JP2000311720A - Full charge determining method for battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a full charge determining method for a battery capable of highly accurately determining full charge. SOLUTION: Full charge of a battery is determined by a rate of voltage change per a unit time or a unit charged quantity (S12, S13). Especially, a constant current terminal voltage Vs, which is a terminal voltage at the time when a designated constant current passes (I=0 is possible), is calculated (S9) by plural pairs of voltage and current data, a rate of change of the constant current terminal voltage Vs is calculated (S10), and full charge is thereby determined. By this method, full charge can be accurately determined even if a charge current is fluctuated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for determining a full charge of a battery, and more particularly to a full charge determination method.

[0002]

2. Description of the Related Art In recent years, for example, high performance and long life Ni-MH battery cells have been used for batteries used in electric vehicles. As a method for determining the full charge of a Ni-MH battery, Japanese Patent Application Laid-Open No. Hei 7-146612 proposes a method of determining that the battery is fully charged when the rate of voltage change per unit time dV / dt is lower than the previous time.

[0003]

However, in the full charge determination system using the voltage change rate, the charging current I
Of the battery, the resistance voltage drop ΔVr of the battery, which is a value obtained by multiplying the charging current I by the internal resistance r of the battery, changes, thereby decreasing the voltage change rate and erroneously determining that the battery is fully charged.

[0004] The present invention has been made in view of the above problems, and has as its object to provide a battery full charge determination method capable of determining full charge with high accuracy.

[0005]

According to the battery full-charge judging method of the present invention described in claim 1, since the battery is fully charged based on the voltage change rate per unit time or unit charge amount, Full charge can be determined with higher accuracy than other methods, for example, a method of determining full charge based on battery temperature or battery voltage. Further, in this configuration, a constant current terminal voltage Vs which is a terminal voltage at the time of a predetermined constant current (I = 0 is also possible) is calculated from a plurality of pairs of voltage / current data, and the rate of change of the constant current terminal voltage Vs is Calculate full charge. For example, the internal resistance of the battery is obtained from a plurality of pairs of voltage / current data, the internal resistance is multiplied by a current to obtain the internal voltage drop of the battery, and the internal voltage drop is subtracted from the terminal voltage V to obtain the open voltage. This open-circuit voltage is defined as a constant current conversion voltage Vs referred to in the present invention, and the voltage change rate (dVs /
dAh or dVs / dt). After all, if there are a plurality of pairs of voltage / current data, it is apparent that a constant current conversion voltage Vs at the time of a predetermined constant current can be obtained from them.

With this configuration, it is possible to accurately determine the full charge even if the charging current fluctuates. In addition, since the fluctuation of the output current of the charging device can be allowed, the circuit configuration of the charging device can be simplified. In addition, various charging devices having different output current values can be used, and for example, there is no problem even if the charging station is changed. Furthermore, although the internal resistance of the battery changes with the battery temperature, even if the terminal voltage V fluctuates due to the internal resistance change due to this temperature change, it can be compensated at the same time. Variations in the relationship with the charging current I can also be compensated.

The voltage / current data means a pair of a terminal voltage V and a charging current value i at a predetermined simultaneous point. According to the configuration of the second aspect, in the battery full-charge determination method according to the first aspect, further, when the amount of change in the terminal voltage or the battery temperature per unit charge is near a positive peak value, the battery is fully charged. Since the determination is made, the full charge can be determined more accurately.

More specifically, for example, in an alkaline secondary battery such as a nickel-metal hydride battery, the remaining capacity has a large voltage change rate in a low level region, and this voltage change rate rapidly decreases with charging. When the state of charge is in the middle level region, the voltage change rate becomes a small and substantially constant value (the terminal voltage V increases at a substantially constant increase rate). In a region where the remaining capacity is high, the charge becomes difficult to be absorbed (stored) in the battery electrode, and the internal resistance increases due to the start of electrolysis of the electrolytic solution. As the drop increases, the voltage change rate sharply increases. afterwards,
In the vicinity of the full charge, the increase in the internal resistance is saturated because the charge is no longer absorbed (stored) in the battery electrode, and as a result, the increase in the internal voltage drop of the battery due to the stop of the increase in the internal resistance is stopped. The rate of change is reduced. Finally, the battery voltage decreases due to a decrease in the electrolysis voltage due to heat generation, and the voltage change rate becomes negative.

