Method for correcting the errors of a current integral determined by means of current sensors in a storage device

Abstract

The invention relates to a method for correcting errors in a current integral determined by means of current sensors in a storage device. It is characterized in that the cell fission in a battery cell is determined by measuring the cell voltage around a reference point, and further subsequent cell voltage values ​​are recorded and compared with the cell voltage value at the reference point.

Description

The invention relates to a method for correcting the errors of a current integral determined by means of current sensors in a storage device.With the aid of current sensors, in a storage device, in particular in traction batteries as are used in motor vehicles, the state of charge (SOC), the battery capacity and the state of aging (SOHC) related to the battery capacity can be determined. In the case of very precise current sensors being used for this purpose, even with small measurement errors of the current sensors, erroneous results can result in integration over a long period of time. In particular, this is the case when the current is integrated over a very long period of time for a determination of the battery capacity with respect to the state of aging (SOHC). Even if very accurate current sensors are used, even small measurement errors integrating over a period of time lead to erroneous results.A method for compensating the planning state (SoC) of a battery is known from EP 1 801 604 B1 for a motor vehicle operated with a battery. EP 1 801 604 B1 is concerned throughout the application with the so-called SoC, i.e. the "State of Charge", in an electric motor-driven car. In particular, EP 1 801 604 B1 discloses a method for compensating an expected SoC of a battery, so that more accurate values can be obtained for this purpose. The determination of the state of aging (SOHC) related to the battery capacity is not described in EP 1 801 604 B1.It is therefore an object of the invention to avoid the disadvantage of the prior art and in particular to specify a method with which the state of aging (SOHC) related to the battery capacity can be corrected.According to the invention, this object is achieved by the features of claim 1. Developments of the invention of an advantageous type are the subject matter of the dependent claims.It is very decisive in the method according to the invention that, in order to correct the errors of a current integral determined by means of current sensors in a storage device, the cell voltage in a battery cell is determined by a cell voltage measurement about a reference point and further cell voltage intervals are recorded and are compared with a reference point of a cell voltage or a cell voltage value.It is preferred that the cell voltage and thus the determined value is determined by both the temperature and the hysteresis.In order to be able to determine the state of aging (SOHC) related to the battery capacity, current values are integrated over a predefined period of time.In order to avoid a current integration error during the summing up, it is preferred if the current values recorded are corrected and stored.It is particularly preferred if the correction of the stored values is dependent on how much energy and / or charge has been enforced since the previous correction of the integration error of the current values.In order to avoid current integration errors, it is advantageous if the determined cell voltage values are compared with the cell voltage values of the reference point.In particular, in the case of the measured cell voltage value not corresponding to the cell voltage value of the reference point, it is advantageous if the charge difference of the voltage measurement value from the reference point is determined via the quiescent voltage characteristic curve of the battery cell.In order to be able to handle the integration errors better, it is advantageous if the charge throughput and the integration time with the integration error are stored in the control device of the battery.In an advantageous embodiment, the offset measurement error of the current sensor is actively used during operation of the battery for correcting the current measurement and thus the integration error, which has to be corrected in order to reach the reference point, is reduced.In addition to the method for SoC determination according to the invention, in which a current is integrated over a long period of time, the invention also provides a battery management system for managing a battery and for outputting a state of charge of a battery to an engine control unit of a vehicle, wherein the battery management systema device for determining the state of aging (SOHC) related to the battery capacity, andintegrating the current values over a predetermined period of time, andcorrected and stored for integration errors.The invention will be described below with reference to the drawings, without limitation thereto. The only enclosed FIG. 1 shows: a) a curve of the SoC (state of charge) over time, wherein some SOHC measurement points are indicated on the curve; b) the real error As at various measurement points arranged downstream of the reference point.FIG. 1 ashows the time profile along a time axis t of the SoC (state of charge) with some SOHC measurement points.In particular, FIG. 1 ashows the curve 1 of a curve of the SoC (state of charge) over time t of a battery. As can be seen from FIG. 1 a, measurement points 3, so-called SOHC measurement points, are evaluated at a plurality of times on the basis of the curve profile of the SoC curve (state of charge) and are determined for subsequent SOHC measurement points, the deviation of which from the reference value 5 of the voltage measurement.The real errors As, i.e. the deviations which result in the course of the SoC curve, are shown in FIG. 1 b. The course of the deviation curve is designated with 10. Identical times to the measurement points 3 in the deviation profile are drawn one above the other. Due to the fact that a cell voltage is used according to the invention for determining the charge, i.e. the SoC, good comparativeability under the same measurement conditions is ensured. The initially determined reference point 5 is always compared with the original reference point 5 on the basis of the cell voltage measurements carried out at other measurement points 3. If deviations from the current value or cell voltage value at the reference point 5 are determined in the determined SOHC values, this value is corrected. The correction of the stored values is dependent on how much energy or charge has been enforced since the last correction. If the measured voltage value does not correspond exactly to the value at the stored reference point 5, but lies at a limited distance from the reference point 5, the charge difference of the measured voltage value at the reference time 5 can be determined via quiescent voltage characteristic curve of the battery cell. The calculated current integration value, which in turn gives a statement about the state of the battery, is adjusted by this charge difference, so that the current integration error is minimized.The invention makes it possible for the first time to minimize the current integration error on the basis of the measurement method used, namely the cell voltage measurement. The invention makes use of the fact that the cell voltage of a lithium-ion battery correctly reflects the state of charge.These conditions are recognized in the invention. If the current integral is not 0 over a longer period of time under these conditions, the current integration around the indicated value is incorrect. This value is used for the SOHC determination and stored measurement points are corrected. This allows a more accurate determination of the capacity of a battery than the sensor allows. The invention thus allows a more accurate determination of the aging and the energy content of a battery.References included in the specificationThis list of documents cited by the applicant has been produced in an automated manner and is only included for the better information of the reader. The list is not part of the German patent application or utility model application. The DPMA does not take any adhesion for any faults or omissions.Patent Literature citedEP 1 801 604 B1

