JP3947952B2 - Battery full charge judgment method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a battery charging device, and more particularly to full charge determination thereof.
[0002]
[Prior art]
In recent years, for example, high-performance and long-life Ni-MH batteries 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. 7-14612 proposes a method for determining a full charge when the voltage change rate dV / dt per unit time drops from the previous time.
[0003]
[Problems to be solved by the invention]
In the full charge determination based on the voltage change rate dV / dt in the alkaline secondary battery such as the Ni-MH battery described above, an error occurs in the full charge determination due to the change in the voltage change rate dV / dt due to the change in the charging current. was there.
In response to this problem, the present applicant has developed a method of determining full charge by detecting a positive peak value of the voltage change rate dV / dAh per unit charge amount.
[0004]
That is, the voltage change rate dV / dAh in the alkaline secondary battery decreases rapidly at the beginning of charging, becomes almost constant at the middle of charging, and increases rapidly at the end of charging (because electrolysis of the electrolyte starts), Since it reaches a peak at full charge and then suddenly decreases to a negative value (because it generates heat and the electrolysis voltage decreases), it detects the peak value of the voltage change rate dV / dAh (also referred to as a positive peak value). By determining as charging, full charging can be accurately determined even if there is some variation in charging current. In this full charge determination method, the peak becomes small when the temperature becomes high, and the peak disappears when the temperature becomes higher. Therefore, when the voltage change rate dV / dAh becomes 0 or a negative value, the full charge is determined. It is determined.
[0005]
However, even with this voltage change rate dV / dAh, when the charging current fluctuates, the voltage fluctuates by the amount of this current change × battery internal resistance, and the voltage change rate dV / dAh before full charge is caused by this voltage fluctuation. It turned out that there is a problem that becomes a positive peak value. In addition, even when the internal temperature of the battery fluctuates, there is a possibility that the voltage change rate dV / dAh becomes a positive peak value before the battery is fully charged.
[0006]
A high-accuracy constant current charger can be used to prevent the charging current from changing, but it is expensive. In addition, the charger may supply power to other loads whose load impedance varies during battery charging, such as a charger mounted on an electric vehicle. In this case, the charging current of the battery is also affected. It is not easy to prevent.
[0007]
The present invention has been made in view of the above problems, and an object of the present invention is to provide a battery full charge determination method capable of determining full charge with high accuracy.
[0008]
[Means for Solving the Problems]
According to the battery charging device of the present invention described in claim 1, the full charge of the battery is determined based on the amount of change in voltage per unit charge amount.
In this way, the full charge is determined not by the rate of change of voltage per unit time as in the prior art but by the amount of change per unit charge, so the peak size will change even if the charge current varies. Therefore, full charge can be accurately determined.
[0009]
Further, since full charge is determined not by the absolute value of the terminal voltage or temperature but by the amount of change thereof, a decrease in detection accuracy due to variations in sensor error or battery characteristics can be avoided.
Further, when the voltage change rate per unit charge amount is in a region larger than a predetermined positive threshold and the voltage change rate reaches 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 region smaller than the threshold value, the terminal voltage of the battery fluctuates due to the change in the charging current described above, and thus the voltage change rate dV / dAh has a positive peak value. The problem of erroneous determination can be solved.
[0010]
In other words, even if the charging current fluctuates considerably, the positive peak value of the voltage change obtained by multiplying this current change by the internal resistance of the battery is much smaller than the positive peak value at full charge at room temperature because the internal resistance is small. Therefore, a change in voltage change rate dV / dAh due to a change in charging current is not determined to be fully charged.
The predetermined positive threshold value may be a constant value or a value obtained by adding a positive constant value to the minimum value of the voltage change rate dV / dAh at the time of current charging. The difference between the positive peak value and the minimum value of the voltage change rate dV / dAh may be multiplied by a predetermined ratio. Furthermore, 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.