Therefore, a full charge exists near the positive peak value of the voltage change rate. According to a third aspect of the present invention, in the battery full charge determination method according to the first aspect, the voltage change rate further includes a voltage change rate per unit charge amount. This makes it possible to determine the full charge more accurately. More specifically, when the charging current I varies at the voltage change rate dV / dt per unit time, not only the variation of the terminal voltage V due to the variation of the charging current I but also the charging amount Ah after the unit time varies as described above. Will be. That is, since the internal resistance r varies depending on the state of the charge amount Ah, the charge amount A due to the variation of the charge current I in the voltage change rate per unit time dV / dt.
There is a problem that h varies and the internal resistance r varies, which appears in the terminal voltage V.

[0010] On the other hand, in the voltage change rate per unit charge amount dV / dAh, the unit charge amount dAh which is a denominator is:
Since this is actually measured by current integration, this problem does not occur. As a result, the fluctuation of the charging current I is smaller in dV / dAh than in dV / dt, and the accuracy is higher. According to the configuration described in claim 4, in the battery full-charge determination method according to any one of claims 1 to 3, voltage / current data is periodically sampled.

In this configuration, the plurality of pairs of voltage / current data are obtained by changing the charging current I during the sampling period. In this way, the constant current conversion voltage Vs can be easily obtained for each sampling period. According to the configuration of the fifth aspect, in the battery full charge determination method according to the fourth aspect, charging periods T1, T2, and T3, which are at least three sub-sampling periods, are provided for each sampling period at least sequentially. Voltage / current data is obtained for each charging period T1, T2, T3, and the voltage / current data of charging periods T1, T3 before and after charging period T2 is obtained.
The constant current conversion voltage Vs is obtained from the interpolated voltage / current data and the voltage / current data in the charging period T2 by interpolating the current data.

In this way, the voltage variation based on the difference in the charge amount Ah between the plurality of charge periods due to the progress of the charge during the sampling period (the internal voltage drop due to the change in the internal resistance due to the change in the charge amount Ah). (Based on the change) can cause an error in the constant current conversion voltage Vs. According to the configuration of claim 6, in the battery full charge determination method of claim 5, furthermore, each charging period T1,
A plurality of pairs of voltage and current data are obtained for each of T2 and T3, and average voltage and current data are obtained for each of the charging periods T1, T2 and T3. The constant current conversion voltage Vs is obtained from the obtained average voltage and current data. Ask for.

Since the number of data is large in this way, S
The N ratio can be improved. According to the configuration of claim 7, in the battery full charge determination method according to claim 6, the end point of the charge period T1, the start point and end point of the charge periods T2 and T3 are further set to the start point of the charge period T1. Is determined when the charge amount Ah reaches a predetermined value when the charge amount Ah is set to 0, that is, the charge amount Ah.

In this way, the problem that the charging state changes in each voltage / current data sampling period due to the fluctuation of the charging current I and the change in the charging state is reflected in the internal resistance is solved. According to the configuration of claim 8, in the battery full charge determination formula according to any one of claims 5 to 8, the charging current value ip1 in the charging period T1 is further set as the current charging current value i in the charging period T1. Do not make that change.
In this case, the current is set to two of the charging periods T2 and T3.
It becomes only one time and it becomes easy.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, a preferred embodiment in which the battery full-charge judging method of the present invention is applied to a nickel-metal hydride battery mounted on an electric vehicle will be specifically described with reference to the following examples.

