JP2003168489A - Detecting method of charging/discharging state of alkaline storage battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a detecting method of charging/discharging state of a battery with high accuracy and high reliability, after the battery has gone through complicated operational processes in which complicated charging and discharging have been mingled, when detecting the charging/discharging state of an alkaline storage battery having a nickel electrode as a positive electrode. <P>SOLUTION: It is a method of detecting the charging/discharging state of the battery based on the correlation between an open-circuit voltage of the battery and the charging/discharging state. The estimated value of the open- circuit voltage is calculated by removing the voltage change value resulting from the hysteresis phenomenon of the nickel electrode, which has been produced by power conduction history, from the measured voltage of the battery. Moreover, the detect is carried out based on correlation between the charging or discharging state and the open-circuit voltage of the battery in the charging process, or the open-circuit voltage of the battery in the discharging state. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for detecting the charge / discharge state of an alkaline storage battery, such as a nickel-hydrogen storage battery or a nickel-cadmium storage battery, in which a nickel electrode is applied to a positive electrode. On the other hand, the present invention relates to a method for accurately detecting the charge / discharge state.

[0002]

2. Description of the Related Art Conventionally, as a method for detecting the charge / discharge state of a battery, there is a method for obtaining the charge / discharge state based on the initial charge / discharge state (hereinafter, referred to as a flow rate). In the case of this method, there is an error between the amount of electricity supplied and the amount of change in the charging / discharging state of the battery due to the fact that the charging efficiency of the battery is less than 100% and the amount of electricity lost by self-discharge is ignored. Occurs. Therefore, there is a problem in that the errors are accumulated as the cycles are repeated or the time elapses, so that the detected charging / discharging state is greatly deviated.

When the usage of the battery goes through a 100% charged state or a 100% discharged state, it is possible to correct the charge / discharge state calculated value each time. Therefore, even if the energization method is applied, the error caused is small. However, all batteries are 100% charged or 1
It does not mean that it is used after the state of 100% discharge. Rather, it is often used in a situation in which complicated charging / discharging that does not reach a 100% charged state or a 100% discharged state is repeated. Under such circumstances, it was difficult to accurately detect the charge / discharge state by the electrification method.

On the other hand, a method of detecting the charging / discharging state by utilizing the correlation between the battery voltage and the charging / discharging state of the battery can be considered.
For example, attempts have been made to detect the charging / discharging state by actually measuring the open circuit voltage (hereinafter referred to as V _o ) of the battery (the measured value is hereinafter referred to as V _om ). However, since V _om is affected not only by the charging / discharging state of the battery but also by the history before the V _om measurement, there is a large error when trying to detect the charging / discharging state by simply using V _om as V _o at that time. there were.

In Japanese Patent Laid-Open No. 11-346444, an open circuit voltage correction amount is calculated from the operation history of the battery, the open circuit voltage is corrected by the calculated amount to obtain a correction voltage, and the battery voltage is calculated from the correction voltage. A method of detecting the state of charge (SOC) has been proposed. The operation history referred to in this publication is a self-discharge history from the end of the previous use to the start of the current use, and the correction amount is calculated from the history. However, the accuracy of detection is not sufficient even by the method proposed in this publication.

Further, Japanese Laid-Open Patent Publication No. 11-135159 describes a method of estimating the remaining capacity from the terminal voltage (open circuit voltage) when the discharge current and the charging current do not substantially flow for a predetermined time or longer. According to this method, the influence of the energization history on the open circuit voltage can be eliminated as much as possible.
However, in the case of this method, the charging / discharging state cannot be detected until it is left in the non-energized state for a predetermined time or longer. Therefore, there is a drawback that the demand for detecting the charge / discharge state of the battery at any given time cannot be met.

JP-A-6-59003 and JP-A-9-
Japanese Patent No. 96665 proposes a method of estimating the remaining capacity of a battery from the VI characteristics of the battery. This method attempts to detect the charging / discharging state of the battery in the energized state, but the target battery is in the discharging state, and the discharge current value is equal to or higher than a predetermined value and the value increases. There was a drawback limited to.