[0011]
In addition, in the battery charger of the present invention described in claim 1, When the voltage change rate dV / dAh is 0 or a predetermined negative value, it is determined that the battery is fully charged, and it is not determined that the battery is fully charged when the voltage change rate is 0 to a positive threshold.
In this way, it is possible to determine full charge even at a high temperature, and even if at normal temperature it is not possible to determine full charge due to overlooking the positive peak value determination, and even after shifting to an overcharge state, the voltage change rate dV / When dAh becomes 0 or a negative value, it can be re-determined as full charge, so that overcharge can be prevented at an early stage.
[0012]
Claim 2 Claims according to the arrangement described 1 In the battery full charge determination method described above, the positive threshold is further set to the battery temperature. Phase That is, even if the positive peak value of the voltage change rate dV / dAh on the two-dimensional plane with the voltage change rate dV / dAh and the charge amount Ah as two axes becomes smaller as the temperature rises, Accordingly, the positive threshold value is also reduced, so that a highly accurate full charge determination can be performed regardless of the temperature change.
[0013]
Claim 4 According to the described configuration, claims 1 to 3 In the battery full charge determination method described in any one of the above, a constant current terminal voltage Vs that is a terminal voltage at a predetermined constant current (I = 0 is also possible) is calculated from a plurality of pairs of voltage / current data, and this constant voltage is determined. Full charge is calculated from the rate of change of the current terminal voltage Vs. For example, the internal resistance of the battery is obtained from a plurality of pairs of voltage / current data, the internal resistance of the battery is obtained by multiplying the current by the internal resistance, and the open voltage is obtained by subtracting the internal voltage drop from the terminal voltage V. The voltage change rate (dVs / dAh or dVs / dt) may be obtained using the open-circuit voltage as the constant current conversion voltage Vs referred to in the present invention. After all, if there are a plurality of pairs of voltage / current data, it is obvious that the constant current conversion voltage Vs at a predetermined constant current can be obtained from them.
[0014]
In this way, the full charge can be accurately determined even if the charging current varies. 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. Furthermore, various charging devices with variable output current values can be used. For example, even if the charging station is changed, no problem occurs.
Furthermore, although the internal resistance of the battery changes depending on 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. It is also possible to compensate for fluctuations in the relationship with the charging current I.
[0015]
The voltage / current data means a pair of the terminal voltage V and the charging current value i at a predetermined simultaneous point.
Claim 5 Claims according to the arrangement described 4 Further, in the battery full charge determination method described above, the voltage / current data is periodically sampled, and 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.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, preferred embodiments of the battery charging device of the present invention will be specifically described with reference to the following examples.
[0017]
【Example】
FIG. 1 is a block diagram of a charging device for an electric vehicle.
(Overall configuration of the device)
Reference numeral 1 denotes an assembled battery, which is formed by connecting a large number of battery modules 2 in series. The battery module 2 consists of ten unit cells connected in cascade. 3 is a temperature sensor, 4 is a current sensor, 5 is a voltage detection circuit that detects the voltage across each battery module 2, 6 is a temperature detection circuit that detects the temperature of the battery module 2, and 7 is the charge / discharge current of the assembled battery 1. Is a current detection circuit for detecting These detection circuits 5 to 7 are constituted by A / D converters in this embodiment, but may be constituted by dedicated circuits.
[0018]
8 is a charge control circuit with a built-in microcomputer for receiving a signal from each of the detection circuits 5 to 7 and controlling the output current (charge current) of the charger 9, and the charger 9 is assembled battery 1 with a predetermined constant current. Connected to charge. 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 related to the full charge determination of the charge control circuit 8 will be described later. Each of 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 a charger 9 and an external controller (not shown).