[0016]

FIG. 1 is a block diagram of a charging device for an electric vehicle. (Overall Configuration of Apparatus) 1 is an assembled battery, which is formed by connecting a number of battery modules 2 in series. Battery module 2 is 1
It consists of zero cascaded unit cells. Reference numeral 3 denotes a temperature sensor, 4 denotes a current sensor, 5 denotes a voltage detection circuit for detecting a voltage between both ends of each battery module 2, and 6 denotes a battery module 2.
Is a temperature detection circuit for detecting the temperature of the battery 1; and 7 is a current detection circuit for detecting the charge / discharge current of the assembled battery 1. Although these detection circuits 5 to 7 are constituted by A / D converters in this embodiment, they may be constituted by dedicated circuits.

Reference numeral 8 denotes a charge control circuit built in a microcomputer for receiving signals from the respective detection circuits 5 to 7 and controlling an output current (charge current) of the charger 9. The charger 9 operates at a predetermined constant current. It is connected to charge the assembled battery 1. The charge control circuit 8 actually performs other routines such as discharge control and battery protection control in addition to charge control including a full charge determination operation as a battery controller. The operation of the charge control circuit 8 relating to the full charge determination will be described later. The detection circuits 5 to 7 and the charge control circuit 8 constitute a battery controller 10, and the battery controller 10 can communicate with the charger 9 and an external controller (not shown).

(Characteristics of nickel hydrogen battery) Rated capacity is 1
FIG. 2 shows the relationship between the charging capacity (charging amount) and the module voltage at the time of constant current (10 A) charging of the battery module 2 of 00 Ah. The module voltage V increases consistently with an increase in the charge capacity (also called charge amount) Ah, and the rate of change (increase rate) of the voltage V increases immediately before full charge (100 Ah), and then decreases. I understand. In addition,
The temperature in FIG. 2 is the temperature (environmental temperature) of the outer surface of the case of the battery module 2 and is different from the temperature detected by the temperature detection circuit 6.

FIG. 3 shows the charge amount A in charging the battery of FIG.
4 shows the relationship between h and the voltage change rate dV / dAh. From FIG. 3, it can be seen that the voltage change rate rises remarkably immediately before full charge, reaches a positive peak when fully charged, then drops sharply, and then becomes negative. Also, the positive peak decreases as the temperature increases, and the positive peak decreases considerably when the temperature exceeds 40 ° C.
It can be seen that at 0 ° C., the voltage V decreases conversely before reaching full charge (100 Ah).

FIG. 4 shows the charge amount Ah at each charge current value.
And the voltage change rate dV / dAh. From FIG.
It can be seen that the voltage change rate dV / dt changes when the charging current changes. (Full charge determination operation) Next, a charge control operation including a full charge determination operation, which is the gist of this embodiment, will be described below with reference to the flowchart of FIG.

First, this charge control operation is started by input of a charge signal from the outside, first, each unit is initialized, and the charger 9 starts charging with a predetermined constant current (10 A). The timer starts counting (S1). Next, from the detection circuits 5 to 7, the terminal voltage VB and the charging current I
B, the battery temperature TB is read (S2), and the time from the start of charging is read from the built-in timer (S3).

Note that the terminal voltage VB, the charging current IB, and the battery temperature TB may be read at predetermined intervals (for example, 100 msec) using an interrupt routine. Next, a charge abnormality determination is made (S4). If abnormal, a charge or more process such as an alarm issuance or charge stop is performed (S5), and the routine ends. Note that the charging abnormality in this embodiment is when the charging time is abnormally long and exceeds a predetermined reference time, or when the battery temperature is abnormally high and exceeds the predetermined reference temperature and it is not expected to detect a positive peak value. Shall be specified.

If it is not determined in S4 that the charging is abnormal, it is checked whether or not a flag Flag indicating full charge is set (ON). If the flag is set, equal charge processing is performed (S7). End the routine. If the flag is off, the time difference between the previous count time of the built-in timer and the current count time is calculated, and the time difference is multiplied by the read charging current IB to calculate the current charge amount. The charge amount Qg is obtained by accumulating the previous charge amount (S8).

