JP3877509B2 - Battery system leakage detection method and detection circuit - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method and circuit for detecting battery leakage.
[0002]
[Prior art]
Battery leakage has the harmful effect of corroding the equipment. Furthermore, in a high voltage battery system used for an electric vehicle or the like, the leakage causes electric shock. For this reason, it is important to detect battery leakage as quickly as possible.
[0003]
Circuits for detecting battery leakage are described in, for example, Japanese Patent Application Laid-Open Nos. 5-109436 and 10-12284. In the leak detection circuit described in these publications, a dedicated electrode for detecting leak is disposed at the leak location.
[0004]
[Problems to be solved by the invention]
The leakage detection circuit described in the above publication detects the leakage by detecting the resistance because the electrical resistance of the electrode decreases when a leakage current flows due to leakage from the battery. This structure is complicated because it is necessary to provide a dedicated electrode. In particular, in a battery system in which a large number of batteries are connected in series, in order to detect leakage of a large number of batteries, it is necessary to provide a dedicated electrode with a unique and complicated structure, and the manufacturing cost is extremely high. There are disadvantages.
[0005]
The present invention was developed with the object of solving these drawbacks. An important object of the present invention is to provide a battery system leakage detection method and detection that can detect battery leakage with a very simple structure. It is to provide a circuit.
[0006]
[Means for Solving the Problems]
[0008]
In the liquid leakage detection method according to claim 1 of the present invention, a plurality of fixed resistors 10 that are connected in series are arranged close to the surfaces of the plurality of batteries 2, and the electrodes of any one of the batteries 2 are arranged. The leakage of the battery 2 is detected by detecting the current leaking to any one of the fixed resistors 10.
[0009]
The leakage detection circuit according to claim 2 of the present invention has a voltage dividing resistor 6 connected in parallel with the + -output terminal 5 of the battery system in which a plurality of batteries 2 are connected in series. The voltage dividing resistor 6 is connected to a temperature sensor 3 connected in series fixed to the surface of the plurality of batteries 2. Further, the liquid leakage detection circuit detects the voltage at the voltage detection point of the voltage dividing resistor 6 with the voltage detection circuit. When the battery 2 leaks and the leakage current of the temperature sensor 3 flows from the electrode, the voltage value detected by the voltage detection circuit changes and the leakage of the battery 2 is detected.
[0010]
The leakage detection circuit according to claim 3 of the present invention has a voltage dividing resistor 6 connected in parallel with a +-output terminal 5 of a battery system in which a plurality of batteries 2 are connected in series. The voltage dividing resistor 6 is connected to a series-connected fixed resistor 10 fixed to the surfaces of the plurality of batteries 2. Furthermore, the liquid leakage detection circuit detects the voltage at the voltage detection point of the voltage dividing resistor 6 with the voltage detection circuit. When the battery 2 leaks and the leak current of the fixed resistor 10 flows from the electrode, the voltage value detected by the voltage detection circuit changes and the leak of the battery 2 is detected.
[0011]
The leak detection circuit connects the middle point of the voltage dividing resistor 6 to the ground, and detects the voltage between the ground and the output terminal 5 by the voltage detection circuit so as to balance the ground as the middle point. The liquid can be detected.
[0012]
The battery system is, for example, a power source for driving an automobile, and can isolate the power source from the automobile chassis by insulating the ground connecting the midpoint of the voltage dividing resistor 6 from the automobile chassis.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings. However, the embodiment described below exemplifies the leakage detection method and the detection circuit of the battery system for embodying the technical idea of the present invention, and the present invention describes the leakage detection method and the detection circuit as follows. Not specific to anything.
[0014]
Further, in this specification, in order to facilitate understanding of the scope of claims, the numbers corresponding to the members shown in the examples are referred to as “the scope of claims” and “the means for solving the problems”. It is added to the member shown by. However, the members shown in the claims are not limited to the members in the embodiments.
[0015]
The leakage detection circuit 4 of the battery system shown in the circuit diagrams of FIGS. 1 and 2 uses the temperature sensor 3 to detect leakage of the battery. This circuit diagram is mounted on an electric vehicle that drives a motor by driving a motor with a battery system. In a battery system in which battery leakage is detected, a plurality of batteries 2 are connected in series, and a temperature sensor 3 that detects the temperature by a change in resistance is fixed to the surface of each battery 2.
