Classifications

• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
  • G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
  • G01R31/36—Arrangements for testing, measuring or monitoring the electrical condition of accumulators or electric batteries, e.g. capacity or state of charge [SoC]
  • G01R31/389—Measuring internal impedance, internal conductance or related variables

Definitions

• the invention relates to a method for determining a relative portion of a complex internal resistance of a battery.
• this can be understood as the determination by a battery sensor (IBS) connected to the battery.
• IBS battery sensor
• An internal resistance of a battery typically describes the magnitude of voltage changes in relation to the current changes applied to the battery, for example according to Ohm's Law.
• the real part of the internal resistance of the battery above an excitation frequency of about 100 Hz is particularly interesting.
• inductive components contribute to the complex resistance of the battery, and at significantly lower frequencies, capacitive components.
• An intelligent battery sensor offers the possibility of measuring current and voltage at a frequency of at least 1000 Hz and by evaluating both signals to infer the real part of the resistance.
• the battery current is usually ge ⁇ measured using a shunt resistor.
• the voltage signal at the shunt resistor is amplified and amplified via a fast, time-discrete analog-digital (AD) converter converted to digital values.
• the battery voltage is fed via a voltage divider into an AD converter.
• the measured current and voltage values undergo filtering, are differentiated and the quotient is formed. This is done according to Ohm's law R dU / dI. A suitable downstream averaging and normalization can then lead to the final value of the internal resistance. In this determination method, however, the real part of the internal resistance is not determined, but rather the absolute value of the complex impedance Z, as shown schematically in FIG. 1, for example.
• the exciting frequency is given by the electrical system, which makes it variable and unpredictable. This leads to strong fluctuations.
• the determination of the internal resistance, in particular with laboratory means, can usually be carried out with a special measuring device which determines the complex impedance Z (f) at a frequency of, for example, 1 kHz. For this purpose, a small sinusoidal current, usually with 1000 Hz, of the battery becomes active impressed. The voltage change caused by this current on the battery is measured and the real and imaginary part of the impedance Z are determined by means of the resulting phase shift.
• the resulting real resistance R is then the real resistance of the battery.
• the problem for an application in a battery sensor is the comparatively high effort to actively impart a current, so that this method is predominantly found in laboratory measuring instruments.
• the invention relates to a method for determining a real part of a complex internal resistance of a battery, comprising the following steps:
• the calculation of the real part of the internal resistance is based on a differential equation based on the battery model.
• the differential equations associated with the battery model are determined.
• the calculated differential equations are converted into their time-discrete counterpart, the difference equations, since the measured values present for the calculation of the internal resistance are, in particular, time-discrete.
• these difference equations or differential equations are resolved according to the real part of the complex internal resistance of the battery to be determined.
• a frequency-independent real part can also be simply spoken of a real part.
• To connected devices can be, for example, components that are typically present in a vehicle, in particular electronic Steuerungsvor ⁇ directions, lights, alternators, other components of a vehicle lighting, ignition or comfort items such as electric windows or motors of an electric seat adjustment.
• the measurement is performed without exciting the battery or imparting an excitation signal to it.
• This can be understood in particular to mean that there are no components which specifically impose a current or a voltage of the battery for the purpose of measurement.
• Such components which are typically expensive, can thus be dispensed with, which significantly improves the usability of the method, especially in vehicles for the mass market.
• the rule may, in particular based on a He ⁇ equivalent circuit diagram of the battery. Such a replacement circuit diagram will be described below and also with reference to the drawing at ⁇ , so that reference can be made to the comments below.
• model parameters L, R x and C x can in particular be functions of a state of charge (SOC), a temperature and / or a battery capacity.
• At least the battery voltage values (U), the battery current values (I), first and second derivatives of the battery voltage values (U) can be included in the calculation specification first, second and third time derivatives of the battery ⁇ current values (I) received.
• Calculation rules with such values have proven to be advantageous for typical applications. Exemplary calculation rules are given below.
• the calculation rule may be given by the following formula:
• OCV Open Clamp Voltage
• the calculation rule can specify that the real part is to be determined as the slope of a straight line which approximates points in a two-dimensional coordinate system having an x-axis and a y-axis, wherein the calculation rule plots applied terms on the x-axis and indicating on the y-axis.
• the real part can be determined. Examples of this are given below.
• the calculation rule can specify in particular that the term dt dt is plotted on the x-axis and the term is plotted on the y-axis dt dt dt dt dt is applied. Such a procedure has proved particularly advantageous in the case in which OCV can not be assumed to be constant.
• the slope a thus corresponds to the real resistance R.
• this can also indicate, for example, that the term dt dt is plotted on the x axis and the term dt dt dt dt is plotted on the y axis.
• the calculation rule may indicate in particular that at least two different regression methods are used for loading ⁇ humor of a respective real part, wherein a distance between the respectively determined real parts is a measure of the quality of the calculation.
• the Zuver ⁇ permeability can be increased in the determination of the real part.
