JP2011017546A - Device and method for diagnosing deterioration of lead battery for vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable diagnosis of deterioration of a lead battery in an optional timing.SOLUTION: After a prescribed time Xs passes till solving of polarization in the lead battery 2 from stopping of power supply from a DC-DC converter 3 to a weak electrical system load 1, ECU 5 reads a discharge current An of the lead battery 2 measured by a current sensor 6 and battery voltage Vn measured by a battery sensor 7, and determines the lead battery 2 as deteriorated when the read battery voltage Vn is a determination threshold Vs decided according to the discharge current An, or below.

Description

  The present invention relates to a deterioration diagnosis apparatus and a deterioration diagnosis method for diagnosing deterioration of a lead battery used as a power source for a weak electric load of a vehicle.

  Conventionally, as a deterioration diagnosis device for diagnosing deterioration of a lead battery for a vehicle, when an instantaneous voltage drop of the lead battery at the time of engine cranking is measured and the instantaneous voltage drop at the time of cranking is below a predetermined threshold Moreover, what determines that the lead battery has deteriorated is known (for example, refer patent document 1).

JP 2005-127202 A

  However, the deterioration diagnosis device described in Patent Document 1 is configured to determine the deterioration of the lead battery by comparing the instantaneous voltage drop of the lead battery with the threshold value at the time of engine cranking. There was a problem that diagnosis could not be performed.

  The present invention has been developed to solve the above problems, and provides a vehicle lead battery deterioration diagnosis device and deterioration diagnosis method capable of diagnosing lead battery deterioration at an arbitrary timing. The purpose is that.

  The present invention stops power supply from a power supply unit connected so as to be able to supply power to a weak power system load to the weak power system load, and is a predetermined period from when the power supply is stopped until the polarization in the lead battery is eliminated. The discharge current and battery voltage of the lead battery are measured after a lapse of time, and it is determined that the lead battery is deteriorated when the battery voltage is equal to or less than a determination threshold value determined according to the discharge current.

  According to the present invention, the deterioration of the lead battery is determined on the basis of the discharge current and the battery voltage in the state where the polarization is eliminated regardless of the instantaneous voltage drop of the lead battery at the time of engine cranking. Deterioration diagnosis of the lead battery can be performed.

It is a figure which shows the structure of the power supply system of 1st Embodiment. It is a figure explaining that the instantaneous low voltage at the time of the large current discharge of a lead battery has a proportional relationship with a deterioration degree. It is a figure explaining that the relationship between an instantaneous low voltage and a deterioration degree changes according to a discharge current. It is a graph which compares and shows each change of the battery voltage when charging / discharging is periodically repeated with a fixed current with respect to the lead battery which deteriorated and the lead battery which is new and does not deteriorate. It is a flowchart which shows the flow of a series of processes which ECU performs when performing deterioration diagnosis of a lead battery. It is a figure which shows the structure of the power supply system of 2nd Embodiment. It is a figure which shows the structure of the power supply system of 3rd Embodiment.

  Hereinafter, specific embodiments of the present invention will be described in detail with reference to the drawings.

[First Embodiment]
FIG. 1 shows a configuration when the present invention is applied to a weak power system of a general hybrid vehicle.
This power supply system includes a lead battery 2 that serves as a power source for a weak electric system load 1 of a vehicle. A DCDC converter 3 is connected to the weak electric system load 1 and the lead battery 2. The DCDC converter 3 converts the high voltage from the lithium ion battery 4, which is a power source for driving the vehicle, into a weak voltage and supplies power to the weak electric system load 1 and the lead battery 2. That is, in this power supply system, it is possible to supply power from both the lead battery 2 and the DCDC converter 3 to the weak electric system load 1, and when the charge state of the lead battery 2 is reduced, the DCDC converter The lead battery 2 can be charged with the electric power from 3. The vehicle driving power source may be a high output battery, and for example, a nickel metal hydride battery may be used in addition to the lithium ion battery 4.

