JP2013032947A - Device and method for calculating internal resistance value - Google Patents

Abstract

A secondary battery internal resistance value calculation apparatus and internal resistance calculation method capable of accurately detecting a deterioration state of a secondary battery and avoiding the influence of aging deterioration and the like.
A capacitor is connected so as to be in parallel with a battery, and a series circuit of a first resistor and a first switch is connected therebetween. Further, one end of the second resistor 35 is connected between the first resistor 32 and the capacitor 33 via the second switch 34, and the first switch 31 and the second switch 34 are switched complementarily. When the first switch 31 is on, the capacitor 1 is charged from the battery 1, and the time constant τ _chg is the internal resistance value Rb of the battery 1, the resistance value R1 of the first resistor 32, the internal resistance value Rc of the capacitor 33, and the capacitance. Using C, τ _chg = (Rb + R1 + Rc) C. Based on the calculation with the time constant τ _dchg = (R1 + Rc) C when the capacitor 33 is discharged, the internal resistance value Rb of the battery 1 is obtained.
[Selection] Figure 2

Description

  The present invention relates to a device for detecting the state of charge of a secondary battery, and in particular, it can accurately calculate the internal resistance value in order to detect the state of deterioration while avoiding the effects of deterioration over time using a capacitor. The present invention relates to an internal resistance value calculation device and an internal resistance value calculation method for a secondary battery.

  A battery (secondary battery) mounted on the vehicle needs to be sufficiently charged to supply voltage to the starter when the engine is started. Therefore, it is important that the state of charge of the battery can be accurately detected.

  Conventionally, as shown in Patent Documents 1 and 2, the discharge current value and the terminal voltage value (release voltage value and discharge voltage value) when an inrush current flows when the ignition switch of the vehicle is turned on are obtained. A method of sampling, calculating an internal resistance value from the sampled value, and detecting the degree of deterioration is used.

JP 2008-8703 A JP 2009-226996 A

  However, since the sampled current value or voltage value is an instantaneous value in several tens of milliseconds, the error is relatively large, and the calculated internal resistance value varies. In addition, the calculated internal resistance value is affected by the internal resistance value of the starter, but the internal resistance value of the starter is also subject to deterioration over time, and may not be accurately calculated.

  The present invention has been made in view of such circumstances, and is capable of detecting a deterioration state of a secondary battery with high accuracy and avoiding the influence of aged deterioration and the like, and an internal resistance value calculation device for a secondary battery, It is an object to provide a method for calculating internal resistance.

  In the internal resistance value calculating device according to the first invention, one terminal is connected to one electrode side of the secondary battery via a series circuit of a first switch and a first resistor, and the other terminal is the other side of the secondary battery. A capacitor connected to the electrode side of the second resistor, one terminal connected via a second switch between the first resistor and the capacitor, and a second resistor whose other terminal is connected to the other electrode side of the secondary battery And means for switching on / off the first switch and the second switch in a complementary manner to switch charging / discharging of the capacitor, and means for measuring the potential on one terminal side of the capacitor after switching by the means at a plurality of time points. A means for calculating a time constant at the time of charging and a time constant at the time of discharging based on the measured potentials at a plurality of points in time, and the inside of the secondary battery from the calculated time constant at the time of charging and discharging Means for calculating the resistance value; Characterized in that it comprises.

  The internal resistance value calculation device according to the second invention is characterized in that the resistance values of the first resistance and the second resistance are substantially equal.

  An internal resistance value calculation device according to a third aspect of the invention is characterized in that the internal resistance value of the secondary battery is calculated by dividing the calculated difference between charging and discharging by the capacity of the capacitor. To do.

  In the internal resistance value calculating apparatus according to a fourth aspect of the present invention, the capacitor is an electric double layer capacitor.

  In the internal resistance value calculation method according to the fifth aspect of the invention, one terminal of a capacitor is connected to one electrode side of the secondary battery via a series circuit of a first switch and a first resistor, and the other terminal of the capacitor is connected to the electrode. Connect to the other electrode side of the secondary battery, connect one terminal of the second resistor via the second switch between the first resistor and the capacitor, and connect the other terminal to the other electrode side of the secondary battery The first switch is turned on, the second switch is turned off, the capacitor is charged with the power supplied from the secondary battery, and the potential on the one terminal side of the capacitor after charging is started at a plurality of times. The second switch is turned off, the second switch is turned on, the capacitor is discharged, the electric potential at one terminal side of the capacitor after starting the discharge is measured at a plurality of time points, and the measured potentials at the plurality of time points are measured. Based on the above Calculating the constants and the time constant during discharge when the charging of the capacitor, and calculates the internal resistance of the secondary battery from a time constant during charging and discharging was calculated.