• basically only one regression method can be used.
• calculation rule can specify that the real part is calculated according to the following formula:
• Xi are the values of the term plotted on the x-axis at time t ⁇ ,
• yi are the values of the y-axis term at time t ⁇
• the calculation rule can also specify that the real part is calculated at each measurement time as a quotient of a first term and a second term. Again, suitable formulas have been found which are suitable for determining a real part. For example, the calculation rule may specify that the first term dt dt is and the second term is.
• the battery may advantageously be a lead-acid battery.
• Such batteries have proven themselves in particular for use in motor vehicles, and it has been shown that the inventive method is applicable before ⁇ geous, especially for such batteries. It should be understood, however, that under a battery, typically a rechargeable battery is meant here, which may be referred to for example as Ak ⁇ kumulator. It should be noted in this regard that for batteries used in motor vehicles, the term battery, especially car battery, has prevailed.
• the battery voltage values (U) and / or the battery current values (I) may be used filtered or unfiltered. Filtering can improve the accuracy of the calculation, while eliminating filtering can reduce the need for computational power. According to a further aspect of the invention, a control device is set up to carry out a method according to one of the preceding claims.
• the specified device has a memory and a processor.
• the specified method is stored in the form of a Compu ⁇ terprogramms in the memory and the processor is provided for performing the method when the computer program from the memory is loaded into the processor.
• a computer program comprises program code means for performing all the steps of one of the specified methods when the computer program is executed on a computer or one of the specified devices.
• a computer program product comprises a program code which is stored on a data carrier and the compu ⁇ terlesbaren, when executed on a data processing device, carries out one of the methods specified.
• a battery sensor comprises a specified control device.
• a vehicle includes a specified battery sensor.
• the invention further relates to a battery arrangement with a battery, in particular a lead-acid battery and such a device. Moreover, the invention relates to a computer-readable non-volatile storage medium containing program code, in the execution of which a processor performs the method according to the invention.
• Fig. 2 an electrical equivalent circuit diagram of a lead-acid battery.
• the invention is based on an electrical equivalent circuit diagram of the battery, which is parameterized such that it maps the nen ⁇ resistance of the battery to be measured.
• Such an equivalent circuit diagram is reproduced in FIG. 2, where L denotes an inductance, R the internal resistance, C x a capacitance, R x a capacitance C x parasitic resistance, and OCV an open terminal voltage.
• the open terminal voltage OCV may in particular depend on parameters such as a temperature T or a state of charge SOC.
• the model can also be extended by additional elements compared to Figure 2: resistors R, capacitances C, inductors L, nonlinear elements, Warburg element, etc., It can also be parameterized depending on the battery state (state of charge, temperature, etc.).
• the calculation of the real part of the internal resistance then takes place on the basis of a differential equation based on the battery model.
• the differential equations associated with the battery model are determined, and in a further step these equations are resolved according to the value R to be determined.
• R the value of the battery model
• the value R represents the real internal resistance of the battery. If OCV were constant, then the real resistance at any time by means of the following simplifying ⁇ fanned equation could be calculated:
• the derivatives of current and voltage after the time (d / dt) can be calculated, for example, in a microcontroller (yC) by differentiation.
• the value R is then independent of frequency.
• the real resistance can be determined, for example, by a least square analysis (regression line).
• regression line the term X determined from measured values is determined on a virtual x-axis
• the virtual y-axis is used to plot the calculated term Y
• the determination of the real part of the internal resistance of a battery, in particular a lead-acid battery can be More generally, for example, by applying a method with the following steps:
• the resistance may be determined by regression analysis of a plurality of values of Xi and Y ⁇ .
• derivatives of higher order time may also be used, for example, as follows:
• the squared distances of the Yi values of calculated Y values can be used: i
• the quadratic distances of the Xi values of calculated X values can be used to find the balance line between Xi and Y ⁇ :
• the quadratic distances of the value pairs Xi Yi can also be minimized from the calculated equalization line:
• the difference between the resistance R from different calculation methods can be used as a measure of the quality or the error of the resistance.
• offset B can be set to 0, which simplifies the calculation (here, for the quadratic Yi values of calculated Y values):
• the calculation of the time derivative can be determined, for example, by subtraction:
• the input values of current and voltage can be both filtered and unfiltered in the regression calculation.
• steps of the method according to the invention can be carried out in the order given. However, they can also be executed in a different order.
• the method according to the invention can be carried out in one of its embodiments, for example with a specific combination of steps, in such a way that no further steps are carried out. However, in principle also further steps can be carried out, even those which are not mentioned.

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• General Physics & Mathematics (AREA)
• Secondary Cells (AREA)
• Measurement Of Resistance Or Impedance (AREA)

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• 2015
  • 2015-09-29 DE DE102015218797.7A patent/DE102015218797A1/de active Pending
• 2016
  • 2016-09-29 EP EP16774935.7A patent/EP3356835A1/de active Pending
  • 2016-09-29 WO PCT/EP2016/073231 patent/WO2017055428A1/de active Application Filing
  • 2016-09-29 CN CN201680069442.9A patent/CN108291943B/zh active Active

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