(Constant current conversion voltage Vs calculation processing)
A constant current conversion voltage Vs calculation process is performed. This processing will be described below with reference to FIG. (Data Sampling) First, it is checked whether or not the flag F2 indicating that the full charge is being determined is 0 (off) (S90). If it is off, the flag F2 is set to 1 (on) (S91), and S9
Proceed to 2.

In S92, it is determined whether or not the full charge determination period has been reached. If so, the process proceeds to S93, and if not, the process returns to S2. Note that whether or not the full charge determination period has been reached is determined by calculating the charge amount ΔQg (= the charge amount Qg ′ at the start of the previous full charge determination operation from the current charge amount Qg from the previous full charge determination operation in S9 and below). If the difference ΔQg has reached the predetermined unit charge / discharge amount Ahx, a full charge determination of S93 or less is performed. Otherwise, it is premature to perform the full charge determination, and the process returns to S2.

In S93, it is checked whether or not the unit charge difference ΔAh, which determines the timing of sampling the voltage / current data, has reached a predetermined threshold value Ahy. If not, the process returns to S2. VB, I
B, the charge amount Qg is read and stored, and the unit charge amount difference ΔA
The data sampling routine for resetting h to 0 is repeated 12 times.

Next, the voltage / current data V for the first three times
Average voltage / current data VBM1, IBM from B, IB
1 (referred to as the average voltage / current data in the previous period)
Average voltage / current data VBM2 and IBM2 (referred to as medium-term average voltage / current data) are obtained from the voltage / current data VB and IB for the last three times, and the voltage / current data V for the last three times are obtained.
Average voltage / current data VBM3, IBM from B, IB
3 (referred to as late average voltage / current data).

When the first three data sampling routines have been completed, a command is issued to the charger 9 to lower the charging current by ΔI (here, 3 A) from the previous average current data IBM1. Thereafter, the above data sampling routine is performed six times with this charging current (7 A if there is no variation), and thereafter, the charger 9 is again commanded to obtain ΔI (here, 3 I) from the medium-term average current data IBM 2.
A), and then the data sampling routine is performed three times with this charging current (10 A if there is no variation).

As a result, the twelve sets of voltage / current data VB, IB and the charge amount Qg are obtained by the twelve consecutive data sampling routines to be performed, and the average voltage / current data VBM1, IBM1, medium-term average voltage / current data VBM2, IB and M2, and late-term average voltage / current data VBM3, IBM3 can be obtained. Note that the data of each charge amount Qg is a unit charge amount difference Δ
Ah will be different.

FIG. 7 is a timing chart showing the data sampling timing. Reference numerals 101 to 103 denote the first three data sampling timings.
8 to 110 indicate the last three data sampling timings. (Calculation of internal resistance r) Next, the average voltage / current data V
BM1, IBM1, medium term average voltage / current data VBM
2, IB and M2, late average voltage / current data VBM3,
The internal resistance r is calculated by the IBM 3 (S94).

First, the average voltage / current data VBM
1, IBM1 and late average voltage / current data VBM3, I
An average voltage Vm1 and an average current im1 are obtained from BM3. From the average voltage Vm1, the average current im1, and the medium-term average voltage / current data VBM2, IBM2, the battery 1
Is calculated (S94). r = ΔVm / Δm Here, ΔVm is calculated by the equation of Vm1−VBM2, and ΔI
m is calculated by the equation of im1-IBM2.

(Calculation of Constant Current Converted Voltage Vs) Next, a constant current converted voltage Vs is calculated by the following equation based on the obtained internal resistance (S95). Vs = − (reference constant current (here, 10 A) −average current)
× r + average voltage The average current is the average value of the last three current data IB, and the average voltage is the average value of the last three voltage data VB.

The reference constant current (here, 10 A) can be set to an arbitrary value, and may be set to 0. in this case,
The constant current conversion voltage Vs is an open voltage. Next, the flag F
2 is reset to 0, and the process proceeds to S10. In S10, a voltage change rate dV / dAh is calculated from the calculated constant current converted voltage Vs.