[0019]
(Characteristics of nickel metal hydride battery)
FIG. 2 shows the relationship between the charging capacity (charge amount) and the module voltage at the time of constant current (10 A) charging of the battery module 2 having a rated capacity of 100 Ah. The module voltage V increases consistently with an increase in charge capacity (also referred to as charge amount) Ah, the rate of change (increase rate) in voltage V increases immediately before full charge (100 Ah), and then decreases. I understand. 2 is the temperature of the outer surface of the case of the battery module 2 (environmental temperature), and is different from the temperature detected by the temperature detection circuit 6.
[0020]
FIG. 3 shows the relationship between the charge amount Ah and the voltage change rate dV / dAh in the battery charge of FIG.
From FIG. 3, it can be seen that the voltage change rate rises significantly immediately before full charge, reaches a positive peak at full charge, then the voltage change rate decreases rapidly, and then the voltage change rate becomes negative. It can also be seen that as the temperature increases, the positive peak becomes smaller, and when the temperature exceeds 40 ° C., the positive peak becomes considerably smaller. At 50 ° C., the voltage V decreases conversely before reaching full charge (100 Ah).
[0021]
FIG. 4 shows the relationship between the charge amount Ah and the voltage change rate dV / dAh at each charge current value.
FIG. 4 shows that the voltage change rate dV / dt varies as the charging current varies.
(Full charge judgment operation)
Next, the charge control operation including the full charge determination operation, which is the gist of this embodiment, will be described below with reference to the flowchart of FIG.
[0022]
First, this charging control operation is started by the input of an external charging signal. Initialization of each part is performed first, charging the battery charger 9 with a predetermined constant current (10 A) is started, and the built-in timer is counted. Is started (S1).
Next, the terminal voltage VB, the charging current IB, and the battery temperature TB are read from the detection circuits 5 to 7 (S2), and the time from the start of charging is read from the built-in timer (S3).
[0023]
Of course, 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, charge abnormality determination is performed (S4), and if it is abnormal, processing more than charging such as alarm notification and charge stop is performed (S5), and the routine is terminated. 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 detection of a positive peak value cannot be expected. Shall be specified.
[0024]
If it is not determined that charging is abnormal in S4, it is checked whether or not the flag Flag indicating full charge is set (ON). If it is set, equal charge processing is performed (S7), and the routine is terminated. To do.
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 current charge amount is calculated by multiplying this time difference by the read charging current IB. The charge amount Qg is obtained by accumulating the previous charge amount (S8).
[0025]
(Constant current conversion voltage Vs calculation process),
Next, a constant current conversion voltage Vs calculation process is performed. This process will be described below with reference to FIG.
(Data sampling)
First, it is checked whether or not the flag F2 indicating full charge determination is 0 (off) (S90). If it is off, the flag F2 is set to 1 (on) (S91), and the process proceeds to S92.
[0026]
In S92, it is determined whether or not the full charge determination period is reached. If YES, the process proceeds to S93, and if not, the process returns to S2. Whether or not the full charge determination period has been reached is determined by calculating the charge amount ΔQg accumulated from the previous full charge determination operation of S9 or less (= the charge amount Qg ′ at the start of the previous full charge determination operation from the current charge amount Qg). When the difference ΔQg reaches a predetermined unit charge / discharge amount Ahx, a full charge determination of S93 or less is performed. Otherwise, the full charge determination is premature and the process returns to S2.
[0027]
In S93, it is checked whether or not the unit charge amount difference ΔAh for determining the timing for sampling the voltage / current data has reached the predetermined threshold value Ahy. If not, the process returns to S2, and if reached, the voltage / current data VB, IB The data sampling routine for reading and storing the charge amount Qg and resetting the unit charge amount difference ΔAh to 0 is repeated 12 times.
[0028]
Next, average voltage / current data VBM1 and IBM1 (referred to as previous term average voltage / current data) are obtained from the first three voltage / current data VB and IB, and from the next six voltage / current data VB and IB. Average voltage / current data VBM2 and IBM2 (referred to as medium-term average voltage / current data) are obtained, and average voltage / current data VBM3 and IBM3 (late-term average voltage / current data) from the last three voltage / current data VB and IB. Ask).
