JP4670256B2 - Battery status detection method - Google Patents

Description

  The present invention relates to a battery state detection method, and more particularly to a battery state detection method for detecting a battery state such as remaining capacity and SOC.

  In recent years, the role of battery state monitoring and battery state control has become more and more important as the load on batteries used in automobiles, portable devices, and the like has become higher. For example, in the case of a battery for an automobile, a technique for keeping the battery in a battery state suitable for these uses is desired in order to cope with idle stop start (ISS) or regenerative charging performed to reduce exhaust gas. Lead batteries are one of the typical batteries that can be applied to these applications.

  Conventionally, internal resistance, discharge voltage, open circuit voltage, remaining capacity, state of charge, etc. have been used as parameters representing battery state or measurement parameters for calculating battery state. For example, regarding a vehicle battery, various techniques for calculating a battery state by comparing a voltage map at the time of starting an engine and a data map obtained by measuring DC internal resistance in advance have been proposed (see, for example, Patent Document 1). In addition, a technique for detecting the degree of battery deterioration from an open circuit voltage in a fully charged state is also known.

JP-A-7-63830

  Measurement of the battery state from the open circuit voltage is highly accurate, but the open circuit voltage cannot be measured while using the battery or for a while immediately after use. For this reason, the measurement of the battery state from the open circuit voltage cannot be used alone for real-time detection of the battery state, and is used in combination with current integration. However, current integration accumulates errors over time, so for applications such as ISS where internal resistance and discharge voltage measurement timings exist, recalculate the battery state from the discharge voltage and internal resistance and calculate the internal resistance. Detect battery status. However, since the battery state calculated from the open circuit voltage is replaced with the battery state calculated from the discharge voltage or internal resistance, the accuracy may be deteriorated.

  An object of the present invention is to provide a battery state detection method capable of accurately detecting a battery state in view of the above case.

In order to solve the above-mentioned problem, the present invention is a battery state detection method, comprising a plurality of calculation methods for calculating at least one battery state of a battery, and according to the time from the start of discharge of the battery. Te a most accurate calculation method adopted by the at least one battery state detection to that batteries state detecting method of the plurality of calculation methods, the first is to discharge a predetermined time after the start of the battery The at least one battery state is calculated by a calculation method, and after the predetermined time has elapsed, the at least one battery state is calculated by a second calculation method, and the first calculation method is obtained from an open circuit voltage. correcting the battery state current integration, the second calculation method is characterized that you correct the at least one battery state obtained from the internal resistance or the discharge voltage in the current integration.

  The present invention has a plurality of calculation methods for calculating at least one battery state of the battery, and adopts the most accurate calculation method among the plurality of calculation methods according to the time from the start of battery discharge. Therefore, the battery state can be detected with high accuracy.

In the present invention, Jo Tokoro time, the proportionality constant when the error in the current integration is assumed to be proportional to the time alpha, the first operation on the error from the true value of the battery state calculated in the second calculation method When the value obtained by subtracting the error from the true value of the battery state calculated by the method is β, it is expressed by β / α.

  According to the present invention, there are a plurality of calculation methods for calculating at least one battery state of a battery, and the most accurate calculation method among the plurality of calculation methods according to the time from the start of battery discharge. Therefore, the effect that the battery state can be detected with high accuracy can be obtained.

  Hereinafter, an embodiment in which the present invention is applied to a remaining capacity detection device for detecting the remaining capacity of a lead battery for a vehicle will be described with reference to the drawings.

(Constitution)
As shown in FIG. 1, the remaining capacity detection device 11 of the present embodiment is fixed to the side surface of the lead battery 1 on the side away from the vent plug of the lead battery 1 and calculates the remaining capacity Q of the lead battery 1. A microcomputer (hereinafter simply referred to as a microcomputer) 8 is provided. For the lead battery 1, for example, 80D26 with 6 positive electrodes, 7 negative electrodes, and 6 cells in series, having a nominal 12 V, 5 hour rate capacity 55 Ah can be used. A sensor insertion hole is formed in the partition wall in the central part of the battery case of the lead battery 1, and a temperature sensor 7 such as a thermistor is inserted into the sensor insertion hole and fixed with an adhesive.

  The microcomputer 8 includes a CPU that functions as a central processing unit, a ROM that stores data such as a basic control program for the remaining capacity detection device 11 and a map that will be described later, a RAM that functions as a work area for the CPU, an A / D converter, and a host. An interface for communicating with the vehicle-side microcomputer 10 is included.

