METHOD AND DEVICE FOR ASCERTAINING A STATE OF HEALTH OF A BATTERY FOR A MEANS OF TRANSPORTATION

Abstract

A method and to a device for ascertaining a state of health of a battery for a transportation device. The method includes: charging the battery until a predefined target voltage is reached in a first charging phase of the battery, ascertaining a first voltage value of the battery at a first predefined point in time after the predefined target voltage has been reached in a relaxation phase of the battery, ascertaining a second voltage value of the battery at a second predefined point in time, deviating from the first predefined point in time, in the relaxation phase of the battery, ascertaining a piece of information about the state of health of the battery based on a change of the second voltage value with respect to the first voltage value, and using the piece of information in the transportation device and/or in an external server.

Claims

1-11. (canceled)

12. A method for ascertaining a state of health of a battery for a transportation device, comprising the following steps: charging the battery until a predefined target voltage is reached in a first charging phase of the battery; ascertaining a first voltage value of the battery at a first predefined point in time after the predefined target voltage has been reached in a relaxation phase of the battery; ascertaining a second voltage value of the battery at a second predefined point in time, deviating from the first predefined point in time, in the relaxation phase of the battery; ascertaining a piece of information about a state of health of the battery based on a change of the second voltage value with respect to the first voltage value; and using the piece of information about the state of health of the battery in transportation device and/or in an external server.

13. The method as recited in claim 12, wherein the predefined target voltage corresponds to a voltage value in a range of 80% to 100% of an end-of-charge voltage of the battery.

14. The method as recited in claim 13, wherein the range is of 85% to 98% of the end-of-charge voltage of the battery.

15. The method as recited in claim 13, wherein the range is of 90% to 97% of the end-of-charge voltage of the battery.

16. The method as recited in claim 12, further comprising: charging the battery in a second charging phase until an end-of-charge voltage of the battery is reached in response to a termination of the relaxation phase of the battery.

17. The method as recited in claim 12, further comprising: ascertaining a cell balancing need of the battery; and carrying out a cell balancing as a function of the ascertained cell balancing need, the cell balancing being carried out: immediately prior to the first charging phase, and/or in response to a termination of the relaxation phase.

18. The method as recited in claim 12, wherein the ascertainment of the state of health is carried out only when: a charge state of the battery, prior to the charging in the first charging phase, corresponds to a predefined minimum charge state, and/or a temperature of the battery is within a predefined temperature range.

19. The method as recited in claim 12, wherein a predefined target temperature for the battery is established prior to a start of the relaxation phase.

20. The method as recited in claim 12, wherein the change of the second voltage value with respect to the first voltage value is ascertained based on a difference, and/or a gradient.

21. The method as recited in claim 12, wherein the charging of the battery takes place based on an AC charging process or a DC charging process.

22. The method as recited in claim 12, wherein the piece of information about the state of health of the battery is used to: compare the state of health of the battery to respective states of health of a multitude of batteries of further transportation devices, and/or automatically classify it into a state of health class using a machine learning method.

23. The method as recited in claim 12, wherein, as a function of a result of the ascertainment of the state of health of the battery: an information message is output to a driver of the transportation device, the information message encompassing a recommendation for a future charging behavior, and/or a future driving behavior, and/or future usage time periods, and/or a point in time for a battery replacement; and/or usage options of the transportation device are automatically adapted based on predefined criteria.

24. A device for ascertaining a state of health of a battery for a transportation device, comprising: an evaluation unit; a data input; and a data output; wherein the evaluation unit is configured, in conjunction with the data input, o charge the battery until a predefined target voltage is reached in a first charging phase of the battery, to ascertain a first voltage value of the battery at a first predefined point in time after the predefined target voltage has been reached in a relaxation phase of the battery, to ascertain a second voltage value of the battery at a second predefined point in time, deviating from the first predefined point in time, in the relaxation phase of the battery, and to ascertain a piece of information about the state of health of the battery based on a change of the second voltage value with respect to the first voltage value, and in conjunction with the data output, to use the piece of information about the state of health of the battery in the transportation device and/or in an external server.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Exemplary embodiments of the present invention are described hereafter in greater detail with reference to the figures.

[0025] FIG. 1 shows a flowchart illustrating steps of one exemplary embodiment of a method according to the present invention.

[0026] FIG. 2 shows a diagram illustrating profiles of a voltage, of a current, and of a charge state while a method according to the present invention is carried out for ascertaining a state of health of a battery.

