JP4441213B2 - Battery charge state calculation device - Google Patents

Description

  The present invention relates to a battery charge state calculation device that detects a state of remaining capacity (that is, a charge state) in a state where a battery used in a vehicle or the like is in use.

As a conventional method for estimating the remaining capacity of a battery (that is, a method for estimating the state of charge of a battery), the battery terminal open voltage is used as the initial value of the state of charge (SOC) of the battery, and the battery charge / discharge current is integrated. A method of correcting with a value is generally known.
Patent Document 1 discloses that a battery that takes into account the polarization can be obtained by obtaining an accurate IV (current-voltage) approximation line that takes into account the polarization of the battery. A “capacity computing device” is disclosed.

  The battery capacity calculation device in consideration of the polarization disclosed in this Patent Document 1 “collects the voltage and current of a battery that causes a discharge current to flow through a vehicle load to obtain a voltage-current characteristic, and obtains this voltage-current characteristic. Is used to estimate the current voltage of the battery, and the current state of charge of the battery is determined from this estimated voltage, while the collected current first reaches the high current of the battery's maximum polarization occurrence, and the current is When a predetermined current value below a large current is first reached, the battery voltage at this time is regarded as the estimated voltage when the maximum polarization effect remains in the state where the influence of the maximum polarization remains, and the estimated voltage when this maximum polarization effect remains "The state of charge is corrected using the difference from the open circuit voltage of the battery at the start of travel".

JP 2001-174535 A (FIG. 1 and paragraph 0039)

In recent years, for example, in idling stop vehicles that aim at low emissions and low fuel consumption, a function to stop the engine during idling is provided, so that power that can be restarted after the engine is stopped is stored in the battery. It is necessary to accurately grasp the state of charge (that is, the remaining capacity of the battery) during use of the battery.
However, it is difficult to accurately estimate the remaining battery capacity because the battery open-circuit voltage and battery capacity change due to the amount of battery fluid, deterioration (softening, corrosion, sulfation, etc.), battery temperature, and polarization. there were.

  The present invention has been made to solve such a problem, and the remaining capacity of the battery currently in use is not affected by the change or deterioration of the battery fluid amount under the current conditions of a predetermined application. It is an object of the present invention to provide a battery charge state calculation device that can easily grasp (calculate) a state, in other words, a state of charge (SOC) of a battery that is currently in use.

  The battery charge state calculation device according to the present invention includes a battery voltage detection means for detecting a battery voltage, a battery current detection means for detecting a battery current, the battery voltage detection means and the battery current detection at a plurality of sampling points. First, the current-voltage characteristic of the battery in the first state, which is currently in use, is approximately obtained using the voltage value and current value detected by the means, and is stored as the first current-voltage characteristic. Current-voltage characteristic storage means, and second current-voltage characteristic storage means for preliminarily storing the second current-voltage characteristic in the second state in which the amount of energy that can be extracted is smaller than that in the first state, The predetermined current value storage means for storing the predetermined load current value of the battery, and the first current-voltage characteristic storage means for storing the first load The first battery voltage (Vc) when the battery current is the predetermined load current value is calculated using the current-voltage characteristics of the battery, and the battery current is calculated using the second current-voltage characteristics. Battery voltage calculation means at a predetermined load for calculating the second battery voltage (Vc0) at the time of the above, and the first and second battery voltages (Vc, Vc0) calculated by the battery voltage calculation means at the predetermined load ), For example, a conversion map for deriving the state of charge of the battery from the voltage difference ΔV (Vc−Vc0) is prepared in advance, and the state of charge for calculating the state of charge of the battery in the first state is prepared. And an arithmetic means 7.

In the battery charge state calculation device according to the present invention, in the first current-voltage characteristic storage means, the voltage Vc at a predetermined load current (assumed to be discharged) stored in the predetermined current value storage means. In the first current-voltage characteristic storage means, performance level detection such as Vo, Vc-performance level conversion map prepared in advance is performed from the voltage Vo when the load current is zero (not flowing). detecting a performance level of the battery using means 8, it is characterized in that to correct the battery state obtained from the above KiTakashi conductive state calculating means.

In addition, the battery charge state calculation device according to the present invention uses the performance level correction gain calculation means 8 such as a performance level-correction gain conversion map prepared in advance from the battery performance level obtained by the performance level detection means. obtain a correction gain that was observed in the characteristics of the battery, and corrects the battery state of charge obtained by the above KiTakashi conductive state calculating means.