In the present invention, a capacitor is connected to one electrode side of the secondary battery via a series circuit of a first switch and a first resistor. One terminal of the capacitor is connected to the first switch and the first resistance side, and the other terminal is connected to the other electrode side of the secondary battery. Note that any electrode of the secondary battery is connected to a fixed potential, for example, grounded. When the first switch is turned on, the secondary battery is discharged and the capacitor is charged. Further, a second resistor is connected between the first resistor and the capacitor via a second switch. One terminal of the second resistor is connected to the capacitor side, and the other terminal is connected to the other electrode side of the rechargeable battery. When the first switch is turned off and the second switch is turned on after the capacitor is charged, the capacitor is discharged. Capacitor charging / discharging is switched by complementarily turning on / off the first switch and the second switch. At this time, the potential on one terminal side of the capacitor being charged and the potential on one terminal side of the capacitor being discharged are measured at multiple points in time, and time constants (τ _chg , τ _dchg ) are calculated based on these measured values. To do. A time constant during charging (τ _chg = R _chg C) in a circuit configuration including a secondary battery, a first resistor and a capacitor, and a time constant during discharge in a circuit configuration including a capacitor and a second resistor (τ _dchg = From R _dchg C), it is possible to calculate the internal resistance value of the secondary battery by canceling the internal resistance value of the capacitor using the known resistance values of the first resistance and the second resistance. At this time, the resistance values of the first resistor and the second resistor are appropriately set so as not to be excessive compared with the internal resistance value of the secondary battery.

In the present invention, since the resistance values of the first resistor and the second resistor are equal, the difference between the time constant τ _chg at the time of charging and the time constant τ _dchg at the time of discharging is taken to _obtain the first resistance and the second resistance. The resistance value component of the resistor can be removed, and the internal resistance value of the secondary battery can be easily calculated.

In the present invention, the difference between the calculated time constant τ _chg during charging and the time constant τ _dchg during discharging is divided by the capacity of the capacitor to calculate the internal resistance value of the secondary battery. Since the circuit configuration at the time of charging is a configuration in which the internal resistance of the secondary battery, the first resistor and the capacitor are connected in series, the time constant τ _chg (= R _chg C) at the time of charging is the internal resistance of the secondary battery. Using the value Rb, the resistance value R1 of the first resistor, and the internal resistance value Rc of the capacitor,
τ _chg = (Rb + R1 + Rc) C (1)
It can be expressed as. Similarly, since the circuit configuration at the time of discharge is such that the capacitor and the second resistor are directly connected, the time constant τ _dchg (= R _dchg C) at the time of discharge is the internal resistance value Rc and the second resistance of the capacitor. Resistance value R2 (= R1) of
τ _chg = (Rc + R1) C (2)
It can be expressed as. Therefore, the internal resistance value Rb of the secondary battery can be calculated by dividing the time constant difference (= expression (1) −expression (2)) by the capacitance C of the capacitor. At this time, since the resistance values of the first resistor and the second resistor are equal, calculation is possible only by taking a difference, and even if the internal resistance value of the capacitor changes due to aging or temperature dependence, it is canceled out.

  In the present invention, the capacitor is an electric double layer capacitor. Since the internal resistance is relatively low, there is little influence on the calculation of the internal resistance of the secondary battery, and deterioration due to charge / discharge is small.

  In the case of the present invention, instead of using the voltage value and current value at the time of inrush current, it is calculated using the time constant of the potential change at the time of charging the capacitor from the secondary battery, so from the instantaneous value at the time of inrush current However, since the voltage value at the time of charging with a small error is used, the accuracy of the calculated internal resistance value is increased. In addition, the time constant at the time of charging and discharging the capacitor is used to calculate the resistance value of each resistor and the internal resistance value of the capacitor, so the change in the internal resistance value due to aging of circuit components other than the secondary battery In addition, the temperature dependency of the internal resistance value can be avoided.

  In addition, when the capacitor is composed of an electric double layer capacitor and the voltage of the secondary battery is equal to or lower than the voltage of the electric double layer capacitor, even if the electric double layer capacitor and the secondary battery remain connected, When the electric potential of the double layer capacitor becomes equal to the electric potential of the secondary battery, charging to the electric double layer capacitor, that is, discharging from the secondary battery is stopped, so that the risk of overdischarge from the secondary battery can be avoided. it can.

