Fault Detection Circuit for Battery Pack Connecting Wire

Abstract

The present invention discloses a fault detection circuit for a battery pack connection line. By setting voltage-dividing resistors in the detection circuits corresponding to the even-numbered or odd-numbered battery cells, it can be ensured that the light-emitting diodes in the corresponding detection circuits cannot be lit regardless of abnormal situations such as misconnection or omission of the battery connection lines of the battery pack, and the fault conditions of the connection lines of the battery pack can be accurately detected. Moreover, by connecting a voltage-resistant diode in series between the light-emitting diode and the negative electrode of the battery or connecting a diode in reverse parallel across the two ends of the light-emitting diode, it can be guaranteed that the light-emitting diode will not be broken down and damaged regardless of any misconnection of the connection lines.

Description

Technical Field

[0001] The present invention relates to the field of battery management, and more particularly, to a fault detection circuit for a battery pack connection line. Background Art

[0002] In large energy storage systems, the required battery capacity and voltage are relatively large. Usually, multiple single cells need to be connected in series to form a battery pack to increase the voltage, and multiple batteries need to be connected in parallel to form a battery pack to increase the capacity. Since the number of batteries that need to be connected in series / parallel is relatively large, for safety and reliability, and to extend the battery life, it is necessary to manage the electrical performance parameters of each battery pack. A dedicated battery management system (BMS) is required. Among these electrical parameters, the single cell voltage is particularly important and must be limited within a reasonable range. After the single cells are connected in series, the entire battery pack is charged and discharged together, and the current passing through each cell is the same. Due to the differences between single cells, there will inevitably be individual single cells that are fully charged first and individual single cells that are discharged first. To ensure safety and battery life, as long as one cell is fully charged, the entire battery pack must stop charging, and as long as one cell is discharged, the entire battery pack must stop discharging. Therefore, the BMS must monitor each single cell in real time, that is, there are connection lines between the BMS and each single cell. There are numerous battery connection wire harnesses, as Figure 1 shown.

[0003] The installation process of the battery pack requires manual participation, and there will inevitably be many assembly problems such as incorrect battery installation, incorrect connection of wire harness nodes, and unconnected wire harnesses. Especially in repair service stations, the reuse of secondary batteries, etc., there are many temporary workers, and the operation levels of the workers vary, and they do not understand the battery characteristics. Once the connection line of the battery pack is connected incorrectly, the input voltage of the subsequent application circuit will be a negative voltage, and it cannot work properly, and it is very likely to damage the BMS, thereby causing the entire system to malfunction. If the problem is only discovered during system debugging after the battery pack is assembled, the workload of troubleshooting and disassembling the battery box again is huge. Therefore, a simple and reliable detection device is needed on site to immediately test the reliability of the wire harness connection after the wire harness is installed and before the battery box cover is closed.

[0004] The existing method for detecting the wire harness of the battery pack is as follows: Make a wire harness detection board. After the wire harness is connected to the battery, insert the wire harness detection board into the wire harness to determine whether the connection between the wire harness and each single cell is normal. The circuit principle of the detection board is as Figure 2 shown. A detection unit is provided on each battery connection line. The detection unit includes an LED lamp connected in parallel with the battery and a current-limiting resistor connected in series with the LED lamp. When the wire harness corresponding to the battery is connected normally, the input of the corresponding LED lamp is a positive voltage, and the LED lamp is lit; when there is an incorrect wire harness connection, as Figure 3 shown, such as the B N-2 circuit and B N+1If the circuit connection is reversed, the LED N-1 and the LED N+1 The input voltage becomes negative and cannot be lit, and the LED N-1 and R N-1 and the LED N+1 and R N+1 Both of the two series branches have to bear the reverse voltage of two batteries, while the LED N-2 and R N-2 and the LED N+2 and R N+2 Both of the two series branches have to bear the forward voltage of four batteries. Since the reverse voltage withstand of the LED is relatively low, when the connection wire is misconnected by a large margin from the correct position, the LED will be damaged. However, there are two problems with this detection method: when the battery connection wire is not connected, such as Figure 4 in the B N path is disconnected, the corresponding LED of this path can still be normally displayed, and the abnormal state of the connection wire cannot be detected; when the wire harness is misconnected by a large electrical distance (large voltage difference) from the correct position, due to the low reverse voltage withstand of the LED, it is easy to be damaged. SUMMARY OF THE INVENTION

[0005] In view of this, the present invention proposes a fault detection circuit for battery pack connection wires. By setting voltage-dividing resistors in the detection units at intervals, it can be ensured that the light-emitting diodes of the corresponding branches cannot be lit regardless of whether the battery connection wires of the battery pack are misconnected or not connected, and the fault conditions of the battery pack connection wires can be accurately detected.