The battery state of charge computation device according to the present invention, the state of charge of the battery determined by the state of charge calculating means, the battery current determined by the detecting means current (negative charge side and the discharge side is positive from), for example, a value obtained by subtracting the current integrated value obtained by the current integrating means with means to be initialized from the engine stops when KiTakashi conductive state calculating means carried on such engine start, for example, a battery in the battery standards What is divided by the maximum battery capacity such as the nominal battery capacity is the SOC (State Of Charge) of the battery.

Also, paying attention to the fact that the range that the state of charge SOC can take is 0 to 100% and it is meaningless to take a value exceeding this range, the battery state of charge calculation device according to the present invention includes the battery current detection means described above. (negative charge side and a positive discharge side) obtained current from the by current integration means having a means to be initialized for example at KiTakashi conductive state calculating means carried on, such as a battery nominal battery capacity of the battery standards In order to prevent the battery charge state from exceeding the maximum battery capacity or taking a negative value after subtracting the current accumulated value from the battery charge state to the obtained current accumulated value, the upper limit is set to the battery charge state. And a limiter (lower limit) whose lower limit is a value obtained by subtracting the maximum battery capacity from the battery charge state. Is shall.

  The battery charge state computing device according to the present invention includes battery voltage detection means for detecting battery voltage, battery current detection means for detecting battery current, and battery voltage detection means and battery current detection means detected at a plurality of sampling points. The battery current-voltage characteristic in the first state, which is currently in use, is approximately obtained using the voltage value and the current value, and the first current- is stored as the first current-voltage characteristic. Voltage characteristic storage means, second current-voltage characteristic storage means for storing in advance the second current-voltage characteristic in the second state, which has less energy than the first state, and a predetermined load of the battery The predetermined current value storage means storing the current value and the first current-voltage characteristic stored in the first current-voltage characteristic storage means And calculating a first battery voltage when the battery current is the predetermined load current value and calculating a second battery voltage when the battery current is the predetermined load current value using the second current-voltage characteristic. Charge state calculation means for calculating the state of charge of the battery in the first state using the first and second battery voltages calculated by the battery voltage calculation means during load and the battery voltage calculation means during predetermined load The battery state of charge (SOC) of the battery currently in use can be easily and quickly measured under the current conditions of a given application without being affected by changes in battery fluid level, deterioration, battery temperature, etc. The charging state suitable for hybrid cars, electric vehicles, and idle stop vehicles that require constant monitoring of the charging state. Possible to provide a computing device.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
In the drawings, the same reference numerals represent the same or equivalent.
Embodiment 1 FIG.
An embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a block diagram showing a configuration of a battery charge state calculation apparatus according to Embodiment 1. In FIG.
Moreover, FIG. 2 is a figure for demonstrating operation | movement of the battery charge condition calculating apparatus by this Embodiment.
Based on FIG. 1 and FIG. 2, the configuration and operation of the battery charge state calculation device according to the present embodiment will be described.
In FIG. 1, reference numeral 1 denotes voltage detection means for detecting a battery voltage of a battery (not shown) mounted on a hybrid car, an electric vehicle, an idle stop car, and the like, and 2 denotes current detection means for detecting charge / discharge current of the battery. It is.

Reference numeral 3 denotes a first current (I) -voltage (V) characteristic storage means of the battery.
Hereinafter, the “current-voltage characteristics” will be referred to as “IV characteristics”.
The first IV characteristic storage means 3 determines the battery current (load current) of a currently used battery (hereinafter simply referred to as a battery or the battery), which is a target of charge state calculation, at a predetermined load (for example, an engine A plurality of sampling points (indicated by ● in FIG. 2) detected by the voltage detection means 1 and the current detection means 2 when the current from the maximum load in an application such as start-up is changed to the current when the battery load is released. The battery voltage V and battery current I at each point) are stored.
Here, the state of the battery currently in use is referred to as a “first state”.

Then, the first IV characteristic storage means 3 calculates “V = −βI + α” from the stored values of the battery voltage V and the battery current I at a plurality of sampling points, for example, by first-order approximation using the least square method. The first IV characteristic (that is, the IV characteristic in the first state currently used) of the battery expressed by the following formula is calculated and stored. Here, α and β are positive constants.
In addition, the straight line shown with the code | symbol A in FIG. 2 has shown this 1st IV characteristic.

