JP2004006190A - Battery pack system and method for measuring leakage current of battery pack system - Google Patents

Abstract

An object of the present invention is to improve the detection accuracy by detecting insulation in a battery pack system in a state close to when the system is operating.
A battery pack in which a plurality of battery cells are connected in series, a motor, main switches provided between the battery pack and the motor, and a rear stage of the main switches. On the side, a capacitor 8 connected in parallel with the motor 11 and a control circuit 14 are provided. The control circuit 14 controls on / off of the main switches 1a and 1b. Further, when the main switches 1a and 1b are switched from on to off, the control circuit 14 determines the insulation of the circuit system at the subsequent stage of the main switches 1a and 1b based on the potential difference caused by the electric charge accumulated in the capacitor 8. evaluate.
[Selection diagram] Fig. 1

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an assembled battery system and a method for measuring a leakage current of the assembled battery system, and more particularly to evaluation of insulation properties of the assembled battery system.
[0002]
[Prior art]
2. Description of the Related Art In recent years, hybrid vehicles, electric vehicles, and the like have attracted attention due to environmental issues and the like, and various secondary batteries have been developed for that purpose. Lithium ion secondary batteries are high in energy density, excellent in airtightness, and maintenance-free, and thus are excellent as batteries for hybrid vehicles and electric vehicles, but large-sized batteries have not been put to practical use. Therefore, a plurality of small battery cells are connected in series or in parallel to form a battery pack, and a desired voltage and capacity are secured using this battery pack unit.
[0003]
[Problems to be solved by the invention]
By the way, in an assembled battery system including an assembled battery and a load, it is important to ensure insulation in a circuit system. This is because when current leaks from the circuit of the system, the consumption of the battery pack is promoted. In general, the insulation depends on the temperature, and the insulation tends to decrease as the temperature of the system increases. Therefore, the temperature is high when the system is operating, regardless of when the system is stopped, and there is a possibility that the insulation property is greatly reduced.
[0004]
The present invention has been made in view of such circumstances, and an object of the present invention is to improve the detection accuracy by detecting insulation in a battery pack system in a state close to when the system is operating.
[0005]
[Means for Solving the Problems]
In order to solve such a problem, a first invention is directed to an assembled battery in which a plurality of battery cells are connected in series, a load, a main switch in which an assembled battery is connected to a preceding stage, and a load is connected to a succeeding stage, Provided is an assembled battery system including a capacitor connected in parallel with a load and a control circuit at a stage subsequent to a main switch. This control circuit controls on / off of the main switch. Further, when the main switch is switched from on to off, the control circuit evaluates the insulation of the circuit system on the subsequent stage of the main switch based on a potential difference caused by the electric charge stored in the capacitor.
[0006]
Here, in the first invention, it is preferable that the control circuit evaluates insulation by measuring a leakage resistance relating to a circuit system on the subsequent stage of the main switch as the first leakage resistance.
[0007]
Further, in the first aspect, a pre-resistive load switch provided in parallel with the main switch may be further provided. In this case, the control circuit controls on / off of the pre-resistive load switch. Also, the control circuit measures the second leakage resistance by temporarily turning off the pre-resistance load switch during a period in which the main switch is turned off and the pre-resistance load switch is turned on. May be. In this case, the control circuit compares the magnitude of the first leakage resistance with the magnitude of the second leakage resistance. This makes it possible to determine whether or not the cause of the leakage is a decrease in insulation due to a rise in temperature during operation of the system.
[0008]
According to a second aspect of the present invention, there is provided an assembled battery in which a plurality of battery cells are connected in series to generate a predetermined high voltage, a load, a main switch in which an assembled battery is connected in a preceding stage, and a load is connected in a succeeding stage, On the rear side of the switch, the capacitor connected in parallel with the load and the main switch are turned on or off, and when the main switch is switched from on to off, the charge stored in the capacitor is used as a high-voltage power supply. And a control circuit for evaluating the insulation of a circuit system on the subsequent stage of the main switch.
[0009]
Here, in the second invention, it is preferable that the control circuit obtains high-voltage power supply information including at least one of a battery voltage, a leakage current, and a leakage resistance from a downstream side of the main switch.
[0010]
Further, in the second aspect, it is desirable that the power to the control circuit is a power supply different from the high-voltage power supply and is supplied from the low-voltage power supply lower than the high-voltage power supply through the insulating transformer.