[0006] According to the fault detection circuit for battery pack connection wires of the present invention, the battery pack includes a plurality of serially connected batteries, the fault detection circuit includes a plurality of detection units, and the plurality of detection units are correspondingly connected to the plurality of single batteries.

[0007] Each detection unit includes an indicating element and a current-limiting resistor. The indicating element is connected in series with the current-limiting resistor, and the series-connected branch is connected in parallel across the battery corresponding to this detection unit.

[0008] In two adjacent detection units, one of the detection units includes a voltage-dividing resistor, and the voltage-dividing resistor is connected in parallel with the battery corresponding to this detection unit. The resistance value of the voltage-dividing resistor is smaller than the resistance value of the current-limiting resistor.

[0009] Preferably, among the plurality of detection units, the detection units including voltage-dividing resistors and the detection units not including voltage-dividing resistors are arranged at intervals.

[0010] Preferably, the voltage-dividing resistor is set in the detection circuit corresponding to the even-numbered battery, or

[0011] Set the voltage dividing resistor in the detection circuit corresponding to the odd-numbered battery cells.

[0012] Preferably, the resistance value of the voltage dividing resistor is set to: (V N +V N+1 -V LN+1 )*r N / (r N +R N+1 )<V LN

[0013] where V N and V N+1 are the voltages of two adjacent battery cells, V LN+1 and V LN are the conduction voltage drops of the indicating element, r N is the resistance value of the voltage dividing resistor, and R N+1 is the resistance value of the current limiting resistor.

[0014] Preferably, the resistance value of the current limiting resistor is set to:

[0015] The indicating element can be lit when the connection wire of the battery pack is normal;

[0016] When the connection wire of the battery pack is abnormal, the magnitude of the current flowing through the indicating element can be limited so as not to exceed the safety current threshold of the indicating element.

[0017] Preferably, the current limiting resistor is a fixed resistor or a PTC thermistor.

[0018] Preferably, each detection unit includes a voltage withstand diode, and the voltage withstand diode is connected in series between the corresponding indicating element and the negative electrode of the battery.

[0019] Preferably, the resistance value of the voltage dividing resistor is set to:

[0020] (V N +V N+1 -V LN+1 -V DN+1 )*r N / (r N +R N+1 )<V LN +V DN

[0021] where V N and V N+1 are the voltages of two adjacent battery cells, V LN+1 and V LN are the conduction voltage drops of the indicating element, V DN is the conduction voltage drop of the voltage withstand diode, r N is the resistance value of the voltage dividing resistor, and R N+1 is the resistance value of the current limiting resistor.

[0022] Preferably, each detection unit includes a first diode, and the first diode is reversely connected in parallel across both ends of the indicating unit.

[0023] Preferably, the indicating element is a light-emitting diode.

[0024] In summary, according to the fault detection circuit for the battery pack connection line of the present invention, by setting the voltage-dividing resistor in the detection circuit corresponding to the even-numbered batteries, or setting the voltage-dividing resistor in the detection circuit corresponding to the odd-numbered batteries, it can be ensured that regardless of abnormal situations such as incorrect connection or missing connection of the battery connection lines of the battery pack, the light-emitting diodes of the corresponding branches cannot be lit, and the fault situation of the connection lines of the battery pack can be accurately detected. And by connecting a voltage-resistant diode in series between the light-emitting diode and the negative electrode of the battery, or reversely connecting a diode in parallel across both ends of the light-emitting diode, it can be ensured that the light-emitting diode will not be damaged regardless of the incorrect connection of the connection line. Brief Description of the Drawings

[0025] Figure 1 is a circuit block diagram of the connection line between the battery pack and the battery management system;

[0026] Figure 2 is a circuit schematic diagram of the wire harness detection board;

[0027] Figure 3 is a circuit schematic diagram of the incorrect connection of the wire harness of the battery pack in the prior art;

[0028] Figure 4 is a circuit schematic diagram of the missing connection of the wire harness of the battery pack in the prior art;

