JP2008547008A - Battery state detection method and apparatus for automobile accumulator - Google Patents

Abstract

  The present invention relates to a method for detecting battery parameters (U2, SOC, Ri) of a battery (1) comprising a plurality of cells (1a to 1l) connected in series, in particular an automobile battery. In order to detect a battery parameter for a group of cells (1a-1l) whose reference potential is not ground, the battery parameter is calculated. Here, the voltage drops in the first cell group (2a) (U1) and drops in the second cell group (1) including the first cell group (2a) and the third cell group (2b) The second voltage (Ug) is measured, and the battery parameters (U2, SOC, Ri) of the third cell group (2b) are the measured first voltage (U1) and second voltage (Ug). ).

Description

  The invention relates to a method for detecting the state of a battery, in particular a vehicle battery, according to the superordinate concept of claim 1, and a corresponding device according to the superordinate concept of claim 7.

  Conventional vehicle batteries (accumulators), such as NiMH batteries or lead hydrochloric acid batteries, usually consist of a plurality of directly connected individual cells, each of which forms a partial voltage of several volts (eg 2V). Here, the number of cells determines the nominal voltage of the battery. A battery with a nominal voltage of 12V contains six cells of approximately 2V each. When the power supply voltage of the in-vehicle power supply is relatively high, for example, 24V or 42V, a plurality of 12V batteries are usually connected in series.

  It is known to use so-called battery status identification devices (BZE) to diagnose vehicle batteries. This is an algorithm (mathematical model) stored in the controller that calculates the current battery state from continuously measured battery parameters such as battery current, battery voltage, and battery temperature. In order to estimate the state of charge, BZE, for example, evaluates the battery's pulse response to current pulses.

  Due to manufacturing tolerances and different external influences (e.g. different temperatures, mechanical loads, aging, etc.), the lifetime of individual cells of a battery or individual (12V) batteries connected in series is not exactly the same . This limits the output capacity of the entire battery. This is because the battery cannot be further discharged when the weakest cell is discharged, and cannot be charged further when the strongest cell is fully charged.

  In order to take into account the different characteristics of individual cells during diagnosis, it is known not only to analyze the state of the entire battery, but also to detect the state of individual cells or the state of individual groups. For this purpose, it is necessary to measure the voltage dropping in the cell and supply it to BZE. However, the measured voltage is not related to different reference potentials. For example, in the case of a 24V battery that includes two 12V batteries connected in series, the reference potential of the first partial battery (with 24V and 12V terminals) is the body when the + 12V reference potential is + 12V and the ground terminal The reference potential of the second partial battery is ground. This causes difficulties in signal processing. This is because the conventional control device has only a signal input terminal designed with ground as a reference potential.

  In order to allow further processing of the signal, the potential difference must be corrected with the voltage sensor of the first partial battery or with the controller. The means for correction is, for example, to relate the voltage of the first partial battery (reference potential + 12V) to ground by means of a differential amplifier. However, the circuit cost is relatively high with this solution.

  Therefore, an object of the method and apparatus of the present invention is to make it possible to easily detect battery parameters of a group of cells whose reference potential is not ground.

  According to the invention, this problem is solved by the features of claims 1 and 7. Other embodiments of the invention are the subject of the dependent claims.

  An important technical idea of the present invention is that the battery parameters (e.g. voltage, state of charge or internal resistance) of a group of cells where the reference potential is not ground, the two other groups related to the same reference potential, preferably ground. Is derived from the voltage of According to the present invention, the battery parameter is detected as follows. That is, the voltage dropped in the first cell group and the voltage dropped in the second cell group including the first cell group and the third cell group are measured, and the battery parameters of the third group are determined. The calculation is based on the two measured voltages. This has the particular advantage that the cell voltage of the third group of cells is not measured and therefore the voltage signal does not have to be processed by another reference potential.

  One cell group can include one or more cells in the present invention. Here, the battery parameter is a battery state parameter, such as a state of charge SOC, an aging state (or output capability) SOH, or other state parameter, as well as an external voltage, an internal resistance R, or any other electrical battery parameter. is there.

  According to the first embodiment of the present invention, the third voltage (U2) dropping in the third cell group can be calculated from the measured first voltage (U1) and the second voltage (Ug). it can. For the third voltage (U2): U2 = Ug-U1. Based on this third voltage, another battery parameter, for example, the state of charge of the third group of cells can be calculated.

  According to another embodiment of the invention, the voltages U2, Ug of the first cell group and the second cell group are first measured, from which the respective battery parameters, for example the state of charge, are calculated, after which the third The battery parameter values for the cell groups are calculated.

  The first and second voltages preferably have the same reference potential, in particular ground.

  The device according to the invention for detecting battery parameters comprises a voltage sensor for measuring the voltage dropping in the first cell group or the second cell group and a calculation unit. This calculation unit is supplied with the measured voltage, from which the calculation unit calculates the battery parameters required for the third group of cells. The voltage sensor preferably has separate sensors for the first cell group and the second cell group. Alternatively, only one voltage sensor can be provided that can switch between the first cell group and the second cell group.

  The voltage sensor preferably has a voltage divider which reduces the measured voltage to a predetermined voltage range.

  The voltage sensor preferably has an A / D converter, which samples and digitizes the analog voltage signal.

Hereinafter, embodiments of the present invention will be described in more detail with reference to the accompanying drawings. FIG. 1 schematically illustrates a configuration for detecting a battery condition parameter according to an embodiment of the present invention.
FIG. 2 shows the main method steps of the method for detecting battery status parameters.