  In addition, the power supply system is provided with an electronic control unit (hereinafter abbreviated as ECU) 5 having a function of controlling the operation of the DCDC converter 3 in accordance with the state of the lithium ion battery 4. The ECU 5 is connected to a current sensor 6 that measures the discharge current of the lead battery 2 and a voltage sensor 7 that measures the battery voltage. The measured values of the current sensor 6 and the voltage sensor 7 are input to the ECU 5. It has become. In the present embodiment, the ECU 5 has a function of diagnosing the deterioration of the lead battery 2 using the measured values of the current sensor 6 and the voltage sensor 7. The operating power source of the ECU 5 is the lead battery 2 or the DCDC converter 3.

  Here, the relationship between the deterioration degree of the lead battery 2, the discharge current, and the battery voltage will be described with reference to FIGS. 2 and 3.

  Immediately after the lead battery 2 starts discharging, the battery voltage instantaneously decreases (the voltage value of the battery voltage instantaneously decreasing immediately after the start of discharging is referred to as instantaneously low voltage). Here, for example, during a large current discharge such as when the engine is cranked by supplying power to the starter, it is generally known that the instantaneous voltage drop decreases as the degree of deterioration of the lead battery 2 increases. ing. That is, when considering the three deterioration degrees having the relationship of deterioration A <deterioration B <deterioration C as the deterioration degree of the lead battery 2, as shown in FIG. The relationship between the low voltage Va, the instantaneous voltage Vb of the lead battery 2 of the deteriorated B and the instantaneous voltage Vc of the lead battery 2 of the deteriorated C is Va> Vb> Vc. It is known that the voltage is proportional.

  However, in the region where the discharge current of the lead battery 2 is small, due to the influence of the polarization of the lead battery 2, as shown in FIG. 3, the instantaneous low voltage Va ′ of the lead battery 2 of the deterioration A and the lead battery 2 of the deterioration B In some cases, the instantaneous voltage Vb ′ and the instantaneous voltage Vc ′ of the deteriorated lead battery 2 may not have a relationship of Va ′> Vb ′> Vc ′, and the degree of deterioration of the lead battery 2 and the instantaneous voltage are proportional. Not necessarily a relationship. For this reason, when the instantaneous low voltage of the lead battery 2 is measured and the deterioration degree is determined, the determination timing is limited to a large current discharge such as when the engine is started.

  Therefore, in the present embodiment, the ECU 5 diagnoses the deterioration of the lead battery 2 based on the discharge current and the battery voltage after a predetermined time has elapsed from when the lead battery 2 starts discharging until the polarization is eliminated. Thus, the deterioration diagnosis of the lead battery 2 can be performed at an arbitrary timing. Specifically, the ECU 5 starts discharging the lead battery 2 by stopping the power supply from the DCDC converter 3 to the weak electric system load 1 in a state where any one of the weak electric system loads 1 is operating. Then, after a predetermined time has elapsed from the stop of power supply of the DCDC converter 3, the discharge current of the lead battery 2 measured by the current sensor 6 and the battery voltage measured by the voltage sensor 7 are read, and the value of the read battery voltage is It is determined that the lead battery 2 is deteriorated when it is equal to or less than a determination threshold value determined according to the read discharge current.

  FIG. 4 shows changes in battery voltage when charging / discharging is repeated periodically (every 20 seconds) at a constant current for a lead battery 2 that has deteriorated and a lead battery 2 that is new and has no deterioration. FIG. In addition, the solid line graph in the figure shows the change in the battery voltage of the lead battery 2 in which the deterioration has occurred, and the broken line graph shows the change in the battery voltage in the lead battery 2 without the deterioration.

  As shown in FIG. 4, immediately after the discharge start time T <b> 1 of the lead battery 2, the battery voltage is drastically reduced in both the lead battery 2 in which deterioration has occurred and the lead battery 2 in which deterioration has not occurred. The degree of decrease in the battery voltage immediately after the start of discharge is influenced by the polarization of the lead battery 2, and therefore does not correspond to the degree of deterioration of the lead battery 2. However, at the timing of T2 when a predetermined time (for example, 5 seconds) has elapsed from the discharge start time T1, the influence of the polarization is eliminated, so that the battery voltage reflects the deterioration degree of the lead battery 2, and the deterioration has occurred. The battery voltage of the lead battery 2 is sufficiently lower than the battery voltage of the lead battery 2 without deterioration. Therefore, by comparing the battery voltage measured at the timing after time T2 with the deterioration determination threshold value, the deterioration diagnosis of the lead battery 2 can be performed regardless of the magnitude of the discharge current. Since the value of the battery voltage depends on the magnitude of the discharge current at that time, the deterioration determination threshold is determined according to the discharge current measured simultaneously with the battery voltage. That is, the determination threshold may be lowered as the discharge current increases.

