Method for determining the amount of available energy of a battery, battery monitoring device and vehicle

Abstract

The invention relates to a battery monitoring device and a method for determining an amount of available energy of a vehicle battery (12) for an emergency pulse. In the method, an internal resistance value of the vehicle battery (12) is determined (S10) from a measured ripple current, a current energy content of the vehicle battery (12) is determined (S12) by means of the internal resistance value and a predetermined battery characteristic curve (20), a temperature value of the vehicle battery (12) is measured (S14), and the amount of available energy of the vehicle battery (12) for an emergency pulse is determined (S16) by means of the current energy content of the vehicle battery (12), a current discharge current and the measured temperature value.

Description

TECHNICAL FIELD

[0001] The present application relates to a method for determining the amount of energy available for an emergency pulse of a vehicle battery, a battery monitoring device configured to carry out the method and a motor vehicle having such a monitoring device. BACKGROUND

[0002] For the energy supply of a vehicle, generally a generator can be used, in newer vehicle types a DC / DC converter can be used, which supplies the on-board electrical system with energy. In the event of a fault, for example, in the event of a fault of the generator or the DC / DC converter during driving, the vehicle battery must ensure the supply of safety-relevant systems, for example the brakes and / or the steering device, until the vehicle comes to a standstill. This energy or power requirement is generally referred to as an emergency pulse. The emergency pulse can be designed to supply electrical energy for a plurality of steering movements of an electrically assisted steering device and / or a brake assist device, which can last for a few seconds to a few minutes.

[0003] Hitherto, conventional vehicles have been started by means of a pinion starter, which indirectly carries out a diagnosis of the vehicle battery by means of a high starting current from the vehicle battery before the start of driving. As a result of a poor start or a failed start, a defective vehicle battery can already be determined before the start of driving. However, in modern vehicles, the starting process is not or not always supported by means of a pinion start and is also not mandatorily supported by the vehicle battery to be diagnosed. This simple diagnosis method is therefore not suitable and does not provide feedback on defective vehicle batteries.

[0004] From DE 10 2009 058 893 A1, a method for monitoring the state of charge of a chargeable battery is known, in which a state of charge value related to the state of charge is determined by means of current integration, and in which a maximum value for upwardly limiting the determined state of charge value, and / or an average value for downwardly limiting the determined state of charge value, and / or a reference value for resetting the state of charge value is determined by means of a battery parameter.

[0005] From DE 10 2017 221 248 A1, a method for determining a current state of charge value of a battery is known, in which one characteristic curve region is provided, which illustrates, for a corresponding different predetermined temperature range, a specific internal resistance of a specific battery type in relation to the state of charge of the specific battery type.

[0006] From DE 103 37 064 A1, a method and a device for determining and / or predicting the high-current loadability of a battery, in particular a starter battery for a motor vehicle, are known. Here, parameters of a model of the battery impedance are determined by evaluating the alternating components of the battery current and the battery voltage. SUMMARY

[0007] The technical problem addressed by the present application is to perform an energy and power diagnosis of a vehicle battery for determining the amount of available energy for an emergency pulse.

[0008] The present application provides a method for determining the amount of available energy of a vehicle battery for an emergency pulse. The method can be performed, for example, by a battery monitoring device which can be configured as a control device, in particular as a microcontroller. The method comprises determining an internal resistance value of the vehicle battery from a measured ripple current as step a). The ripple current refers to a superimposed alternating current or to a zero-mean alternating component of the battery current and / or battery voltage. The ripple current can be measured, for example, on the vehicle battery or on the vehicle electrical system. The step a) for determining the internal resistance value from the measured ripple current is known from the prior art, in particular from the above-mentioned DE 103 37 064 Al. Subsequently, the method comprises determining a current energy content of the vehicle battery by means of the internal resistance value and a predetermined battery characteristic curve as step b), measuring a temperature value of the vehicle battery as step c), and determining the amount of available energy of the vehicle battery for an emergency pulse by means of the current energy content of the vehicle battery, a current discharge current and the measured temperature value as step d).