It is a block diagram which shows the structure of the state detection apparatus in this Embodiment. It is a block diagram which shows the circuit structure of the state detection apparatus in this Embodiment. It is a graph which shows the voltage change (at the time of charge) of the capacitor | condenser in this Embodiment. It is a block diagram which shows the circuit structure of the state detection apparatus in this Embodiment. It is a graph which shows the voltage change (at the time of discharge) of the capacitor | condenser in this Embodiment.

Hereinafter, the present invention will be specifically described with reference to the drawings showing embodiments thereof.
In the following embodiments, detection of the state of a battery that supplies power to a vehicle-mounted load mounted on a vehicle will be described.

  FIG. 1 is a block diagram showing a configuration of a state detection device according to the present embodiment. The state detection device 3 is connected to the positive voltage side (+ B) between the battery 1, which is a lead battery whose negative electrode side is grounded, and the load 2 that receives power from the battery 1. The load 2 is, for example, a plurality of ECUs (Electronic Controller Units). Each ECU is connected to a power line in a bus shape and is supplied with power.

  The state detection device 3 includes a first switch 31, a first resistor 32, a capacitor 33, a second switch 34, a second resistor 35, and a control unit 36 that controls them.

  The capacitor 33 has one terminal connected to the positive voltage side of the battery 1 and the other terminal grounded and connected in parallel with the battery 1. A series circuit of a first switch 31 and a first resistor 32 is connected between the positive voltage side of the battery 1 and one terminal of the capacitor 33. When the first switch 31 is turned on, the positive voltage side of the battery 1 and the capacitor 33 are connected via the first resistor 32, and the capacitor 33 can be charged. The first switch 31 is off when no measurement for state detection is performed. A second resistor 35 is connected between the first resistor 32 and the positive electrode of the capacitor 33 via a second switch 34. One end of the second resistor 35 opposite to the second switch is grounded. When the second switch 34 is turned on, the capacitor 33 and the second resistor 35 are connected, the charged capacitor 33 is discharged, and a current flows through the second resistor 35.

  The control unit 36 uses a processor such as a CPU (Central Processing Unit) or an MPU (Micro Processing Unit) to control on / off of the first switch 31 and the second switch 34. The control unit 36 can store information in a memory (not shown). The control unit 36 includes a voltage detection element, and measures the potential of the terminal of the capacitor 33 on the battery 1 side.

  The state detection device 3 configured in this way calculates the internal resistance value of the battery 1 under the control of the control unit 36 periodically or when any trigger is detected such as when the engine is stopped. The state of the battery 1 is detected by a change in resistance value. For example, when the internal resistance value increases above a predetermined value, the state detection device 3 determines that the battery 1 is in a deteriorated state and turns on the warning lamp. Various known methods may be used as a method of determining the deterioration state using the internal resistance value.

  Details of the measurement of the internal resistance value of the battery 1 by the control unit 36 of the state detection device 3 will be described. For example, before starting the engine, the control unit 36 turns on / off the first switch 31 and the second switch 34 as will be described below, and measures the voltage value of the capacitor 33 between them at a plurality of points in time. The internal resistance value of is calculated.

  First, the control unit 36 turns on the first switch 31 and turns off the second switch 34 in order to start measurement for state detection. FIG. 2 is a block diagram showing a circuit configuration of the state detection device 3 in the present embodiment. The circuit configuration shown in FIG. 2 shows a case where the first switch 31 is on and the second switch 34 is off. In FIG. 2, Rb represents the internal resistance value of the battery 1, and Rc represents the internal resistance value of the capacitor 33. C represents the capacity of the capacitor 33. R1 represents the resistance value of the first resistor 32 and the second resistor 35. That is, in the present embodiment, the resistance values of the first resistor 32 and the second resistor 35 are equal.

  When the control unit 36 turns off the second switch 34 and turns on the first switch 31, the battery 1 is discharged, and charging of the capacitor 33 is started as shown by the arrow in FIG. 2. Charging is completed when the potential of the capacitor 33 becomes equal to the potential of the battery 1. Until this charging is completed, the control unit 36 measures voltage values at a plurality of points in time and stores them in a built-in memory (not shown). When the capacitor 33 is an electric double layer capacitor and its withstand voltage (usable upper limit voltage) is lower than the voltage of the battery 1, the control unit 36 stops charging when the potential of the capacitor 33 reaches the withstand voltage. Control both switches.

