DE102014220079A1 - Method for calibrating a sensor of a battery management system - Google Patents

Abstract

The invention relates to a method for calibrating a sensor of a battery management system (1), wherein the sensor is suitable for detecting a charging parameter when charging an associated battery (2) at a charging station (3). According to the invention, the charge current IStation (4) and / or the charging voltage UStation (4) are discharged by the charging station (3) during charging of the battery (2) with a charging current (4) delivered by the charging station (3) at a charging voltage UStation (5). 5), the charging parameter is detected by the sensor of the battery management system (1) in the form of a charging current IBMS or a charging voltage UBMS, a measurement difference between the charging current IBMS and the charging current IStation or the charging measurement voltage UBMS and the charging voltage UStation and the determined measurement difference as the sensor correction value used to calibrate the sensor.

Description

The invention relates to a method for calibrating a sensor of a battery management system during a charge of an associated battery at a charging station. The invention further relates to a battery management system for a battery system having a battery, wherein the battery management system has a sensor which is suitable for detecting a charging parameter when charging the battery at a charging station.

State of the art

Hybrid and electric vehicles use battery packs, often in Li-ion technology, which consist of a large number of series-connected electrochemical cells. A battery management system is used to monitor the battery pack, also referred to below as the battery, and in addition to a safety monitoring to ensure the longest possible life.

The battery management has various sensors for measuring, for example, current, voltage and temperature. A current sensor for measuring a current flowing through the battery is of great importance, since a current value determined by it is generally used for determining the state of charge (SOC). In this case, the state of charge of the battery can be determined more precisely the more precisely an actually flowing current can be determined by the current sensor.

Furthermore, the monitoring of a continuous current output by the battery and of a peak current, the monitoring of which is relevant to safety and whose level can be decisive for the guarantee of guarantee services, is often carried out on the basis of a current sensor. The more precisely a current that can be delivered by the battery can be determined, the smaller the safety buffer can be chosen to compensate for possible measurement inaccuracies.

In addition, battery packs often have a voltage sensor for determining a pack voltage, which can be used to make the sum of the voltages of the series-connected electrochemical cells plausible. Furthermore, the battery can have a voltage sensor for determining a link voltage, which can be measured on the line connection side behind a contactor, via which a network can be connected to the battery. Based on a possible difference between a pack voltage and a link voltage, a diagnosis of the contactor can be made.

Such voltage sensors are usually calibrated installed in the battery during their production. Following this, usually no further calibration takes place, which compensates for possible age-related sensor value deviations.

From the JP2013090473 For example, an energy storage device and method is known for detecting abnormalities of a current sensor of a vehicle. For this purpose, a controller compares the detection values of first current sensors in the energy storage device and second current sensors in a charging device located on-board the vehicle, which is supplied via a charging cable from an external power source.

The JP 2012-080712 describes an in-vehicle vehicle charging device that allows charging of a vehicle battery even when a sensor provides an abnormal value. The vehicle charging device has sensors on the input side, as well as on the output, whose values are compared by an error detection device in order to detect the detection error.

The amount of charge transferred from a source of energy when charging a battery is determined from a time-integrated product of a charging current and an associated charging voltage. Charging current and charging voltage are therefore also collectively referred to as charging parameters. Furthermore, in the following, currents and voltages which are detected by a sensor of the battery management system, referred to as I _BMS and U _BMS , as well as currents and voltages, which are determined by a stationary charging station, referred to as I _station or U _station .

Disclosure of the invention

Provided according to the invention is a method for calibrating a sensor of a battery management system, wherein the sensor is suitable for detecting a charging parameter when charging an associated battery at a charging station. In this case, at a charge of the battery with an output from the charging station when a charging voltage U _station charging current I _station (i) by the charging station, the charging current I _station and / or the charging voltage is detected U _station, (ii) the charging parameters by the sensor of the battery management system detected in the form of a charging current I _BMS or a charging voltage U _BMS , (iii) a measurement difference of the charging current I _BMS and the charging current I _station or the charging voltage U _BMS and the charging voltage U _Station determined and (iv) the determined measurement difference as a sensor correction value for calibration used by the sensor.