[0029] Figure 5 is a circuit diagram of the first embodiment of the fault detection circuit for the battery pack connection line according to the present invention;

[0030] Figure 6 is a circuit schematic diagram of the missing connection of the wire harness of the battery pack according to the present invention;

[0031] Figure 7-1 is a circuit diagram of the second embodiment of the fault detection circuit for the battery pack connection line according to the present invention;

[0032] Figure 7-2 is a circuit diagram of the third embodiment of the fault detection circuit for the battery pack connection line according to the present invention. Detailed Embodiment

[0033] The following will describe some preferred embodiments of the present invention in conjunction with the accompanying drawings, and clearly and completely describe the technical solutions in the embodiments of the present invention. However, the described embodiments are only partial embodiments of the present invention, rather than all embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts belong to the scope of protection of the present invention.

[0034] The ordinal numbers such as "first" and "second" cited in the present invention are merely identifiers and do not have any other meanings, such as a specific order, etc. Moreover, for example, the term "first end" itself does not imply a position limitation on the "second end", and the term "second end" itself does not imply a position limitation on the "first end".

[0035] Reference Figure 5 is a circuit diagram of a fault detection circuit for a battery pack connection line according to the present invention. The battery pack in the embodiments of the present invention includes a plurality of serially connected batteries, such as Figure 5 the N - 2 to N + 2 exemplified, but the number is not limited thereto, as Figure 1 shown, each battery in the battery pack is connected to a battery management system (BMS).

[0036] Reference Figure 5 , the fault detection circuit in this embodiment includes a plurality of detection units. The plurality of detection units are correspondingly connected to the plurality of single - cell batteries. Among them, each detection unit includes an indicating element and a current - limiting resistor. The indicating element is in series with the current - limiting resistor, and the series - connected branch is connected in parallel across the two ends of the battery corresponding to this detection unit. The indicating element is a light - emitting diode LED, and the current - limiting resistor is resistor R as Figure 5 shown. The positive electrode of the battery is connected to the anode of the light - emitting diode through the current - limiting resistor. Those skilled in the art know that the positions of the light - emitting diode LED and the current - limiting resistor can be interchanged.

[0037] For convenience of description, each battery and the corresponding detection unit in each path are denoted as an overall unit B N , thus, the corresponding battery is denoted as N, the light - emitting diode is denoted as LED N , and the current - limiting resistor is denoted as R N . In this embodiment, the batteries, light - emitting diodes, and current - limiting resistors in each overall unit are devices with the same parameters, which are also the same in the following text. In this embodiment, among two adjacent detection units, one detection unit includes a voltage - dividing resistor, and the voltage - dividing resistor is connected in parallel with the battery corresponding to this detection unit. For example, in the N - th path overall unit, it includes a voltage - dividing resistor r N , the voltage - dividing resistor r N is connected across the positive and negative electrodes of battery N.

[0038] In an embodiment according to the present invention, among the multiple detection units, the detection units including voltage-dividing resistors and the detection units not including voltage-dividing resistors are arranged at intervals. Specifically, the voltage-dividing resistor is arranged in the detection circuit corresponding to the even-numbered battery section, or the voltage-dividing resistor is arranged in the detection circuit corresponding to the odd-numbered battery section. As Figure 5 shown, the N-2nd detection unit, the Nth detection unit, and the N+2nd detection unit respectively include a voltage-dividing resistor r N-2 , a voltage-dividing resistor r N and a voltage-dividing resistor r N+2 .

[0039] Furthermore, the resistance value of the voltage-dividing resistor is smaller than the resistance value of the current-limiting resistor. Specifically, the resistance value of the voltage-dividing resistor is set as:

[0040] (V N +V N+1 -V LN+1 )*r N / (r N +R N+1 )<V LN

[0041] where V N , V N+1 are the voltages of two adjacent batteries, V LN+1 , V LN are the conduction voltage drops of the indicating element, r N is the resistance value of the voltage-dividing resistor, and R N+1 is the resistance value of the current-limiting resistor. Among them, the resistance value of the current-limiting resistor R N is set as: it can light up the light-emitting diode LED N when the connection wire of the battery pack is normal; it can limit the current flowing through the indicating element not to exceed the safety current threshold of the light-emitting diode when the connection wire of the battery pack is abnormal.