[0029]
When the first three times of this data sampling routine are completed, the charger 9 is instructed to reduce the charging current by ΔI (here, 3A) from the previous average current data IBM1. Thereafter, the above data sampling routine is executed 6 times with this charging current (7A if there is no variation), and then the charger 9 is again commanded to increase by ΔI (here 3A) from the medium-term average current data IBM2. Thereafter, the data sampling routine is executed three times with this charging current (10 A if there is no variation).
[0030]
Eventually, 12 sets of voltage / current data VB, IB and charge amount Qg are obtained by the 12 data sampling routines executed in succession, from which the previous average voltage / current data VBM1, IBM1, Average voltage / current data VBM2, IB and M2, and late average voltage / current data VBM3, IBM3 can be obtained. Note that the data of each charge amount Qg is different by unit charge amount difference ΔAh.
[0031]
FIG. 7 is a timing chart showing the data sampling timing. 101 to 103 indicate the first three data sampling timings, and 108 to 110 indicate the last three data sampling timings.
(Internal resistance r calculation)
Next, the internal resistance r is calculated from the previous period average voltage / current data VBM1, IBM1, the middle period average voltage / current data VBM2, IB and M2, and the latter period average voltage / current data VBM3, IBM3 (S94).
[0032]
First, the average voltage Vm1 and the average current im1 are obtained from the previous period average voltage / current data VBM1, IBM1 and the latter period average voltage / current data VBM3, IBM3. The internal resistance r of the battery 1 is calculated from the average voltage Vm1, the average current im1, and the medium-term average voltage / current data VBM2 and IBM2 by the following equation (S94).
r = ΔVm / Δm
ΔVm is calculated by the formula of Vm1-VBM2, and ΔIm is calculated by the formula of im1-IBM2.
[0033]
(Constant current conversion voltage Vs calculation)
Next, the constant current conversion voltage Vs is calculated by the following formula based on the obtained internal resistance (S95).
Vs =
-(Reference constant current (here 10A)-average current) x r + average voltage
The average current is the average value of the current data IB for the last three times, and the average voltage is the average value of the voltage data VB for the last three times.
[0034]
Note that the reference constant current (here, 10 A) can be an arbitrary value, and may be zero. In this case, the constant current converted voltage Vs is an open circuit voltage.
Next, the flag F2 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.
[0035]
In this embodiment, the constant current conversion voltage Vs calculated in S9 of the previous routine (hereinafter referred to as the previous value of the constant current conversion voltage Vs) and the value of the charge amount Qg (the period for calculating the constant current conversion voltage Vs). In this embodiment, the amount of charge Qg at the time of the sixth data sampling in S9 of the previous routine is referred to as the previous value of the amount of charge Qg). The constant current converted voltage Vs calculated in S9 (hereinafter referred to as the previous value of the constant current converted voltage Vs) and the charge amount Qg (the value of the charge amount Qg at the time of the sixth data sampling of S9 in this routine) (Referred to as the current value of the charge amount Qg).
[0036]
Voltage change rate dVs / dAh
= (Current value of constant current converted voltage Vs−Previous value of constant current converted voltage Vs) / (Current value of charge amount Qg−Previous value of charge amount Qg)
(Determination of whether the battery has been charged more than the discharge amount)
Next, it is determined whether or not the cumulative charge amount Qg from the start of the current charge is larger than the cumulative discharge amount Qs in the previous discharge (S11). This is to reduce the probability of erroneous full charge determination by taking advantage of the fact that the battery is not normally fully charged unless at least the previous discharge amount Qs is charged in consideration of the charge loss.
[0037]
(Full charge judgment at normal temperature by 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, whether or not the peak value is positive is determined based on whether or not the voltage change rate dVs / dAh tends to increase and then decreases.
[0038]
This step S12 will be described in more detail with reference to the flowchart shown in FIG.
