the maximum charge state MAX, so that in the operation phase P2, the guaranteed useful stroke is ensured. Finally, it is transferred to the operating phase P3, if the guaranteed Nutzhub can not be guaranteed due to the achievement of the physical power limit SOC2. In this case, the minimum charge state is maintained in the range of the physical power limit.

In the control of the energy storage according to 2 the state of charge of the energy storage is estimated and based on these estimates the achievement of the maximum state of charge and of the minimum state of charge is determined. The display of the state of charge or the range correlated therewith in the vehicle cockpit is thus based on these estimated values. This has the disadvantage that the range displayed in the vehicle already decreases shortly after commissioning of the motor vehicle or its energy storage, which can lead to customer dissatisfaction. Likewise, a vehicle delivered due to the capacity fluctuations of the energy storage have a much lower range than expected, which is also unsatisfactory for the buyer of the vehicle. In addition, estimation errors can occur in the determination of the state of charge, which can lead to a corresponding correction occurring in the detection of an estimation error sudden change in coverage in the vehicle cockpit and leads to confusion of the driver and associated dissatisfaction. Another problem of controlling the 2 is that the energy storage is always charged to the fully charged state. Since a degradation occurs just before reaching the fully charged state (ie, the energy storage can only be charged with reduced current due to reaching a maximum voltage of the battery cells), it takes a very long time until the charging process is completed.

In order to solve the above problems, the energy storage in the vehicle of the embodiment described herein is based on the diagram of FIG 3 controlled. 3 shows in analogy to 2 a diagram showing along the abscissa the aging A of the energy storage and along the ordinate the state of charge SOC. To clarify capacity fluctuations of the energy storage during commissioning is again in the upper range of 3 a distribution V indicated. Further shows 3 in the same way as 2 the capacity K of the energy storage device, the fully charged state SOC2 correlating with this capacity, and the lower physical power limit SOC1. The commissioning of the energy storage is in 3 indicated by the vertical line L1 '. In contrast to 2 There are now four operating phases BP1, BP2, BP3 and BP4, which are separated from each other by corresponding vertical lines L2 ', L3' and L4 '. The maximum permitted state MAX and the minimum permitted state MIN are analogous to those in 2 represented by solid lines.

The achievement of the maximum charge state MAX with external charge of the energy storage is in the control of the 3 analogous to 2 detected via a state of charge estimation. A major difference in the control of 3 opposite the 2 However, it is that the Nutzhub NH is fixed in an initial operating phase BP1 and no longer based on estimated states of charge, but on variables, ie on the basis of the current integral (ie the amount of charge) or the power integral (ie the amount of energy) is determined , In other words, during operation of the motor vehicle, after a charge of the energy store via an external charging station to the maximum charge state MAX, the change in the state of charge or the discharge of the energy store is detected via a current or power measurement.

If the current or power measurement indicates that the fixed effective load NH is used up, no further discharge of the energy store is permitted and the vehicle cockpit indicates that the energy store has been discharged. The range specification in the vehicle cockpit is thus based on the measurement of the consumption of a fixed effective lift NH. Consequently, the range indication is independent of the actual fully charged state of the corresponding energy store and of estimated values. It can be guaranteed in this way a constant range indication without fluctuations and thereby the customer satisfaction can be increased.

Another advantage of controlling the 3 is that in the operating phase BP1 and also in the subsequent operating phase BP2 and partially in the operating phase BP3 is not loaded to the fully charged state SOC2, but only up to a percentage value of less than 100% of this fully charged state (for example, between 95% and 99%). In this way, the achievement of the degradation of the energy storage is avoided at the end of the charging process, whereby the charging process can be performed faster.

Since the Nutzhub NH can not be maintained permanently due to the capacity decrease of the energy storage over time, is finally transferred to an operating phase BP2. This operating phase is initiated when the minimum charge state MIN reaches a limit value GW. The threshold is defined such that at this threshold, the difference between the minimum charge state MIN and the physical power limit SOC1 reaches a threshold that is, for example, between 2% and 3% of the maximum charge state when the energy store is started. In the second operating phase BP2 and in the further operating phases BP3 and BP4, the control of the electrical energy store is again based on the estimate of the charge states.

