Computer-implemented method for calculating the charging energy of an energy storage device in an electric vehicle.

Abstract

Computer-implemented method for calculating the charging energy of an energy storage device of an electric vehicle, comprising the following steps: - Determination of an initial resistance value of the charging cable (101) at an initial temperature; - Calculation of a maximum electrical resistance of a charging cable (101) (S1) wherein the maximum electrical resistance is calculated by adding the first resistance value and a first tolerance value; - Calculation of a minimum electrical resistance of the charging cable (101) (S1); - Determination of an average resistance value from the maximum resistance and the minimum resistance (S2); - Performing a charging process of the energy storage device using the charging cable (101) (S3); - Calculation of charging energy using the average resistance (S4).

Description

[0001] The present invention relates to a computer-implemented method according to claim 1 for calculating the charging energy of an energy storage device of an electric vehicle. For the purposes of this description, an energy storage device is understood to be, in particular, a rechargeable battery.

[0002] Calculating the charging energy is crucial when charging an electric vehicle at a publicly accessible energy source. The charging energy used to recharge the battery is typically paid for by the electric vehicle user. Therefore, the exact amount of charging energy required should be known as precisely as possible. Otherwise, the energy source operator or the electric vehicle user risks being disadvantaged.

[0003] For the purposes of this description, an energy source is understood to be, in particular, a device designed to provide energy for charging electric vehicles. For this purpose, the energy source may, for example, be connected to an electrical supply network and have a connection for a charging cable, which can then be used to connect the energy source to the electric vehicle. Such an energy source may also be referred to as a charging station.

[0004] Methods for carrying out a charging process of an energy storage device of an electric motor vehicle are known from DE 10 2017 209 450 A1 and DE 10 2017 221 298 A1.

[0005] In contrast, the present invention aims to create a method that enables the calculation of the charging energy transferred to the energy storage device. Furthermore, such a system is to be created.

[0006] This problem is solved by a method according to claim 1 and by a system according to claim 9. Embodiments of the invention are specified in the dependent claims.

[0007] To calculate the charging energy transferred to the energy storage device, it is advantageous to know the resistance of the charging cable used during the charging process. Knowing this resistance allows the current and voltage at the energy source to be measured. The charging energy can then be calculated from the resistance, current, and voltage. It is essential to avoid any systematic disadvantage to the electric vehicle user or the energy source operator; random errors within the limits of measurement accuracy are regulated by calibration law.

[0008] First, the maximum and minimum resistance of the charging cable are calculated. An initial resistance value is determined at a specific temperature. This initial resistance value can be measured or calculated. The maximum electrical resistance is calculated by adding the initial resistance value to an initial tolerance value. This tolerance value can be used, in particular, to account for measurement or calculation inaccuracies.

[0009] The maximum and minimum resistances can be calculated, for example, taking into account tolerances and / or different temperatures. An average resistance value is then determined from the maximum and minimum resistances. This average resistance value could, for example, be the arithmetic mean of the maximum and minimum resistances.

[0010] The energy storage device is then charged using the charging cable. The charging cable can, for example, connect a power source to a charging port on the electric vehicle. The charging energy is calculated using the average resistance value. This charging energy can be, in particular, the energy used to charge the energy storage device. Using the average resistance value is advantageous because this value is likely to exhibit a relatively small deviation from the actual value during the charging process. Furthermore, any deviations from the actual value are statistically random errors, the significance of which decreases with repeated use of different charging cables. There is no systematic error, the significance of which would accumulate even with repeated use of different charging cables.

[0011] According to one embodiment of the invention, the charging cable can electrically connect a contact point of the energy source to the energy storage device during the charging process. The contact point can be the point where one end of the charging cable electrically contacts a cable of the energy source. The energy source can include measuring means configured to measure an electrical charging current and an electrical charging voltage. The charging current and voltage can be measured at the contact point by the measuring means during the charging process. Preferably, the electrical charging current and voltage are measured throughout the entire charging process. The charging energy can then be calculated using the charging current and voltage.

[0012] In this way, the measuring instruments in the energy source can be used to calculate the electrical energy transferred to the energy storage device with relative accuracy. Since the average resistance is known, no additional cables are needed to run to the electric vehicle to measure the charging current and voltage directly at the vehicle.

[0013] According to one embodiment of the invention, a second resistance value of the charging cable can be determined at a second temperature. This second resistance value can, for example, be measured or calculated. The minimum electrical resistance can be calculated by subtracting a second tolerance value from the second resistance value. This second tolerance value can, in particular, serve to account for measurement or calculation inaccuracies. The second tolerance value can, for example, be identical to the first tolerance value. Alternatively, the second tolerance value can take into account the contact resistances of the measuring instruments.

[0014] According to one embodiment of the invention, the second temperature can be lower than the first. This is particularly advantageous because the actual resistance of the charging cable is often greater at higher temperatures than at lower temperatures.

[0015] According to one embodiment of the invention, the charging current and / or the charging voltage can be time-dependent during the charging process. Due to varying charging voltages and currents during the charging process, systematic deviations of the actual resistance of the charging cable from the average resistance value that occur at certain charging voltages or currents can be less significant. The accuracy of the method is thus increased.

[0016] According to one embodiment of the invention, the charging energy can be calculated by first calculating a time-dependent charging power, which is then integrated over time. The time-dependent charging power can be calculated from the average resistance, the charging voltage, and the charging current.

[0017] According to one embodiment of the invention, the charging power can be calculated according to the following formula: P(t)=I(t)*(U(t)−R*I(t)), where P(t) is the charging power, I(t) is the charging current, U(t) is the charging voltage, and R is the average resistance.

