JP4507720B2 - Deterioration determination method and deterioration determination device for lead acid battery - Google Patents

Description

  The present invention relates to a deterioration determination method and a deterioration determination device for a lead storage battery, and more particularly, to a deterioration determination method and a deterioration determination device for determining deterioration of a lead storage battery from an open circuit voltage and an engine start voltage.

  Conventionally, lead-acid batteries mounted on vehicles are always float-charged by an alternator during driving, and the load is limited to lamps, etc., so it is not charged too deep and is almost always fully charged and used. It has been. In recent years, however, environmental awareness has increased, and it has become necessary to reduce carbon dioxide emissions from vehicles. Especially in large buses and trucks, a system vehicle with an idle stop function that stops the engine when the vehicle is stopped, such as waiting for a signal. Has been increasing.

  In such a system car, loads such as air conditioners and car stereos when the engine is stopped are all covered by power from lead-acid batteries, so the number of cases where the deep discharge state increases and the remaining capacity of the battery decreases compared to the conventional case will increase. is expected. Along with this, the deterioration of the battery is also expected to be accelerated. On the other hand, since the output of the lead storage battery depends on the remaining capacity and deterioration, if the remaining capacity of the battery becomes small while the engine is stopped, there will be insufficient output to start the engine, and the engine will be May be lost. Therefore, detecting the deterioration of the lead storage battery is particularly important for ensuring engine start.

  As a specific example of detecting the deterioration state of a lead-acid battery, a fully charged battery is discharged for a short time, and a battery voltage drop amount (hereinafter referred to as a discharge voltage drop amount) at the time of discharge from a battery voltage before the discharge. A method for detecting a deterioration state from a relationship diagram between a battery capacity and a voltage drop during discharge obtained in advance has been proposed (see, for example, Patent Document 1). This method uses the fact that a lead-acid battery that has deteriorated and has a reduced capacity has a high internal resistance and a large voltage drop during discharge. As long as the state is reflected, the deterioration state of the lead storage battery can be detected appropriately.

Japanese Patent No. 3192794

  However, some lead-acid batteries that have actually been used for engine starting for a long period of time have a very high battery capacity despite the fact that there is almost no difference between the fully-degraded battery and the voltage drop during discharge. It turned out that many things which became small were seen. Hereinafter, when such a battery is referred to as a deteriorated battery A, the deteriorated battery A has almost no discharge capacity even after being slightly discharged from a full charge, and there is no sign in use for starting an automobile engine. For example, the engine cannot be started simply by turning on the light for a while.

  The inventor examined the characteristics of the deteriorated battery A in detail. As a result, it was found that in the deteriorated battery A, the amount of voltage drop during discharge greatly increases only by slightly discharging from the fully charged state. FIG. 1 schematically shows this, and shows the relationship between the open circuit voltage OCV and the discharge voltage Vst of the lead storage battery. In creating FIG. 1, as an experimental method, a lead storage battery was mounted on a vehicle, the engine was started, and the minimum voltage when the battery voltage dropped was measured. A cell motor for starting the engine was used as a discharge load. After conducting an engine start experiment in a certain state of charge, that is, in a certain OCV, the battery was removed from the vehicle. The battery was discharged with a predetermined amount of electricity by an electronic load discharge device and left until the OCV was stabilized. The battery was mounted on the vehicle again and an engine start experiment was conducted. By repeating this, the discharge voltage from 100% to 0% of the state of charge (SOC) of the battery was measured. Since the discharge load in FIG. 1 is engine start, the discharge voltage is hereinafter referred to as engine start voltage Vst.

  The open circuit voltage is an indicator of the state of charge of the battery, and for a certain open circuit voltage, a certain state of charge corresponds one-to-one. In FIG. 1, the region where the open circuit voltage is high is the region where the charge state is high, and the point where the open circuit voltage is the highest is the fully charged state. As shown in FIG. 1, two types of batteries (new battery, deteriorated battery A) are each fully charged at around 12.9V. In a new battery, when the open circuit voltage is lowered, that is, when the state of charge is lowered by discharging from a fully charged state, Vst is also lowered accordingly. Vst is a measure of the output of the lead storage battery. When Vst drops below a certain level, the engine cannot be started. On the other hand, in the deteriorated battery A, the engine starting voltage Vst is not significantly different from that of a new battery in a fully charged state (OCV = 12.9 V). However, when the deteriorated battery A is discharged a little, Vst rapidly decreases. That is, with the deteriorated battery A, if it is accidentally discharged during use for starting the engine, there is a high possibility that the engine cannot be started immediately. And the deterioration determination of the deteriorated battery A is impossible by the method using the voltage drop amount at the time of discharge in Patent Document 1 described above.