[0008]

Among the conventional methods, most of the methods for detecting the charging / discharging state from the battery voltage are based on a curve showing the correlation between the charging / discharging state of the battery and V _o, which is prepared in advance. However, as described above, it was difficult to accurately estimate V _o . When the battery is overcharged or over-discharged, the battery characteristics are deteriorated, and the electrolytic solution is decomposed to generate gas, which may increase the internal pressure of the battery and cause liquid leakage. Therefore, it is extremely important to detect the charging / discharging state of the battery and control the charging / discharging. INDUSTRIAL APPLICABILITY As described above, the present invention is in a situation in which complicated charging / discharging that does not reach a 100% charged state or a 100% discharged state is repeated, and the battery is charged during charging or discharging. It is intended to provide a method for accurately detecting a discharge state.

[0009]

The present invention is a method for detecting the charge / discharge state of an alkaline storage battery having a nickel electrode as a positive electrode by the correlation between the charge / discharge state and the open circuit voltage (V _o ) of the battery. In the method of estimating the open circuit voltage (V _o ) by the open circuit voltage (V _oe ) obtained by the calculation based on the measured value (V _m ) of the battery voltage, the open circuit voltage (V _oe ) is calculated. At this time, the method for detecting the charge / discharge state of an alkaline storage battery is characterized by removing an error caused by a hysteresis of an open circuit voltage caused by a history of energization.

The present invention relates to the charging / discharging state of an alkaline storage battery having a nickel electrode as a positive electrode, the charging / discharging state of the battery and the open circuit voltage (V _ocs ) of the battery in the charging process or the open circuit of the battery in the discharging process. It is a method for detecting a charge / discharge state of an alkaline storage battery, which is characterized in that it is obtained from a correlation of voltage (V _ods ). Here, V _ocs and V _ods mean that a constant current is continuously applied to the battery and the battery
It refers to the open circuit voltage when charged from the OD 100% state and the open circuit voltage when discharged from the DOD 100% state.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION (Hysteresis behavior of battery voltage)
An embodiment of the present invention will be described below with reference to the drawings. Figure 1
Is the charge of the nickel hydrogen battery measured at a temperature of 20 ° C.
Discharged state (Discharged as a measure of the charge / discharge state of the battery below
Measured results of open circuit voltage and adopting depth, noted as DOD)
It is a graph which shows. The upper curve shown by the solid line in the figure is
Continuously energize the battery with a constant current and a DOD of 100%.
Open circuit voltage when charging from the state
Voltage (V_ocs)) Is shown. The lower curve is the constant current
Is continuously energized to discharge the battery from the state where the DOD is 0%
Open circuit voltage at the time of {open circuit voltage (V
_ods)) Is shown.

The open circuit voltages V _oc and V _od are represented by one curve if the charge or discharge temperature is constant. As shown in the figure, V _oc and V _od do not overlap,
Shows hysteresis. The hysteresis is a phenomenon peculiar to an alkaline storage battery having a nickel electrode as a positive electrode. The open circuit voltage of the battery is all in the region surrounded by the hysteresis curve.

The broken line in the figure shows the voltage value that can be finally obtained when the battery is left in each DOD for a long period of time, and shows the open circuit voltage (V _o ) which is not affected by the energization history. The open circuit voltage has a correlation with the DOD, and if the temperature is constant, the DOD
It is a value that is uniquely determined by Therefore, if this V _o can be estimated quickly and accurately, D will be highly accurate and accurate.
OD detection becomes possible.

The measured voltage (V _m ) of the battery can be expressed by the following formula, and FIG. 2 shows the structure of V _m . V _m = V _o + (R × I) + V _h , V _o ≈V _oe V _h = V _a + V _c V _oe : Estimated value of V _o (V) R: Internal impedance of battery (Ω) I: Actual voltage measurement Charge or discharge current (A) at time (charge current is positive, discharge current is negative) V _oh : Open circuit voltage V _{a of} battery including fluctuation due to hysteresis and temperature dependence: Open circuit voltage derived from hysteresis Fluctuation value (V) V _c : fluctuation value (V) derived from temperature dependence of open circuit voltage

Actually, V _oe is obtained to estimate V _o required for DOD detection. Therefore, it is necessary to correct by subtracting (R × I) + V _h from V _m in the above equation.