Reference numeral 4 denotes second IV characteristic storage means. The second IV characteristic storage means 4 stores “V = −β” in the second state in which the amount of energy that can be extracted from the battery is small. A theoretical second IV characteristic represented by the formula of I + α ′ ″ is stored in advance.
Here, α ′ and β ′ are also positive constants.
A straight line indicated by a symbol B in FIG. 2 indicates a second IV characteristic.

The above-mentioned “second state” of the battery is, for example, a case of a “deep discharge state” in which the battery is deteriorated, the remaining capacity is reduced, and the battery is discharged to a near unusable state, or a state close thereto. This means that the amount of energy that can be extracted from the battery is low.
The theoretical second IV characteristic in the “deep discharge state” is that even when the battery is in a deteriorated state and a discharge current exceeding a predetermined load current (for example, a current necessary for starting the engine) is passed. This is the minimum line IV characteristic capable of ensuring a battery voltage higher than the required predetermined voltage. Here, the IV characteristic of the minimum line used as a boundary with the “unusable area” described in the figure is, for example, the minimum voltage at which the engine can be started, or a control unit ( (Including audio etc.) as the operation limit. In other words, the state of charge of the battery here means that not only the performance as a battery but also the minimum that the entire system including the connected electrical load is established is set to SOC = 0. It becomes the inside code B.

Reference numeral 5 denotes predetermined current value storage means in each application (for example, engine start). The predetermined current value storage means 5 stores, for example, current values necessary for engine start.
6 is a battery voltage calculation means at a predetermined load, and the battery voltage calculation means 6 at the predetermined load is a first IV characteristic (that is, stored in the first IV characteristic storage means 3). The battery current is set to a predetermined current value (engine start current (engine start current Ic)) using a predetermined current value (for example, engine start current Ic) stored in the predetermined current value storage means 5 and the current IV characteristics of the battery in use. The battery voltage Vc (see FIG. 2) at the time of Ic) is calculated.
The “battery voltage when the battery has a predetermined load (predetermined current value)” obtained from the first IV characteristic is referred to as a first battery voltage.
Therefore, the calculated battery voltage Vc is the first battery voltage.

Further, the battery voltage calculation means 6 at a predetermined load includes a second IV characteristic stored in the second IV characteristic storage means 4 and a predetermined current value stored in the predetermined current value storage means 5. Is used to calculate the battery voltage Vc0 (see FIG. 2) when the battery current is a predetermined current value.
The “battery voltage when the battery has a predetermined load (predetermined current value)” obtained from the second IV characteristic is referred to as a second battery voltage.
Therefore, the calculated battery voltage Vc0 is the second battery voltage.
In FIG. 2, Vo and Vo0 are battery voltages when the battery current is zero (when the load is released) in the first and second IV characteristics, respectively.

When the battery application is “engine start”, the battery is unusable if the battery current deteriorates until the battery voltage becomes Vc0 or less when the engine current is the engine start current Ic.
7 is an SOC (charged state) calculating means. The SOC (charged state) calculating means 7 uses the battery voltage Vc calculated by the battery voltage calculating means 6 at a predetermined load and the battery voltage Vc0 to charge the battery. (Ah) is obtained, and the SOC (charge state) is calculated from the current integrated value ΣI obtained by the current integrating means 9 for integrating the current value of the current detecting means 2 and the correction gain.

  It can be determined that the larger the index representing the calculation result is, the more the remaining capacity of the battery is, and the energy is still remaining, and the smaller the index is, the smaller the remaining capacity is, which is close to the state of deterioration.

  Since the second IV characteristic is stored in advance in the second IV characteristic storage unit 4, the second battery voltage can be easily calculated in a short time.

  As described above, the battery state-of-charge computing device according to the present embodiment approximately obtains the IV characteristics (first IV characteristics) of the battery in the first state that is currently in use. The first IV characteristic storage means 3 for storing in advance and the battery's IV characteristic (second IV characteristic) in the second state where the amount of energy that can be extracted is smaller than that in the first state are stored in advance. A first battery voltage when the battery current is the predetermined load current value is calculated using the second IV characteristic storage means 4 and the first IV characteristic, and the second I Using the -V characteristic, the battery voltage calculation means 6 at a predetermined load for calculating the second battery voltage when the battery current is the predetermined load current value, and the calculated first and second battery voltages are used. The battery in the first state Charging state calculation means 7 for calculating the charging state of the battery, so that it is not affected by the change, deterioration, battery temperature, etc. of the battery liquid amount, and the charging state ( SOC) can be grasped (determined) easily and in a short time, and charging suitable for a battery for a hybrid car, an electric vehicle, an idle stop vehicle, etc. that always requires monitoring of the state of charge (remaining capacity) A state calculation device can be provided.