  An object of the present invention is to provide a deterioration determination method and a deterioration determination apparatus capable of accurately determining deterioration of a lead-acid battery in a deterioration mode that cannot be detected by a decrease in discharge voltage.

  In order to solve the above-described problem, a first aspect of the present invention is a deterioration determination method for determining deterioration of a lead storage battery from an open circuit voltage (Vo) and an engine start voltage (Vst), at two different times. An open circuit voltage (Vo1, Vo2) of the lead storage battery and an engine start voltage (Vst1, Vst2) at the first engine start after each of the two different times are measured, and the measured open circuit voltages (Vo1, Vo2). ) And the engine starting voltage (Vst1, Vst2), and a deterioration state determination coefficient (α = ΔVst / ΔVo) obtained by dividing the difference in engine starting voltage (ΔVst = Vst2−Vst1) by the difference in open circuit voltage (ΔVo = Vo2−Vo1). ), And the calculated deterioration state determination coefficient (α) is a certain value or more, and the open circuit voltage (Vo1,. If o2) is above a certain voltage value, it is determined that the lead storage battery is deteriorated, comprising.

  Moreover, the 2nd aspect of this invention is the deterioration determination apparatus which determines deterioration of a lead storage battery from open circuit voltage (Vo) and engine starting voltage (Vst), and the open circuit voltage (Vo1) of the said lead storage battery in two different time. , Vo2) and a voltage measuring means for measuring an engine starting voltage (Vst1, Vst2) at the first engine starting after each of the two different times, and an open circuit voltage (Vo1, Vst2) measured by the voltage measuring means Vo2) and the engine start voltage (Vst1, Vst2), the deterioration state determination coefficient (α = ΔVst /) obtained by dividing the difference in engine start voltage (ΔVst = Vst2−Vst1) by the difference in open circuit voltage (ΔVo = Vo2−Vo1). A deterioration coefficient calculating means for calculating (ΔVo), and the deterioration state determination coefficient (α) calculated by the deterioration coefficient calculating means is a certain value or more, And a deterioration determining means for determining that the lead storage battery is deteriorated when the open circuit voltages (Vo1, Vo2) at two different times measured by the voltage measuring means are equal to or higher than a certain voltage value. .

  In the present invention, when the deteriorated battery A is compared with a new battery, the deterioration of the lead storage battery is determined by focusing on the fact that the change in Vst with respect to the change in OCV is large in the high OCV region. That is, the open circuit voltages (Vo1, Vo2) at two different times and the engine start voltages (Vst1, Vst2) at the first engine start after each of those times are measured. From these, the deterioration state determination coefficient (α = ΔVst / ΔVo) is calculated by dividing the difference in engine starting voltage (ΔVst = Vst2−Vst1) by the difference in open circuit voltage (ΔVo = Vo2−Vo1). Next, when the deterioration state determination coefficient (α) is a certain value or more and the open circuit voltages (Vo1, Vo2) are a certain voltage value or more, it is determined that the lead storage battery is deteriorated. The threshold value (constant value) of the open circuit voltage (Vo1, Vo2) should also be determined by the actual usage of the lead acid battery, but as a result of the test, about 12.5V is appropriate as a lead acid battery for starting an automobile engine. It turned out to be. Similarly, the degradation condition determination coefficient (α) should be determined according to the actual usage form of the lead storage battery. However, as a result of the test, about α = 2 is appropriate as a lead storage battery for starting an automobile engine. There was found.

  According to the present invention, the lead-acid battery is deteriorated when the deterioration state determination coefficient (α) is a certain value or more and the open circuit voltages (Vo1, Vo2) at two different times are more than a certain voltage value. Therefore, it is possible to detect the deterioration of the lead-acid battery in the deterioration mode that cannot be detected by the decrease in the discharge voltage, and to prevent the engine starting failure that could not be completely prevented conventionally. be able to.

  Hereinafter, embodiments in which the present invention is applied to an internal combustion engine system such as a gasoline engine vehicle or a diesel engine vehicle will be described.

