DE102012201726A1 - Device for recognizing incorrect voltage measuring conduits for e.g. lithium batteries, has evaluation circuit determining whether voltage measuring conduits are in fault condition and measuring determined voltages from conduits - Google Patents

Abstract

The device has controlled semiconductor switching elements (S1-S4) arranged in such a manner that the switching elements includes a capacitive element (C1) of low pass elements loaded in a first switching state, where the capacitive element of the low pass elements in a second switching state is un-loaded by the switching element. A measuring unit determines the voltage provided on voltage measuring conduits (L0-L5) in the second switching state. An evaluation circuit determines whether the conduits are in fault condition and allows the determined voltages to be measured from the conduits. An independent claim is also included for a method for recognizing an incorrect voltage measuring conduits for multi-cellular, serial interconnected re-loadable batteries for a battery management system.

Description

background

Rechargeable batteries are now widely used and due to climate change, further demand is expected in the future. Rechargeable energies are used, for example, in the context of electromobility as well as the storage of ecological energy in times of high energy production and low energy consumption. In this case, rechargeable batteries are usually built today multicellular, with the individual cells are connected in series. The serial connection enables a higher output voltage of the cells, so that the line cross-sections of the supplied consumers can be lower.

In the area of electromobility, for example, multicellular, serially connected rechargeable batteries based on lithium technology are used. These reach a voltage of up to several 100 volts. In this case, a plurality of cells are connected in series, for example 100 or more.

Battery management systems are used to monitor the cells. These have the task to monitor the loading of individual cells, d. H. to cause the charge in the event of an undervoltage and to adjust the charge in the event of an overvoltage. This increases the overall availability of the rechargeable battery. On the other hand, this measure should also serve as protection, since overcharged batteries can lead to fires or explosions.

For this purpose, common battery management systems (BMS) on a variety of voltage measurement lines, with which the voltage of each cell can be measured.

For this purpose, a so-called passive cell balancing method is usually used. In this case, charge is taken out of one or more individual cells via a resistor R and converted into heat. The voltage measuring line are equipped (in addition to a parasitic low-pass filter) with a low-pass filter to improve the signal quality.

Particularly in the field of electromobility, the environmental requirements for batteries are particularly challenging, since strong vibrations and / or shocks by the drive and / or by the infrastructure properties and / or thermal stress act on the systems and their cables. Each of the aforementioned exemplary influences can lead to individual lines, in particular also voltage measuring lines, damaged z. B. detached or separated.

A disadvantage of the previous battery voltage measurement systems is that they can not reliably detect a faulty voltage measurement line and this can lead to misinterpretations with respect to the state of charge of a cell. This is due to the fact that the voltage does not drop directly to 0 volts, in particular immediately after the occurrence of a fault in the voltage measuring line, but rather remains at the cell voltage level due to the presence of a low-pass voltage measured at the battery management system BMS. As a result, the BMS assumes that, in the charging scenario, the affected cell voltages do not change, although they may change. U. have already reached significantly above their maximum value of the cell voltage.

This not only creates a risk and a reduction in life for the rechargeable battery itself, there is also a risk for self-powered with the rechargeable battery devices and facilities themselves. This is especially true for lithium-based batteries, as they have only low tolerances against surges.

Brief description of the invention

It is an object of the invention to obviate at least some of the aforementioned disadvantages and to provide a device for detecting faulty voltage measurement lines.

The invention achieves the object by providing a device for detecting faulty voltage measurement lines for multicellular, series-connected rechargeable batteries for a battery management system, wherein the battery management system comprises a plurality of voltage measurement lines for contacting cells of a multicellular, series-connected rechargeable battery, wherein the Voltage measuring lines continue to each have a low-pass element with an associated capacitive element. The device comprises a plurality of switching elements, wherein a switching element is arranged such that the switching element can discharge an associated capacitive element of one of the low-pass elements in a first switching state while the associated capacitive element of the low-pass element can not be discharged in a second switching state via the switching element , Furthermore, the invention has a measuring arrangement, which allows to detect a voltage on each of the voltage measuring lines in the second switching state, and an evaluation circuit, which allows from the determined voltages of a voltage measuring line to be able to determine whether the voltage measuring line is faulty or not.

Furthermore, the object is achieved by providing a corresponding method.

Brief Description

The invention will be explained in more detail below with reference to the figures, in which shows

1 a schematic structure of a schematic device according to the prior art, and

2 a schematic flow and schematized devices according to aspects of the invention.

Detailed illustration of the invention

Before describing embodiments of the invention in more detail below, it should first be noted that the invention is not limited to the described components or the described method steps. Furthermore, the terminology used is not a restriction but has only exemplary character. Insofar as the singular is used below in the description and the claims, the plural is included in each case, unless the context explicitly excludes this.

In 1 FIG. 2 shows a schematic layout of a schematized exemplary device BMS according to the prior art.