[Method of Calculating V _oe from V _{m When} DOD Before Battery Voltage Measurement is Known or Estimated] This method uses DO at a certain point before voltage measurement.
This method can be applied when D can be estimated. Figure 2
FIG. 3 schematically shows how the open circuit voltage (V _h : including hysteresis variation due to energization) with respect to DOD fluctuates with respect to DOD.

The V _oc of the target battery during the charging process varies along the curve of V _oc1 in FIG. Further, V _od of the target battery in the discharging process changes along V _od1 . Therefore,
The behavior of V _oc or V _od differs depending on V _{h of} the target battery.

[0018] For example, when in the region of V _h of the battery in question, the V _{o c} battery in the charging process, changes slowly with respect to the as DOD indicated by the arrows in FIG. On the other hand, V _od of the battery in the process of discharging changes abruptly with respect to DOD as shown by the arrow in the figure.

When the V _h of the battery of interest is in the region of, even if the DOD changes by an equal amount due to energization, the change of V _oc of the battery is smaller than the change of V _od .

When the V _h of the target battery is in the range of, even if the DOD changes by an equal amount due to energization, the change of V _oc of the battery is larger than the change of V _od .

When V _h of the target battery is in the region of, V _oc of the battery during charging rises sharply as compared with the case of in the region of ~, and along the curve of V _oc in the figure. fluctuate. In addition, since V _od of the battery at the time of discharging fluctuates along V _od , the V _od decreases more slowly than in the case of the regions 1 to 4.

In this method, the diagram showing the relationship between the battery voltage and the DOD shown in FIG. 2 is divided into small sections on both the vertical axis and the horizontal axis, and the energization history, the variation value of V _oh and the V _oh value are divided for each section.
_{In this} method, data is acquired in advance regarding the relationship of _a and the measured data of the battery to be applied is collated to calculate V _a .

Since the fluctuation of V _oh varies depending on the initial position of V _oh as described above, it is possible to improve the accuracy by dividing the ordinate as small as possible. For the same reason, it is desirable that the horizontal axis be divided into as small sections as possible. Specifically, 0.01 to about the vertical axis.
It is desirable to divide 0.04V as one division and 1 to 3% as one division on the horizontal axis.

(Recording of energization history) The amount of energized electricity is recorded as follows. Vs: A value obtained by subtracting the voltage fluctuation value based on the internal impedance of the battery from the measured voltage (V _m ) of the battery. ΔDOD: Amount of change in DOD before and after energization (value determined by energization amount). However, when the absolute value of this variable exceeds a predetermined value, this variable is reset and recorded as 0%.

Taking the case where the DOD of the target battery changes as shown in FIG. 3, for example, ΔDOD is 1%.
If it is reset when the value exceeds, the energization history is recorded as follows. ΔDOD [1] = + 1 ΔDOD [2] = − 1 ΔDOD [3] = + 1 ΔDOD [4] = + 1 ΔDOD [5] = − 1 ΔDOD [6] = − 1 ΔDOD [7] = − 1 In the above, ΔDOD [ The value of [m] is either +1 or -1.

(Calculation of voltage fluctuation value by energization history) FIG. 4
A flow chart showing the procedure for calculating the hysteresis voltage is shown in FIG. First, in step 1, it is confirmed whether or not the absolute value of ΔDOD exceeds a predetermined value. In order to improve accuracy, it is better to set the predetermined value smaller. This predetermined value is preferably 0.1 to 1.0% in terms of ΔDOD.

When ΔDOD does not exceed the predetermined value,
The difference between V _oc and V _od due to the hysteresis is small and can be ignored.

In step 2, ΔDOD is reset to 0% and a predetermined value is recorded in ΔDOD [m]. At this time, if the predetermined value is set to 1%, δDOD is 1%.
When it exceeds, either +1 or -1 is entered.