[0011]
A battery pack in which a plurality of battery cells are connected in series, a load, a main switch in which a battery pack is connected in a preceding stage, and a load is connected in a subsequent stage, and a main switch in which a load is connected in a subsequent stage are connected in parallel with the load. Provided is a method for measuring a leakage current of a battery pack system having a capacitor. This measuring method includes a step of switching a main switch from on to off, a step of detecting a potential difference caused by electric charges accumulated in a capacitor, and measuring a leakage current relating to a circuit system on a subsequent stage of the main switch based on the potential difference. And steps.
[0012]
BEST MODE FOR CARRYING OUT THE INVENTION
FIG. 1 is a configuration diagram of a battery pack system applied to a hybrid vehicle. This assembled battery system mainly includes an assembled battery unit 9, a capacitor 8, an inverter 10, and a motor 11. The battery pack unit 9 and the external devices 8, 10, 11 are connected via connectors 15a, 15b. The battery pack unit 9 supplies power to the motor 11 corresponding to a load. The output of the motor 11 serving as the power source of the vehicle is set by the inverter 10 under the control of a controller (not shown). The inverter 10 converts a DC current supplied from the battery pack unit 9 into a three-phase AC current. The motor 11 is a three-phase AC motor, and a three-phase AC current is supplied from the inverter 10. The capacitor 8 is connected in parallel to the inverter 10 and the motor 11, and has a large capacity of about several thousand μF. As will be described later, when the ignition key is turned on from off, that is, at the initial stage of operation of the battery pack system, first, the capacitor 8 is precharged.
[0013]
The assembled battery unit 9 mainly includes the assembled battery 2, various switches 1, 3, 4, the control circuit 14, and the low-voltage power supply systems 5, 6, 7, and 13. The assembled battery 2 generates a predetermined high voltage by connecting a plurality of battery cells in series. In the present embodiment, a thin-plate laminate cell in which a lithium-ion battery represented by a manganese-based, cobalt-based, nickel-based battery, or the like is covered with a laminate sheet is used.
[0014]
The positive electrode of the battery pack 2 and the positive connector 15a are connected by a positive wiring 16a. The wiring 16a is provided with a main switch 1a and a pre-resistive load switch 3a in parallel with the switch 1a. The pre-resistance load switch 3a has a structure in which a switch and a resistor are connected in series. The rear side of the main switch 1a (that is, the motor 11 side) is connected to the control circuit 14 via the relay switch 4a.
[0015]
On the other hand, the negative electrode of the battery pack 2 and the negative connector 15b are connected by a negative wiring 16b. The main switch 1b is provided on the wiring 16b, and a pre-resistance load switch 3b is provided in parallel with the switch 1b. The pre-resistance load switch 3b has a structure in which a switch and a resistor are connected in series. The rear side of the main switch 1b is connected to the control circuit 14 via the relay switch 4b.
[0016]
Power for the control circuit 14 is supplied from a low-voltage power supply system. This low-voltage power supply system includes a leading edge transformer 6, devices 7 and 13 provided on its primary side, and devices 5 and 12 provided on its secondary side. The low-voltage power supply 13 is a power supply different from the battery pack 2 that is a high-voltage power supply, and has a voltage lower than the voltage of the battery pack 2. As such a power supply 13, for example, a battery (12V) mounted on a vehicle can be used. The DC voltage from the power supply 13 is converted into AC by a switching circuit 7 that repeats ON / OFF at a predetermined frequency, and then supplied to the primary side of the insulating transformer 6. Further, the AC voltage output to the secondary side of the insulating transformer 6 is rectified in the bridge circuit 12 and then converted to DC in the three-terminal regulator 5. Then, this DC voltage (for example, 5 V) is supplied to the control circuit 14 as a power supply voltage for the control circuit 14.
[0017]
The control circuit 14 controls on / off of the main switch 1, the pre-resistive load switch 3, and the relay switch 4. Specifically, when the battery pack system is stopped, all the switches 1, 3, and 4 are off. As a result, the battery pack 2 is completely electrically separated from the subsequent circuit system. Next, when starting the battery pack system by turning the ignition key from off to on, only the pre-resistance load switch 3 is turned on, and the main switch 1 and the relay switch 4 are kept off. The reason why the main switch 1 is not turned on in the early stage of operation of the system is to prevent an excessive precharge current (current necessary for initially charging the large-capacity capacitor 8) from flowing. In this initial stage, the capacitor 8 is precharged by using the pre-resistance load switch 4 provided in parallel with the main switch 1 while reducing the current by the resistance. Then, after the precharging of the capacitor 8 is completed, the pre-resistive load switch 4 is turned off and the main switch 1 is turned on. During operation of the system, only the main switch 1 is turned on, and the assembled battery 2 at the preceding stage of the main switch 1 and the motor 11 at the subsequent stage are electrically connected. When the ignition key is turned off from on to stop the battery pack system, only the relay switch 4 is turned on, and the main switch 1 and the relay switch 4 are turned off.