[0016]
In the battery system, as shown in FIG. 3, a plurality of module batteries 1 are connected in series. Each module battery 1 is formed by connecting a plurality of batteries 2 in series and connecting them in a straight line. In the module battery 1, the temperature sensors 3 are fixed to the surfaces of all the batteries 2, and all the temperature sensors 3 are connected in series. In the module battery 1, a temperature sensor 3 is disposed on the surface of the battery 2, the outside of the temperature sensor 3 is covered with a heat shrinkable tube, and the temperature sensor 3 is adhered and fixed to the surface of the battery 2. A plurality of temperature sensors 3 fixed to the surface of one module battery 1 are linearly connected in series and placed in a tube, and the tube is thermally contracted and fixed to the surface of the battery 2. Since the tube is open at both ends, the leakage of the battery 2 enters from the opening. The liquid leaking into the tube electrically connects the electrode of the battery 2 to the temperature sensor 3. Since the state in which the electrode and the temperature sensor 3 are insulated is in a normal state, when any electrode of the battery 2 is brought into contact with the temperature sensor 3, the leakage can be determined. The liquid leaking into the tube is connected to the temperature sensor 3 in the tube in a low resistance state, and since the liquid does not move, the liquid leak can be reliably detected.
[0017]
However, in the battery system, it is not always necessary to put the temperature sensor in a tube and fix it to the surface of the battery, and it is also possible to fix the temperature sensor directly to the surface of the battery that is insulating the surface. The battery system leaks by connecting to the lead of the temperature sensor where the battery leakage is closest.
[0018]
In the illustrated battery system, all module batteries 1 are connected in series, and temperature sensors 3 fixed to all the module batteries 1 are also connected in series. The battery 2 of the module battery 1 is a rechargeable battery such as a nickel-hydrogen battery, a lithium ion secondary battery, or a nickel-cadmium battery. The temperature sensor 3 is a PTC. However, all elements whose electrical resistance changes with temperature, such as a thermistor, can be used for the temperature sensor.
[0019]
The liquid leakage detection circuit 4 includes a voltage dividing resistor 6 connected in parallel with the + -output terminal 5 of the battery system, an operational amplifier 7 for detecting the voltage at the voltage detection point of the two voltage dividing resistors 6, and an operational amplifier 7. And a differential amplifier 8 for comparing the outputs. The voltage dividing resistor 6 is composed of two series resistors, and the middle point of the two voltage dividing resistors 6 connected in series is connected to the ground. The midpoint of the voltage dividing resistor 6 is a connection point while connecting two resistors. The temperature sensor 3 connected in series also has one end connected to the ground, and the temperature sensor 3 is connected to the middle point of the voltage dividing resistor 6 through the ground.
[0020]
The voltage dividing resistor 6 has a voltage detection point in the middle. In order to adjust the voltage at the voltage detection point, the circuit shown in the figure uses the voltage dividing resistor 6 as a variable resistor. The variable resistor can adjust the voltage at the voltage detection point using the slider as a voltage detection point. In the illustrated circuit, two voltage dividing resistors 6 are variable resistors, but one voltage dividing resistor can be a variable resistor and the other voltage dividing resistor can be a fixed resistor.
[0021]
The two voltage dividing resistors 6 are adjusted so that the voltages at the voltage detection points are equal in a state where no leakage occurs. In order to realize this, the two voltage dividing resistors 6 have the same overall resistance value, and the resistance ratios of the voltage dividing resistors 6 are also the same. The voltage dividing resistor 6 shown in the figure has a resistance of 10 kΩ and 1 MΩ connected in series. The voltage dividing resistor 6 outputs the voltage at both ends as 1/101 to the voltage detection point. For example, if the output voltage of the battery system is 240 V and the voltage dividing resistor 6 has the resistance value shown in the figure, the potential difference between the middle point of the voltage dividing resistor 6 and the voltage detection point, that is, the + side output voltage V1 and the-side output voltage V2 Becomes 240 × 1/2 × 1/101, which is 1.19V.
[0022]
The operational amplifier 7 amplifies the + side output voltage V1 and the − side output voltage V2 with the same amplification factor, or outputs the output to the differential amplifier 8 with a buffer amplifier having an amplification factor of 1. The + side output voltage V1 and the-side output voltage V2 are the same voltage with respect to the midpoint, but +-is opposite. In order to input the + side output voltage V1 and the-side output voltage V2 whose +-are opposite to each other to the differential amplifier 8 in phase, either one of the operational amplifiers 7 inverts the output and outputs it. The differential amplifier 8 compares the outputs of the two operational amplifiers 7 and outputs the result. If the voltage values of the + side output voltage V1 and the − side output voltage V2 are the same, the same voltage is input to the differential amplifier 8 so that the output of the differential amplifier 8 is 0V. Therefore, when the battery 2 is not leaking, the output voltage of the differential amplifier 8 is 0V.