  A positive terminal of the lead battery 1 is connected to a central terminal of an ignition switch (hereinafter referred to as IGN switch) 9 through a current sensor 6. The IGN switch 9 has an OFF terminal, an ON / ACC terminal, and a START terminal in addition to the center terminal, and can be switched and connected in a rotary manner.

  The output terminal of the current sensor 6 is connected to an A / D converter built in the microcomputer 8, and the Hall voltage output from the current sensor 6 is converted into a digital value by the A / D converter. Can be captured as a digital value. Further, the bipolar terminals of the lead battery 1 are connected to another A / D converter built in the microcomputer 8, and the microcomputer 8 can take in the voltage across the lead battery 1 as a digital value. Furthermore, the output terminal of the temperature sensor 7 is connected to another A / D converter, and the microcomputer 8 can capture the temperature of the lead battery 1 as a digital value. Note that the remaining capacity detection device 11 includes such wiring.

  On the other hand, a starter 3 for starting the engine 4 by transmitting the rotational driving force to the rotating shaft of the engine 4 via a clutch mechanism (not shown) is disposed on the vehicle side. Further, the rotation shaft of the engine 4 can transmit power to the generator 2 via a clutch mechanism (not shown). When the engine 4 is in a rotating state, the generator 2 is operated via this clutch mechanism. Then, the electric power from the generator 2 is supplied (charged) to the auxiliary machine 5 such as an air conditioner and a radio or the lead battery 1. Such engine control and the like are executed by the vehicle-side microcomputer 10.

  The ON / ACC terminal of the IGN switch 9 is connected to one end of the generator 2 through the auxiliary machine 5 and a rectifying element that allows current flow in one direction. The START terminal is connected to one end of the starter 3. Furthermore, the other end of the generator 2, the starter 3 and the auxiliary machine 5, the negative terminal of the lead battery 1, and the microcomputer 8 are connected to the ground, respectively.

  Here, the principle of detection (calculation) of the remaining amount Q of the lead battery 1 by the remaining amount extending device 11 of the present embodiment will be described with reference to FIG. The remaining amount extending device 11 includes a first calculation method for calculating a current remaining capacity of the lead battery 1 obtained by correcting the remaining capacity Q1 of the lead battery 1 obtained from an open circuit voltage (OCV) by current integration, and a high rate discharge. A second calculation method of calculating the current remaining capacity of the lead battery 1 obtained by correcting the remaining capacity Q2 of the lead battery 1 obtained from the internal resistance R of the lead battery 1 at the time of current integration, from the start of discharge of the lead battery 1 The remaining capacity of the higher accuracy of the first and second calculation methods is calculated as the remaining capacity Q of the lead battery 1 and output to the vehicle microcomputer 10 according to the time.

  The remaining capacity Q1 of the lead battery 1 obtained from the OCV is more accurate than the remaining capacity Q2 of the lead battery 1 obtained from the internal resistance (the measurement error of the remaining capacity of the lead battery 1 from the OCV is due to the remaining capacity of the lead battery from the internal resistance. Less than the capacity measurement error.) Therefore, while the error due to the integrated current is small, it is better to calculate the current remaining capacity of the lead battery 1 by the first calculation method than to calculate the current remaining capacity of the lead battery 1 by the second calculation method. Measurement error can be reduced (increased accuracy). The proportionality constant assuming that the error due to current integration is proportional to time is α, (calculation error of the remaining capacity of the lead battery 1 from the internal resistance R−calculation error of the remaining capacity of the lead battery 1 of the lead battery from the OCV ) Is a constant β, a time during which the remaining capacity by the first calculation method can be maintained with higher accuracy than the remaining capacity by the second calculation method after the start of discharge, in other words, by the second calculation method after the start of discharge. The time tOCV until the remaining capacity becomes effective is represented by tOCV = β / α (hereinafter, this mathematical expression is referred to as Expression 1). Therefore, if the remaining capacity of the lead battery 1 is calculated by the first calculation method from the start of discharge of the lead battery 1 to tOCV, and after the lapse of tOCV, the remaining capacity can be calculated with high accuracy. .

(Operation)
Next, with reference to a flowchart, the operation of the remaining capacity detection device 11 of the present embodiment will be described with a CPU of the microcomputer 8 (hereinafter simply referred to as a CPU) as a subject. When the microcomputer 8 is powered on, the CPU executes a remaining capacity calculation routine for calculating the remaining capacity Q of the lead battery 1.

  As shown in FIG. 3, in the remaining capacity calculation routine, first, in step 102, it is determined whether or not the current flowing through the current sensor 6 is a predetermined value (for example, 0.05 A) or more. It is determined whether the terminal is connected to the ON / ACC terminal or the START terminal.