[0018]
Further, the control circuit 14 also evaluates the insulation of the circuit system on the subsequent stage of the main switch 1. When the ignition key is switched from ON to OFF, immediately after that, the control circuit 14 switches the main switch 1 from ON to OFF and switches the relay switch 4 from OFF to ON. By turning off the main switch 1, the subsequent stage of the main switch 1 is electrically separated from the battery pack 2. However, since the accumulated charges remain in the capacitor 8, a potential difference (capacitor voltage) corresponding to the accumulated charges is generated between the positive wiring 16a and the negative wiring 16b. The control circuit 14 evaluates the insulation of the system immediately after the system is stopped by detecting the potential difference. In other words, the charge stored in the capacitor 8 is used as a high-voltage power supply, and the insulation of the circuit system on the subsequent stage of the main switch 1 is detected and evaluated.
[0019]
FIG. 2 is a circuit diagram of a bridge circuit forming a part of the control circuit 14. This bridge circuit includes five resistors 17a to 17e. Two resistors 17a and 17b are provided in series between the contact point of the positive-side relay switch 4a and the negative-side relay switch 4b. Immediately after the system is stopped, the relay switches 4a and 4b are turned on. Therefore, a voltage value obtained by dividing the above-described capacitor voltage by the two resistors 17a and 17b is the voltage of the node A. Then, an analog value corresponding to the voltage of the node A is digitized through an A / D converter. Therefore, output data from the A / D converter is uniquely specified according to the capacitor voltage. The control circuit 14 measures the leakage resistance based on the digitized output data, and evaluates the insulation of the circuit system on the downstream side of the main switch 1 based on the leakage resistance.
[0020]
For example, by calculating the rate of change of the leakage resistance over time, it is possible to determine whether or not the insulation property has decreased, in other words, whether or not a leakage current has occurred. In this case, if the rate of change is greater than a predetermined value, it is determined that the insulation is reduced, and if it is less than or equal to the predetermined value, it is determined that the insulation is not reduced. Alternatively, the presence or absence of a decrease in insulation may be determined based on the value of the leakage resistance at a point in time when a predetermined time (for example, about 5 seconds to about 10 seconds) has elapsed since the system was stopped. In this case, when the value of the leakage resistance is equal to or less than a predetermined value, it is determined that the insulation property is reduced. When the value is larger than the predetermined value, it is determined that the insulation property is not reduced. Further, a decrease in insulation may be evaluated based on a leakage pattern as shown in FIG.
[0021]
As described above, according to the present embodiment, immediately after stopping the battery pack system, the evaluation of the insulation of the battery pack system, in other words, the measurement of the leakage current is performed, so that good accuracy can be secured. There is. As described above, as the temperature of the system increases, the insulation of the system tends to decrease due to this. Therefore, it is difficult to accurately evaluate the insulation of the circuit system downstream of the main switch 1 in a low temperature state. Therefore, in the present embodiment, the insulation property is evaluated immediately after the system is stopped, that is, in a high temperature state substantially equal to that during the operation of the system, so that the insulation property in the operation state can be detected and evaluated well.
[0022]
In addition, the lithium ion battery has characteristics that the leakage current inside the battery is extremely small and energy can be stored for a long period of time. When a signal or power is obtained from the preceding stage of the main switch 1, it causes overdischarge during long-term storage. On the other hand, when obtained from the subsequent stage of the main switch 1 as in the present embodiment, such overdischarge occurs. Can be avoided.
[0023]
Further, by arranging battery-related information processing in a high-voltage system, it is possible to simplify signal isolation (separation) and reduce costs.