(Positive threshold setting and judgment of increasing tendency)
In this embodiment, whether or not the tendency has been increased is determined by whether or not the voltage change rate dVs / dAh is larger in the positive direction than the threshold value Vth. 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).
[0039]
Vth = K · ΔI · r + Voffset + ΔV
K is a correction coefficient due to 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 conversion voltage Vs due to the fluctuation of the charging current. Voffset is a value determined by the offset voltage of the current change detection system and the like, 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 conversion voltage Vs at the time of constant current charging, and here is a value equal to the voltage change rate dVs / dAh in the middle of charging at normal temperature.
[0040]
In the next S121, when the voltage change rate dVs / dAh is larger than the threshold value Vth, it is determined that the voltage tends to increase, and the process proceeds to S123. Otherwise, the process proceeds to S13.
(Determining a decreasing trend)
In order to reduce the noise error, the moving average value of 5 times immediately before the voltage change rate dVs / dAh is obtained (S123), and this moving average value is the 3rd consecutive moving average. It is checked whether or not the value has become smaller (S124). If it has become smaller, it is determined that there is a decreasing tendency, and the process proceeds to S15. If not, the process proceeds to S13 to determine full charge at high temperature.
[0041]
(Full charge judgment at high temperature)
Next, for full charge determination at high temperature, it is determined whether the voltage change rate dVs / dAh is continuously 0 or less (or less than a predetermined negative value) (S13). The flag Flag indicating charging is set to OFF (that is, 0) (S14). If so, the flag Flag indicating full charge is set to ON (that is, 1) (S15), and the process returns to S2.
[0042]
In S11, if the charge amount Qg is smaller than Qs, the process proceeds to S13 because the storage capacity of the battery is reduced when the battery is at a high temperature, and the battery may be fully charged early. This is because it is necessary to make a charge determination.
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.
[0043]
(Example effect)
In the full charge determination operation of this embodiment described above, since full charge is determined not by the rate of change per unit time of voltage as in the prior art but by the amount of change per unit charge amount, the charging current varies. However, since the peak size does not change, full charge can be accurately determined.
[0044]
Further, since full charge is determined not by the absolute value of the terminal voltage or temperature but by the amount of change thereof, a decrease in detection accuracy due to variations in sensor error or battery characteristics can be avoided.
In addition, when the voltage change rate per unit charge amount is in a region larger than a predetermined positive threshold and the voltage change rate reaches 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 change in the charging current described above. As a result, the voltage change rate dV / dAh has a positive peak value. The problem of erroneous determination as charging can be solved.
[0045]
Further, there are a plurality of problems that the fluctuation of the charging current becomes a voltage fluctuation related to the internal resistance of the battery, the voltage change rate dV / dAh fluctuates, and the reliability of the full charge determination by the voltage change rate dV / dAh is lowered. Since the constant current conversion voltage Vs is obtained from the voltage / current data of the set and the full charge determination is performed at the voltage change rate dVs / dAh of the constant current conversion voltage Vs, it is canceled by the compensation process. It can be carried out.
[0046]
In this embodiment, even if the charger 9 is changed and the charging current varies, the constant current conversion voltage Vs can be calculated independently of the charging current. For example, even if a plurality of charging stations are used. There is also an effect that the reliability of the full charge determination is not lowered.
In addition, when the voltage change rate dV / dAh is 0 or a predetermined negative value, it is determined that the battery is fully charged. Therefore, the battery can be fully charged even at a high temperature. Even if the state is shifted to the overcharged state, the full charge can be redetermined when the voltage change rate dV / dAh becomes 0 or a negative value, so that overcharge can be prevented at an early stage.
[0047]
In addition, by setting the threshold value Vth as in the above formula (Vth = K · ΔI · r + Voffset + ΔV), it is possible to prevent erroneous detection of a voltage change due to a change in internal resistance or an error in the detection system as a peak. Therefore, the full charge detection accuracy can be improved.