  FIG. 1 shows a configuration for detecting a battery parameter, for example, a state of charge SOC of the battery 1. Here, the battery 1 has two 12V accumulators 2a and 2b connected in series, each of which is composed of a plurality of individual cells 1a to 1f to 1g to 1l.

A mathematical battery model 7 is provided for calculating battery parameters, and this battery model is stored in the control device 6 as software. In the model 7, for example, the state of charge SOC of the accumulators 2a and 2b or the entire battery 1 can be obtained from the pulse response of the voltages U1, U2 to Ug to the current pulse. (With a slight modification of the circuit, the battery parameters of the individual cells 1a to 1l or groups of cells can also be detected.)
Furthermore, this structure has a first voltage sensor 4 and a second voltage sensor 5. The first voltage sensor 4 measures the voltage U1 that drops in the first accumulator 2a, and the second voltage sensor 5 measures the voltage Ug that drops in the entire battery 1.
The analog measurement values U1 and Ug are digitized by an A / D converter (not shown) and supplied to the control device 6 digitally.
A current 1 flowing through the battery 1 is measured by a current sensor 3. One or more temperature sensors (not shown) can be provided for temperature measurement.

Here, the control device 6 has only an interface related to ground. Therefore, it is not easy to supply the voltage U2 having another reference potential to the control device 6. In order to still be able to detect the voltage U2 or another battery parameter for the accumulator 2b, the battery model 7 is implemented so that the voltage U2 or the battery parameter of the accumulator 2b is calculated from the voltages U1 and Ug. ing. For voltage U2, the following equation holds:
U2 = Ug-U1
The pulse response to the current pulse from the calculated voltage U2 is evaluated taking into account the battery current 1 and the battery temperature T, so that the charge state SOC of the accumulator 2b or other battery parameters such as aging state (SOH) or internal resistance Ri is calculated.

  Alternatively, the battery parameters (SOC, SOH, Ri) of the second accumulator 2b can be detected without calculating U2. That is, the battery parameter is obtained from the corresponding parameters of the first accumulator 2a and the entire battery 1. In this case, the charge state SOC of the first accumulator 2a and the whole battery 1 is obtained by the battery model 7, and the charge state SOC of the second accumulator 2b is calculated therefrom. Other parameters can also be calculated from this state of charge.

  FIG. 2 shows in a flowchart the main method steps for detecting the state of charge SOC of the second accumulator 2b. First, in step 10, the voltage U1 dropping in the first accumulator 2 a is measured, and in step 11, the voltage Ug dropping in the entire battery 1 is measured by the sensors 4 and 5 and supplied to the control device 6. Next, in step 12, the battery model 7 calculates a voltage U2 that drops in the second accumulator 2b, and in step 13 determines the state of charge SOC of the second accumulator 2b.

FIG. 1 schematically illustrates a configuration for detecting a battery condition parameter according to an embodiment of the present invention. FIG. 2 shows the main method steps of the method for detecting battery status parameters.

Explanation of symbols

1 Entire battery
1a ~ 1l individual cell
2a, 2b accumulator
3 Current sensor
4 Voltage sensor
5 Voltage sensor
6 Control unit
7 Mathematical battery model
10-13 method steps
U1 Voltage drop in the first accumulator 2a
U2 Voltage drop in the second accumulator 2b
Voltage drop across Ug battery
l Battery current
T Battery temperature
SOC state of charge
SOH output capability
Ri Internal resistance

Claims (10)

In the battery parameter (U2, SOC, Ri) detection method for a battery comprising a plurality of cells connected in series,
The first voltage (U1) dropping in the first cell group (2a) is measured,
The second voltage (Ug) dropping in the second cell group (1) having the first cell group (2a) and the third cell group (2b) is measured,
The battery parameters (U2, SOC, Ri) of the third cell group (2b) are calculated based on the measured first voltage (U1) and second voltage (Ug). Feature method. The method of claim 1, wherein
The voltage (U2) dropping in the third cell group (2b) is calculated from the measured first voltage (U1) and second voltage (Ug). The method of claim 1, wherein
The battery parameters (SOC, Ri) of the first cell group (2a) are calculated based on the first voltage (U1), and the second cell group (based on the second voltage (Ug)). A battery parameter (SOC, Ri) for 1) is calculated, and a battery parameter (SOC, Ri) for the third cell group (2b) is calculated based on the two values. The method according to any one of claims 1 to 3,
The method according to claim 1, wherein the first voltage (U1) and the second voltage (Ug) have the same reference potential. The method of claim 4, wherein
The method of claim 1, wherein the reference potential is ground. In the method according to any one of claims 1 to 5,
A method characterized in that the state of charge is calculated. In a battery parameter (U2, SOC, Ri) detection device for a battery comprising a plurality of cells (1a to 1l) connected in series,
A first voltage sensor (4) for measuring a first voltage (U1) dropping in the first cell group (2a);
A second voltage sensor (5) for measuring a second voltage (Ug) dropping in a second cell group (1) having the first cell group (2a) and the third cell group (2b) When,
A calculation unit (7) to which the two measured voltages (U1, Ug) are supplied,
The calculation unit calculates the battery parameters (U2, SOC, Ri) of the third cell group (2b) based on the two voltages (U1, Ug). The apparatus of claim 7,
The device characterized in that the first and second voltage sensors (4, 5) have voltage dividers. The apparatus according to claim 7 or 8,
The first and second voltage sensors (4, 5) have an A / D converter. In the device according to any one of claims 7 to 9,
The calculation unit (7) calculates the state of charge (SOC).

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