[0009] In other words, first an internal resistance value of the vehicle battery is determined from a measured ripple current by a known method. By means of this determination method, in addition, an ohmic component of the vehicle battery can be derived, wherein the internal resistance can be used to predict a voltage drop in the case of a high current load, i.e. to predict the performance of the vehicle battery. In order to determine the performance, in particular a voltage change occurring during an emergency pulse can be determined from the determined internal resistance value and a known current difference. In addition, in addition to the performance of the vehicle battery, the current energy content or current charge content of the vehicle battery can be determined from the internal resistance value by means of a predetermined battery characteristic curve. The battery characteristic curve can be predetermined here in accordance with the requirements and / or specifications of the vehicle battery, in particular in accordance with the design of the vehicle battery. The battery characteristic curve can preferably be determined by measurement. Subsequently, a current temperature value of the vehicle battery of the vehicle battery can be measured and used together with the previously determined current energy content of the vehicle battery and a current discharge current in order to determine the amount of available energy present in the vehicle battery for an emergency pulse. Based on the electrochemical properties of the vehicle battery, the amount of available energy, for example the extractable electrical quantity, is not constant, but is related to the temperature and the currently flowing discharge current. Thus, the amount of available energy is not a constant quantity, but varies not only by charging and discharging, but also by the current discharge current, which refers to the current discharge intensity. The amount of available energy can preferably be determined by means of the above-mentioned characteristic quantities in accordance with the Arrhenius equation and / or the Peukert equation.

[0010] The temperature value can be determined, for example, by means of a temperature sensor, and the current discharge current can be determined by means of a current sensor. The energy content or charge content can be understood as the amount of energy, in particular the amount of charge, which can be present in the vehicle battery. The energy content or charge content can preferably be a value having the physical unit "ampere hours". Correspondingly, the internal resistance value can also be understood as a value of the internal resistance of the vehicle battery, which can be specified, for example, with the physical unit "ohms". The amount of available energy refers to the current and / or voltage of the vehicle battery, which can actually be freely provided and withdrawn from the vehicle battery for implementing an emergency pulse.

[0011] The present application produces the advantage that the vehicle battery can be continuously monitored by the permanently present ripple in the ripple current and that the internal resistance value of the vehicle battery can be determined. By extrapolation from the internal resistance value to the current energy content, the vehicle battery can be diagnosed and predicted at any time of the vehicle operation, in particular for providing an emergency pulse. Overall, a simple and inexpensive possibility of implementing energy and power diagnosis on the vehicle battery is obtained.

[0012] The present application also comprises embodiments which produce additional advantages.

[0013] One embodiment provides, after step d), in addition as step e) checking whether the amount of available energy is below a preset emergency energy threshold value, and as step f), generating a warning signal if step e) is answered in the affirmative. In other words, an emergency energy threshold value is provided, which can be preset, for example, in accordance with the energy required for an emergency pulse, wherein the amount of available energy can thus be checked to see whether it is above or below the emergency energy threshold value. If it is determined that the amount of available energy is below the preset emergency energy threshold value, a warning signal can be generated. It is preferably possible to preset a safety buffer in the emergency energy threshold value, so that an emergency pulse can still be implemented when the emergency energy threshold value is reached. The following advantage is produced by this embodiment, namely that a warning signal can be generated in good time before the amount of available energy is too small for implementing an emergency pulse.

[0014] It is preferably provided that the display device of the vehicle and / or the vehicle control device of the vehicle are / is controlled by means of the warning signal, wherein the vehicle control device, in the event of receipt of the warning signal, brings the vehicle into an emergency operating mode. In other words, a warning can be displayed on the display device of the vehicle by means of the warning signal, by implementing the method for determining the amount of available energy and / or the vehicle control device can be controlled, which, in the event of receipt of the warning signal, brings the vehicle into an emergency operating mode. The emergency operating mode here refers, for example, to an economy mode in which safety-irrelevant power-consuming functions of the vehicle can be deactivated and / or the vehicle speed is limited, so that the vehicle can still be parked safely. The following advantage is produced thereby, namely that the safety of the vehicle, in particular of the vehicle driver, can be improved.