[0018] According to one embodiment of the invention, the charging cable can be designed as a fast charging cable. For the purposes of this description, this means in particular that the charging cable is suitable for carrying out the charging process with a power output of more than 20 kW. Preferably, the charging process is carried out with such a power output.

[0019] The system according to claim 9 comprises an energy source and a charging cable. The system is configured to charge a motor vehicle energy storage device when the energy storage device is electrically connected to the energy source via the charging cable. The energy source is configured to calculate the charging energy using the average resistance of the charging cable. The energy source may also be configured to perform various process steps previously described in connection with the method.

[0020] Further features and advantages of the present invention will become clear with reference to the following description of preferred embodiments and the accompanying figures. The same reference numerals are used for identical or similar steps and for steps with identical or similar functions. To distinguish such steps, one or more apostrophes may be appended. This shows Fig. 1 a schematic flowchart of a process according to an embodiment of the invention; and Fig. 2 a schematic view of a system according to an embodiment of the invention.

[0021] In the first step, S1, the maximum and minimum resistance of a charging cable are calculated. This calculation can be performed after one or more resistance measurements. In this case, the maximum resistance can be calculated by adding a tolerance to a resistance measured at a first temperature. The minimum resistance can be calculated by subtracting a tolerance and any contact resistances to be considered from a resistance measured at a second temperature. The first temperature can be higher than the second temperature.

[0022] In step S2, an average resistance value is then calculated from the maximum and minimum resistances. This average resistance value can, for example, be the arithmetic mean of the maximum and minimum resistances.

[0023] In step S3, the energy storage device is charged using the charging cable. The charging energy used to charge the energy storage device is calculated in step S4 using the average resistance. This can be done, for example, by first calculating a time-dependent charging power P(t) according to the following formula: P(t)=I(t)*(U(t)−R*I(t)).

[0024] Here, I(t) is the time-dependent charging current, U(t) is the time-dependent charging voltage, and R is the average resistance.

[0025] The charging energy can be calculated from the charging power by integrating it over time. This has the advantage of further reducing any statistical error present in the calculation of the charging power.

[0026] Tests have shown that with a maximum resistance of 11.0 mΩ and a minimum resistance of 5.5 mΩ, and an average resistance of 8.25 mΩ, a random error of between 0.03% and 0.46% occurs in the calculation of the charging energy. This error also depends on the charging current and voltage. The higher the current, the higher the error; the higher the voltage, the lower the error. The error of 0.46% mentioned above was determined at a voltage of 300 V and a current of 500 A. The error of 0.03% was determined at a voltage of 1000 V and a current of 100 A.

[0027] In Fig. Figure 2 represents an energy source 100 in the form of a charging station. The energy source 100 can be connected to a terminal 102 of an electric vehicle via a charging cable 101 to charge the vehicle's energy storage system. For reliable billing, the energy used to charge the energy storage system needs to be determined. Due to the significant resistance of the charging cable 101, this energy cannot be determined directly within the energy source 100.

[0028] The resistance of the charging cable 101 must not be neglected, especially in some countries due to legal regulations, as this would constitute a systematic error that would always financially disadvantage the user of the electric vehicle.

[0029] For these reasons, the average resistance value for the charging cable 101, as above with reference to Fig.As described in section 1, the charging energy is determined and calculated using this average resistance value. The charging current and voltage within energy source 100 are measured.

Claims

[1] Computer-implemented method for calculating a charging energy of an energy storage device of an electric vehicle, comprising the following steps: - determining a first resistance value of the charging cable (101) at a first temperature; - Calculating a maximum electrical resistance of a charging cable (101) (S1), wherein the maximum electrical resistance is calculated by adding the first resistance value and a first tolerance value; - Calculation of a minimum electrical resistance of the charging cable (101) (S1); - Determination of an average resistance value from the maximum resistance and the minimum resistance (S2); - carrying out a charging process of the energy storage device using the charging cable (101) (S3); - Calculation of charging energy using the average resistance value (S4). [2] Method according to claim 1, characterized byin that the charging cable (101) electrically connects a contact point of an energy source (100) to the energy store during the charging process, wherein the energy source (100) comprises measuring means, wherein the measuring means are designed to measure an electrical charging current and an electrical charging voltage, wherein the charging current and the charging voltage are measured at the contact point during the charging process, and wherein the charging energy is calculated using the charging current and the charging voltage. [3] Method according to one of the preceding claims, characterized by that a second resistance value of the charging cable (101) is determined at a second temperature, wherein the minimum electrical resistance is calculated by subtracting a second tolerance value from the second resistance value. [4] Method according to the preceding claim, characterized by that the second temperature is lower than the first temperature. [5] Method according to one of the preceding claims, characterized by that the charging current and / or the charging voltage are / is time-dependent. [6] Method according to one of the preceding claims, characterized by that the charging energy is calculated by first calculating a time-dependent charging power, which is then integrated over time. [7] Method according to the preceding claim, characterized by that the charging power is calculated according to the following formula: P(t)=I(t)*(U(t)−R*I(t)), where P(t) is the charging power, I(t) is the charging current, U(t) is the charging voltage and R is the mean resistance. [8] Method according to one of the preceding claims, characterized by that the charging cable (101) is designed as a quick charging cable. [9] System comprising an energy source (100) and a charging cable (101), wherein the system is designed to charge an energy storage device of an electric vehicle when the energy storage device is electrically connected to the energy source (100) via the charging cable (101), and wherein the energy source (100) is designed to carry out a method according to one of the preceding claims.

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