[0027] FIG. 3 shows a schematic overview of a device according to the present invention in conjunction with a means of transportation.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS

[0028] FIG. 1 shows a flowchart illustrating steps of one exemplary embodiment of a method according to the present invention for ascertaining a state of health of a battery for a means of transportation. In step 100 of the method according to the present invention, a lithium-ion high-voltage battery is charged, in conjunction with an evaluation unit according to the present invention, which is a microcontroller here, until a predefined target voltage of 4.1 V is reached in a first charging phase of the battery. In step 200 of the method according to the present invention, a first voltage value of the battery is ascertained at a first predefined point in time after the predefined target voltage has been reached in a relaxation phase of the battery. Since the ascertainment of the first voltage value takes place immediately after completion of the first charging phase, the first voltage value here corresponds to the value of the target voltage of 4.1 V. In step 300 of the method according to the present invention, a second voltage value of the battery is ascertained at a second predefined point in time, deviating from the first predefined point in time, in the relaxation phase of the battery. Here, the second voltage value is ascertained 20 minutes after the ascertainment of the first voltage value. The second voltage value corresponds to a value of 3.8 V. In step 320 of the method according to the present invention, a cell balancing need of the battery is ascertained after the relaxation phase has ended. Due to a relatively large variance of the voltage values of respective cells of the battery, in step 340 of the method according to the present invention a passive cell balancing is initiated by the evaluation unit. After completion of the cell balancing, in step 400 of the method according to the present invention, a piece of information about the state of health of the battery is ascertained with the aid of the evaluation unit, based on a change of the second voltage value with respect to the first voltage value. For this purpose, a difference between the first voltage value and the second voltage value of 0.3 V is calculated with the aid of the evaluation unit. Thereafter, the evaluation unit compares the value for the difference to an assignment table, which is stored in a memory unit connected to the evaluation unit in terms of information technology. Based on the assignment table, a good state of health is ascertained for the battery due to the small difference between the first and second voltage values. In step 500 of the method according to the present invention, the ascertained piece of information about the state of health of the battery is transferred with the aid of the evaluation unit via a vehicle electrical system of the means of transportation to a combination instrument of the means of transportation, in which the piece of information about the state of health of the battery is displayed in the form of an information text.

[0029] FIG. 2 shows a diagram illustrating profiles of a voltage U, of a current I, and of a charge state SoC while a method according to the present invention is being carried out for ascertaining a state of health of a battery. In a first charging phase P1, the battery is charged at a constant charge current (CC charging) of 1.5 A until a target voltage 40 of 4.1 V is reached. In a relaxation phase P2 following the first charging phase P1, among other things, a first relaxation behavior 90 of the battery is shown, which corresponds to a good state of health of the battery. The state of health of the battery is ascertained based on a voltage difference between a first voltage value 50, which is measured at a first point in time 60 (start of relaxation phase P2), and a second voltage value 55, which is measured at a second point in time 65 (end of relaxation phase P2). Additionally, a second relaxation behavior 92 and a third relaxation behavior 94 are shown by way of example, which the battery may have at different aging states. Second relaxation behavior 92 corresponds to a very good state of health, while third relaxation behavior 94 corresponds to a poor state of health of the battery. In a second charging phase P3, the battery is initially again charged at a constant charge current of 1.5 A, followed by a charging with a constant voltage (CV charging), until a maximum charge state SoC of the battery is reached. In the event that the relaxation behavior of the battery corresponds to second relaxation behavior 92 or third relaxation behavior 94, voltage curve U is accordingly continuously continued in second charging phase P3, proceeding from the end value of the respective voltage of the respective relaxation behavior 92, 94 (not shown).

[0030] FIG. 3 shows a schematic overview of a device according to the present invention in conjunction with a means of transportation. The device includes an evaluation unit 10, which is an ASIC here and which includes a data input 12 and a data output 14. Evaluation unit 10 is additionally connected to a memory unit 20 in terms of information technology. With the aid of data input 12, evaluation unit 10 is connected to a sensor system 35 of a battery 30 of the means of transportation in terms of information technology. With the aid of data output 14, evaluation unit 10 is connected to a charger 98 of the means of transportation, which is connected between an external energy source 96 (charging station) and battery 30. Based on this configuration, the device according to the present invention is configured to carry out above-described method steps according to the present invention to ascertain an instantaneous state of health of battery 30. The method steps are implemented with the aid of a computer program, which is executed by evaluation unit 10.