The battery management system BMS, which is shown schematically as a dashed rectangle, is connected via voltage measurement lines L ₀ , L ₁ , L ₂ , L ₃ , L ₄ to cells Cell 1, Cell 2, Cell 3, Cell 4. The voltage measurement lines each have a low pass. Thus, the voltage measuring line L _{0 has} a low pass made up of a resistor R ₀ and the capacitor C ₁ . Accordingly, the other voltage measuring lines L ₁ , L ₂ , L ₃ , L _{4 have} a low pass.

In this case, adjacent voltage measuring lines may have a common associated capacitive element in the respective low-pass element, for. B. voltage measuring lines L ₀ , L ₁ have capacitor C ₁ as a common associated capacitive element.

For measurement purposes, the voltage measurement lines on a cell are selected by a multiplexer MUX and the applied voltage is sampled via an analog-to-digital converter ADC.

If an error occurs, as is the case with the voltage measuring line L ₃ , ie the line to the cells Cell 3 and Cell 4 is interrupted, the voltage of the cells Cell 3 and Cell 4 can no longer be reliably measured since the voltage between line L ₄ and Line L ₃ as well as the voltage between line L ₃ and line L ₂ - especially immediately after the occurrence of a fault - does not drop directly to 0 Volt on the voltage measuring line, but by the presence of a low-pass the voltage measured at the battery management system BMS voltage remains at about cell voltage level , As a result, the BMS assumes that, in the charging scenario, the affected cell voltages do not change, although they may change. U. have already reached significantly above their maximum value of the cell voltage.

In contrast to this is in 2 a schematic flow and schematized devices according to aspects of the invention shown.

Here, the voltage measuring lines L ₀ , L ₁ , L ₂ , L ₃ , L _{4 are} supplemented by switching elements S ₁ , S ₂ , S ₃ , S ₄ .

In a first, closed state of these switching elements respectively associated with the capacitive element C _1, C ₂ can be S _1, S _2, S _3, S _4, C _3, C ₄ discharged. In a second, open state, these switching elements, the respective associated capacitive element C _1, C ₂ can be S _1, S _2, S _3, S _4, C _3, C _{4 are} not discharged.

For the measurement of the cell voltage, the switching elements S ₁ , S ₂ , S ₃ , S ₄ in the second, open state and the voltage measurement lines to a cell are selected by a multiplexer MUX and sampled the applied voltage via an analog-to-digital converter ADC. However, it is also possible to scan several cells in parallel over a larger number of analog-to-digital converters ADC.

However, in order to be able to carry out an identification of one or more faulty voltage measuring lines within the meaning of the invention, the switching elements are selectively controlled before a measurement.

In a first step 10 the switching elements S ₄ and S _{2 are} short-circuited, so that the charge which is located on the capacitors C ₄ and C ₂ is discharged, ie the voltage across the capacitors C ₄ and C ₂ is approximately at V ₄ = V ₂ = 0 volts. In this case, flows through the voltage measuring lines L ₁ , L _2, a current I _bal (solid arrow) while in the voltage measuring lines L ₃ , L ₄ because of the faulty voltage measurement lines L ₃ no current can flow, ie I = 0 (dotted arrow).

Ie. a first subset of the switching elements will be brought into the first switching state before a first measurement.

The voltage of the other capacitors C ₃ and C ₁ may also be affected by the switching behavior. For example, the voltage across capacitor C _{3 increases} to the voltage of cells Cell 4, Cell 3 and Cell 2. The voltage across capacitor C ₁ remains at the voltage of the cell Cell 1.

Now the switching elements S ₄ and S _{2 are} opened again and the voltage measuring lines L ₀ , L ₁ , L ₂ , L ₃ , L ₄ are now in a conventional manner in one step 20 sampled. In this case, because of the faulty voltage measuring line L _3, the capacitor C ₄ can no longer be charged and the capacitor C ₃ can no longer be discharged. The capacitor C ₂ is in turn charged to the voltage of the cell Cell 2.

Consequently, an overvoltage can be detected on cell cell 3, the z. B. is stored in a memory MEM1. On cell Cell 4, however, an undervoltage will now be determined, the z. B. is stored in a memory MEM2.

In a further step 30 Now the switching elements S ₃ and S _{1 are} short-circuited, so that the charge, which is located on the capacitors C ₃ and C ₁ is discharged, ie the voltage across the capacitors C ₃ and C ₁ is approximately to V ₃ = V ₁ = 0 volts. In this case, flows through the voltage measurement lines L ₀ , L _1, a current I _bal (solid arrow) while in the voltage measurement lines L ₂ , L ₃ because of the faulty voltage measurement lines L ₃ no current can flow, ie I = 0 (dotted arrow).

Ie. a second subset of the switching elements will be brought into the first switching state before a first measurement. The first and the second subset are disjoint.