  FIG. 5 is a flowchart showing a flow of a series of processing executed by the ECU 5 when performing deterioration diagnosis of the lead battery 2 in the power supply system of the present embodiment. The deterioration diagnosis shown in FIG. 5 can be executed at any timing when any one of the weak electric loads 1 is operating. For example, it is detected that the operation of the weak electric loads 1 is unstable. Or when a diagnosis start instruction is input by a vehicle occupant's switch operation or the like.

  When the flow of FIG. 5 is started, the ECU 5 first starts discharging the lead battery 2 by stopping the power supply from the DCDC converter 3 to the weak electric system load 1 in step S101, and sets the predetermined time Xs. Start the timer count to measure. Stopping the power supply from the DCDC converter 3 to the weak load 1 may be realized, for example, by lowering the conversion voltage of the DCDC converter 3, or by providing a switch on the output side of the DCDC converter 3, and temporarily turning this switch on. Alternatively, it may be realized by turning it off. The predetermined time Xs may be set to a time sufficient to eliminate the influence of polarization from the start of discharge of the lead battery 2, and an optimal time (for example, 5 seconds) may be obtained in advance by experiments or the like.

  Thereafter, in step S102, the ECU 5 stands by until the predetermined time Xs has elapsed since the power supply stop of the DCDC converter 3, and when the predetermined time Xs has elapsed (determination of YES in step S102), the process proceeds to step S103. To do.

  Next, in step S103, the ECU 5 measures the discharge current An of the lead battery 2 measured by the current sensor 6 at the present time (after the elapse of a predetermined time Xs from the stop of the power supply of the DCDC converter 3) and the voltage sensor 7. The battery voltage Vn of the lead battery 2 is read.

  Next, the ECU 5 restarts the power supply from the DCDC converter 3 to the weak electric system load 1 in step S104. Note that the resumption of power supply to the DCDC converter 3 may be performed at any timing as long as the discharge current and battery voltage of the lead battery 2 are measured.

  Next, in step S105, the ECU 5 sets a determination threshold value Vs for determining deterioration of the lead battery 2 in accordance with the discharge current read in step S103. The determination threshold value Vs for each discharge current may be determined in advance by an experiment or the like and stored in the internal memory of the ECU 5 or the like.

  Next, in step S106, the ECU 5 compares the battery voltage Vn read in step S103 with the determination threshold value Vs set in step S105, and determines whether the battery voltage Vn is equal to or lower than the determination threshold value Vs. When the battery voltage Vn is equal to or lower than the determination threshold value Vs, fail safe control for protecting the lead battery 2 is executed in step S107. The fail-safe control here is, for example, control that limits the discharge from the lead battery 2 to the weak electrical load 1 by increasing the conversion voltage of the DCDC converter 3. Further, the deterioration of the lead battery 2 may be notified to the vehicle occupant by outputting a warning sound or the like, and the battery replacement may be encouraged.

  As described above in detail with specific examples, in the power supply system of the present embodiment, the polarization in the lead battery 2 after the ECU 5 stops the power supply from the DCDC converter 3 to the weak electric system load 2. After the elapse of a predetermined time Xs until the battery is eliminated, the discharge current An of the lead battery 2 measured by the current sensor 6 and the battery voltage Vn measured by the voltage sensor 7 are read, and the battery voltage Vn at this time is It is determined that the lead battery 2 is deteriorated when it is equal to or lower than the determination threshold Vs determined according to the discharge current An. Therefore, according to the power supply system of the present embodiment, the lead battery 2 is used at a time other than the timing at which a large current is discharged from the lead battery 2, such as when the engine is started by supplying power to the starter and cranking the engine. It is possible to appropriately determine whether or not the battery is deteriorated, and the deterioration diagnosis of the lead battery 2 can be performed at an arbitrary timing.