  If the determination in step 102 is negative, that is, if the center terminal of the IGN switch 9 is connected to the OFF terminal (ignition is off), the ignition is off in step 104. It is determined whether 6 hours have passed since then. Note that the determination as to whether or not the ignition has been turned off can be made by assuming that the ignition has been turned off when the current flowing through the current sensor 6 becomes less than a predetermined value, as described above. This can be determined by starting the time count by the CPU internal clock.

  When a negative determination is made at step 104, the process returns to step 102. When an affirmative determination is made, the OCV of the lead battery 1 is captured at the next step 106. Accordingly, the OCV of the lead battery 1 is measured every 6 hours after the ignition is turned off. In the next step 108, the remaining capacity Q1 of the lead battery 1 corresponding to the OCV measured in step 106 is calculated from the Q-OCV map shown in Table 1 below, stored in the RAM, and the process returns to step 102. In addition, the Q-OCV map shown in Table 1 is for a new 80D26. For batteries of different types, a Q-OCV map corresponding to the battery may be used. Further, in the case of a deteriorated battery, the remaining capacity Q can be appropriately calculated from the OCV by using the Q-OCV map after correcting it according to, for example, the deterioration state (SOH) of the battery.

  On the other hand, when the determination in step 102 is affirmative, that is, when the center terminal of the IGN switch 9 is connected to the ON / ACC terminal or the START terminal (ignition is in the on state), in step 122 The current I flowing through the lead battery 1, the discharge voltage E, the temperature T, and the current time t of the lead battery 1 are measured.

  In the next step 124, it is determined from the current I measured in step 122 whether or not the IGN switch 9 is connected to the START terminal. FIG. 5 schematically shows the current flowing through the lead battery 1 (current sensor 6) when the engine is started. The current waveform of the lead battery 1 at the start of the engine is such that after the start of energization of the engine start current when the IGN switch 9 is located at the START position (time ts), a rapid first-stage pulse discharge to the starter 3 is performed. The current waveform falls sharply and a peak appears after about 50 ms (time tp). After that, the engine start is completed after a few attenuations. Although the current waveform is affected by the structure of the engine 4, the friction of the clutch connecting the engine 4 and the starter 3, etc., the waveform is generally as shown in FIG. Accordingly, in step 124, it is possible to determine whether or not the IGN switch 9 is connected to the START terminal by determining whether or not a large current of a predetermined value or more has flowed.

  If the determination in step 124 is negative, the process proceeds to step 136. If the determination is affirmative, in next step 126, it is determined whether or not the engine has been started for the first time after the OCV measurement (see step 106). For such a determination, for example, a known flag can be used. If the determination in step 126 is negative, the process proceeds to step 132. If the determination is affirmative, in the next step 128, it is determined whether the OCV measured in step 106 is 12.2V or higher. This 12.2 V is for a new 80D26, and for a deteriorated battery, it may be corrected according to SOH or the like as described above.

  If the determination in step 128 is negative, the process proceeds to step 132. If the determination is affirmative, in step 130, the internal resistance individual difference δ of the lead battery 1 is calculated as δ = internal resistance R−R (I, OCV, T ) And is stored in the RAM. The internal resistance R is, for example, R = ΔE / ΔI = (voltage E measured at the previous step 122−voltage E measured at the current step 122) / (current I measured at the step 122−current measured at the current step 122) I). On the other hand, R (I, OCV, T) is an apportioning calculation by applying the OCV, current I, and temperature T measured in Step 106 and Step 122 to the Q-OCV-ITR map shown in Table 2 below. It is possible to calculate by doing.

  In step 132, the internal resistance R is calculated in the same manner as in step 130. Therefore, when an affirmative determination is made in step 128, the internal resistance R has already been calculated in step 130, so there is no need to calculate again. In the next step 134, the internal resistance (R + δ) corrected by adding the internal resistance individual difference δ of the lead battery 1 stored in the RAM in step 130 to the current I, temperature T, and internal resistance R measured in step 122. Is applied to the Q-OCV-ITR map in Table 2 and the distribution is calculated to calculate the remaining capacity Q2 of the lead battery 1 at the time of high rate discharge, and the process proceeds to step 136.

  In step 136, it is determined whether or not the current time t measured in step 122 has passed the time tR described above. In the present embodiment, the accuracy of current integration is ± 6 Ah / h due to the performance limitations of the low-cost current sensor 6 and the A / D converter built in the microcomputer 8. Further, from experience, the error of the remaining capacity Q from the OCV in the lead battery 1 (80D26) is ± 3 Ah, and the measurement error of the remaining capacity Q from the internal resistance R is ± 15 Ah. At this time, α = 6 Ah / h, β = 15 Ah−3 Ah = 12 Ah, and tOCV = tR = 2h from Equation 1 described above. For this reason, in step 136, tR was calculated as 2h.

