JPH11234917A - Charger for combined batteries - Google Patents

Abstract

PROBLEM TO BE SOLVED: To permit correction of variation regardless of no-load cell voltage, by calculating the capacitance of combined batteries to correct variation when the combined batteries are in a capacitance calculable region at start of charging, charging the combined batteries in a region where the capacitance cannot be calculated until they are returned to the capacitance calculable region, and then correcting variation. SOLUTION: A cell battery controller 3 is connected with a battery controller 5 for charging, and the control terminal D on the cell battery controller is connected with the base of a transistor 22 between the cell battery controller and an adjustment circuit 2 for capacitance adjustment. The no-load terminal voltages of cell batteries a are detected. If the average no-load voltage is not less than a reference voltage, the capacitance can be calculated from terminal voltages, and the capacitance of cell batteries of large capacitance is adjusted to a virtual target voltage. If the average no-load voltage is less than the reference voltage, charging is started. When the reference voltage is reached, charging is stopped and the capacitance is adjusted. Thus the capacitance can be adjusted regardless of the terminal voltage at start of charging, and charging can be performed without damage to combined batteries.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a battery pack charging apparatus capable of correcting variations when charging a battery pack regardless of the voltage of a cell battery.

[0002]

2. Description of the Related Art When charging a battery pack, it is necessary to adjust the capacity according to the variation of each cell battery. For example, an apparatus as shown in FIG. 8 is used as a variation correction apparatus for adjusting the capacity. An adjustment circuit 2 composed of a resistor 21 and a transistor 22 forming a switching circuit is connected to both terminals of each cell battery a constituting the assembled battery.
The cell battery controller 30 detects the terminal voltage at the time of no load from both terminals of the cell battery, and determines the variation by comparing with the average voltage of the cell battery. For a cell battery higher than the average voltage, the transistor 22 in the adjustment circuit 2 is turned on,
Control is performed to discharge at a capacity corresponding to the deviation from the average voltage. As a result, the capacity of the cell battery having the average voltage or more is adjusted, and even if the battery is charged based on the average voltage, the battery can be charged without overcharging and without damaging the assembled battery.

[0003]

However, the above capacity adjustment is performed based on the no-load open voltage of each cell battery at the start of charging, and the capacity and the open voltage need to be in a proportional relationship. . For lithium ion batteries,
Although the relationship between the capacitance and the open-circuit voltage is proportional, as shown in FIG. 9, the proportional relationship changes with the change in the open-circuit voltage.
That is, if the open-circuit voltage is equal to or higher than the predetermined lower limit, the capacity and the open-circuit voltage are in a linear relationship.
The relationship between capacitance and open circuit voltage becomes complicated. Therefore, when the battery pack is a lithium-ion battery, if the terminal voltage at the start of charging is less than the lower limit of calculation, the discharge capacity cannot be easily calculated, and there has been a problem that the variation correction cannot be performed accurately. The present invention has been made in view of the above problems, and provides a battery charger for an assembled battery capable of accurately correcting variation regardless of the terminal voltage at the start of charging even in the case of a proportional relationship in which the terminal voltage and the capacity change. The goal is.

[0004]

Therefore, the present invention has a charging means for charging an assembled battery with a predetermined current, a voltage detecting means for detecting a terminal voltage of a cell battery of the assembled battery, Average voltage calculating means for calculating an average voltage of the battery;
A voltage comparing unit that compares the calculated average voltage with a predetermined reference voltage; and an adjusting unit that performs capacity adjustment by discharging the cell battery. By detecting the no-load terminal voltage and comparing the average no-load voltage of the cell battery calculated by the average voltage calculating means with a predetermined reference voltage, the terminal voltage of the cell battery becomes an area where the battery capacity can be calculated. In the area where the capacity can be calculated, the cell battery whose deviation is large in the positive direction with respect to the average no-load voltage is discharged by the adjusting means with a capacity corresponding to the deviation. In a battery charger for performing correction, a power calculating means for calculating output power from the capacity of the battery pack, and an internal resistance of the battery pack based on a calculated value of the power calculating means. An internal resistance calculating means, a voltage estimating means for calculating a voltage drop in the internal resistance at the time of charging based on a charging current and an internal resistance of the charging means, and estimating a terminal voltage of the cell battery at no load; An estimated voltage comparing means for comparing the terminal voltage estimated by the above with the reference voltage is provided, and a comparison between the average no-load voltage of the cell battery calculated by the average voltage calculating means and a predetermined reference voltage,
When it is determined that the terminal voltage of the cell battery is in a region where the battery capacity cannot be calculated, the charging by the charging unit is started, and the no-load terminal voltage estimated by the voltage estimating unit is compared with the reference voltage. When it is determined that the battery capacity can be calculated from the battery terminal voltage, charging is stopped, and the voltage detecting means detects the no-load terminal voltage of the cell battery, and calculates the calculated no-load average voltage of the cell battery. And a variation correction based on the deviation of the cell battery.