[0023]
When any battery 2 leaks and its electrode is connected to the temperature sensor 3, the leaked electrode of the battery 2 is connected to the ground via the temperature sensor 3. In this state, the balance is lost, and the + side output voltage V 1 and the − side output voltage V 2 are not the same, and a differential voltage is output from the differential amplifier 8. Therefore, the leakage of the battery 2 can be detected by the voltage output from the differential amplifier 8. For example, as shown by the arrow Z in FIG. 2, when the battery 2 connected to the negative side of the output terminal 5 leaks, the positive side output voltage V1 is -4.52V and the negative side output voltage V2 is -6. The differential voltage is output from the differential amplifier 8 at 90V. For this reason, the leakage of the battery 2 can be detected by the output of the differential amplifier 8.
[0024]
In FIG. 2, the temperature sensor 3 is connected in series and connected to the microcomputer 9. The microcomputer 9 detects the electric resistance of all the temperature sensors 3 and monitors the battery temperature. Since the electrical resistance of the PTC used for the temperature sensor 3 rapidly increases when the temperature becomes higher than the set value, the microcomputer 9 can detect the battery temperature by detecting the series resistance of all the temperature sensors 3. The temperature sensor 3 connected in series has one side connected to the ground and the other side connected to the power source in order to energize and flow current.
[0025]
Furthermore, the leakage detection circuit 4 shown in FIG. 4 insulates the ground connected to the middle point of the voltage dividing resistor 6 and the temperature sensor 3 from the chassis ground of the automobile. That is, the ground of the leak detection circuit 4 is not connected to the chassis ground. The leak detection circuit 4 is insulated and coupled to the microcomputer 9 without sharing the ground with the insulation circuit 11 such as light or a transformer. The leakage detection circuit 4 can prevent leakage due to leakage of the battery system. For this reason, even if the battery system leaks, there is no electric shock by touching the chassis of the automobile.
[0026]
The above leakage detection circuit cannot detect leakage at the center of the battery system. This is because even if the center of the battery system is grounded and connected to the ground, there is no difference between the + side output voltage V1 and the − side output voltage V2, and the same state as when no leakage occurs is obtained. FIG. 5 shows a leakage detection circuit that can also detect leakage in the center of the battery system. The leak detection circuit 4 uses an amplifier having a + − input terminal for the operational amplifier 7. The operational amplifier 7 for detecting the + side output voltage V 1 has a + side input terminal connected to the voltage dividing resistor 6. The operational amplifier 7 for detecting the negative output voltage V2 has a negative input terminal connected to the voltage dividing resistor 6. The negative input terminal of the operational amplifier 7 that detects the positive output voltage V1 and the positive input terminal of the negative output voltage V2 are connected to the middle point of the balance resistor 13. The balance resistor 13 connects two resistors in series and is connected in parallel with the voltage dividing resistor 6. The midpoint of the balance resistor 13 is a connection point while connecting two resistors. The two balance resistors 13 have resistance values that make the midpoint voltage substantially equal to the midpoint voltage of the voltage dividing resistor 6.
[0027]
In the liquid leakage detection circuit 4 of FIG. 5, the balance resistor 13 and the voltage dividing resistor 6 have resistance values shown in the figure. The balance resistor 13 has a battery system voltage of 300V and a midpoint voltage of 146.7V. In a state where the battery system does not leak, that is, a state where the battery system does not leak, the + side output voltage V1 is 0.465V and the − side output voltage V2 is −0.421V. When the leakage detection circuit 4 is connected to the ground by leakage at the center of the battery system or at the output terminal side that is more positive than the center, both the + side output voltage V1 and the-side output voltage V2 are positive. It becomes a voltage value. On the other hand, when a leakage occurs on the negative output terminal side from the center of the battery system, both the positive side output voltage V1 and the negative side output voltage V2 become negative voltage values. Therefore, the leakage detection circuit 4 can detect leakage of the battery 2 very easily by using +/− of the output signals from the two operational amplifiers 7.
[0028]
Further, the leakage detection circuit 4 can also detect a leakage by a difference voltage between the + side output voltage V1 and the-side output voltage V2. This is because, in a state where the battery system does not leak, the + side output voltage V1 is 0.465V and the − side output voltage V2 is −0.421V, which are substantially equal. Therefore, when the + side output voltage V1 and the-side output voltage V2 are substantially equal, it can be determined that the battery system does not leak. However, the voltage dividing resistor, which is a variable resistor, can be adjusted so that the + side output voltage V1 and the-side output voltage V2 become the same voltage in a state where the battery system does not leak.