  The method of measuring data necessary for specific determination is as follows. First, at an arbitrary timing t1, the open circuit voltage OCV of the lead storage battery is measured and is designated as Vo1. Next, the engine starting voltage is measured at the timing closest to t1. This is Vst1. Then, this lead acid battery is used as usual. While in use, depending on the mode of use, the SOC changes due to repeated discharge and charge, and the OCV changes accordingly. Then, the lead storage battery is used for a certain period, and at the timing t2 when the OCV changes, the OCV of the lead storage battery is measured and is designated as Vo2. The period of use is preferably short so that the battery does not deteriorate with time (for example, the period between t1 and t2 is preferably within one month). Further, the value of Vo2 must be somewhat different from the value of Vo1, but a state in which the measurement condition is sufficiently satisfied is realized in a normal use state of the lead storage battery.

  Subsequently, the engine starting voltage is measured at the timing closest to t2, and this is set as Vst2. The data may be measured at a higher frequency according to necessity, but in some cases, such as when a lead storage battery is used with a charge control device, Vo1 and Vst1 may be discharged by the discharge device immediately after measurement. Thus, Vo2 and Vst2 can be measured immediately, and the determination can be speeded up.

  Next, an open circuit voltage difference (ΔVo = Vo2−Vo1) and an engine start voltage difference (ΔVst = Vst2−Vst1) are calculated, and the engine start voltage difference (ΔVst) is calculated as an open circuit voltage difference (ΔVo). The divided deterioration state determination coefficient (α = ΔVst / ΔVo) is calculated.

  Next, it is determined whether the deterioration condition determination coefficient (α) is 2.0 or more and the open circuit voltages (Vo1, Vo2) at two times are 12.5V or more. It determines with having deteriorated, and in the case of negative determination, it determines with the lead acid battery not having deteriorated. And when it determines with the lead acid battery having deteriorated, in order to alert | report to a driver, a predetermined signal is output. As such a notification form, for example, a signal may be input to the gate of a thyristor that lights and latches an LED disposed on the lead storage battery side, or may be displayed on a liquid crystal display device. Further, the battery controller that performs the above-described measurement, calculation, and determination may be notified by communication to a vehicle controller that is a host controller of the battery controller, and the vehicle controller may display on the installation panel.

  In addition, inexpensive AD converters, microprocessors, etc. are currently available for data collection (voltage measurement), calculation (calculation) of degradation condition determination coefficient (α), determination of degradation, and notification of results. It is also possible to configure an integrated determination device, and one configuration example will be described below.

  As shown in FIG. 2, the battery controller 10 as a deterioration degree determination device functions as a subordinate device of the vehicle controller 20 that performs vehicle-side control of the engine or the like, a CPU that functions as a central processing unit, and the battery controller 10. A microcomputer 2 having a ROM in which a basic control program is stored, a RAM that serves as a work area for the CPU and temporarily stores data, an EPROM 3 connected to an external bus of the microcomputer 2 and functioning as a nonvolatile memory, a lead-acid battery 1 includes an A / D converter as a part of voltage measuring means for converting an analog voltage into a digital voltage, and an interface for performing communication with the vehicle controller 20, and the vehicle controller 20 is connected by a communication line. Connected with. The A / D converter can be a general-purpose product and needs to be measured with an accuracy of several mV within the operating voltage range of the lead-acid battery 1. Therefore, the resolution is 14 bits or more and the response speed is 1 data / second. Is desirable.

  A positive external output terminal of the lead storage battery 1 is connected to a central terminal of an ignition switch (hereinafter abbreviated as IGN) 11. The IGN11 has an OFF terminal, an ON / ACC terminal, and a START terminal in addition to the central terminal. The central terminal and any of these OFF, ON / ACC, and START terminals can be switched in a rotary manner. is there. An MG 12 serving as a load of the lead storage battery 1 and representing a motor generator, a starter, a generator, and the like is connected to the ON / ACC terminal and the START terminal side of the IGN 11. On the other hand, the negative electrode external output terminal of the lead storage battery 1 is connected to the ground.

  Therefore, the microcomputer 2 of the battery controller 10 can take in the voltage between both ends of the lead storage battery 1 as a digital value, and functions as a voltage measurement means, a deterioration coefficient calculation means, a deterioration determination means, and the lead storage battery 1 deteriorates. When it is determined that the vehicle controller 20 is informed, the vehicle controller 20 is notified by communication. Note that Vo1 and Vst1 are stored in the EPROM 3, and when the deterioration state determination coefficient (α) is calculated, Vo1 and Vst1 are read out.