In the operating phase BP2, the minimum charge state is kept constant at the limit value GW and the maximum charge state decreases due to the aging-related reduction of the capacity of the energy store. However, in the operation phase BP2, the maximum charge state is kept at the same percentage value with respect to the fully charged state as in the operation phase BP1. Finally, the operating phase BP3 is transitioned when the actual payload reaches a percentage value of the initial payload NH. This percentage value may e.g. correlate with a capacity value that is guaranteed for a certain period of operation of the energy storage. At the beginning of the operating phase BP3, the minimum charge state MIN is at the threshold value SW, which corresponds to the limit value GW at the beginning of the second operating phase, since the minimum charge state remains constant within the second operating phase BP2.

In the operating phase BP3, the maximum state of charge and the minimum state of charge are changed in such a way that the useful stroke is maintained in this phase. For this purpose, in a first section of the operating phase BP3, the percentage value of the fully charged state SOC2, which is set for the maximum charge state MAX, is increased, so that the maximum charge state more and more approaches the fully charged state. If, based on this measure, the useful lift can no longer be guaranteed without exceeding the limit SOC2, the minimum charge state MIN is reduced, whereas the maximum charge state MAX corresponds to the fully charged state SOC2. As soon as a constant useful lift can no longer be maintained due to reaching the power limit SOC1, the operation phase BP4 is entered, in which the maximum charge state remains at the fully charged state and the minimum charge state essentially corresponds to the physical power limit SOC1, possibly taking into account a buffer ,

The embodiment of the invention described above has a number of advantages. In particular, in an initial phase of operation of the energy store after its startup, the energy available via the energy store is fixedly determined and determined by means of a current measurement or power measurement. In this way, a constant range for the vehicle can be ensured, and there are no sudden changes in the range due to capacity fluctuations or errors in the estimation of the state of charge. In addition, a rapid charging of the energy storage is ensured by the fact that the charging is only up to a maximum state of charge, which is below the fully charged state of the energy storage, so that is not or only partially loaded in a degradation phase of the energy storage.

LIST OF REFERENCE NUMBERS

1

motor vehicle

2

energy storage

3

control unit

A

Aging of the energy storage

SOC

SOC

V

distribution

P1, P2, P3

operating phases

BP1, BP2, BP3, BP4

 operating phases

L1, L1 '

Commissioning of the energy storage

L2, L3

Transitions between the operating phases P1 to P3

L2 ', L3', L4 '

Transitions between the operating phases BP1 to BP4

K

Capacity of the energy storage

SOC1

physical power limit

SOC2

Fully charged condition

MIN

Minimum state of charge

MAX

Maximum charge level

NH

Maximum charge amount (payload)

GW

limit

SW

threshold

Claims (15)