Such a method offers several advantages. A first advantage is that a sensor of a battery management is verifiable. At a charging station, in particular for a hybrid or electric vehicle, a precisely determined amount of charge is delivered, not least for billing purposes. For this purpose, the sensors for determining the amount of charge, ie the sensors for determining the output charging current and the existing charging voltage U _{station must be} calibrated. Such a calibration is usually to be ensured by an operator of a charging station, for example by regular checks. In the method according to the invention, a measurement difference is determined from a charge measurement current I _BMS determined by the battery management system and the charge current I _station or a charge measurement voltage U _BMS determined by the battery management system and the charging voltage U _Station . The determination of this difference thus allows a comparison of a value determined by a sensor of the battery management system with a value determined by the charging station, the latter should have a high reliability due to a calibration of the charging station. For example, all sensors of a vehicle battery are jointly exposed to environmental influences that act on the vehicle. Advantageously, the method allows a comparison with a battery management not associated, and in the case of a vehicle battery not on board the vehicle and also usually calibrated current or voltage reference.

Another advantage of the method is that sensor errors are reliably detectable, whereby a check of the sensors is vornehmbar with each charge of the battery. The inventive method thus offers the advantage of a regular sensor diagnosis without the need for additional time overhead.

Furthermore, the inventive method offers the advantage that a sensor of a battery management system regularly, i. at every charge, not only verifiable, but also calibratable. The calibration also takes place without additional time, i. in the case of a vehicle battery, for example, without a workshop visit. From a frequent implementation of the method, i. On the basis of a frequently checked, possibly recalibrated and thus reliably detecting sensor of a battery management system, there are a number of further advantages. Thus, the state of charge of the battery SOC (state of charge) are precisely determined, which allows an accurate statement about an available residual charge or possible residual power. Furthermore, the aging state SOH (State of Health) of the battery can be determined more precisely. Furthermore, precise measurements allow the reduction of safety tolerances. In addition, subtle differences between voltages determined by the battery management system, for example between link voltage and pack voltage, must be determined more precisely, as a result of which battery-internal diagnoses, for example for contactor diagnostics, can be made more precisely.

Advantageously, the method is carried out such that the value of the charging parameter is transmitted from the charging station to the battery management system of the battery, and the battery management system carries out the calculation of the measuring difference. Such an embodiment allows for an efficient implementation of the method, since only a unidirectional data transmission method, for the transmission of the data from the station to the battery, is required for the method. In an alternative embodiment, in which charging current I _BMS or charging voltage U _BMS are transmitted from the battery to the charging station in order to calculate the difference there, a determined measurement difference or a sensor correction value would have to be transmitted to the battery in a further transmission with a bidirectional data transmission method ,

Advantageously, the transmission is secured by a handshake protocol. Handshake is generally understood as a receipt operation. In a corresponding handshake method, two participants involved in a data transmission synchronize after each transmission process by immediate acknowledgment signals. Since the method intervenes in the determination of sensitive battery parameters, a faulty transmission of a charging parameter, which could lead to incorrect calibrations, can cause serious consequences. A transmission of the charging parameter is therefore advantageously acknowledged by the battery. Moreover, the transfer advantageously takes place in a method which transmits the received value back to the sender or which contains information, e.g. a check digit used to verify the accuracy of the received data.

The method is advantageously carried out such that the value of the charging parameter changes over time and the sensor correction value is determined for different values of the charging parameter. Since a sensor error does not have to be constant over a range of values of the variable detected by the sensor, such an embodiment allows the creation of a value table (also called a lookuptable) or a correction characteristic curve, by means of which a corrected sensor value can be assigned to each sensor value determined.

Advantageously, a continuous or stepwise change in the value of the Charging parameter. Such an implementation first allows, with each step, a transmission of the value of the charging parameter, which is set by the charging station in the subsequent time interval. By repeating this procedure, a correction characteristic can be determined step by step. Alternatively or additionally, there is a continuous change in the charging parameter, in which a value of a charging parameter detected in the charging station is quasi continuously transmitted to the battery management system as a result of the transmission. For example, a constant charging current I _station causes a continuously rising charging voltage U _station . A continuous transmission of the charging voltage U _Station allows in the battery management system a determination of an associated continuous charging measuring voltage U _BMS .