In this embodiment, the constant current conversion voltage Vs (hereinafter referred to as the constant current conversion voltage Vs) calculated in S9 of the previous routine.
s) and the value of the charge amount Qg (the charge amount at the center of the period for calculating the constant current converted voltage Vs. In this embodiment, the sixth data of S9 in the previous routine is used). This is the value of the charge amount Qg at the time of sampling, which is referred to as the previous value of the charge amount Qg), the constant current converted voltage Vs (hereinafter referred to as the previous value of the constant current converted voltage Vs) calculated in S9 of this routine, and the charge amount. From the value of Qg (the value of the charge amount Qg at the time of the sixth data sampling in S9 of the current routine, referred to as the current value of the charge amount Qg), it is obtained by the following equation.

Voltage change rate dVs / dAh = (current value of constant current converted voltage Vs−previous value of constant current converted voltage Vs) /
(Current value of charged amount Qg−previous value of charged amount Qg) (Determination of whether or not the battery has been charged more than the discharged amount) Next, the cumulative charged amount Qg from the start of the current charging is the cumulative discharged amount Qs in the immediately preceding discharge. (S1)
1) If it is larger, go to S12; if not, go to S13. This is to reduce the probability of erroneous full charge determination by taking advantage of the fact that the battery will not normally be fully charged unless at least the immediately preceding discharge amount Qs is charged in consideration of charge loss and the like.

(Judgment of Full Charge at Normal Temperature Based on Positive Peak Value) Next, it is determined whether or not the obtained voltage change rate dVs / dAh is a positive peak value (S12). In this embodiment, the determination as to whether the peak value is the positive peak value is made based on the voltage change rate dVs / d.
After Ah has increased, it is determined whether or not Ah has decreased.

Step S12 will be described in more detail with reference to the flowchart shown in FIG. (Setting of Positive Threshold and Judgment of Increasing Trend) In this embodiment, whether or not the increasing tendency has occurred is determined by the voltage change rate dVs
It is determined whether / dAh is greater than the threshold value Vth in the positive direction. In this embodiment, since the threshold value VtH is a variable value, the threshold value VtH is calculated by the following equation before the above determination (S121).

Vth = K · ΔI · r + Voffset + ΔV Here, K is a correction coefficient based on the internal resistance, and is set to a predetermined value between 0 and 1, for example, 0.5. ΔI is an assumed fluctuation range of the average current. Therefore, K · ΔI
R is a value proportional to the change width of the constant current converted voltage Vs due to the change of the charging current. Voffset is a value determined by the offset voltage or the like of the current change detection system, and is an amount related to the fluctuation amount of the constant current conversion voltage Vs when there is no current change. ΔV is a normal voltage increase amount of the constant current converted voltage Vs at the time of constant current charging, and is set to a value equal to the voltage change rate dVs / dAh in the middle stage of charging at normal temperature.

In the next S121, the voltage change rate dVs / d
If Ah is larger than the threshold value Vth, it is determined that the voltage is increasing and the process proceeds to S123. Otherwise, the process proceeds to S1.
Proceed to 3. (Determination of decreasing tendency) To determine whether the tendency has increased, the moving average value of five times immediately before the voltage change rate dVs / dAh is obtained in order to reduce the noise error (S123). Then, it is checked whether the moving average value has become smaller than the immediately preceding moving average value (S124). If the moving average value has become smaller, it is determined that the tendency has decreased, and the process proceeds to S15.
Then, a full charge judgment at high temperature is performed.

(Judgment of Full Charge at High Temperature) Next, it is judged whether or not the voltage change rate dVs / dAh is 0 or less (or a predetermined negative value or less) twice consecutively for the judgment of full charge at high temperature. (S13), otherwise, the flag F indicating full charge
The flag is turned OFF (ie, 0) (S14), and if so, the flag indicating full charge is turned ON (ie, 1) (S15), and the process returns to S2.

In S11, the charge amount Qg is changed to Qs
The reason for proceeding to S13 when it is smaller is that when the battery is in a high temperature state, the power storage capacity of the battery is reduced, and the battery may be fully charged at an early stage. . In S15, it is determined that the battery is fully charged, a flag Flag indicating full charge is set, and the process returns to S2.