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Claims

Method for correcting the errors of a current integral determined by means of current sensors in a storage device, characterized in that the cell voltage in a battery cell is determined by a cell voltage measurement about a reference point (5) and further subsequent cell voltage values (3) are recorded and compared with the cell voltage value reference point (5).Method according to Claim 1, characterized in that, in addition to the cell voltage, the temperature and the hysteresis are determined.Method for determining the state of aging (SOHC) related to the battery capacity using a method according to one of Claims 1 to 2.Method for determining the state of aging (SOHC) related to the battery capacity according to Claim 3, characterized in that current values are integrated over a predefined period of time in order to determine the state of aging (SOHC) related to the battery capacity.Method for determining the state of aging (SOHC) related to the battery capacity according to Claim 4, characterized in that the current values are corrected and stored in order to avoid a current integration error.Method for determining the state of aging (SOHC) related to the battery capacity according to Claim 5, characterized in that the correction of the stored values is dependent on how much energy and / or charge has been enforced since the previous correction of the integration error.Method for determining the state of aging (SOHC) related to the battery capacity according to one of Claims 3 to 6, characterized in that, in the case of the measured cell voltage value not being equal to the cell voltage value of the reference point, the charge difference of the voltage measured value from the reference point is determined via the quiescent voltage characteristic curve of the battery cell.Method for determining the state of aging (SOHC) related to the battery capacity according to one of Claims 3 to 7, characterized in that the charge throughput and the integration time with the integration error are stored in the control unit of the battery.Method for determining the state of aging (SOHC) related to the battery capacity according to one of Claims 3 to 8, characterized in that the offset measurement error of the current sensor is actively used during operation of the battery for correcting the current current measurement and the integration error which has to be corrected in order to reach the reference point is thus reduced.A battery management system for managing a battery and outputting a state of charge of the battery to an engine control unit of a vehicle using electric power, the battery management system comprising: a battery capacity related aging state (SOHC) determining device wherein current values are integrated for a predetermined period of time and the current integration errors are corrected and stored.

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