[0029]
The leak detection circuit 4 in FIG. 5 uses the resistance value shown in the figure as the balance resistor 13 and the voltage dividing resistor 6, and the temperature sensor 3 as PTC. When the Z point of the battery system leaks, the + side output voltage V1 The negative side output voltage V2 changes to the following voltage value, and the differential voltage becomes as large as 40V. Therefore, leakage of the battery system can be detected by the difference voltage between the + side output voltage V1 and the-side output voltage V2.
+ Side output voltage V1 ............- 20.95V
-Side output voltage V2 ......- 21.66V
[0030]
However, this leakage detection circuit changes both the + side output voltage V1 and the-side output voltage V2 when the battery leaks, so both the + side output voltage V1 and the-side output voltage V2 are detected. Without detection, the battery leakage can be detected by detecting one of the output voltages.
[0031]
In the above leakage detection circuit 4, since the temperature sensor 3 fixed to the battery 2 is used in combination with the leakage sensor, leakage can be detected without providing a dedicated sensor for detecting leakage. However, the liquid leakage detection method and circuit of the present invention are configured by fixing a fixed resistor 10 on the surface of the battery 2 in place of the temperature sensor 3 as shown in FIG. Leakage can be detected. In the leak detection circuit 4 as well, the + side output voltage V1 and the-side output voltage V2 when no liquid leaks are the same voltage as the circuit shown in FIG. For example, when the leakage detection circuit 4 leaks at points A, B, and C in FIG. 6, the + side output voltage V1 and the-side output voltage V2 have the following voltage values.
[0032]
(1) Leakage at side A + side output voltage V1 …… -18.98V
-Side output voltage V2 …… -19.69V
(2) Leak at point B + side output voltage V1 …… -15.22V
-Side output voltage V2 …… -16.02V
(3) Leak at point C + side output voltage V1 …… 14.04V
-Side output voltage V2 ... 13.33V
[0033]
As described above, also in the leakage detection circuit 4 that detects the leakage of the battery system with the fixed resistor 10, when the battery 2 leaks and leaks, both the + side output voltage V1 and the-side output voltage V2 are both. The voltage value is either positive or negative. Therefore, the leakage of the battery 2 can be detected very easily with the + and-of the output signals from the two operational amplifiers 7. However, the leakage detection circuit 4 can also detect leakage from the difference voltage between the + side output voltage V1 and the-side output voltage V2 in the same manner as the leakage detection circuit shown in FIG.
[0034]
Furthermore, since the resistance of the fixed resistor 10 does not change like the temperature sensor, the leak detection circuit 4 shown in FIG. 6 can also specify the leak location by the output voltage. The leakage detection circuit 4 detects the leakage of the battery 2 by detecting these output voltages because any of the batteries 2 leaks and the voltages of the + side output voltage V1 and the-side output voltage V2 change. While being able to detect, a leak location can also be specified.
[0035]
In the above leakage detection circuit and leakage detection method, a plurality of batteries 2 are connected and a temperature sensor 3 and a fixed resistor 10 are fixed to each battery 2. However, the leak detection method and leak detection circuit of the present invention can also detect a leak by fixing a temperature sensor or a fixed resistor to one battery. As shown in FIG. 7, this leakage detection circuit can be detected by a circuit that can detect a leakage due to a difference in current flowing between the positive side and the negative side of the battery 2. The leakage detection circuit 4 in this figure amplifies and compares the voltages at both ends of the current detection resistor 12 connected to the + side and the − side by the operational amplifier 7. The resistance value of the current detection resistor 12 connected to the + side and the − side of the battery 2 is equal to the amplification factor of the operational amplifier 7, and the output of the differential amplifier 8 is 0 in a state where no leakage occurs. When the battery 2 leaks and leaks from +, the leakage current does not flow through the current detection resistor 12 connected to the + side, and the leakage current flows only through the current detection resistor 12 connected to the − side. The output voltage of the operational amplifier 7 on the side becomes higher than that of the operational amplifier 7 on the + side, and the differential amplifier 8 outputs a voltage. Therefore, the leakage due to the leakage of the battery 2 can be detected from the output of the differential amplifier 8.
[0036]
A battery system including a plurality of batteries can detect a leak by fixing a temperature sensor or a fixed resistance to any one of the batteries without fixing the temperature sensor or the fixed resistance to all of the batteries.