(Effect of Embodiment) In the above-described full charge determination operation of this embodiment, full charge is determined based on the change rate per unit charge amount, not the change rate per unit time of voltage as in the related art. Therefore, the magnitude of the peak does not change even if the charging current varies, so that the full charge can be accurately determined.

Also, not the absolute values of the terminal voltage and the temperature,
Since the full charge is determined based on the amount of change, it is possible to avoid a decrease in detection accuracy due to a sensor error or a variation in battery characteristics. When the voltage change rate per unit charge is in a region larger than a predetermined positive threshold value and the voltage change rate has a substantially positive peak, it is determined that the battery is fully charged, and the voltage change rate is positive. Since it is not determined that the battery is fully charged in a positive region smaller than the threshold value, the terminal voltage of the battery fluctuates due to the above-described change in the charging current, and the voltage change rate dV / dA
It is possible to solve the problem that h has a positive peak value, and as a result, it is erroneously determined that the battery is fully charged.

In addition, the fluctuation of the charging current becomes a voltage fluctuation in relation to the internal resistance of the battery, and the voltage change rate dV / dAh fluctuates, thereby lowering the reliability of the full charge determination based on the voltage change rate dV / dAh. Is corrected by a compensation process of obtaining a constant current conversion voltage Vs from a plurality of sets of voltage / current data and performing a full charge determination at a voltage change rate dVs / dAh of the constant current conversion voltage Vs, so A charge determination can be made.

In this embodiment, even if the charger 9 is changed or the charging current fluctuates, the constant current conversion voltage Vs can be calculated independently of the fluctuation. For example, a plurality of charging stations are used. However, there is an effect that the reliability of the full charge determination does not decrease. Further, when the voltage change rate dV / dAh is 0 or a predetermined negative value, it is determined that the battery is fully charged.
At normal temperature, even if the battery cannot be determined to be fully charged due to overlooking the positive peak value determination and shifts to an overcharged state, then if the voltage change rate dV / dAh becomes 0 or a negative value, it is determined again that the battery is fully charged. As a result, overcharging can be prevented early.

(Modification) The threshold value Vth is set to a voltage change rate d at a capacity of 85% to 95% of the full charge capacity of the battery.
It can be set equal to the value of V / dAh. In this way, the correct positive peak value can be reliably determined to be fully charged, and the false positive peak value due to current fluctuation can be satisfactorily eliminated.

However, 85% to 95% of the full charge capacity of the battery
Since the value of the voltage change rate dV / dAh at% capacity varies depending on the battery temperature, the relationship between the battery temperature and the threshold value Vth is stored in advance in a map, and the detected battery temperature is substituted into this map. A threshold may be determined. Also,
10% of battery charge current x 10% of full charge capacity of battery
Since the positive threshold value is set to be larger than the product of the internal resistance at the capacity of 80% and the charging current changes by 10%, it is possible to accurately determine the full charge.

The predetermined positive threshold value may be a constant value, or may be a value obtained by adding a positive constant value to the minimum value of the voltage change rate dV / dAh during the current charging. The difference between the positive peak value and the minimum value of the voltage change rate dV / dAh at the time may be multiplied by a predetermined ratio. Further, since the positive peak value of the voltage change rate dV / dAh changes depending on the temperature, the positive peak value may be changed depending on the detected temperature. The relationship between the magnitude of the positive peak value of the voltage change rate dVs / dAh and the temperature is stored in a map in advance, the magnitude of the positive peak value is predicted based on the detected temperature, and the magnitude and the voltage change rate dVs / dAh are estimated. The difference from the minimum value of dAh may be multiplied by a predetermined coefficient to obtain a positive threshold value Vth. Threshold Vt
h is the expected voltage change rate dVs / dAh at the time of full charge.
(Positive peak value) and the maximum expected positive peak value at the time of non-full charge. The magnitude of the positive peak value at the time of the previous full charge is stored, and this stored value is corrected by the temperature difference between the previous time and the current time to obtain the current positive peak value,
A predetermined coefficient (for example, 0.5) is obtained by subtracting the minimum value of the current voltage change rate dVs / dAh from the positive peak value.
May be used as the current threshold value Vth.