[0015] Furthermore, it is preferred to provide the emergency energy threshold by a preset emergency pulse energy and a preset end-of-discharge energy (Entladeschlussenergie or end-of-discharge voltage) of the vehicle battery. In other words, the available amount of energy is checked by the emergency energy threshold whether it is still sufficient to ensure the supply of the system for emergency actions. Here, in addition to the physical power of the emergency pulse, i.e. the emergency pulse energy, the minimum voltage or end-of-discharge energy which the vehicle battery must have before the end of discharge is also taken into account. This means that not only the minimum energy or minimum voltage for the emergency pulse is taken into account by the emergency energy threshold, but also the end-of-discharge energy for the vehicle battery. This results in the advantage that sufficient energy can be taken into account to implement the emergency pulse, which increases the safety.

[0016] A further embodiment provides that the current energy content of the vehicle battery, in particular the current charge content of the vehicle battery, is provided as a function of the current internal resistance of the vehicle battery by a battery characteristic curve, wherein the battery characteristic curve is determined by at least one previous measurement. In other words, the relationship between the current internal resistance value and the current energy content is provided by the battery characteristic curve. The battery characteristic curve can be determined in advance, preferably by one or more measurements of the vehicle battery, and thus provides a good estimate of the current energy content. This embodiment results in the advantage that the energy content of the battery can be determined by the continuously determinable internal resistance value, by which an energy diagnosis of the vehicle battery can be achieved. The battery characteristic curve can be provided in a data memory, for example as a look-up table or as a function of the energy content with respect to the internal resistance value.

[0017] In a further embodiment, it is provided that the battery characteristic curve is preset according to the manufacturer, the nominal capacity, the battery technology and / or the service life of the vehicle battery. In other words, the battery characteristic curve can be related to a plurality of battery variables which are taken into account in the battery characteristic curve depending on the used vehicle battery. In particular, the battery variables can be determined by previous measurements. The battery technology, for example, means whether it is a wet battery, a gel battery or an absorbed glass mat battery (AGM). This embodiment results in the advantage that the battery variables can be taken into account for the battery characteristic curve, thereby improving the accuracy in determining the current energy content and thus the available amount of energy.

[0018] In another embodiment, the current energy content of the vehicle battery is determined within a preset critical range of the battery characteristic curve. The critical range of the battery characteristic curve refers to a defined range of low energy content (i.e., when the vehicle battery is nearly depleted) on the battery characteristic curve. This critical range can be preset, for example, by an internal resistance threshold in the battery characteristic curve, from which a low energy content still sufficient for an emergency pulse is expected. This embodiment offers the advantage that, within the battery characteristic curve range, under dynamic load conditions, i.e., during discharge, the internal resistance value changes relatively rapidly, and therefore the error in determining the energy content is small. Thus, the accuracy in determining the energy content can be improved.

[0019] Another embodiment specifies that the current discharge current is measured and / or preset using a preset discharge current value. In other words, to determine the amount of energy available, the discharge current of the vehicle battery is measured and / or the discharge current can be preset by a discharge current value, which can be selected to be quite high, thereby complying with the safety limits used to determine the amount of energy available. The discharge current value can preferably be preset using the discharge current typically expected in normal operation of the vehicle battery. This embodiment provides the advantage that the amount of energy available for emergency pulses can be determined more accurately.