Advantageously, a step-by-step change of a charging parameter takes place only after a successful handshake, since a faulty assignment of a supposed, optionally previously set charging parameter to a charging parameter actually set by the charging station can lead to incorrect calibrations.

Advantageously, the method is carried out in such a way that the measurement difference is compared with a threshold value above which error signaling takes place. Such an implementation of the method makes it possible to detect both errors in the calibration and sensor defects and to signal. In the case of carrying out the method in a vehicle battery, a driver can be signaled the presence of an error.

Advantageously, the implementation of the method with a charging voltage U _{station takes place} as a charging parameter. In such an implementation of the method, the charging voltage U _{station is} transmitted, for example, to the battery. The battery management system of the battery determines the load measurement voltage U _BMS via a voltage sensor to be calibrated and calculates the associated measurement difference ΔU. This is stored and used as a sensor correction value UΔ. This is done, for example, by adding the sensor correction value UΔ to the value of a voltage U _BMS determined by the sensor. Advantageously, the determination of the sensor correction value UΔ does not take place for a single voltage value U _BMS but for at least a portion of its value range.

If the charging voltage U _station increases by the charging station, for example gradually, with an associated charging current is adjusted for each charging voltage U _Station I _Station, a respectively corresponding measurement difference .DELTA.U is determined for the respective charging voltage U _station. This is stored in the form of a sensor correction characteristic UΔ (U _BMS ), so that an associated sensor correction value UΔ is available for a value U _BMS determined by the voltage sensor.

Advantageously, the implementation of the method with a charging current I _{station takes place} as a charging parameter. In such an implementation of the method, the charging current I _{station is} transmitted to the battery, for example. The battery management system of the battery determines the charging current I _BMS via a current sensor to be calibrated and calculates the associated measurement difference ΔI. This is stored and used as the sensor correction value IΔ. This is done, for example, by adding the sensor correction value IΔ to the value of a current I _BMS determined by the sensor. Advantageously, the determination of the sensor correction value IΔ does not take place for a single current value I _BMS but for at least a portion of its value range.

If the charging current I _station is incrementally increased by the charging station, for example by raising or lowering the charging voltage U _station until an associated charging current I _{station is} established, a respectively associated measuring difference ΔI is determined for the respective charging current I _station . This is stored in the form of a sensor correction characteristic IΔ (I _BMS ), so that an associated sensor correction value IΔ is available for a value I _BMS determined by the current sensor.

Advantageously, the method is carried out with a negative charging current I _station or a discharge current as a charging parameter. By, for example, a lowering of the charging voltage U _station below the pack voltage or under the link voltage, a reversal of the charging current I _{station can be achieved} in a discharge current, via the change in the same way a sensor correction characteristic IΔ (I _BMS ) can be determined.

Advantageously, the method is performed for calibrating a sensor of a battery management system, which is used to determine the capacity of the battery. A determination of the capacitance based on a calibrated by this method sensor allows an accurate determination of their height, which allows, for example, a precise calculation of an available range or remaining range of a hybrid or electric vehicle.

In the battery management system according to the invention for a battery system having a battery, which has a sensor which is suitable to detect a charging parameter when the battery is charged at a charging station, it is provided that it is set up (i) the size of a battery when charging by means of a Charging station system externally detected charging voltage U _station and / or system externally detected charging current I _station read (ii) via the sensor to detect a charging current I _BMS or a charging voltage U _BMS as a charging parameter, (iii) a measurement difference of the charging current I _BMS and the charging current I _Station or the charging voltage U _BMS and the charging voltage U _Station to determine and (iv) to use the determined measurement difference as a sensor correction value for calibration of the sensor. The battery management system is in particular a battery management system for carrying out the above-mentioned method.

drawings

The invention will be explained in more detail with reference to the accompanying drawings with reference to preferred embodiments.

