DE102017200209B4 - Method for determining a capacity information, motor vehicle and server describing an instantaneous total capacity of an electrochemical energy store supplying a motor vehicle - Google Patents

Abstract

Method for determining a capacity information describing an instantaneous total capacity of an electrochemical energy store (3) supplying a motor vehicle (1), comprising the following steps:
- Recording a temporal voltage curve (9) on the energy storage device (3) during a charging process of the energy storage device (3);
- Selecting a portion (17) of a defined state of charge over a load state of reference voltage waveform (16) in dependence on the voltage curve (9);
- determining a loading stroke information describing the change (20) of the state of charge variable as a function of the selected section (17); and
Determining the capacity information as a function of the loading stroke information and a charge quantity information which describes a charge quantity received by the energy store (3) during the charging process.

Description

The invention relates to a method for determining a capacity information describing an instantaneous total capacity of an electrochemical energy store supplying a motor vehicle. In addition, the invention relates to a motor vehicle and a server.

In partially or completely electrically operated motor vehicles, in particular electric motor vehicles or plug-in hybrid motor vehicles, the determination of the total capacity of an electrochemical energy store is of importance in order to correctly calculate the remaining range of the motor vehicle. Known methods for determining corresponding capacity information evaluate large changes in the state of charge and require long rest periods of, for example, at least one hour in order to achieve a quiescent voltage adjustment.

However, suitable operating situations rarely occur in the aforementioned motor vehicles for such a determination of the capacity information, since charging and driving phases often alternate immediately without pauses. The capacity information can then only be determined at irregular intervals. As a result, when determining further quantities describing the state of the energy store, a wrong amount of available charge is used as a basis. The determination of a residual range for the user of the motor vehicle is also erroneous in the sequence.

The publication DE 10 2013 201 529 A1 discloses a method for monitoring at least one traction battery of a motor vehicle, wherein base data for the prediction of a deep discharge state of the at least one traction battery are determined by a battery monitoring system associated with the motor vehicle.

The publication DE 10 2015 203 803 A1 discloses a method in which a vehicle is controlled based on state observation in conjunction with a battery of the vehicle according to battery model parameters for battery cells of the battery. These are received by a vehicle controller during a drive cycle of the vehicle in response to measurements from an off-board computing device. The feedback relates to a battery model of the cells. The measurements are sent to the computing device by the controller during the drive cycle.

The publication US 2014 379 183 A1 discloses a computer-implemented method in which data is continuously received that describes one or more conditions affecting the range of a vehicle operated by at least one battery. Based on these data, range information is dynamically calculated that describes a distance to which the vehicle can travel until a discharge of the battery.

The publication DE 11 2009 001 553 T5 discloses a method for battery capacity estimation. The battery capacity is determined as a function of the change in state of charge and net charge flow. However, there is no consideration of reference voltage values.

The object of the invention is to improve the determination of a capacity information describing the instantaneous total capacity of an electrochemical energy store supplying a motor vehicle.

The object is achieved by a method according to claim 1, a motor vehicle according to claim 12 and a server according to claim 13. Particular embodiments are specified in the subclaims.

• - Erfassen eines zeitlichen Spannungsverlaufs am Energiespeicher während eines Ladevorgangs des Energiespeichers;
• - Auswählen eines Abschnitts eines über eine Ladezustandsgröße definierten Referenzspannungsverlaufs in Abhängigkeit des Spannungsverlaufs;
• - Ermitteln einer die Veränderung der Ladezustandsgröße beschreibenden Ladehubinformation in Abhängigkeit des ausgewählten Abschnitts; und
• - Ermitteln der Kapazitätsinformation in Abhängigkeit der Ladehubinformation und einer Ladungsmengeninformation, welche eine während des Ladevorgangs durch den Energiespeicher aufgenommene Ladungsmenge beschreibt.

To achieve this object, a method of the type mentioned above is proposed according to the invention with the following steps:

• - detecting a temporal voltage curve at the energy store during a charging process of the energy store;
• Selecting a portion of a reference voltage waveform defined by a state of charge magnitude as a function of the voltage profile;
• Determining a loading stroke information describing the change in the state of charge variable as a function of the selected section; and
• - Determining the capacity information in dependence of the loading stroke information and a charge amount information, which describes a recorded during the charging by the energy storage charge amount.