  When a negative determination is made in step 136 (the maximum time tmax has not elapsed), in step 138, the remaining capacity Q1 of the lead battery 1 calculated from the OCV in step 108 is corrected by the integrated current value in step 134. Since the accuracy is higher than when the remaining capacity Q2 of the lead battery 1 calculated from the resistance is corrected by the current integrated value, the remaining capacity Q of the lead battery 1 is calculated by Q = Q1−current integrated value. On the other hand, when the determination is affirmative (when the maximum time tmax has elapsed), in step 140, it is better to correct the remaining capacity Q2 of the lead battery 1 calculated from the internal resistance with the current integrated value of the lead battery 1 calculated from the OCV. Since the accuracy is higher than when the remaining capacity Q1 is corrected with the current integrated value, the remaining capacity Q of the lead battery 1 is calculated from Q = Q2−current integrated value. The integrated current value is a value of (current I measured in step 122) × (processing time Δt of one routine from step 102 to step 142) from the time when the ignition is turned on to the current time t. It can be calculated by summing up.

  In the next step 142, the remaining capacity Q of the lead battery 1 is output to the vehicle-side microcomputer 10 via the interface, and the process returns to step 102. The vehicle-side microcomputer 10 transmits the remaining capacity Q of the lead battery 1 notified from the microcomputer 8 to a panel control unit (not shown) that controls the vehicle installation panel. The remaining capacity Q is displayed. Therefore, the driver can grasp the battery state of the lead battery 1 by looking at the installation panel.

(Action etc.)
Next, functions, effects, and the like of the remaining capacity detection device 11 of the present embodiment will be described.

  In the remaining capacity detection device 11 of the present embodiment, a first calculation method for calculating the current remaining capacity of the lead battery 1 obtained by correcting the remaining capacity Q1 of the lead battery 1 obtained from the OCV by current integration, and at the time of high rate discharge A second calculation method for calculating the current remaining capacity of the lead battery 1 in which the remaining capacity Q2 of the lead battery 1 obtained from the internal resistance R of the lead battery 1 is corrected by current integration; According to t, the more accurate remaining capacity of the first and second calculation methods is calculated as the remaining capacity Q of the lead battery 1, so that the lead battery 1 is compared with the conventional remaining capacity detecting device. Can be calculated with high accuracy.

  That is, the remaining capacity Q1 of the lead battery 1 is calculated from the OCV during the discharge pause when the ignition is off (step 108), and after the ignition is turned on (after the start of discharge), the error due to current integration is small. Until the time tOCV, the calculation is performed by the first calculation method (step 138). After the time tOCV has elapsed, the remaining capacity Q2 of the lead battery 1 calculated from the internal resistance is high in accuracy, so the calculation is performed by the second calculation method. (Step 140), the calculation accuracy of the remaining capacity Q of the lead battery 1 is increased.

  Further, in the remaining capacity detecting device 11 of the present embodiment, when calculating the remaining capacity Q2 of the lead battery 1 by the second calculation method, the internal resistance of the lead battery 1 is corrected by the internal resistance individual difference δ, and Q− Since it is applied to the OCV-ITR map (step 134), the accuracy of the remaining capacity Q2 of the lead battery 1 and thus the remaining capacity Q of the lead battery 1 calculated by the second calculation method can be improved. .

  In the present embodiment, an example is shown in which the remaining capacity Q1 of the lead battery 1 is calculated while the discharge is stopped (step 108). However, immediately after the ignition is turned on, the remaining capacity Q1 is calculated, and step 142 is performed. Then, after the remaining capacity Q of the lead battery 1 is output to the vehicle-side microcomputer 10, the process may return to step 122.

  Further, in the present embodiment, taking into account that the lead battery 1 is a vehicle battery, an example is shown in which the engine start is the measurement timing of the internal resistance. However, the present invention is not limited to this, and an air conditioner or the like is used. The start time of use of the auxiliary machine 5 may be set as the measurement timing of the internal resistance. Further, in the present embodiment, an example is shown in which the remaining capacity Q of the lead battery 1 is calculated when the ignition is on in relation to the display on the installation panel. However, the remaining capacity Q of the lead battery 1 during the discharge pause is shown. For applications that require this notification, the calculation result in step 108 may be notified (output).