  FIG. 3 is a graph showing the voltage change (during charging) of the capacitor 33 in the present embodiment. The horizontal axis shows the passage of time, and the vertical axis shows the voltage of the capacitor 33. The graph shown in FIG. 3 is obtained by plotting the results obtained by simulating the voltage change due to charging from the battery 1 up to a time 10 times the time constant τ.

The control unit 36 may measure at a plurality of time points among the voltage changes shown in the graph of FIG. 3 and obtain the voltage change by approximation based on the measurement result. And the control part 36 calculates _| requires time constant (tau) _chg from the time change of a voltage. At this time, the time constant τ _chg is expressed by the equation (1) as described above.
τ _chg = R _chg C = (Rb + R1 + Rc) C (1)

  Next, the control unit 36 turns off the first switch 31 and turns on the second switch 34. Note that, for example, one minute is waited from when the first switch is turned on to when it is turned off. FIG. 4 is a block diagram illustrating a circuit configuration of the state detection device 3 according to the present embodiment. The circuit configuration shown in FIG. 4 shows a case where the first switch 31 is off and the second switch 34 is on.

  When the control unit 36 turns off the first switch 31 and turns on the second switch 34, the capacitor 33 is disconnected from the battery 1, and the terminal on the battery 1 side of the charged capacitor 33 is grounded via the second resistor 35. Is done. Therefore, discharging from the capacitor 33 is started as shown by the arrow in FIG. The discharge ends when the potential of the capacitor 33 becomes equal to the ground potential (zero V). Until this discharge is completed, the control unit 36 measures voltage values at a plurality of points in time and stores them in a built-in memory (not shown).

  FIG. 5 is a graph showing a voltage change (when discharging) of the capacitor 33 in the present embodiment. The horizontal axis shows the passage of time, and the vertical axis shows the voltage of the capacitor 33. The graph shown in FIG. 5 is obtained by plotting the results obtained by simulating the voltage change due to the discharge up to a time 10 times the time constant τ.

The control unit 36 may measure the voltage changes shown in the graph of FIG. 5 at a plurality of time points and obtain the voltage change by approximation based on the measurement result. And the control part 36 calculates _| requires time constant (tau) _dchg from the time change of a voltage. At this time, the time constant τ _dchg is expressed by the equation (2) as described above.
τ _dchg = R _dchg C = (R1 + Rc) C (2)

Then, the control unit 36 calculates the internal resistance value Rb of the battery 1 using the obtained time constants τ _chg and τ _dchg . Specifically, equation (2) is subtracted from equation (1). The subtraction result is expressed by equation (3).
τ _{chg −τ dchg} = RbC (3)
If the subtraction result is divided by the capacitance C of the capacitor 33, the internal resistance value Rb of the battery 1 can be calculated as in the following equation (4).
τ _{chg −τ dchg} / C = Rb (4)

  In order to calculate the internal resistance value Rb of the battery 1 with high accuracy as in the above formulas (1) to (4), the resistance value R1 of the first resistor 32 and the second resistor 35 and the capacitance of the capacitor 33 are calculated. It should be configured with C set appropriately. For example, the resistance value R1 and the capacitance C of the capacitor 33 are set as follows. The internal resistance value Rb of the battery 1 that is a lead battery mounted on the vehicle is about 10 to 30 mΩ. In order to detect the change in the internal resistance value Rb, R1 should be a value that is about the same as or slightly larger than the internal resistance value Rb. Therefore, for example, the one with about 0.1Ω is used. As for the capacitance C of the capacitor 33, when the capacitor 33 is composed of an electric double layer capacitor, if the output voltage when the battery 1 is fully charged is 12.8V, the capacitance per capacitor of the electric double layer capacitor is 12.8V. Since the withstand voltage is 2.3 to 2.5 V, six capacitors are connected in series, and one capacitor is 60 F so that it is 10 F or less. In order to sufficiently measure the change in the voltage value for calculating the internal resistance value Rb, it is desirable to appropriately determine the capacity C by design so that about 5 to 10 times the time constant is 1 minute. The internal resistance value Rc of the capacitor 33 should also be the same or slightly larger value in order to detect a change in the internal resistance value Rb. Therefore, it is desirable to use a capacitor of 0.1 to 0.3Ω · F. However, the resistance value or capacity of each component is not limited to these numerical values, and can be adjusted by cooling or the like.

  In the state detection device 3 according to the present embodiment, since a large current can be considered to flow, the wiring should be configured to withstand the large current.