Show it

1 an example of an arrangement of a battery system at a charging station for carrying out the method according to the invention;

2 an example of a time course of a charging current I _station and a charging current I _BMS in carrying out an embodiment of the method according to the invention;

3 an example of a function of a sensor correction value IΔ in response to a load measuring current I _BMS ;

4 an example of a time course of a charging voltage U _station and a charging measurement voltage U _BMS in carrying out an embodiment of the method according to the invention;

5 an example of a function of a sensor correction value UΔ as a function of a load measuring voltage U _BMS.

1 shows an example of an arrangement of a battery system 10 at a charging station 3 to carry out an embodiment of the method according to the invention.

The battery system 10 has a battery 2 on which of a battery management system 1 is managed. This is indicated by the battery management system 1 a plurality of sensors, not shown here, for detecting voltages, for example the pack voltage as a voltage across the battery pack or, for example, the link voltage as a voltage at a consumer output of the battery 2 on.

The battery system 10 is from a charging station 3 via a charging cable 12 loaded. It flows in the charging cable 12 one from the charging station 3 discharged charging current I _station 4 at a charging voltage U _station 5 , The charging current I _station 4 and the charging voltage U _station 5 are from a control device 11 in the charging station 3 adjustable. Charging voltage U _station 5 and charging current I _station 4 be in the charging station 3 from calibrated measuring instruments I and U.

Furthermore, there is between the charging station 3 and the battery system 10 , in particular between the charging station 3 and the battery management system 1 the battery 2 a data connection 13 , This can be carried out both cordless and as a line. About the data connection 13 is a value of a charging parameter, for example the charging current I _station 4 or the charging voltage U _station 5 from the charging station 3 to the battery management system 1 the battery 2 transmittable. Transmission may be through a handshake protocol between the battery management system 1 and the control device 11 be secured. The control device 11 is set up, the value of the charging parameter, ie the charging current I _station 4 or the charging voltage U _station 5 change the time and the changed value to the battery management system 1 over the data connection 13 to convey. The battery management system 1 is set up to determine the sensor correction value for various values of the charging parameter and to use it to calibrate the sensor.

With the arrangement, a procedure is carried out in such an embodiment that by the control device 11 a continuous or stepwise change of the value of the charging parameter takes place. In this case, a respective change of a loading parameter takes place only after a successful handshake.

After a successful handshake is through the control device 11 the charging station 3 the in 2 shown charge current I _station 4 changed or reset as a loading parameter. On the part of the battery management system 1 Then, by means of a current sensor to be calibrated, the determination of the current voltage in 2 shown charging current I _BMS 6 ,

Alternatively, by the control device 11 the charging station 3 in the 4 shown charging voltage U _station 5 changed or reset as a loading parameter. On the part of the battery management system 1 is carried out by a voltage sensor to be calibrated, the determination of also in 4 shown charging voltage U _BMS 7 ,

The battery management system 1 determines a measuring difference 8th . 9 from the charging current I _BMS 6 and the charging current I _station 4 or the charging voltage U _BMS 7 and the charging voltage U _station 5 . which is used as sensor correction value IΔ for calibrating the current sensor to be calibrated or sensor correction value UΔ for calibrating the voltage sensor to be calibrated.

2 shows an example of a time course of a charging current I _station 4 and a charging current I _BMS 6 in carrying out an embodiment of the method according to the invention, in which the charging current I _station 4 gradually increased, here at intervals of 20A.

3 shows an example of a function of a sensor correction value IΔ in response to a load measuring current I _BMS 6 , To create the function was a charging current I _station 4 as in 2 increased in increments of 20A and a respective load measurement current I _BMS 6 determined. The difference between charging current I _station 4 and a charging current I _BMS 6 was via the charging current I _BMS 6 applied. At a charging current I _station 4 from 60A was from the battery management system 1 a charging current I _BMS 6 at the rate of 65A. The difference between charging current I _station 4 and charging current I _BMS 6 is for a load measurement current I _BMS 6 at 65A accordingly -5A. Is from the battery management system 1 If a current value of 65A is detected, add -5A as the sensor correction value. Since no continuous determination of the value pairs from charging current I _station 4 and charging current I _BMS 6 was carried out, the sensor correction values IΔ (I _BMS ) was between the given values for the charging current I _BMS 6 interpolated.