  Furthermore, although the remaining capacity is exemplified as the battery state of the lead battery 1 in the present embodiment, the accuracy can be improved even by calculating the battery state such as the internal resistance, the discharge voltage, the open circuit voltage, and the charged state. Accordingly, the plurality of battery states of the lead battery 1 may be calculated in the same manner as the remaining capacity calculation exemplified.

  Next, an example of the remaining capacity detection device manufactured according to the above embodiment will be described. The remaining capacity detector manufactured for comparison is also shown. The remaining capacity detection devices of the example and the comparative example differ from the above-described embodiment in which the microcomputer 8 is connected to the vehicle-side microcomputer 10 in that the microcomputer 8 is connected to a notebook computer. Therefore, the remaining capacity Q of the lead battery 1 is output to the notebook computer, and the output data is displayed on the display of the notebook computer and stored in the memory of the notebook computer.

Example 1
In the remaining capacity detection device of the first embodiment, the CPU is caused to execute the remaining capacity calculation routine shown in FIG.

(Comparative Example 1)
In the remaining capacity detection device of Comparative Example 1, the CPU was caused to execute the remaining capacity calculation routine shown in FIG. This remaining capacity calculation routine is different from the battery state calculation routine of the first embodiment in that step 141 is executed instead of steps 136 to 140 in FIG. That is, when the remaining capacity detection device of Comparative Example 1 detects engine start even within the time tOCV, the remaining capacity Q2 obtained from the internal resistance at the time of engine start is corrected with the integrated current value, and the remaining capacity Q of the lead battery 1 is calculated. did.

(test)
An actual vehicle test was conducted on a vehicle equipped with a 2500 cc engine and an 80D26 battery. As for the running pattern, the engine was stopped after 10 minutes at a constant speed of 40 km, the ignition was turned on while stepping on the brake for 1 minute, the engine was restarted, and this was repeated 21 times. The lead battery is charged while the engine is operating, and the lead battery is charged as a whole when the engine is operated for 10 minutes even if the brake is applied for 1 minute to discharge the battery.

  Table 3 shows the calculation results of the remaining capacity Q of the remaining capacity detection devices of Example 1 and Comparative Example 1 with time. The time shown in Table 3 is the time from the start of charging / discharging of the lead battery 1. Since there is no current integration or engine start at time 0, the calculation result of the remaining capacity Q represents Q1 obtained from the OCV. The true value was determined by measuring the remaining capacity until the test battery was discharged at a rate of 5 hours and the voltage dropped to 10.5 V.

  As is apparent from Table 3, the remaining capacity detection device of Comparative Example 1 has an error more than the remaining capacity detection device of Example 1 in the remaining capacity Q calculation results of 15 minutes, 50 minutes, and 90 minutes within tOCV (2 hours). It was getting bigger. Therefore, it can be seen that the remaining capacity detection device of Example 1 is excellent.

  The present invention relates to a battery state detection method capable of accurately detecting a battery state, and contributes to the manufacture and sale of a remaining capacity detection device in which this method is implemented, and thus has industrial applicability.

It is a schematic block diagram of the remaining capacity detection apparatus of embodiment to which this invention is applied. It is explanatory drawing for demonstrating the remaining capacity detection principle of the lead battery of the remaining capacity detection apparatus of embodiment. It is a flowchart of the battery state calculation routine which CPU of the remaining capacity detection apparatus of embodiment performs. 6 is a flowchart of a battery state calculation routine executed by a CPU of a remaining capacity detection device of Comparative Example 1; It is explanatory drawing which shows typically the waveform of the electric current which flows into the lead battery at the time of engine starting.

Explanation of symbols

1 Lead battery (battery)
8 Microcomputer 11 Remaining capacity detector

Claims (2)

A plurality of calculation methods for calculating at least one battery state of the battery, and adopting the calculation method with the highest accuracy among the plurality of calculation methods according to the time from the start of discharge of the battery; a that batteries state detecting method to detect one of the battery state until said discharge start after a predetermined time of the battery is computed said at least one battery state at the first computing method, after the predetermined time the The at least one battery state is calculated by a calculation method of 2, the first calculation method corrects the at least one battery state obtained from an open circuit voltage by current integration, and the second calculation method is an internal resistance or the battery state detecting method characterized that you correct the at least one battery state current integration obtained from the discharge voltage. The predetermined time, the relative error from the true value of the at least one battery state error is calculated proportional constant when it is assumed to be proportional to the time alpha, before Symbol second computing method in current integration the battery state according to claim 1, a value obtained by subtracting the error from the true value of the at least one battery state calculated in the first calculation method when the beta, characterized by being represented by the beta / alpha Detection method.