The voltage of the other capacitors C ₄ and C ₂ may also be affected by the switching behavior. For example, the voltage across capacitor C _{4 increases} to the voltage of cells Cell 4, Cell 3. The voltage across capacitor C ₂ remains at the voltage of the cell Cell 2.

Now, the switching elements S ₃ and S _{1 are} opened again and the voltage measuring lines L ₀ , L ₁ , L ₂ , L ₃ , L ₄ are now in a conventional manner in one step 40 sampled. In this case, because of the faulty voltage measuring line L _3, the capacitor C ₃ can no longer be charged and the capacitor C ₄ can no longer be discharged. The capacitor C ₁ is in turn charged to the voltage of the cell Cell 1.

Consequently, an overvoltage can be detected on cell cell 4, the z. B. is stored in a memory MEM1. On cell Cell 3, however, an undervoltage will now be detected, the z. B. is stored in a memory MEM2.

In this case, the memory MEM1 and MEM2 can be identical to the previously mentioned memory, with the results simply being added, or else the memory can be present twice, so that the chronological course of the measurement can also be correlated with the switching states.

Now, in another step 50 be evaluated whether a faulty voltage line is present. In the example shown cells Cell 3 and Cell 4 are shown over both measurements with both overvoltage and undervoltage. Thus, as the faulty voltage measuring line, the voltage measuring line L ₃ common to the two cells Cell 3 and Cell can be identified.

Ie. By means of the invention it is possible to find faulty voltage measuring lines and thus to increase safety drastically.

It is particularly preferred if the switching elements S ₁ , S ₂ , S ₃ , S _{4 are} controlled semiconductor switching elements and thus allows integration into integrated circuits.

The particular combination of elements and features in the foregoing description of embodiments is merely exemplary. Furthermore, of course, combinations and replacement and replacement of the respective elements and embodiments are possible. Clearly, other variations, modifications and other implementations by a person skilled in the art are not excluded but are also associated with the spirit and spirit of the invention.

Claims (6)

A device for detecting faulty voltage measurement lines for multicellular, series-connected rechargeable batteries for a battery management system, the battery management system having a plurality of voltage measurement lines for contacting cells of a multicell, serially connected rechargeable battery, the voltage measurement lines each further having a low pass element with an associated one having capacitive element, comprising A plurality of switching elements, wherein a switching element is arranged so that the switching element can discharge an associated capacitive element of one of the low-pass elements in a first switching state while the associated capacitive element of the low-pass element can not be discharged in a second switching state via the switching element, a Measuring arrangement, which allows to detect a voltage on each of the voltage measuring lines in the second switching state, • an evaluation circuit, which allows to determine from the determined voltages of a voltage measuring line, whether the voltage measuring line is faulty or not. Apparatus according to claim 1, characterized in that adjacent voltage measuring lines have a common associated capacitive element in the respective low-pass element. Apparatus according to claim 1 or 2, characterized in that the switching elements are controlled semiconductor switching elements. Device according to one of the preceding claims, characterized in that a first subset of the plurality of switching elements are brought into the first switching state before a first measurement, and that a second subset of the plurality of switching elements are brought into the first switching state before a second measurement, wherein the plurality of switching elements have a serial arrangement and the first subset of even-numbered switching elements in the serial arrangement and the second subset of odd-numbered switching elements in the serial arrangement are formed. A method of detecting faulty voltage sense lines for multicellular rechargeable batteries for a battery management system, the battery management system comprising a plurality of voltage sense lines for contacting cells of a multicellular rechargeable battery, the voltage sense lines each further comprising a low pass element with an associated capacitive element A plurality of switching elements, wherein a switching element is arranged so that the switching element can discharge an associated capacitive element of one of the low-pass elements in a first switching state while the associated capacitive element of the low-pass element can not be discharged via the switching element in a second switching state, A measuring arrangement which makes it possible to determine a voltage on each of the voltage measuring lines in the second switching state, • An evaluation circuit which allows to determine from the determined voltages of a voltage measuring line whether the voltage measuring line is faulty or not, comprising the steps Driving a first subset of switching elements into the first switching state and after a predetermined time has elapsed, driving the first subset of switching elements into the second switching state, the plurality of switching elements having a serial arrangement and forming the first subset of even numbered switching elements in the serial arrangement , subsequently Measuring the voltage measurement lines to obtain first voltage measurements, Driving a second subset of switching elements into the first switching state and after a predetermined time has elapsed, driving the second subset of switching elements into the second switching state, wherein the second subset of odd-numbered switching elements are formed in the serial arrangement, subsequently Measuring the voltage measurement lines to obtain second voltage measurements, • evaluate on the basis of the measured first and second voltage measurement values whether a voltage measurement line is faulty. A method according to claim 5, characterized in that the evaluation of a faulty voltage measuring line on the basis of measured over- and under-voltages of adjacent cells of the faulty voltage measuring line takes place.

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