In the above embodiment, the internal resistance r was calculated using the current pattern shown in FIG.
The charging current value is changed periodically and stepwise for each Ah,
The internal resistance r can be detected by detecting the terminal voltages VB of two adjacent periods having different charging currents. (Sampling method 1 for other voltage / current data)
In the above embodiment, 12 data samplings are performed for each unit charge amount ΔAh, and first three data samplings are performed in a charging period T1 in which charging is performed at a predetermined charging current value ip1 (10A). A charging period in which six data samplings are performed in a charging period T2 in which charging is performed at a predetermined charging current value ip2 (7A), and a final three data samplings are performed in a charging period in which charging is performed at a predetermined charging current value ip1 (10A). At T3, the constant current conversion voltage Vs is obtained from the average value of each voltage / current data in the charging period T1 and the average value of the voltage / current data in the charging period T3.

However, each voltage / current data for calculating the internal resistance may be sampled as follows. That is, first, the charging current is set to a predetermined charging current value ip1.
(Here, 10 A), and after a lapse of a predetermined time from this setting or after charging by a predetermined charge amount, the first sampling of the voltage / current data is performed. Next, the charging current is set to ip1
Is set to a predetermined charging current value ip2 (in this case, 7 A) different from the above, and after a lapse of a predetermined time or after charging a predetermined amount of charge from this setting, the second sampling of the next voltage / current data is performed. Next, the obtained voltage / current data VB, IB
From the calculation of the internal resistance and the constant current conversion voltage V
s is calculated.

By doing so, it is possible to eliminate variations in the voltage value and the current value from when the charging current value is set to when the charging current actually reaches the value, and more accurate voltage / current data VB, IB can be obtained. (Other voltage / current data sampling method 2)
In the other voltage / current data sampling method 1, after the second sampling of the voltage / current data, the charging current is reset to the original ip1 again, and after a lapse of a predetermined time or a predetermined time from this resetting. After the charge, the third sampling of the next voltage / current data is performed. Next, voltage / current data VB, IB of the obtained first voltage / current and the next voltage / current data of the third time are obtained, and the interpolated voltage / current data VB, IB and the second The calculation of the internal resistance and the calculation of the constant current conversion voltage Vs are performed from the voltage / current data VB and IB of the second time by the above-described method.

In this way, since the parameter change due to the progress of charging can be canceled by the above-described interpolation processing, more accurate voltage / current data VB and IB can be obtained. (Other Calculation Methods of Voltage Change Rate dVs / dAh) The above-described voltage change rate dVs / dAh may be obtained as follows.

First, the first value of the first constant current converted voltage Vs is obtained using the voltage / current data VB and IB obtained by the other voltage / current data sampling method 1 or 2. At a point in time after the sampling of the voltage / current data VB and IB, which is the basis for calculating the first value of the constant current conversion voltage Vs, is delayed by a predetermined charge amount value dAh, the above-described other voltage / current data The following voltage / current data VB and IB are sampled by the sampling method 1 or 2, and the second value of the constant current conversion voltage Vs is obtained using the obtained voltage / current data VB and IB. The voltage change rate dVs / dAh is obtained by dividing the difference between the first value and the second value of Vs by the predetermined charge amount value dAh.

When the other sampling method 1 for voltage / current data is used for sampling the voltage / current data VB and IB, the first and second values of the constant current conversion voltage Vs are calculated. Voltage / current data V which is the basis of
As the sampling time of B and IB, the second sampling time of the voltage / current data at the charging current value ip2 (here, 7A) in the other voltage / current data sampling method 1 can be selected. preferable.