Embodiment 2. FIG.
FIG. 3 is a block diagram showing a configuration of the SOC calculation means 7 shown in FIG. 1 according to the second embodiment.
In the figure, 31 denotes ΔV−C for obtaining the battery charge state C from the voltage difference (Vc−Vc0) ΔV of the second battery voltage Vc0 already explained in FIG. 1 as well as the first battery voltage Vc already explained in FIG. The converting means 32 is a maximum battery capacity calculating means for obtaining the maximum battery capacity Cmax obtained by multiplying the nominal battery capacity of the battery by the correction gain described in FIG. 4, and 33 is the current integrated value ΣI obtained first. An upper limiter for limiting by the battery charge state C. Similarly, 34 is a lower limit for limiting the previously limited ΣI by subtracting the previously determined maximum battery capacity Cmax from the previously determined battery charge state C. It is a limiter.

  Next, the form of a present Example is demonstrated. A voltage difference ΔV between the first battery voltage Vc and the second battery voltage Vc 0 is obtained, and the battery charge state C is detected by the ΔV-C conversion means 31. The method is, for example, a one-dimensional map with the voltage difference ΔV (V) on the X axis and the battery charge state (Ah) C on the Y axis, and the correction gain with the voltage difference ΔV (V) on the X axis. The Y-axis may be obtained in advance from the battery characteristics, for example, as a two-dimensional map (see FIG. 5) with the battery charge state (Ah) C as the Z-axis.

  Next, the maximum battery capacity currently used (Ah) is obtained from the nominal battery capacity (Ah) of the battery and the correction gain using the maximum battery capacity calculation means 32. In the case of a new battery, the actual battery capacity is generally larger than the nominal battery capacity. However, the maximum battery capacity varies depending on how the battery is used and other factors including the environment in which the battery has been placed. In general, the maximum battery capacity tends to be small depending on the usage time, but it is not uniform depending on how it is used. In order to correct this, the nominal battery capacity is corrected by the correction gain obtained from the performance level described in FIG.

  Next, the current integrated value ΣI is limited using the upper limiter 33 at a value with the battery charging state (Ah) obtained by the ΔV-C conversion means 31 as an upper limit. The current value I indicates a positive value during discharging and a negative value during charging. This is to be suppressed because when the discharge continues and the current integrated value ΣI becomes larger than the value of the battery charge state C, the SOC value beyond that indicates a negative value. Similarly, a value obtained by subtracting the maximum battery capacity Cmax obtained by the maximum battery capacity calculation means 32 from the battery charge state (Ah) obtained by the ΔV-C conversion means 31 for the current integrated value ΣI ′ having passed through the upper limit limiter 33 is the lower limit. The lower limiter 34 is used to limit the value. This suppresses this because charging continues and the value obtained by subtracting the current integrated value ΣI from the value of the battery charge state C exceeds 100% in the SOC calculation part ahead.

Embodiment 3 FIG.
FIG. 4 is a block diagram showing a configuration of the performance level determination / correction means 8 shown in FIG. 1 according to the third embodiment.
41 is a performance level determination means for determining a performance level from the first battery voltage Vc and the battery voltage Vo when the battery current is zero (when the load is released) in the first IV characteristic, and 42 is a performance level determination. This is a performance level correction gain calculation means for obtaining a correction gain from the performance level obtained by the means 41.

  Next, the form of a present Example is demonstrated. In the first battery voltage Vc and the first IV characteristic, the performance level detection means 8 is used based on the battery voltage Vo when the battery current is zero (when the load is released), and the performance level of the battery currently in use Is detected. When the open-circuit voltage is plotted on the horizontal axis and the first battery voltage Vc is plotted on the vertical axis, the battery has a characteristic that the plotted value transitions to the right as the degree of deterioration progresses. For example, using this, in the first IV characteristic, the battery voltage Vo when the battery current is zero (when the load is released) is set to the X axis, the first battery voltage Vc is set to the Y axis, and the performance level is set. A two-dimensional map (see FIG. 6) for the Z axis is prepared in advance, and the performance level is detected. The influence of the performance level also affects the ΔV-C conversion and the maximum battery capacity Cmax. Since the performance level is not proportional, it is difficult to directly use it for correction of ΔV-C conversion. Therefore, for example, a correction gain is obtained by using the performance level correction gain calculation means 42 on a map (see FIG. 7) with the performance level as the X-axis and the correction gain as the Y-axis, and is used for subsequent corrections so that linear interpolation is possible.