The invention is based on the idea of identifying a section in the reference voltage curve described by way of the state of charge quantity, for example a state-of-charge (SOC), which corresponds to the voltage profile detected over the time during the charging process of the electrochemical energy store. From the section can then determine the loading stroke information as a change in the state of charge state during the charging process, resulting in additional Considering the amount of charge absorbed during the charging process, the available capacity of the energy storage device can be determined. In other words, the real time waveform is re-normalized based on the known reference voltage curve to the state of charge state and set the amount of charge in relation to the charge state caused by the change in the state of charge state. The total age-related capacity of the energy store may be expressed as the product of the current and time, for example in ampere-hours.

The capacity information can be determined by the method according to the invention during the charge cycles occurring regularly in battery-powered vehicles (BEV) and plug-in hybrid motor vehicles (PHEV) and is updated for later calculations of further state information of the energy store, for example the range of the motor vehicle to disposal. The user of the motor vehicle can thus be informed more reliably about the state of the energy store.

The energy store used in the context of the method according to the invention is in particular an energy storage cell of an energy storage device of the motor vehicle formed from a plurality of energy storage cells. Accordingly, the method according to the invention can also be carried out in parallel or consecutively for a respective energy storage cell, it being possible to combine respectively determined capacity information with an energy storage device information describing the state of the energy storage device.

The temporal voltage curve can be detected by means of a measuring device of the motor vehicle as a terminal voltage of the energy store. It can be based on a constant charging current through the energy storage during the charging process, so that the source or open circuit voltage of the energy storage only has a constant offset to the detected voltage curve. Accordingly, the voltage curve can be detected by measuring the open circuit voltage of the energy storage. Furthermore, the amount of charge information can be detected by integration of the electric current through the energy storage over time.

The selection of the section and / or the determination of the loading stroke information and / or the determination of the capacity information can take place by means of a computing device. The computing device can be completely implemented within the motor vehicle. However, as will be described in more detail below, it is preferred if the functions of the computing device are distributed between a motor vehicle-side and a motor vehicle-external part of the computing device.

The reference voltage profile is expediently stored within the computing device. In particular, the reference voltage profile describes a characteristic curve of a voltage over the state of charge state, preferably the SOC. The reference voltage profile can be determined by measuring the relationship between a voltage of a reference energy store and its state of charge indicated on the basis of the state of charge quantity. The reference energy storage may be the energy storage or an energy storage device of this type. Preferably, a reference voltage profile determined during cell qualification, in other words at the factory, is used. The selection of the section of the reference voltage profile takes place, for example, by associating at least two pairs of voltage values of the voltage profile and reference voltage values of the reference voltage profile relative to one another.

In the method according to the invention, it is preferred if the section is selected such that a deviation between reference voltage values of the reference voltage profile and voltage values of the voltage curve satisfies a deviation criterion. In other words, along the reference voltage curve, a section can be searched which is as similar as possible to the detected voltage curve. For this purpose, an optimization method can be used which minimizes a deviation between the voltage profile and the reference voltage profile. The deviation criterion can also provide that the sum of deviation metrics between mutually assigned values of the voltage profile and the reference voltage profile falls below a threshold value.

The change in the charge state variable can be determined on the basis of two state of charge values for the state of charge whose reference voltage values are each assigned to a voltage value of the voltage profile, in particular a voltage value at the beginning and a voltage value at the end of the charging process. After the selection of the appropriate section of the reference voltage curve, it is therefore possible to determine two reference voltage values within the section and the charge state values assigned to them, which indicate, for example, the SOC in percent. The difference of these state of charge values then gives the change in the state of charge state resulting from the charging process as described by the loading stroke information.

In a concrete embodiment of the method according to the invention, it is provided that the recorded charge amount is extrapolated from a discharged to a charged state of the energy storage based on the change of the state of charge variable described by the loading stroke information taking into account a change in the state of charge state. In this case, it may be assumed, for example, that the change in the state of charge is proportional to the received charge amount, so that the total current capacity is calculated by dividing the received charge amount by the ratio of the change in the charge state quantity during charging to the change of the charge state variable from the discharged to the charged state can. The calculation of the capacity information can be implemented particularly efficiently in this way.