[0037]
【The invention's effect】
The battery system leakage detection method and detection circuit of the present invention have the advantage that battery leakage can be detected with an extremely simple structure. It leakage detection method and detection circuit of the present invention is, in close proximity to the surface of the battery, and arranged a fixed resistance, leakage of the battery by detecting a current that leaks to the electrode or al fixed resistance of the battery This is because the liquid is detected. The leakage detection method and detection circuit, as is traditional, without providing a dedicated electrode for detecting the leakage of the battery, liquid leakage by effectively utilizing the fixed resistor that is disposed in the battery to Since it is detected, the manufacturing cost can be reduced as an extremely simple structure without complicating the circuit configuration.
[0038]
Further, the liquid leakage detection circuit according to claims 2 and 3 of the present invention has a feature that the liquid leakage can be reliably detected as a simple circuit configuration. These leakage detection circuits connect a voltage dividing resistor connected in parallel with the output terminal of the battery system to a temperature sensor or a fixed resistor, and detect the voltage of the voltage dividing resistor to detect battery leakage. This is because it is detected. These leakage detection circuits reliably detect battery leakage because the voltage detected by the voltage detection circuit changes when the battery leaks and a temperature sensor or fixed resistor leakage current flows from the electrode. it can.
[0039]
The liquid leakage detection circuit according to claim 5 of the present invention uses the battery system as a power source for running the automobile and insulates the ground from the automobile chassis, so that even if the battery system leaks, the automobile chassis is touched. To prevent electric shock.
[Brief description of the drawings]
1 is a schematic diagram of a leakage detection circuit of a battery system according to an embodiment of the present invention. FIG. 2 is a circuit diagram of a leakage detection circuit of the battery system shown in FIG. 1. FIG. 3 is a perspective view of the battery system shown in FIG. FIG. 4 is a circuit diagram of a leakage detection circuit of a battery system according to another embodiment of the present invention. FIG. 5 is a circuit diagram of a leakage detection circuit of a battery system according to another embodiment of the present invention. FIG. 7 is a circuit diagram of a leakage detection circuit of a battery system according to another embodiment of the invention. FIG. 7 is a circuit diagram of a leakage detection circuit of a battery system according to another embodiment of the present invention.
DESCRIPTION OF SYMBOLS 1 ... Module battery 2 ... Battery 3 ... Temperature sensor 4 ... Liquid leakage detection circuit 5 ... Output terminal 6 ... Voltage dividing resistor 7 ... Operational amplifier 8 ... Differential amplifier 9 ... Microcomputer 10 ... Fixed resistor 11 ... Insulation circuit 12 ... Current detection resistor 13 ... Balance resistance

Claims (5)

  A plurality of fixed resistors (10) connected in series with each other are arranged close to the surface of the plurality of batteries (2), and any one of the fixed resistors ( A leakage detection method for a battery system, which detects a leakage current of the battery (2) by detecting a current leaking to 10).   A voltage dividing resistor (6) is connected in parallel with the + − output terminal (5) of the battery system in which a plurality of batteries (2) are connected in series. Connected to a series-connected temperature sensor (3) fixed to the battery surface, and the voltage detection circuit detects the voltage at the voltage detection point of the voltage dividing resistor (6), and the battery (2) leaks. The leakage detection circuit of the battery system detects the leakage of the battery (2) by changing the voltage value detected by the voltage detection circuit when leakage current of the temperature sensor (3) flows from the electrode.   A voltage dividing resistor (6) is connected in parallel with the + − output terminal (5) of the battery system in which a plurality of batteries (2) are connected in series. The battery (2) leaks when the voltage detection circuit detects the voltage at the voltage detection point of the voltage dividing resistor (6) connected to the series-connected fixed resistor (10) fixed on the battery surface. The leakage detection circuit of the battery system detects the leakage of the battery (2) by changing the voltage value detected by the voltage detection circuit when the leakage current of the fixed resistor (10) flows from the electrode. The middle point of the voltage dividing resistor (6) is connected to the ground, and the voltage between the ground and the output terminal (5) is detected by the voltage detection circuit so that the ground is balanced as the middle point. The leak detection circuit for a battery system according to claim 2 , wherein the leak detection circuit detects a leak of the battery. 5. The leakage detection circuit for a battery system according to claim 4 , wherein the battery system is a power source for driving the vehicle, and the ground connecting the midpoint of the voltage dividing resistor (6) is insulated from the chassis ground of the vehicle. .

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