(Modification)
The threshold value Vth can be set equal to the voltage change rate dV / dAh at a capacity of 85% to 95% of the full charge capacity of the battery. In this way, it is possible to reliably determine that the correct positive peak value is fully charged, and to favorably eliminate false positive peak values due to current fluctuations.
[0048]
However, since the value of the voltage change rate dV / dAh in the capacity of 85% to 95% of the full charge capacity of the battery varies depending on the battery temperature, the relationship between the battery temperature and the threshold value Vth is stored in advance in the map, The threshold value may be obtained by substituting the detected battery temperature into this map.
In addition, a positive threshold value is set larger than the product of 10% of the battery charging current × 10% to 80% of the battery full charging capacity and the internal resistance, so that the charging current changes by 10%. Can accurately determine full charge.
[0049]
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 at the time of current charging. The difference between the positive peak value and the minimum value of the change rate dV / dAh may be multiplied by a predetermined ratio. Furthermore, 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 advance in the map, the magnitude of the positive peak value is predicted based on the detected temperature, and the magnitude and the voltage change rate dVs / The positive threshold value Vth may be obtained by multiplying the difference from the minimum value of dAh by a predetermined coefficient.
The threshold value Vth may be about half of the difference between the expected positive peak value of the voltage change rate dVs / dAh at full charge) and the expected maximum positive peak value at non-full charge. The magnitude of the positive peak value at the time of the last 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. From this positive peak value to the current voltage change rate The current threshold value Vth may be obtained by multiplying a value obtained by subtracting the minimum value of dVs / dAh by a predetermined coefficient (for example, 0.5).
[0050]
In the above embodiment, the internal resistance r is calculated using the current pattern shown in FIG. 7, but the charging current value is simply changed periodically and stepwise for each unit charging amount ΔAh, and the charging currents are adjacent to each other. If the terminal voltage VB in two periods is detected, the internal resistance r can be detected.
(Other voltage / current data sampling method 1)
Further, in the above-described embodiment, data sampling is performed 12 times for each unit charge amount ΔAh, and the data sampling is initially performed 3 times during the charging period T1 in which charging is performed with a predetermined charging current value ip1 (10A). The next six data samplings are performed during the charging period T2 in which charging is performed at a predetermined charging current value ip2 (7A), and the last three data samplings are performed at a predetermined charging current value ip1 (10A). In the charging period 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.
[0051]
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, 10A), and after a predetermined time has elapsed from this setting or after charging a predetermined amount of charge, the first voltage / current data sampling is performed. Next, the charging current is set to a predetermined charging current value ip2 (in this case, 7A) different from ip1, and after the predetermined time has elapsed from this setting or after charging a predetermined amount of charge, sampling of the next voltage / current data for the second time is performed. I do. Next, the internal resistance and the constant current converted voltage Vs are calculated from the obtained voltage / current data VB and IB by the above-described method.
[0052]
By doing this, it is possible to eliminate variations in voltage value and current value from when the charging current value is set until the charging current actually settles to that value, and to obtain more accurate voltage / current data VB and IB. be able to.
(Other voltage / current data sampling method 2)
Furthermore, in the other voltage / current data sampling method 1, after the second voltage / current data sampling, the charging current is reset to the original ip1, and after a predetermined time has elapsed since the resetting. Alternatively, after charging a predetermined amount of charge, the third voltage / current data sampling is performed for the third time. Next, voltage / current data VB and IB for interpolation between the obtained first voltage / current and the next voltage / current data for the third time are obtained. The internal resistance and the constant current converted voltage Vs are calculated from the second voltage / current data VB and IB by the above-described method.
[0053]
In this way, parameter changes due to the progress of charging can be canceled by the interpolation process, so that more accurate voltage / current data VB and IB can be obtained.
(Other voltage change rate dVs / dAh calculation methods)
The voltage change rate dVs / dAh described above may be obtained as follows.