  In such a configuration example, the microcomputer 2 (its CPU) needs to grasp when the engine is started. When the engine is started, the voltage of the lead-acid battery 1 rapidly decreases and then increases. Therefore, for example, the vehicle controller is notified that the IGN 11 is connected to the ON / ACC terminal, the discharge voltage of the lead storage battery 1 is measured (captured) every predetermined sampling time, and the lowest voltage is set as the engine starting voltage. Vst may be set. Further, even when no notification is received from the vehicle controller 20, as indicated by a dotted line in FIG. In this example, the battery controller 10 needs to have an A / D converter for current measurement connected to the current sensor 4. The microcomputer 2 captures the current value from the A / D converter for current measurement, and if it is less than a predetermined value (for example, 0.1 A), it is assumed that the IGN 11 is connected to the OFF terminal, and the captured current value is When the value is equal to or greater than the predetermined value, the discharge voltage of the lead storage battery 1 is measured (captured) every predetermined sampling time, and the lowest voltage may be set as the engine starting voltage Vst.

  Next, the reference value (constant value) of the deterioration state determination coefficient (α) and the reference value (constant voltage value) of the open circuit voltages (Vo1, Vo2), which are criteria for determining whether or not the lead storage battery 1 is deteriorated. An embodiment carried out for setting will be described.

  As the internal combustion engine system described above, a gasoline engine vehicle with an electronically controlled fuel injection device with a displacement of 2000 cc was selected. The lead-acid battery 1 installed in the new vehicle is of JIS standard 55B24 size.

(Experiment 1)
A deteriorated battery A of JIS55B24 having a nominal capacity of 36 Ah was prepared. The deteriorated battery A is a private car that has been used for about 34,000 years as a mileage. First, the deteriorated battery A was fully charged at a constant voltage of 14.5 V, 15 hours, and a 5-hour rate of limiting current (7.2 A). After complete charging, the battery was discharged at a 5 hour rate current to a final voltage of 10.5 V, and the capacity was confirmed. The capacity was 8.9 Ah. After the capacity measurement, the deteriorated battery A was charged again under the same conditions to be fully charged.

  Subsequently, the deteriorated battery A was attached to a gasoline engine vehicle. The terminal voltage of the deteriorated battery A was measured without starting the engine. At this time, the car key was pulled out so as to minimize the standby current of the car. This voltage was defined as the open circuit voltage Vo1.

  Next, the engine start key was operated to start the engine while measuring and recording the battery terminal voltage with a general digital recorder with a sampling rate of 1.0 ms. The engine starting voltage Vst1 was obtained from the obtained time / terminal voltage curve. Once the deteriorated battery A was removed from the automobile, it was connected to an electronic load discharge device and discharged at a 5 hour rate current for 10 minutes. The battery was left for 1 hour after discharge, mounted again on the automobile, and the open circuit voltage Vo2 and the engine starting voltage Vst2 were measured in the same manner as the measurement procedure for Vo1 and Vst1. Then, α was calculated from the obtained Vo1, Vst1, Vo2, and Vst2.

(Experiment 2)
A new battery of JIS55B24 having a nominal capacity of 36 Ah was prepared. The battery was discharged at a current of 5 hours to a final voltage of 10.5 V, and the capacity was confirmed. The capacity was 37 Ah. After the capacity measurement, the battery was charged under the same conditions as the deteriorated battery A and was fully charged. Thereafter, Vo1, Vst1, Vo2, and Vst2 were measured and α was calculated in the same manner as in Experiment 1 described above. Table 1 below shows the above experimental results.

  Comparing the discharge capacities of the deteriorated battery A and the new battery, the new battery has a nominal capacity of 36 Ah or more, and the deteriorated battery A has a capacity of 23.7%. There is almost no difference in the amount of voltage drop during discharge when these batteries are fully charged, and it is difficult to determine the deterioration state of the battery from this value. On the other hand, when α is compared, the deteriorated battery A has a value of about five times that of a new battery, and the deterioration state can be determined with high sensitivity.