In steps 4 to 6, the voltage fluctuation value (R × I) due to the internal impedance of the battery and the temperature fluctuation value V _c are subtracted to calculate V _{o h including the} error due to the hysteresis.

In steps 7 to 9, it is detected whether the battery is in a charged state or a discharged state at the time of measuring the battery voltage or immediately before, and either V _oc or V _od is calculated according to the detected value, and the value is calculated. Subtract. In step 7, the voltage difference a between V _ocs and V _ods corresponding to the DOD obtained by adding the energization history to the V _{oh of} the battery obtained in step 6 and the known DOD is obtained. As the known DOD to be applied at this time, the initial DOD value is applied when ΔDOD exceeds the predetermined value for the first time, and the DOD value calculated by the result of one routine before is applied otherwise.

Further, in step 8, δDOD
From the history of [m] and the voltage difference a obtained in step 7, the fluctuation value V _h of V _o based on hysteresis is calculated.

The history of ΔDOD [m] is the sum total of ΔDOD [1] = + 1 to ΔDOD [7] = − 1 in the example of FIG. 4, that is, −1. This history changes the voltage fluctuation value V _a due to hysteresis.

The history of ΔDOD [m] is roughly classified into the following four. (1) The sign of ΔDOD [m] (m indicates the voltage measurement time point) is +, and the sign of ΔDOD [m−1] before that is +.
If it is. (2) The sign of ΔDOD [m] is +, and ΔDOD [m]
The sign of -1] is-. (3) The sign of ΔDOD [m] is −, and ΔDOD [m]
The sign of −1] is +. (4) The sign of ΔDOD [m] is-and ΔDOD [m]
The sign of -1] is-.

The fluctuation of V _o due to hysteresis is usually Δ
It becomes large when the sign of DOD [m] and the sign of ΔDOD [m-1] are switched. Therefore, among the above four categories,
In the case of (2) and (3) variations in V _o becomes greater than that of (1) and (4).

Therefore, to further improve the accuracy, ΔDO
It is desirable to previously store the variation data of V _o for each classification of D [m] and utilize it.

Next, in step 10, the voltage variation (Vc) due to the temperature dependence of V _o shown by the broken line in FIG. 2 is subtracted, and V _oe ≈V _o is set to the final V applied to the detection of the charging / discharging state. Estimate _o . By correcting with the present V _a, it is possible to calculate V _oe excluding the influence of hysteresis, which is the main object of the present invention, and it is possible to detect the charge / discharge state with high accuracy.

Further, since V _a is attenuated with the lapse of time from the time when the energization is stopped until the time when the voltage is actually measured, the data regarding the correlation between the energization history and V _a is accompanied by the lapse of time of V _a. It is desirable to obtain the attenuation data and correct it.

[Method 1 for Detecting DOD from V _ocs or V _ods ] As shown in FIG. 1, the open circuit voltage (V _ocs ) of the battery in the charging process or the open circuit voltage of the battery in the discharging process as shown in FIG. (V _ods ) has a correlation. The method is a method of estimating V _o of the target battery and detecting DOD by utilizing the correlation between V _o and DOD, and applying V _ocs or V _{ods instead} of V _o .

Actual voltage of battery (V_m) Is expressed as
Be done. V_m= V_ocse(Or V_odse) -RxI + V_he V_ocs(Or V_ods) ≒ V_ocse(Or V_odse) V_he= V_b+ V_c In the above formula, V_ocse(Or V_odse): Opening the charging (or discharging) process
Circuit voltage V_ocs(Or V_ods) Estimated value (V), V_m: Battery voltage (measured value) (V) V_b: V of circuit voltage caused by energization history_ocs(Or V
_odsValue from () V_c: V_oc(Or V_odV due to the temperature dependence of_oof
Variation value (V) R: Internal impedance of battery (Ω) I = current value of battery when measuring voltage (A) Is.

The procedure for determining V _ocse (or V _odse ) by this method is the same as the procedure for determining V _oe of the target battery, and detailed description thereof will be omitted.