[0054]
First, the first value of the first constant current converted voltage Vs is obtained using the voltage / current data VB, IB obtained by the other voltage / current data sampling method 1 or 2, and the constant current conversion is performed. When the voltage / current data VB, IB, which is the basis for calculating the first value of the voltage Vs, is delayed by a predetermined charge amount value dAh from the sampling time of the voltage / current data VB, the above-described other voltage / current data sampling method 1 Or the next voltage / current data VB, IB is sampled by 2 and the obtained voltage / current data VB, IB is used to obtain the second value of the constant current converted voltage Vs. The voltage change rate dVs / dAh is obtained by dividing the difference between the first time value and the second time value by the predetermined charge amount value dAh.
[0055]
When the above-described sampling method 1 of other voltage / current data is used for sampling of the voltage / current data VB, IB, the calculation of the first value and the second value of the constant current conversion voltage Vs The sampling time of the voltage / current data VB and IB is the sampling time of the second voltage / current data at the charging current value ip2 (7A in this case) in the other voltage / current data sampling method 1 described above. Is preferably selected.
[0056]
In addition, when using the other voltage / current data sampling method 2 described above for sampling the voltage / current data VB and IB, the basis for calculating the first and second values of the constant current conversion voltage Vs The sampling time of the voltage / current data VB and IB is the third sampling time of the voltage / current data at the charging current value ip1 (here, 10A) in the other voltage / current data sampling method 2 described above. Is preferably selected.
[Brief description of the drawings]
1 is a block diagram of a charging device used in Example 1. FIG.
FIG. 2 is a characteristic diagram showing the relationship between the charge capacity (charge amount) and the module voltage during constant current charging of the battery module 2;
FIG. 3 is a characteristic diagram showing a relationship between a charge capacity (charge amount) and a module voltage change rate during constant current charging of the battery module 2;
FIG. 4 is a characteristic diagram showing the relationship between the charging capacity (charge amount) and the module voltage change rate when the battery module 2 is charged with various charging current values.
FIG. 5 is a flowchart showing a full charge determination method of this embodiment.
6 is a flowchart showing a part of the full charge determination method shown in FIG. 5; FIG.
7 is a timing chart showing a data sampling timing and a charging current forcibly changing state in FIG. 6; FIG.
FIG. 8 is a flowchart showing a part of the full charge determination method shown in FIG. 5;

Claims (5)

The voltage change rate per unit charge amount is calculated from the battery terminal voltage V and the charge amount Ah obtained at the time of charging,
A battery full charge determination method in which the voltage change rate is in a region greater than a predetermined positive threshold and the voltage change rate is substantially positive peak, and is determined to be full charge,
When the voltage change rate is 0 or a predetermined negative value, it is determined that the battery is fully charged,
A battery full charge determination method, wherein the battery is not determined to be fully charged in a region where the voltage change rate is greater than 0 and less than the positive threshold value . The battery full charge determination method according to claim 1,
Said positive threshold, the full charge determination method of cell and changes with a correlation to the temperature of the battery. In the battery full charge determination method according to claim 1 or 2 ,
The battery is a nickel metal hydride battery, wherein the battery is fully charged. In the battery full charge determination method according to any one of claims 1 to 3 ,
A plurality of voltage / current data consisting of a pair of data of the terminal voltage V and data of the charging current I are detected, and the terminal voltage at a predetermined value of the charging current I based on the plurality of pairs of voltage / current data or A constant current conversion voltage Vs, which is a voltage having a predetermined correlation with it, is calculated, and a rate of change (dVs / dAh) of the constant current conversion voltage Vs per unit charge amount or unit time is obtained as the voltage change rate. A battery full charge determination method characterized by the above. In the battery full charge determination method according to claim 4 ,
A battery full-charge determination method, wherein the plurality of pairs of voltage / current data are obtained by changing the charging current I during the sampling period of the voltage / current data.

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