In order to determine a particularly precise capacity information which takes into account the current operating conditions of the energy store, the reference voltage curve can be selected as a function of at least one operating parameter of the energy store determined on the motor vehicle side from a characteristic map comprising a multiplicity of reference voltage courses. In this case, values of the operating parameter or vectors of different operating parameters can each be assigned a characteristic curve of the characteristic field. As an operating parameter, a charging current flowing during the charging process, in particular substantially constant, charging current and / or an internal resistance of the energy store and / or a temperature of the energy store can be used.

In order to realize the aforementioned distributed determination of the capacity information, it is preferred if a computing device is used for carrying out at least part of the steps, comprising a motor vehicle-side control device and a server externally communicating with the control device, at least a part of the functions of the computing device on the server. As a result, calculating and / or memory-intensive steps of the method according to the invention can also be carried out efficiently.

Particularly preferably, the selection of the section of the reference voltage curve and / or the selection of the reference voltage curve from the map, in particular stored on a memory device of the server, are performed on the server side. This allows, for example, the use of particularly detailed and accordingly memory-intensive maps. The data volumes required for this purpose can exceed the storage capacities of the control device. Alternatively or additionally, the ascertaining of the capacity information in dependence on the loading stroke information and the charge quantity information can also be carried out on the server side.

The control device and the server may each have a communication device or be connected to such a device for the transmission of data. The wireless communication can take place for example via a mobile radio connection. In particular, the control device can be designed as a battery management controller (BMC). The server is preferably a back-end server, which is operated, for example, by the manufacturer of the motor vehicle.

The object underlying the invention is further achieved according to the invention by a motor vehicle having an electrochemical energy store, which is set up to carry out the method according to the invention. In particular, the motor vehicle has a control device which can be used in the method as the computing device or as part of the computing device.

Finally, the problem underlying the invention is achieved according to the invention by a server which is set up to carry out the method according to the invention, in which at least part of the steps is carried out using the computing device which controls the motor vehicle-side control device and the server that communicates with the control device wirelessly wherein at least part of the functions of the computing device is performed on the server.

All embodiments of the method according to the invention can be analogously transferred to the motor vehicle according to the invention and the server according to the invention, so that even with these the aforementioned advantages can be achieved.

• 1 eine Prinzipskizze eines erfindungsgemäßen Kraftfahrzeugs und eines erfindungsgemäßen Servers;
• 2 einen zeitlichen Spannungsverlauf während eines Ladevorgangs eines Energiespeichers des Kraftfahrzeugs;
• 3 einen zeitlichen Ladungsmengenverlauf während eines Ladevorgangs des Energiespeichers des Kraftfahrzeugs;
• 4 ein Kennfeld mehrerer Referenzspannungsverläufe über eine Ladezustandsgröße für unterschiedliche Ladeströme; und
• 5 einen aus dem Kennfeld ausgewählten Referenzspannungsverlauf und den Spannungsverlauf über die Ladezustandsgröße.

Further advantages and details of the invention will become apparent from the embodiments described below and with reference to the drawings. These are schematic representations and show:

• 1 a schematic diagram of a motor vehicle according to the invention and a server according to the invention;
• 2 a temporal voltage curve during a charging process of an energy store of the motor vehicle;
• 3 a time charge quantity course during a charging process of the energy storage of the motor vehicle;
• 4 a characteristic diagram of a plurality of reference voltage profiles over a state of charge variable for different charging currents; and
• 5 a selected from the map reference voltage waveform and the voltage waveform on the state of charge state.

1 shows a schematic diagram of a motor vehicle 1 and a server 2 , which as a backend server for the motor vehicle 1 serves. The car 1 is designed, for example, as an electric motor vehicle (BEV) or plug-in hybrid motor vehicle (PHEV) and can be electrically charged from the public power grid.