[Method 2 for Detecting DOD from V _ocs or V _ods ] This method is used when the battery is continuously charged or discharged until or immediately before the voltage measurement time.
The calculation of _ocse (or V _odse ) is an easy and _plausible method. As shown in FIG. 2, when a battery is charged or discharged, its open circuit voltage asymptotically _approaches V _ocs (or V _ods ) with a DOD change of at least about 5%. Therefore, FIG.
As shown in, R × I caused by energization during voltage measurement
V _ocse (or V _odse ) can be easily calculated by (V) and temperature correction.

【The invention's effect】

According to the first aspect of the present invention, it is possible to accurately detect the charge / discharge state of the alkaline storage battery having the nickel electrode as the positive electrode.

According to the second aspect of the present invention, the charging / discharging state of the alkaline storage battery having the nickel electrode as the positive electrode can be detected with high accuracy as in the first aspect. In addition, for a battery that is continuously charged or discharged, the charge / discharge state can be detected in simple steps.

According to the third aspect of the present invention, the variation value of the open circuit voltage due to the hysteresis in the second aspect can be easily calculated.

[0045]

[Brief description of drawings]

FIG. 1 is a graph showing an open circuit voltage during charging and discharging of a nickel-hydrogen storage battery having a nickel electrode as a positive electrode.

FIG. 2 is a schematic diagram for explaining a variation value due to hysteresis of an open circuit voltage of an alkaline storage battery having a nickel electrode as a positive electrode.

FIG. 3 is a graph for explaining a change in DOD [m] with the operation of a battery.

FIG. 4 is a flowchart showing a procedure for calculating an open circuit voltage (calculated value).

FIG. 5 is an explanatory diagram for explaining a method of calculating a difference between an open circuit voltage (V _o ) and an open circuit voltage (V _ocse ) during charging or an open circuit voltage (V _odse ) during discharging and an actually measured voltage. .

FIG. 6 is a diagram schematically showing a method for calculating V _ocse or V _odse of a battery that is continuously charged or discharged.

[Explanation of symbols]

V₀Battery open circuit voltage V_aOf the open circuit voltage of the battery due to hysteresis
V₀Fluctuation value from V_ocs    Open circuit voltage during battery charging process V_ods    Open circuit voltage during battery discharge process V_bOf the open circuit voltage of the battery due to hysteresis
V_ocseOr V_odse Fluctuation value from

Continued front page    F term (reference) 2G016 CB02 CB03 CB04 CB11 CB12                       CC01 CC03 CC04 CC23                 5G003 BA01 DA07 EA05 GC05                 5H028 BB11                 5H030 AA03 AA04 BB01 BB21 FF43                       FF44

Claims (3)

[Claims] 1. A charging / discharging state of an alkaline storage battery having a nickel electrode as a positive electrode, a charging / discharging state and an open circuit voltage (V
A method of detecting the correlation with _o), a method for estimating the open circuit voltage (V _o) by the battery of the actual measurement voltage (V _m) open-circuit voltage determined by the calculation based on (V _oe) In calculating the open circuit voltage (V _oe ),
Charging / discharging an alkaline storage battery, characterized in that _a voltage fluctuation value (V _a ) from an open circuit voltage (V _o ) caused by a hysteresis of an open circuit voltage caused by energization history is removed from an actually measured voltage (V _m ). State detection method. 2. The charging / discharging state of an alkaline storage battery having a nickel electrode as a positive electrode is defined as the charging / discharging state of the battery and the open circuit voltage (V _ocs ) of the battery in the charging process or the open circuit voltage of the battery in the discharging process ( A method for detecting the charging / discharging state of an alkaline storage battery, which is obtained from a correlation of _Vods ). 3. The open circuit voltage (V _ocs ) of the battery in the process of charging or the open circuit voltage (V) of the battery in the process of discharging.
to seek voltage variation value based voltage difference _ods) and the measured voltage (V _m) the open circuit voltage calculated based on of the batteries (V _b) to the voltage (V _m) measured earlier energization history The method for detecting the charge / discharge state of an alkaline storage battery according to claim 2, which is characterized in that.