[0042] In this embodiment, the current-limiting resistor is an ordinary fixed resistor or a PTC thermistor. When the connection position of the connection wire is very different from the correct position, the forward voltage borne by a certain branch is much greater than the voltage in the normal connection. It is difficult for an ordinary fixed resistor to ensure that the forward current is within the normal working range of the light-emitting diode LED, and thus the LED will also be damaged. According to the characteristics of the PTC thermistor, the greater the current flowing through it, the higher the PTC temperature rise, and the resistance value automatically becomes larger, thereby reducing the current value flowing through, and the LED can be protected from damage.

[0043] According to the detection scheme of this embodiment, when the wire harness of a battery is not connected, as Figure 6 shown, when the wire of the B N th path is not connected, the voltages of the Nth and N+1st batteries, after subtracting the light-emitting diode LEDN+1 After that, the voltage-dividing resistor r N and the current-limiting resistor R N+1 divide the voltage. Since the voltage-dividing resistor r N is smaller than the current-limiting resistor R N+1 in resistance value, the voltage-dividing resistor r N obtains a relatively small voltage. According to the above setting of the resistance value of the voltage-dividing resistor, the voltage it obtains is less than the conduction voltage of the light-emitting diode LED corresponding to this branch N , so that the current-limiting resistor R N connected in parallel with the voltage-dividing resistor r N , the light-emitting diode LED N series branch is not conducting, and thus the light-emitting diode LED N cannot be lit; when all the wire harnesses are connected properly, the voltage of all the LED series branches is determined by the actual battery voltage, the voltage-dividing resistor and the current-limiting resistor do not divide the voltage, and the light-emitting diodes LED of the corresponding branches are normally lit.

[0044] When the wire harness of the battery is connected wrongly, the input voltage of the light-emitting diode LED N becomes negative and thus cannot be lit. As can be seen from the above, according to the wire harness detection scheme of this embodiment, no matter in abnormal situations such as wrong connection or missing connection of the battery connection wires of the battery pack, the light-emitting diodes of the corresponding branches cannot be lit, and the connection wire failure of the battery pack can be accurately detected.

[0045] Reference Figure 7-1 , the second embodiment of the present invention. In this embodiment, a voltage-resistant diode D is added on the basis of the first embodiment. Specifically, each detection unit includes a voltage-resistant diode, and the voltage-resistant diode is connected in series between the corresponding light-emitting diode and the negative pole of the battery. As Figure 7-1 shown in N , the voltage-resistant diode D N is connected between the light-emitting diode LED bat and the negative pole of the battery. In this embodiment, the breakdown voltage value of the voltage-resistant diode is greater than the sum of the highest voltages of the battery pack. For example, for n series-connected batteries, the breakdown voltage value is n*V bat , where V

[0046] Further, in this embodiment, the resistance value of the voltage-dividing resistor is set as:

[0047] (V N +V N+1 -V LN+1 -V DN+1 )*r N / (r N +R N+1 )<V LN +VDN

[0048] Where V N and V N+1 are the voltages of two adjacent batteries, V LN+1 and V LN are the conduction voltage drops of the light-emitting diodes, V DN is the conduction voltage drop of the voltage-resistant diode, r N is the resistance value of the voltage-dividing resistor, R N+1 is the resistance value of the current-limiting resistor.

[0049] Similarly, it can be deduced that when the B N line speed is not connected, the voltages of the Nth and (N + 1)th batteries, after deducting the light-emitting diode LED N+1 and the voltage-resistant diode D N+1 are divided by the voltage-dividing resistor r N and the current-limiting resistor R N+1 According to the above formula, it can be known that the voltage divided by the voltage-dividing resistor r N is less than the sum of the turn-on voltages of the light-emitting diode LED N and the voltage-resistant diode D N such that the branch in series with the light-emitting diode LED N in parallel with the voltage-dividing resistor r N and the voltage-resistant diode D N is not conducting, that is, the LED N cannot be lit.

[0050] This embodiment can also detect the abnormal situation of the battery connection line. And in this embodiment, a voltage-resistant diode is connected in series with the light-emitting diode of each branch, which can increase the reverse voltage resistance of the light-emitting diode LED. Since the reverse voltage resistance of the diode is relatively high, therefore, by selecting an appropriate diode voltage resistance, it can be ensured that any misconnection of the wire harness will not damage the light-emitting diode LED.