[0020] Another implementation specifies that, before activating a vehicle function, the amount of available energy determined in step d) is checked to be sufficient for implementing the vehicle function. If the amount of available energy is insufficient, the activation of the vehicle function is prevented. This means that vehicle functions that place higher demands on energy supply and have insufficient available energy can be disabled before the function begins. If it is determined that the amount of available energy is sufficient, the vehicle function can be activated. A vehicle function refers to a function that provides support, entertainment, and / or comfort to the driver, such as "remote parking assistance." Alternatively or additionally, a vehicle function may also include or support control of the vehicle, wherein the vehicle function is preferably unrelated to safety. In particular, to determine whether the energy is sufficient for the vehicle function, a predetermined functional energy required by the vehicle function can be compared with the amount of available energy. This implementation provides the advantage that additional energy available for emergency pulses can be saved.

[0021] Another embodiment provides that the performance (or power performance) of the vehicle battery is determined by means of the internal resistance value determined in step a) and Ohm's law, wherein, for determining the performance, a voltage change caused by the emergency pulse is determined from the internal resistance value and the known current change for the emergency pulse. In other words, the voltage change or voltage drop of the vehicle battery can be determined by calculating this voltage drop by means of Ohm's law from the internal resistance value and the known current consumption of the emergency pulse. The following advantages arise by this embodiment, namely that the performance of the battery can be estimated quickly and easily.

[0022] Another aspect of the application relates to a battery monitoring device which is configured to carry out the method according to one of the preceding embodiments. The battery monitoring device can preferably be provided as a control device, in particular as a microcontroller. The same advantages and possibilities of variation arise thereby as in the method.

[0023] According to the application, there is also provided a motor vehicle having a vehicle battery and a battery monitoring device. The vehicle battery can be, for example, a starter battery and / or a traction battery of the motor vehicle and in particular comprise a lead-acid battery or a lithium-ion battery. The motor vehicle according to the application is preferably designed as a motor vehicle, in particular as a passenger car or a van, or as a bus or a motorcycle.

[0024] The application also comprises a control device of a motor vehicle. The control device can have a data processing device or a processor device which is designed to carry out an embodiment of the method according to the application. To this end, the processor device can have at least one microprocessor and / or at least one microcontroller and / or at least one FPGA (field-programmable gate array) and / or at least one DSP (digital signal processor). Furthermore, the processor device can have a program code which is designed to carry out an embodiment of the method according to the application when carried out by the processor device. The program code can be stored in a data memory of the processor device.

[0025] The application also comprises an extension of the battery monitoring device according to the application, which has the features already described in connection with the extension of the method according to the application. For this reason, the respective extension of the battery monitoring device according to the application is not described here again.

[0026] The application also comprises combinations of features of the described embodiments. Thus, the application also comprises the following implementation solutions, each of which has a combination of features of several of the described embodiments, unless the embodiments are described as mutually exclusive. BRIEF DESCRIPTION OF DRAWINGS

[0027] Embodiments of the application are described subsequently. To this end:

[0028] Figure 1 A motor vehicle having a battery monitoring device according to an exemplary embodiment is shown schematically;

[0029] Figure 2 A schematic method diagram is shown according to an exemplary embodiment. DETAILED DESCRIPTION

[0030] The embodiments resulting hereinafter are preferred embodiments of the application. In several embodiments, the described components of the embodiments each represent a separate feature of the application which can be considered independently of one another and which each extend the application independently of one another. The disclosure should therefore also include combinations other than those shown of the features of the embodiments. Furthermore, the described embodiments can also be supplemented by further features of the application which have already been described.

[0031] In the drawings, identical reference numerals designate identical elements in each of the numerous figures.

[0032] Figure 1 A schematic motor vehicle 10 is shown having a vehicle battery 12 and a battery monitoring device 14 according to an exemplary embodiment. The vehicle battery 12 can be a lead-acid battery which provides electrical energy to supply the on-board electrical system with energy. The battery monitoring device 14 can be arranged on or in the vehicle battery 12, wherein the battery monitoring device 14 can be configured to determine the amount of energy available for emergency pulses. Here, emergency pulses refer to the supply of electrical energy by the vehicle battery 12 to safety-relevant vehicle systems.