  The present invention is suitable for application to a battery charge state calculation device that detects a state of remaining capacity in a state where a battery used in a vehicle or the like is in use.

It is a block diagram which shows the structure of the battery charge condition detection apparatus by Embodiment 1. FIG. 6 is a diagram for explaining the operation of the battery charge state detection device according to the first embodiment. It is a block diagram which shows the structure of the SOC calculating means by Embodiment 2. FIG. 10 is a block diagram illustrating a configuration of a performance level determination / correction unit according to a third embodiment. It is a block diagram which shows the structure of the (DELTA) V-C conversion means by Embodiment 2. It is a block diagram which shows the structure of the performance level determination means by Embodiment 3. FIG. 10 is a block diagram illustrating a configuration of a performance level correction gain calculation unit according to a third embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Voltage detection means 2 Current detection means 3 1st IV characteristic (current-voltage characteristic) storage means 4 2nd IV characteristic (current-voltage characteristic) storage means 5 Predetermined current value storage means 6 Under predetermined load Battery voltage calculation means 7 SOC (charge state) calculation means 8 performance level determination / correction means 9 current integration means A IV characteristics in the first state B IV characteristics of the minimum line 31 ΔV-C conversion means 32 Maximum battery capacity calculation means 33 Upper limit limiter 34 Lower limit limiter 41 Performance level determination / correction means 42 Performance level correction gain calculation means.

Claims (5)

Battery voltage detection means for detecting the voltage of the battery;
Battery current detection means for detecting the current of the battery;
Using the voltage value and current value detected by the battery voltage detection means and the battery current detection means at a plurality of sampling points, the current-voltage characteristics of the battery in the first state that is currently in use are approximately obtained. First current-voltage characteristic storage means for storing this as a first current-voltage characteristic;
Second current-voltage characteristic storage means for storing in advance a second current-voltage characteristic in a second state in which the amount of energy that can be extracted is smaller than that in the first state;
Predetermined current value storage means for storing a predetermined load current value of the battery;
The first current-voltage characteristic stored in the first current-voltage characteristic storage means is used to calculate the first battery voltage when the battery current is the predetermined load current value, and the second current A battery voltage calculation means at a predetermined load for calculating a second battery voltage when the battery current is at the predetermined load current value using voltage characteristics;
Charge state calculation means for calculating the state of charge of the battery in the first state using the first and second battery voltages calculated by the battery voltage calculation means at the predetermined load. The battery charge state calculation device. In the first current-voltage characteristic storage means, the voltage Vc at the time of a predetermined load current (assumed to be discharged) stored in the predetermined current value storage means, and in the first current-voltage characteristic storage means , from the load current (and not flowing) of the zero voltage Vo of time, to detect the performance level of the battery using the performance level detection means, for correcting the battery state obtained from the above KiTakashi conductive state calculating means The battery state-of-charge computing device according to claim 1. From the performance level of the battery determined from the performance level detection means determines a correction gain that was observed in the characteristics of the battery by performance level correction gain calculating means, correcting the battery state of charge obtained by the above KiTakashi conductive state calculating means The battery state-of-charge computing device according to claim 2, wherein In the state of charge of the battery obtained by the above KiTakashi conductive state calculating means, the battery current determined by the detecting means current (negative charge side, the discharge-side and positive) from the upper KiTakashi conductive state calculating means carried 2. The SOC (State Of Charge) of a battery is obtained by dividing a value obtained by subtracting a current integrated value obtained by a current integrating means having means initialized at times from the maximum battery capacity. 4. The battery charge state calculation device according to any one of 3 above. The battery current detection obtained current from the means (negative charge side, the discharge-side and positive) and current integration determined by current integration means having a means which is initialized at the upper KiTakashi conductive state calculating means carried The value is passed through a limiter (upper limit) whose upper limit is the battery charge state, and is passed through a limiter (lower limit) obtained by subtracting the maximum battery capacity from the battery charge state. The battery charge state calculation device according to claim 4.

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