In this way, the internal resistance value Rb can be calculated with high accuracy by the configuration in which the internal resistance value Rb is calculated by _{obtaining the} time constants τ _chg and τ _dchg when the capacitor 33 is charged and discharged. Therefore, the state of the battery 1 can be detected with higher accuracy.

  Moreover, in this Embodiment, in order to calculate the internal resistance value Rb of the vehicle-mounted battery 1, the state detection apparatus 3 is used. Since the capacitor 33 is also provided inside the state detection device 3 installed in the vicinity of the battery 1, it is naturally affected by the temperature change in the vehicle. Therefore, although the internal resistance value Rc of the capacitor 33 also fluctuates, the internal resistance value Rc of the capacitor 33 is canceled in the process of calculating the internal resistance value Rb of the battery 1 as shown in the equations (1) to (4). Since changes in elements other than the battery 1 such as the resistance values R1 of the first resistor 32 and the second resistor 35 are canceled in the calculation process, the battery 1 is not affected by the value of each element due to aging and temperature change. The internal resistance value Rb can be calculated, and an excellent effect is achieved.

  Further, in the configuration of the state detection device 3 according to the present embodiment, even if the first switch 31 remains on and the battery 1 and the capacitor 33 remain connected due to a malfunction of the control unit 36, the capacitor Since the discharge is stopped when the potential of 33 becomes equal to the potential of the battery 1, the risk of overdischarge can be avoided.

  In the present embodiment, the state detection device 3 is connected to the positive voltage side of the battery 1. However, the present invention is not limited to this, and the positive voltage side of the battery may be connected to a fixed potential, and the state detection device may be connected to the negative voltage side of the battery to calculate the internal resistance value and detect the state.

  In the present embodiment, the state detection device 3 is configured as a device that detects the state of charge of the battery 1 that is a lead battery mounted on the vehicle, and detects the state by calculating the internal resistance value of the vehicle-mounted battery 1. It was. However, the present invention is not limited to this, and can also be applied to the calculation of the internal resistance value of batteries other than lead batteries, and can be widely used as a device for detecting the state of charge of not only the in-vehicle battery but also the secondary battery.

  The disclosed embodiments are to be considered in all respects as illustrative and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

1 Battery (secondary battery)
3 State detection device (Internal resistance value calculation device)
31 First switch 32 First resistor 33 Capacitor (electric double layer capacitor)
34 second switch 35 second resistor 36 control unit (measuring means, calculating means)

Claims (5)

A capacitor having one terminal connected to one electrode side of the secondary battery via a series circuit of a first switch and a first resistor and the other terminal connected to the other electrode side of the secondary battery;
A second resistor in which one terminal is connected between the first resistor and the capacitor via a second switch, and the other terminal is connected to the other electrode side of the secondary battery;
Means for switching between charging and discharging of the capacitor by complementarily turning on and off the first switch and the second switch;
Means for measuring the potential on one terminal side of the capacitor after switching by the means at a plurality of points;
Based on the measured potential at a plurality of time points, a means for calculating a time constant at the time of charging the capacitor and a time constant at the time of discharging;
An internal resistance value calculation device comprising: means for calculating an internal resistance value of the secondary battery from the calculated time constants during charging and discharging. The internal resistance value calculation device according to claim 1, wherein the resistance values of the first resistor and the second resistor are substantially equal. The internal resistance value calculation device according to claim 2, wherein the calculated internal resistance value of the secondary battery is calculated by dividing the calculated difference between charging and discharging times by the capacity of the capacitor. . The internal resistance value calculation device according to claim 1, wherein the capacitor is an electric double layer capacitor. One terminal of a capacitor is connected to one electrode side of the secondary battery via a series circuit of a first switch and a first resistor, and the other terminal of the capacitor is connected to the other electrode side of the secondary battery, One terminal of the second resistor is connected between the first resistor and the capacitor via a second switch, and the other terminal is connected to the other electrode side of the secondary battery,
The first switch is turned on, the second switch is turned off, and the capacitor is charged with the power supplied from the secondary battery,
Measure the potential on one terminal side of the capacitor after starting charging at multiple points in time,
The second switch is turned off and the second switch is turned on to discharge the capacitor.
Measure the potential of one terminal side of the capacitor after starting the discharge at multiple points in time,
Based on the measured potential at multiple points in time, calculate the time constant when charging the capacitor and the time constant when discharging,
An internal resistance value calculation method, wherein the internal resistance value of the secondary rechargeable battery is calculated from the calculated time constants during charging and discharging.

Images