[0033] In order to determine whether the amount of energy available in the vehicle battery 12 is still sufficient for emergency pulses, the battery monitoring device 14 can have a current sensor 16 which can be configured to measure the current of the vehicle battery 12. In particular, the superimposed alternating current of the vehicle battery 12, the so-called ripple current, can be measured. From the measured ripple current, the battery monitoring device 14 can determine the current internal resistance value of the vehicle battery 12 by means of known methods. To this end, the battery monitoring device 14 can have, for example, a central computing unit 18 which can be configured, for example, as a computer processor.

[0034] With the internal resistance value thus determined, the battery monitoring device 14 can then determine the current energy content of the vehicle battery 12 (by determining the current energy content from a predetermined battery characteristic curve 20). To this end, the central computing unit 18 of the battery monitoring device 14 can access, for example, an electronic data store 22 of the battery monitoring device 14 on which the battery characteristic curve 20 can be stored, for example, as a look-up table.

[0035] The battery characteristic curve 20 can in particular provide the current energy content of the vehicle battery 12, in particular the charge content of the vehicle battery 12 as a function of a determined internal resistance, and results from previous measurements, which are determined depending on the manufacturer of the vehicle battery, the nominal capacity of the vehicle battery, the battery technology, for example AGM, and / or the service life of the vehicle battery, which can be known, for example, from the vehicle diagnostic system.

[0036] The current energy content can in particular be determined within a battery characteristic curve range of the battery characteristic curve 20, which represents a critical operating point. Within this critical battery characteristic curve range, that is to say in the case of a poor vehicle battery, the energy content can be determined quickly and without additional dynamics. Furthermore, within the critical battery characteristic curve range, in contrast to a high assumed energy content, the assumed constant relative error in determining the energy content can be small, whereby the error in determining the energy content can be minimized overall.

[0037] In addition, the battery monitoring device 14 can comprise a temperature sensor 24, which can be configured to measure a temperature value of the vehicle battery 12. That is to say, the temperature sensor 24 can determine the current temperature of the vehicle battery 12 and can provide it to the battery monitoring device 14, in particular to the central computing unit 28, for further processing. By means of the previously determined current energy content of the vehicle battery 12, the measured temperature value and the current discharge current, which can also be determined, for example, by means of the current sensor 16, the available amount of energy of the vehicle battery 12, which can be provided for the emergency pulse, can be determined by the battery monitoring device 14. Based on the electrochemical action of the vehicle battery 12, the available amount of energy, that is to say the extractable electrical quantity, can not be constant, but rather is related to the current temperature of the vehicle battery 12 and the current strength of the discharge current flowing. In other words, although no charging of the vehicle battery 12 takes place, but only the discharge current is reduced, or the temperature of the vehicle battery 12 changes, the available amount of energy can increase, for example, again.

[0038] The available amount of energy can then be checked by the battery monitoring device 14 whether it is below a preset emergency energy threshold. The emergency energy threshold can be preset, for example, by a preset emergency pulse energy required for an emergency pulse and a preset end-of-discharge energy which has to be maintained as a minimum energy for the vehicle battery 12. If it is determined that the available amount of energy is below the preset emergency energy threshold, a warning signal can be generated by the battery monitoring device 14, by means of which the display device 26 of the vehicle 10 and / or the vehicle control 28 of the vehicle 10 can be controlled. The display device 26 can preferably display a warning to the vehicle driver that the available amount of energy in the vehicle battery 12 is critical and that the driver should stop the vehicle 10 for safety reasons. Alternatively or additionally, the vehicle control 28 can bring the vehicle 10 into an emergency operating mode by receiving the warning signal, whereby the vehicle 10 can be slowed down, for example, which can additionally increase the safety of the vehicle 10.

[0039] Figure 2 A schematic method diagram for determining the available amount of energy of the vehicle battery 12 for an emergency pulse is shown. In step S10, the internal resistance value of the vehicle battery 12 can be determined from the measured ripple current. Then, in step S12, the current energy content, i.e. the current battery capacity, of the vehicle battery 12 can be determined by the internal resistance value and the predetermined battery characteristic curve 20.