  The above is an example of measurement, and the above experiment was performed using a large number of deteriorated batteries to verify the accuracy of the determination. The results are shown in FIGS. FIG. 3 shows the change in the detection rate for each α when the SOC of the battery determined to be deteriorated is 50% and the reference value of the open circuit voltage (shown as the determination threshold in FIGS. 3 and 4) is changed. It is a thing. When α = 1.0 or 2.0, almost all deteriorated batteries can be detected by setting the reference value of the open circuit voltage to 12.5 V or less. However, when α = 3.0, a battery is generated in which deterioration cannot be detected even when the reference value of the open circuit voltage is further reduced to 12.4V. On the contrary, FIG. 4 shows the change with respect to each α when the reference value of the open circuit voltage is changed as the probability of erroneously determining that a battery having SOH of 50% or more is deteriorated. When α = 2.0 or 3.0, setting the reference value of the open circuit voltage to 12.5 V or more makes the erroneous determination almost negligible. However, when α = 1.0, even if the reference value of the open circuit voltage is 12.6 V or more, the erroneous determination is close to 20%, which is a level that cannot be ignored. From the above results, it is understood that it is optimal to adopt 2.0 as the reference value of α and 12.5 V as the reference value of the open circuit voltage.

  Since the present invention provides a deterioration determination method and a deterioration determination device that can accurately determine deterioration of a lead storage battery in a deterioration mode that cannot be detected by a decrease in discharge voltage, it contributes to the manufacture and sale of lead storage batteries or deterioration determination devices. Has industrial applicability.

It is the graph which showed the relationship between the open circuit voltage of the lead acid battery at the time of engine start in a gasoline engine vehicle, and the voltage at the time of discharge. It is a block circuit diagram which shows the example of 1 structure of a deterioration determination apparatus. It is a graph which shows the change of the detection rate with respect to each (alpha) when changing the reference value of the open circuit voltage which makes determination by setting SOC of the lead storage battery determined to be 50% as 50%. It is the graph which showed the change with respect to each (alpha) when changing the reference value of the open circuit voltage which determines the probability in the case of misdetermining that the lead acid battery of 50% or more of SOH has deteriorated.

Explanation of symbols

1 Lead storage battery 2 Microcomputer (a part of voltage measuring means, deterioration coefficient calculating means, deterioration determining means)
3 EPROM (nonvolatile memory)
10 Battery controller (part of voltage measurement means)

Claims (7)

A deterioration determination method for determining deterioration of a lead storage battery from an open circuit voltage (Vo) and an engine start voltage (Vst),
Measure the open circuit voltage (Vo1, Vo2) of the lead storage battery at two different times and the engine start voltage (Vst1, Vst2) at the first engine start after each of the two different times;
Deterioration obtained by dividing the difference in engine start voltage (ΔVst = Vst2−Vst1) by the difference in open circuit voltage (ΔVo = Vo2−Vo1) from the measured open circuit voltage (Vo1, Vo2) and engine start voltage (Vst1, Vst2). A state determination coefficient (α = ΔVst / ΔVo) is calculated,
When the calculated deterioration state determination coefficient (α) is not less than a certain value and the measured open circuit voltages (Vo1, Vo2) at two different times are not less than a certain voltage value, the lead storage battery is deteriorated. It is determined that
A degradation state determination method including steps.   The deterioration determination method according to claim 1, wherein the constant voltage value is 12.5 V or more.   The deterioration determination method according to claim 1, wherein the certain value is 2.0 or more. In the deterioration determination device that determines the deterioration of the lead storage battery from the open circuit voltage (Vo) and the engine starting voltage (Vst),
Voltage measuring means for measuring an open circuit voltage (Vo1, Vo2) of the lead storage battery at two different times and an engine starting voltage (Vst1, Vst2) at the first engine start after each of the two different times;
Based on the open circuit voltage (Vo1, Vo2) measured by the voltage measuring means and the engine start voltage (Vst1, Vst2), the difference (ΔVst = Vst2-Vst1) of the engine start voltage is calculated as the difference of the open circuit voltage (ΔVo = Vo2-Vo1). ) Deterioration coefficient calculation means for calculating a deterioration state determination coefficient (α = ΔVst / ΔVo) divided by
The deterioration state determination coefficient (α) calculated by the deterioration coefficient calculating means is not less than a certain value, and the open circuit voltages (Vo1, Vo2) at two different times measured by the voltage measuring means are not less than a certain voltage value. In this case, a deterioration determination means for determining that the lead storage battery has deteriorated,
A deterioration determination device comprising:   The deterioration determination apparatus according to claim 4, wherein the constant voltage value is 12.5 V or more.   The deterioration determination apparatus according to claim 4 or 5, wherein the constant value is 2.0 or more.   Non-volatile storage of at least the open circuit voltage (Vo1) measured by the voltage measuring means at the previous time among the two different times and the engine start voltage (Vst1) at the first engine start after the previous time The deterioration degree determination apparatus according to claim 4, further comprising a memory.