[0024]
Note that the control circuit 14 may measure the leakage resistance based on the above-described calculation method at the time of starting the system as well as immediately after the system is stopped. In this case, during a period in which the main switch 1 is turned off and the pre-resistive load switch 3 is turned on (at the time of starting the system), the pre-resistive load switch 3 is temporarily turned off. As a result, the circuit system at the subsequent stage of the pre-resistance load switch 3 is electrically separated from the battery pack 2. In this state, the control circuit 14 measures the second leakage resistance. Then, the magnitude of the first leakage resistance measured immediately after the system is stopped (at high temperature) and the magnitude of the second leakage resistance measured at the time of starting the system (low temperature) are compared. This makes it possible to determine whether or not the cause of the leakage is a decrease in insulation due to a rise in temperature during operation of the system. Specifically, when the difference between the first leakage resistance at high temperature and the second leakage resistance at low temperature is equal to or less than a predetermined value, it can be determined that the cause of the leakage is a factor other than the temperature rise. When the difference between the first leakage resistance at high temperature and the second leakage resistance at low temperature is larger than a predetermined value, it can be determined that the cause of the leakage is a rise in temperature.
[0025]
Further, in the above-described embodiment, the control circuit 14 calculates the leakage resistance from the capacitor voltage. However, the control circuit 14 calculates the high-voltage power supply information including at least one of the battery voltage, the leakage current, and the leakage resistance. Can be obtained from the subsequent stage of the main switch 1.
[0026]
【The invention's effect】
According to the present invention, good accuracy can be ensured by detecting and evaluating the insulation property of the battery pack system immediately after the system is stopped.
[Brief description of the drawings]
FIG. 1 is a configuration diagram of an assembled battery system. FIG. 2 is a circuit diagram of a bridge circuit forming a part of a control circuit. FIG. 3 is an explanatory diagram of a leakage pattern.
1a, 1b Main switch 2 Battery pack 3a, 3b Pre-resistive load switch 4a, 4b Relay switch 5 Three-terminal regulator 6 Insulation transformer 7 Switching circuit 8 Capacitor 9 Battery pack unit 10 Inverter 11 Motor 12 Bridge circuit 13 Low voltage power supply 14 Control circuit 15a, 15b Connectors 16a, 16b Wirings 17a-17e Resistance

Claims (8)

In the assembled battery system,
An assembled battery in which a plurality of battery cells are connected in series;
Load and
A main switch in which the battery pack is connected in the first stage and the load is connected in the second stage,
A capacitor connected in parallel with the load on a subsequent side of the main switch;
When the main switch is turned on or off and the main switch is switched from on to off, an insulation property related to a circuit system at a subsequent stage of the main switch is determined based on a potential difference caused by electric charges accumulated in the capacitor. And a control circuit for evaluating the following. 2. The battery pack system according to claim 1, wherein the control circuit evaluates the insulation by measuring a leakage resistance of a circuit system on a subsequent stage of the main switch. 3. A pre-resistive load switch provided in parallel with the main switch,
The control circuit controls on / off of the pre-resistive load switch, sets the main switch to off, and temporarily turns off the pre-resistive load switch during a period in which the pre-resistive load switch is set to on. 3. The battery pack system according to claim 2, wherein the leakage resistance is measured by setting the leakage resistance to off. The control circuit includes:
A first leakage resistance measured by switching the main switch from on to off, and a period in which the main switch is set to off and the pre-resistive load switch is set to on. 4. The assembled battery system according to claim 3, wherein the magnitude is compared with the second leakage resistance measured by temporarily setting the second leakage resistance to OFF. In the assembled battery system,
A battery pack in which a plurality of battery cells are connected in series to generate a predetermined high voltage,
Load and
A main switch in which the battery pack is connected in the first stage and the load is connected in the second stage,
A capacitor connected in parallel with the load on a subsequent side of the main switch;
When the main switch is turned on or off and the main switch is switched from on to off, the electric charge accumulated in the capacitor is used as a high-voltage power supply to insulate the circuit on the subsequent stage of the main switch. A battery pack system comprising: a control circuit that evaluates performance. The assembled battery according to claim 5, wherein the control circuit acquires high-voltage power supply information including at least one of a battery voltage, a leakage current, and a leakage resistance from a downstream side of the main switch. system. The power supply to the control circuit is a power supply different from the high-voltage power supply, and is supplied from a low-voltage power supply lower than the high-voltage power supply via an insulating transformer. 6. The assembled battery system according to 6. A battery pack in which a plurality of battery cells are connected in series, a load, a main switch in which the battery pack is connected in a preceding stage, and the load is connected in a subsequent stage, and a load in parallel with the load in a stage subsequent to the main switch. A leakage current measurement method for a battery pack system having a capacitor connected to
Switching the main switch from on to off;
Detecting a potential difference caused by the charge stored in the capacitor;
Measuring a leakage current relating to a circuit system at a subsequent stage of the main switch based on the potential difference.

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