Method for controlling an electrical energy store ( 2 ), in particular in a motor vehicle ( 1 ), in which the energy storage ( 2 ) electrical energy for driving the motor vehicle ( 1 ), wherein the electrical energy store is characterized by a first state of charge (SOC1), in which the electrical energy store ( 2 ) provides a predetermined minimum power, and a second state of charge (SOC2), which is the fully charged state of the energy store ( 2 ) and decreases with its operating time, wherein the energy storage ( 2 ) is controlled in a first operating phase (BP1) after its startup in such a way that: - the charging of the energy store ( 2 ) is carried out via an external charging station at most up to a maximum charge state (MAX) which is a percentage value of 100% or less of the second charge state (SOC2), - during operation of the energy store without charge via an external charging station, the electric current and / or the electrical power is measured, which of the energy storage ( 2 ) and recorded by means of a temporal integration of the measured current and / or the measured power, the change in the state of charge (SOC) of the energy store ( 2 ) is detected, wherein based on the detected change in the state of charge (SOC) a discharge of the energy store ( 2 ) is allowed from the maximum charge state (MAX) by a predetermined maximum charge amount (NH), wherein the maximum charge amount (NH) is set such that the maximum charge state (MAX) at startup of the energy store ( 2 ) minus the maximum charge amount (NH) corresponds to a charge state (MIN) which is above the first charge state (SOC1). Method according to claim 1, characterized in that in the first operating phase (BP1) the percentage value of the second state of charge (SOC2), which defines the maximum charge state (MAX), is less than 100% and preferably between 95% and 99% of the second state of charge (SOC2). A method according to claim 1 or 2, characterized in that the maximum charge amount (NH) is between 80% and 90% of the difference between the second and the first state of charge (SOC2, SOC1). Method according to one of the preceding claims, characterized in that the first operating phase (BP1) is terminated when an estimated state of charge (SOC) of the energy store ( 2 ) when reaching a discharge around the maximum charge amount (NH) assumes a limit value (GW) at which the difference by which the limit value (GW) is greater than the first charge state (SOC1) reaches a predetermined threshold. A method according to claim 4, characterized in that the predetermined threshold between 2% and 3% of the maximum state of charge (MAX) at startup of the energy storage ( 2 ) lies. Method according to one of the preceding claims, characterized in that in a second operating phase (BP2), which directly adjoins the first operating phase (BP1), the percentage value of the second state of charge (SOC2), which defines the maximum charge state (MAX), the percentage value from the first phase of operation, but during operation of the electrical energy store ( 2 ) without charge via an external charging station, the state of charge (SOC) of the energy store ( 2 ) and based on this estimate a discharge of the energy store ( 2 ) until the state of charge (SOC) of the energy store ( 2 ) reaches a threshold (SW) above the first state of charge (SOC1) which remains constant during the second phase of operation (BP2). Method according to Claim 6 in combination with Claim 4 or 5, characterized in that the threshold value (SW) corresponds to the limit value (GW) from the first operating phase (BP1). A method according to claim 6 or 7, characterized in that the second operating phase (BP2) is terminated when the difference between the maximum charge state (MAX) and the threshold value (SW) reaches a predetermined amount of charge. A method according to claim 8, characterized in that the predetermined charge amount is a predetermined percentage value of the maximum charge amount (NH), wherein the predetermined percentage value is preferably between 60% and 85%. Method according to one of claims 6 to 9, characterized in that in a third phase of operation (BP3), which directly adjoins the second operating phase (BP2), the percentage value of the second state of charge (SOC2), which defines the maximum state of charge (MAX) , is increased and / or the threshold value (SW) is reduced so that a predetermined difference between the maximum charge state (MAX) and the threshold value (SW) is maintained, wherein in the third operating phase (BP3) in the operation of the electrical energy store ( 2 ) without charge via an external charging station the state of charge of the energy store ( 2 ) and based on this estimate a discharge of the energy store ( 2 ) until the state of charge (SOC) of the energy store ( 2 ) reaches the threshold (SW). A method according to claim 10 in combination with claim 8 or 9, characterized in that the predetermined difference corresponds to the predetermined amount of charge from the second phase of operation. A method according to claim 10 or 11, characterized in that the third phase of operation (BP3) is terminated when the predetermined difference can no longer be met without the first state of charge (SOC1) or the first state of charge (SOC1) plus a buffer or the second state of charge (SOC2) is exceeded. Method according to one of claims 10 to 12, characterized in that in a fourth operating phase (BP4), which directly adjoins the third operating phase (BP3), the maximum state of charge to 100% of the second state of charge (SOC2) and the threshold value (SW) is held on the first state of charge (SOC1) or the first state of charge (SOC1) plus a buffer, wherein in the fourth phase of operation in the operation of the electrical energy store ( 2 ) without charge via an external charging station, the state of charge (SOC) of the energy store ( 2 ) and based on this estimate a discharge of the energy store ( 2 ) until the state of charge (SOC) of the energy store ( 2 ) reaches the first state of charge (SOC1) or the first state of charge (SOC1) plus a buffer. Motor vehicle comprising an electrical energy store ( 2 ), wherein the energy storage ( 2 ) electrical energy for driving the motor vehicle ( 1 ) is characterized and characterized by a first state of charge (SOC1), under which the motor vehicle ( 1 ) no longer through the energy storage ( 2 ) is drivable, and a second state of charge (SOC2), which is the fully charged state of the energy store ( 2 ) and decreases with its service life, wherein the motor vehicle is adapted to the energy storage ( 2 ) in a first operating phase (BP1) after its start-up in such a way that: - the charging of the energy store ( 2 ) is performed via an external charging station at most up to a maximum state of charge (MAX) which is a percentage value of 100% or less of the second state of charge (SOC2), - the electrical current and / or the electric power is measured while the motor vehicle is driving, which of the energy store ( 2 ) and recorded, and by means of a temporal integration of the measured current and / or the measured power, the change in the state of charge (SOC) of the energy storage is detected, wherein based on the detected change in the state of charge (SOC) a discharge of the energy storage ( 2 ) is allowed from the maximum charge state (MAX) by a predetermined maximum charge amount (NH), wherein the maximum charge amount (NH) is set such that the maximum charge state (MAX) at startup of the energy store ( 2 ) minus the maximum charge amount (NH) corresponds to a charge state (MIN) which is above the first charge state (SOC1). Motor vehicle according to claim 14, characterized in that the motor vehicle for implementing a method according to one of claims 2 to 13 is arranged.

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