For this purpose, the motor vehicle 1 an electrochemical energy storage 3 and a measuring device associated therewith 4 on, by means of which a voltage on the energy storage 3 and a through the energy storage 3 flowing current is detected. Motor vehicle side is also a control device 5 , For example, in the form of a Battery Management Controller, which, together with the server 2 a distributed computing device 6 formed. For wireless communication between the controller 5 and the server 2 has the computing device 6 furthermore communication facilities 7 . 8th on, by means of which data between the control device 5 and the server 2 , for example via a mobile network, are interchangeable.

The control device 5 serves to the remaining range of the motor vehicle 1 to determine and a user of the motor vehicle 1 display. To determine this residual range requires a capacity information that the aging-related instantaneous capacity of the energy storage 3 describes. The determination of this capacity information is carried out according to a method for the implementation of the motor vehicle 1 and the server 2 are set up and which is described in detail below using an exemplary embodiment:

2 shows a temporal voltage curve 9 and 3 shows a temporal charge quantity course 10 during a charging process of the energy storage 3 , The voltage curve 9 is through the measuring device 4 as a function of a voltage U _E at the energy storage 3 over time t described.

The measuring device detects this 4 the voltage U _E , which at a substantially constant and such a low charging current that the behavior of reactive components of the energy storage 3 can be assumed to be stationary, only by a constant offset from the open circuit voltage of the energy storage 3 differs. The voltage curve 9 can be corrected accordingly by the measuring device 3 to be provided. As in 2 shown, the tension increases U _E from a lower voltage value 11 from, for example, 3.6 volts nonlinearly to an upper voltage value 12 of, for example, 4.1 volts.

In addition, the measuring device captures 4 through the energy storage 3 during charging, flowing, substantially constant charging current, which over time t is integrated and a charge amount Q describes. This results in the charge quantity course 10 which over time t essentially linear to a charge amount value 13 of, for example, 5.0 amp hours.

To determine the capacity information is on the server 2 a map stored, which a plurality of reference voltage curves one with the energy storage 3 describes the same type of reference energy storage. Each reference voltage curve is via the state of charge SOC , which is typically expressed in percent, and a combination or vector of operating parameters of the energy store 3 assigned. The operating parameters are the charging current, an internal resistance of the energy store 3 and a temperature of the energy storage device used. These operating parameters are also controlled by the controller 5 to the server 2 transmitted, which selects from the extensive map a reference voltage waveform.

4 shows an example of the several reference voltage curves 14 . 15 . 16 a reference voltage U _R comprehensive map of the state of charge state SOC for different charging currents. Here is the reference voltage curve 14 for example, a charging current of 15 amps, the reference voltage curve 15 a charging current of 10 amps and the reference voltage curve 16 assigned a charging current of 3 amperes as operating parameters. For clarity, shows 4 only a section of the map with respect to some charging currents, so that the actual server-side stored map of greater dimensions and much more detailed. The memory requirement for this map is so large that a vehicle-side storage, especially in the control device 5 , is inappropriate.

In the simplified representation of the map according to 4 the server chooses 2 now with reference to the by the controller 5 transmitted charging current of 3 amperes as operating parameters the reference voltage curve 16 out.

5 shows the selected reference voltage curve 16 about the state of charge SOC along with the voltage curve 9 , The server 2 chooses a section in a subsequent process step 17 the reference voltage curve 16 such that the voltage values of the voltage curve 9 in this section, a deviation criterion with respect to reference voltage values of the reference voltage profile assigned to them 16 fulfill. The deviation criterion may, for example, describe an optimization method for the deviation between the voltage profile 9 and in the reference voltage curve 16 in the section 17 to minimize. Figuratively speaking, the voltage curve 9 over the reference voltage curve 16 "Placed" and determined a position of best congruence. In this case, the reference voltage values 20 . 21 the voltage values 11 . 12 (see. 2 ) correspond.

After selecting this section 17 determines the server 2 the state of charge values 18 . 19 , the beginning and end of the voltage curve 9 and thus associated with the beginning and end of the charging process. One side of the server 2 determined loading stroke information thus describes a change 22 the state of charge SOC that resulted from a load on a reference energy store for this voltage waveform. Correspond to the charge state value 18 For example, 30 percent and the state of charge value 19 For example, 95 percent, that's the change 22 the state of charge 65 Percent.