[0040] Furthermore, in step S14, a temperature value of the vehicle battery 12 can be measured and in step S16, the available amount of energy of the vehicle battery 12 available for an emergency pulse can be determined, wherein for this the current energy content of the vehicle battery, the current discharge current and the measured temperature value can be used.

[0041] Additionally, it can be checked in step S18 whether the available amount of energy determined in step S16 is below a preset emergency energy threshold, wherein if it is determined in S18 that the available amount of energy is below the preset emergency energy threshold, a warning signal can be generated in step S20.

[0042] In summary, the examples show how an energy and power diagnosis of the vehicle battery 12 in the on-board power supply network can be provided by the present application to predict an emergency pulse.

Claims

1. A method for determining an amount of available energy of a vehicle battery (12) for emergency pulses, the method having the following steps: a) determining (S10) an internal resistance value of the vehicle battery (12) from a measured ripple current; b) determining (S12) a current energy content of the vehicle battery (12) by means of the internal resistance value and a predetermined battery characteristic curve (20); c) measuring (S14) a temperature value of the vehicle battery (12); and d) determining (S16) an amount of available energy of the vehicle battery (12) for emergency pulses by means of the current energy content of the vehicle battery (12), a current discharge current and the measured temperature value, e) checking (S18) whether the amount of available energy is below a predetermined emergency energy threshold value; f) generating (S20) a warning signal if step e) is answered in the affirmative, an emergency pulse meaning that the vehicle battery supplies a safety-relevant vehicle system with electrical energy. The display device (26) of the vehicle (10) and / or a vehicle control device (28) of the vehicle (10) are controlled by means of the warning signal, wherein the vehicle control device (28) places the vehicle (10) in an emergency operating mode upon receipt of the warning signal. The emergency energy threshold value is predetermined by a predetermined emergency pulse energy of the vehicle battery (12) and a predetermined discharge end energy. The current energy content of the vehicle battery (12) is provided by means of a battery characteristic curve (20) as a function of the current internal resistance of the vehicle battery (12), wherein the battery characteristic curve (20) is determined from at least one previous measurement. The current charge content of the vehicle battery (12) is provided by means of a battery characteristic curve (20) as a function of the current internal resistance of the vehicle battery (12). The battery characteristic curve (20) is predetermined in accordance with the manufacturer, the nominal capacity, the battery technology and / or the service life of the vehicle battery (12). The current energy content of the vehicle battery (12) is determined within a predetermined critical battery characteristic curve range of the battery characteristic curve (20). wherein a safety buffer is preset in the emergency energy threshold, so that the emergency pulse can still be implemented when the emergency energy threshold is reached, wherein The current discharge current is measured and / or predetermined by means of a predetermined discharge current value.

2. The method of claim 1, wherein, Before starting a vehicle function, it is checked whether the amount of available energy determined in step d) is sufficient for implementing the vehicle function, wherein starting of the vehicle function is prevented if the amount of available energy is not sufficient for implementing the vehicle function.

3. The method of claim 2, wherein, The performance of the vehicle battery is determined by means of the internal resistance value determined in step a) and Ohm's law, wherein, for determining the performance, a voltage change caused by an emergency pulse is determined from the internal resistance value and a current change known for emergency pulses.

4. The method of claim 1, wherein, 11. A vehicle monitoring device (14) which is designed to implement the method according to any one of the preceding claims.

5. The method of claim 4, wherein, 12. An automobile (10) having a vehicle battery (12) and a vehicle monitoring device (14) according to claim 11.

6. The method of claim 1, wherein, ​ 7. The method of claim 1, wherein, ​ 8. The method of claim 1, wherein, ​ 9. The method of claim 1, wherein, ​ 10. The method of claim 1, wherein, ​ ​ ​

Images