  Further, in the power supply system of the present embodiment, when the ECU 5 determines that the lead battery 2 has deteriorated, the fail safe control for restricting the discharge from the lead battery 2 to the weak electric system load 1 is executed. Therefore, it is possible to prevent the battery of the lead battery 2 from running out and the power failure of the weak electric system load 1 in advance.

[Second Embodiment]
Next, as a second embodiment of the present invention, an example in which the present invention is applied to a weak power system of an engine starting vehicle will be described.

  The configuration of the power supply system of this embodiment is shown in FIG. In the power supply system of the present embodiment, an alternator 8 that generates electric power by driving the engine is used instead of the DCDC converter 3, and the weak electric system load 1 and the lead battery 2 are connected in parallel to the alternator 8. That is, in this power supply system, it is possible to supply power from both the lead battery 2 and the alternator 8 to the weak electric load 1, and when the charge state of the lead battery 2 is lowered, the alternator 8 The lead battery 2 can be charged with the generated power. Other configurations are the same as those in the first embodiment.

The deterioration diagnosis of the lead battery 2 in this embodiment is performed as follows.
First, the ECU 5 stops the power supply from the alternator 8 to the weak electric system load 1 in a state where any one of the weak electric system loads 1 is operated, thereby starting the discharge of the lead battery 2. Then, as in the first embodiment, the ECU 5 detects the lead battery 2 measured by the current sensor 6 after a predetermined time Xs has elapsed from the stop of the power supply of the alternator 8 until the polarization of the lead battery 2 is eliminated. Discharge battery An and battery voltage Vn measured by voltage sensor 7 are read, and lead battery 2 deteriorates when the value of battery voltage Vn is equal to or lower than determination threshold Vs determined according to discharge current An. Fail control is performed by determining that the

  As described above, in the power supply system of the present embodiment, after the ECU 5 stops supplying power from the alternator 8 to the weak electrical system load 2 and after a predetermined time Xs has elapsed until the polarization in the lead battery 2 is eliminated. Since the deterioration of the lead battery 2 is determined based on the discharge current An and the battery voltage Vn, as in the first embodiment, not only at the time of large current discharge such as at the time of engine start, The deterioration diagnosis of the lead battery 2 can be performed at the timing. Further, by performing fail-safe control when it is determined that the lead battery 2 is deteriorated, it is possible to prevent the battery of the lead battery 2 from running out or the power failure of the weak electric system load 1 in advance.

[Third Embodiment]
Next, as a third embodiment of the present invention, an example in which the present invention is applied to a low power system that uses regenerative power of a hybrid vehicle will be described.

  The configuration of the power supply system of this embodiment is shown in FIG. In the power supply system of the present embodiment, a regenerative motor 9 that generates electric power by rotating wheels is used instead of the DCDC converter 3 and the alternator 8, and the weak electric system load 1 and the lead battery 2 are connected in parallel to the regenerative motor 9. ing. That is, in this power supply system, it is possible to supply power from both the lead battery 2 and the regenerative motor 9 to the weak electric load 1, and when the state of charge of the lead battery 2 decreases, the regenerative motor The lead battery 2 can be charged with 9 generated power. Other configurations are the same as those in the first and second embodiments.

The deterioration diagnosis of the lead battery 2 in this embodiment is performed as follows.
First, the ECU 5 stops the power supply from the regenerative motor 9 to the weak electric system load 1 in a state where any one of the weak electric system loads 1 is operating, thereby starting the discharge of the lead battery 2. Then, as in the first and second embodiments, the ECU 5 is measured by the current sensor 6 after a predetermined time Xs has elapsed from the stop of the power supply to the regenerative motor 9 until the polarization of the lead battery 2 is eliminated. When the discharge current An of the lead battery 2 and the battery voltage Vn measured by the voltage sensor 7 are read and the value of the battery voltage Vn is equal to or less than the determination threshold Vs determined according to the discharge current An, the lead battery It is determined that 2 is deteriorated, and fail control is executed.