The server 2 now calculates the received charge amount described by the charge quantity information on the basis of the change described by the charge lift information 22 the state of charge taking into account a change in the state of charge state from a discharged state ( 0 Percent) to a charged state ( 100 Percent) of the energy store 3 high. In the example used here, during the charging process, the amount of charge 13 of 5.0 amp hours, this results in a momentary capacity of 7.7 ampere residues resulting from a division of the 5.0 amp hours by the change 22 the state of charge of 65 percent.

The capacity information describing the available amount of charge of 7.7 ampere hours is then provided by the server 2 via the communication facilities 7 . 8th to the controller 5 where, for example, to determine a the user of the motor vehicle 1 range to be displayed is used.

According to a further embodiment of the method according to the invention, the computing device 6 completely implemented inside the vehicle, wherein the control device 5 also the functions of the server described above 2 and accordingly to the communication facilities 7 . 8th can be waived. Such a method embodiment is particularly useful when simpler maps are used and / or high memory and computing capacity in the motor vehicle 1 be available.

Claims (13)

Method for determining a capacity information describing an instantaneous total capacity of an electrochemical energy store (3) supplying a motor vehicle (1), comprising the following steps: - Recording a temporal voltage curve (9) on the energy storage device (3) during a charging process of the energy storage device (3); Selecting a section (17) of a reference voltage curve (16) defined by a state of charge as a function of the voltage curve (9), wherein the section (17) is selected such that a deviation between reference voltage values (20, 21) of the reference voltage curve (16) and Voltage values (11, 12) of the voltage curve (9) satisfies a deviation criterion; - determining a loading stroke information describing the change (20) of the state of charge variable as a function of the selected section (17); and Determining the capacity information as a function of the loading stroke information and a charge quantity information which describes a charge quantity received by the energy store (3) during the charging process. Method according to Claim 1 , characterized in that the change (22) of the state of charge magnitude is determined on the basis of two state of charge values (18, 19) for the state of charge whose reference voltage values (20, 21) are associated with a respective voltage value (11, 12) of the voltage curve (9). Method according to one of the preceding claims, characterized in that for the determination of the capacity information, the recorded amount of charge is extrapolated from the unloaded to a charged state of the energy storage device (3) on the basis of the charge state variable variation (22) described by the charge lift information , Method according to one of the preceding claims, characterized in that the reference voltage curve (16) is selected as a function of at least one operating parameter of the energy store (3) determined on the motor vehicle side from a characteristic map comprising a plurality of reference voltage courses (14, 15, 16). Method according to Claim 4 , characterized in that the operating parameter is a charging current flowing during the charging process and / or an internal resistance of the energy store (3) and / or a temperature of the energy store (3) can be used. Method according to one of the preceding claims, characterized in that the amount of charge information is detected by integration of the electrical current through the energy store (3) over time. Method according to one of the preceding claims, characterized in that the voltage curve is detected by measuring the open circuit voltage of the energy store (3). Method according to one of the preceding claims, characterized in that for performing at least a portion of the steps, a computing device (6) is used which comprises a motor vehicle-side control device (5) and a server (2) which communicates wirelessly with the control device (5) , Wherein at least a part of the functions of the computing device (6) on the server (2) is performed. Method according to Claim 8 , characterized in that the selection of the portion (17) of the reference voltage curve (16) and / or the determination of the capacity information depending on the loading stroke information and the charge amount information and / or selecting the reference voltage curve (16) are performed from the map server side. Method according to Claim 9 , characterized in that the map is stored on a storage device of the server (2). Method according to one of Claims 8 to 10 , characterized in that the voltage curve (9) and / or the at least one operating parameter is transmitted from the control device (5) to the server (2) and / or the capacity information is transmitted from the server (2) to the control device (5). Motor vehicle with an electrochemical energy store (3), which is set up to carry out a method according to one of the preceding claims. Server, which participates in the procedure according to one of the Claims 8 to 11 as the motor vehicle external server (2) is established.

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