[0051] Referring to Figure 7-2 , the third embodiment of the present invention. In this embodiment, a first diode D2 is added on the basis of the first embodiment. Each detection unit includes a first diode, and the first diode is reversely connected in parallel across the two ends of the light-emitting diode. This embodiment can also detect the abnormal situation of the battery connection line. And in this embodiment, a first diode is connected in parallel with the light-emitting diode of each branch, which can clamp the reverse voltage of the light-emitting diode LED. Since the conduction voltage drop of the diode D2 is less than the reverse voltage resistance of the light-emitting diode LED, therefore, it can be ensured that any misconnection of the wire harness will not damage the light-emitting diode LED.

[0052] The preferred embodiments of the fault detection circuit for the battery pack connection line according to the present invention have been described in detail above. However, the circuit and beneficial effects of this patent should not be considered to be limited only to the above-described disclosed embodiments. The disclosed embodiments and the accompanying drawings can help better understand the present invention. Therefore, the above-disclosed embodiments and the content of the accompanying drawings of the specification are for better understanding the present invention. The protection scope of the present invention is not limited to the scope defined by this disclosure. Replacements and modifications made by those of ordinary skill in the art to the embodiments of the present invention are within the protection scope of the present invention.

Claims

1. A fault detection circuit for a battery pack connection line, the battery pack comprising a plurality of series-connected single cells, Characterized in that, The fault detection circuit includes a plurality of detection units, and the plurality of detection units are correspondingly connected to the plurality of single cells, Each detection unit includes an indicating element and a current-limiting resistor, the indicating element is connected in series with the current-limiting resistor, and the series-connected branch is connected in parallel across the battery corresponding to this detection unit, Among two adjacent detection units, one of the detection units includes a voltage-dividing resistor, the voltage-dividing resistor is connected in parallel with the battery corresponding to this detection unit, and the resistance value of the voltage-dividing resistor is smaller than the resistance value of the current-limiting resistor.

2. The fault detection circuit according to claim 1, Characterized in that, Among the plurality of detection units, the detection units including voltage-dividing resistors and the detection units not including voltage-dividing resistors are arranged at intervals.

3. The fault detection circuit according to claim 2, Characterized in that, The voltage-dividing resistor is provided in the detection circuit corresponding to the even-numbered battery, or, The voltage-dividing resistor is provided in the detection circuit corresponding to the odd-numbered battery.

4. The fault detection circuit according to any one of claims 1-3, Characterized in that, The resistance value of the voltage-dividing resistor is set to: (V N +V N+1 -V LN+1 )*r N / (r N +R N+1 )<V LN Among them, V N , V N+1 are two adjacent battery voltages, V LN+1 , V LN are the on-voltage drops of the indicating components, r N is the resistance value of the voltage-dividing resistor, R N+1 is the resistance value of the current-limiting resistor.

5. The fault detection circuit according to claim 4, Characterized in that, The resistance value of the current-limiting resistor is set to: The indicating element can be lit when the connection line of the battery pack is normal; When the connection line of the battery pack is abnormal, the magnitude of the current flowing through the indicating element can be limited so as not to exceed the safety current threshold of the indicating element.

6. The fault detection circuit according to claim 5, Characterized in that, The current-limiting resistor is a fixed resistor or a PTC thermistor.

7. The fault detection circuit according to any one of claims 1-3, Characterized in that, Each detection unit includes a voltage-resistant diode, and the voltage-resistant diode is connected in series between the corresponding indicating element and the negative electrode of the battery.

8. The fault detection circuit according to claim 7, Characterized in that, The resistance value of the voltage-dividing resistor is set to: (V N +V N+1 -V LN+1 -V DN+1 )*r N / (r N +R N+1 )<V LN +V DN Among them, V N , V N+1 are two adjacent battery voltages, V LN+1 , V LN is the conduction voltage drop of the indicating component, V DN is the conduction voltage drop of the voltage-resistant diode, r N is the resistance value of the voltage-dividing resistor, R N+1 is the resistance value of the current-limiting resistor.

9. The fault detection circuit according to any one of claims 1-3, Characterized in that, Each detection unit includes a first diode, and the first diode is reversely connected in parallel across the indicating element.

10. The fault detection circuit according to any one of claims 1-3, Characterized in that, The indicating element is a light-emitting diode.

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