When the other voltage / current data sampling method 2 is used for sampling the voltage / current data VB and IB, the first and second values of the constant current converted voltage Vs are calculated. Voltage / current data V which is the basis of
B and IB are sampled at the third voltage / current at the charging current value ip1 (here, 10 A) in the other voltage / current data sampling method 2 described above.
It is preferable to select the sampling point of the current data.

[Brief description of the drawings]

FIG. 1 is a block diagram of a charging device used in a first embodiment.

FIG. 2 is a characteristic diagram showing a relationship between a charging capacity (charging amount) and a module voltage during constant current charging of a battery module 2.

FIG. 3 is a characteristic diagram illustrating a relationship between a charging capacity (charging amount) and a rate of change in module voltage during constant current charging of the battery module 2.

FIG. 4 is a characteristic diagram illustrating a relationship between a charging capacity (charging amount) and a module voltage change rate when charging the battery module 2 at various charging current values.

FIG. 5 is a flowchart illustrating a full charge determination method according to the embodiment.

6 is a flowchart showing a part of the full charge determination method shown in FIG.

FIG. 7 is a timing chart showing a data sampling timing and a charging current forcibly changing state in FIG. 6;

8 is a flowchart showing a part of the full charge determination method shown in FIG.

Claims (8)

[Claims] 1. A battery terminal voltage V and a charging current I at the time of charging are detected to calculate a voltage change rate of a battery per unit charge amount or unit time, and the battery voltage change rate is calculated based on the calculated voltage change rate. A battery full charge determination method for determining full charge, comprising detecting a plurality of pairs of voltage / current data including a pair of data of the terminal voltage V and data of a charging current I, and detecting the plurality of pairs of voltage / current data. The constant current conversion voltage Vs, which is the terminal voltage at a predetermined value of the charging current I or a voltage having a predetermined correlation with the terminal voltage, is calculated based on the above, and the change of the constant current conversion voltage Vs per unit charge amount or unit time. A battery full charge determination method, wherein a rate (dVs / dAh or dVs / dt) is obtained and used as the voltage change rate. 2. The battery full charge determination method according to claim 1, wherein the battery is fully charged when the voltage change rate has a positive peak. 3. The battery full charge determination method according to claim 1, wherein the voltage change rate comprises a voltage change rate per unit charge amount. 4. The battery full charge judging method according to claim 1, wherein said plurality of pairs of voltage / current data are changed by changing said charging current during a sampling period of said voltage / current data. And a battery full charge determination method. 5. The battery charging method according to claim 4, wherein the charging is performed at a predetermined charging current value ip1.
A predetermined charging current value ip2 different from the charging current value ip1
A charging period T2 for performing charging at the charging current value ip1 and a charging period T3 for performing charging at the charging current value ip1 are sequentially provided in the sampling period. The voltage / current data during the charging period T1, the voltage / current data during the charging period T2, The current data and the voltage / current data in the charging period T3 are obtained. The voltages in the charging periods T1 and T3, which are interpolation data of the voltage / current data in the charging period T1 and the voltage / current data in the charging period T3. A battery full charge determination method, wherein the constant current conversion voltage Vs is obtained based on current data and the voltage / current data during the charging period T2. 6. The battery full charge determination method according to claim 5, wherein a plurality of pairs of the voltage / current data are obtained for each of the charging periods T1, T2, T3, and based on the obtained voltage / current data. Average voltage / current data is obtained for each of the charging periods T1, T2, T3, and the obtained average voltage / current data is calculated for each of the charging periods T1, T2, T3.
1, wherein the voltage / current data of T2 and T3 is used as the battery full charge determination method. 7. The battery full-charge judging method according to claim 6, wherein the start time and the end time of each of the charging periods T2 and T3 are:
A full charge determination method for a battery, wherein the charge amount Ah is set to a point in time when the charge amount Ah at the start of the charging period T1 is set to 0 and reaches a predetermined value. 8. The battery full-charge judging method according to claim 5, wherein the charging current value ip1 in a predetermined charging period T1 is a current charging current value i in the charging period T1. A battery full charge determination method characterized in that no change is made.