  As described above, in the power supply system of the present embodiment, the ECU 5 has stopped the power supply from the regenerative motor 9 to the weak electric system load 2 and the predetermined time Xs from when the polarization in the lead battery 2 is eliminated has elapsed. Since the deterioration of the lead battery 2 is determined based on the subsequent discharge current An and the battery voltage Vn, as in the first and second embodiments, it is limited to a large current discharge such as when the engine is started. In addition, the deterioration diagnosis of the lead battery 2 can be performed at an arbitrary timing. Further, by performing fail-safe control when it is determined that the lead battery 2 is deteriorated, it is possible to prevent the battery of the lead battery 2 from running out or the power failure of the weak electric system load 1 in advance.

Hereinafter, as a reference, a correspondence relationship between each of the above-described embodiments and the description of the scope of claims is added.
In the power supply system of each embodiment described above, the current sensor 6 and the voltage sensor 7 correspond to “current measuring means” and “voltage measuring means” recited in the claims. Further, the DCDC converter 3 in the power supply system of the first embodiment, the alternator 8 in the power supply system of the second embodiment, and the regenerative motor 9 in the power supply system of the third embodiment are described in the claims. It corresponds to a “power supply unit”. Further, the ECU 5 that executes the deterioration diagnosis process shown in FIG. 5 corresponds to the “determination means” recited in the claims. In particular, the ECU 5 that executes fail-safe control in step S107 in FIG. 5 corresponds to “discharge limiting means” described in the claims.

  Each of the above-described embodiments is an example of an application of the present invention, and the technical scope of the present invention is not intended to be limited to the contents disclosed as these embodiments. Absent. That is, the technical scope of the present invention is not limited to the specific technical items disclosed in the above-described embodiments, but includes various modifications, changes, alternative techniques, and the like that can be easily derived from this disclosure.

DESCRIPTION OF SYMBOLS 1 Light electric system load 2 Lead battery 3 DCDC converter 4 Lithium ion battery 5 ECU (electronic control unit)
6 Current sensor 7 Voltage sensor 8 Alternator 9 Regenerative motor

Claims (6)

A deterioration diagnosis device for diagnosing deterioration of a lead battery used as a power source of a weak electric system load of a vehicle,
Current measuring means for measuring the discharge current of the lead battery;
Voltage measuring means for measuring the output voltage of the lead battery;
A power supply unit connected so as to be able to supply power to the weak electrical load;
Discontinuing power supply from the power supply unit to the weak power system load, the discharge current measured by the current measuring means after a lapse of a predetermined time from the stop of power supply until the polarization in the lead battery is eliminated, and Determination of determining that the lead battery is deteriorated when the battery voltage measured by the voltage measuring unit is read and the read battery voltage is equal to or less than a determination threshold value determined according to the read discharge current. A deterioration diagnosis apparatus for a lead battery for a vehicle.   The vehicle power supply according to claim 1, wherein the power supply unit is a DCDC converter that converts a high voltage from a high-voltage battery into a weak voltage and supplies power to the low-power load or the lead battery. Lead battery deterioration diagnosis device.   The lead-acid battery deterioration diagnosis apparatus according to claim 1, wherein the power supply unit is an alternator that generates electric power by driving an engine.   The deterioration diagnosis apparatus for a lead battery for a vehicle according to claim 1, wherein the power supply unit is a regenerative motor that generates electric power by rotating wheels.   5. The apparatus according to claim 1, further comprising: a discharge limiting unit that limits discharge of the lead battery when the determination unit determines that the lead battery is deteriorated. 6. Deterioration diagnosis device for lead batteries for vehicles. A method for diagnosing deterioration of a lead battery used as a power source for a weak electric load of a vehicle,
Stopping power supply from the power supply unit connected to be able to supply power to the weak power system load to the light power system load;
Measuring the discharge current and battery voltage of the lead battery after elapse of a predetermined time from stopping the power supply from the power supply unit to the weak electric system load until the polarization in the lead battery is eliminated;
Determining that the lead battery is deteriorated when the measured battery voltage is equal to or less than a determination threshold value determined according to the measured discharge current. Battery deterioration diagnosis method.

Images