4 shows an example of a time course of a charging voltage U _station 5 and a charging measurement voltage U _BMS 7 , The curves show a continuous course, since charging voltage U _station 5 and load measurement voltage U _BMS 7 increase with increasing charge state SOC continuously. In this case, charging voltage U _station 5 and load measurement voltage U _BMS 7 by a frequent transmission of the charging voltage U _station 5 to the battery management system 1 quasi synchronously determined. This, too, corresponds to a gradual change of the loading parameter, the step size being selected to be small.

5 shows an example of a function of a sensor correction value UΔ as a function of a charging measurement voltage U _BMS 7 , The determination of a sensor correction value UΔ (U _BMS ) was carried out analogously to the determination of the sensor correction value IΔ (I _BMS ) in FIG 3 , Unlike the procedure in 3 became the charging voltage U _station 5 changed continuously or in small steps, so that for each load measuring voltage U _BMS 7 an associated sensor correction value UΔ (U _BMS ) is available.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• JP 2013090473 [0007]
• JP 2012-080712 [0008]

Claims (11)

Method for calibrating a sensor of a battery management system ( 1 ), the sensor being suitable for charging a corresponding battery ( 2 ) at a charging station ( 3 ) to detect a charging parameter, characterized in that when charging the battery ( 2 ) with one of the charging station ( 3 ) at a charging voltage U _station ( 5 ) charged charging current I _station ( 4 ) - through the charging station ( 3 ) the charging current I _station ( 4 ) and / or the charging voltage U _station ( 5 ) is detected, - the charging parameter by the sensor of the battery management system ( 1 ) in the form of a charging current ( 6 ) or a charging voltage U _BMS ( 7 ) - a measurement difference ( 8th ) 9 ) from the charging current I _BMS ( 6 ) and the charging current I _station ( 4 ) or the charging voltage U _BMS ( 7 ) and the charging voltage U _Station ( 5 ) and - the determined measuring difference ( 8th ) 9 ) is used as the sensor correction value for calibrating the sensor. Method according to claim 1, characterized in that the value of the charging parameter from the charging station ( 3 ) to the battery management system ( 1 ) of the battery ( 2 ) and the battery management system ( 1 ) the calculation of the measuring difference ( 8th ) 9 ). A method according to claim 2, that the transmission is secured by a handshake protocol. Method according to one of the preceding claims, characterized in that the value of the charging parameter changes over time and the sensor correction value is determined for different values of the charging parameter. A method according to claim 4, characterized in that a continuous or stepwise change of the value of the charging parameter takes place. A method according to claim 5, characterized in that a stepwise change of a loading parameter takes place only after a successful handshake according to claim 3. Method according to one of the preceding claims, characterized in that the measuring difference ( 8th ) 9 ) is compared with a threshold above which an error is signaled. Method according to one of the preceding claims, characterized in that the implementation of the method with a charging voltage U _station ( 5 ) as a loading parameter. Method according to one of the preceding claims, characterized in that the implementation of the method with a charging current I _station ( 4 ) as a loading parameter. Method according to one of the preceding claims, characterized in that the implementation of the method with a negative charging current I _station ( 4 ) or a discharge current as a charging parameter. Battery management system ( 1 ) for a battery ( 2 ) having battery system ( 10 ), the battery management system ( 1 ) has a sensor which is suitable for charging the battery ( 2 ) at a charging station ( 3 ) to detect a charging parameter, characterized in that the battery management system ( 1 ) - the size of a battery when charging ( 2 ) by means of a charging station ( 3 ) External charging voltage U _Station ( 5 ) and / or a system-externally detected charging current I _station ( 4 ), - via the sensor a charging current I _BMS ( 6 ) or a charging voltage U _BMS ( 7 ) as a loading parameter, - a measuring difference ( 8th ) 9 ) from the charging current I _BMS ( 6 ) and the charging current I _station ( 4 ) or the charging voltage U _BMS ( 7 ) and the charging voltage U _Station ( 5 ) and - the determined measuring difference ( 8th ) 9 ) as the sensor correction value to calibrate the sensor.

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