The power calculating means calculates the output power of the battery pack using a power table for storing initial value data, and corrects the calculated power value using a deterioration coefficient indicating a decrease in capacity of the battery pack. It is possible. A temperature sensor is provided in the battery pack, and the power calculation means can correct the calculated outputable power calculation value with a detected temperature value. It is preferable that the adjusting means adjusts the capacity with a value obtained by correcting the discharge capacity corresponding to the deviation between the average no-load voltage and the cell battery with the deterioration coefficient of the battery pack and the battery temperature.

A plurality of the predetermined reference voltages may be set, and the reference voltage may be increased each time the cell battery is discharged to perform the variation correction, thereby performing the variation correction a plurality of times.

[0007] The battery charger for charging the battery pack is used for charging the battery pack loaded in the hybrid vehicle, and while the hybrid vehicle is stopped, the average no-load voltage of the battery and a predetermined value are adjusted so as to perform variation correction. Is compared with the reference voltage, and correction can be performed in a region where variation can be corrected.

[0008]

In the case where the average no-load voltage of the cell battery at the start of charging is lower than a predetermined reference voltage and the battery capacity cannot be calculated from the terminal voltage of the cell battery, charging by the charging means is first started. As the charging progresses, the capacity is restored. The power calculating means calculates the output power from the capacity of the battery pack, and calculates the internal resistance of the battery pack based on the output power. Thus, the voltage drop in the internal resistance during charging is calculated, and the terminal voltage at no load is estimated. By comparing the estimated no-load terminal voltage with the reference voltage, it can be determined whether or not the cell battery has been restored to a region where the terminal voltage and the capacity have a linear relationship. As a result, the capacitance can be adjusted based on the terminal voltage, and an effect that variation correction can be performed regardless of the terminal voltage can be obtained.

When a plurality of the predetermined reference voltages are set, and the reference voltage is increased each time the variation is corrected by discharging the cell battery, the variation correction is performed a plurality of times. The variation is also corrected each time, and an effect is obtained in which the variation can be corrected with high accuracy.

When the battery charger is used for charging a battery pack loaded in a hybrid vehicle, the average no-load voltage of the battery is compared with a predetermined reference voltage while the hybrid vehicle is stopped. If the correction is performed in a region where the variation can be corrected, the assembled battery can be charged when the hybrid vehicle is started.

[0011]

Embodiments of the present invention will be described below with reference to examples. FIG. 1 is a diagram showing a configuration of an embodiment of the present invention. A module battery 1 having n cell batteries a is m
By connecting them in series, an assembled battery is composed of a total of m × n cell batteries. The cell battery is a lithium ion battery, and an adjusting circuit 2 as adjusting means for adjusting the capacity is connected to both terminals of each cell battery. The adjusting circuit 2 includes a discharging resistor 21.
And a transistor 22 forming a switching circuit.

Both terminals of each cell battery are further connected to the E and F terminals of the cell battery controller 3. The cell battery controller 3 is connected to communicate with a battery controller 5 for charging, and a control terminal D is connected to the base of the transistor 22 between itself and the adjustment circuit 2. In FIG. 1, only one adjustment circuit 2 is typically shown, and the connection between the cell battery controller and an adjustment circuit (not shown) is simply indicated by an arrow. A temperature sensor 4 is attached to the assembled battery, and the temperature information of the assembled battery is transmitted to the cell battery controller 3.
Output. Battery controller 5
Has a charging unit as a charging means, and manages a lot of information related to the assembled battery such as charge / discharge information of the assembled battery.

FIG. 2 is a functional block diagram showing the functions of the cell battery controller 3 and the battery controller 5.
The transmission / reception unit 32 and the transmission / reception unit 51 transmit and receive information between the cell battery controller 3 and the battery controller 5 under the control of the control unit 35 and the control unit 52, respectively. In the cell battery controller 3, the voltage detector 31 and the temperature sensor 4 detect the terminal voltage of each cell battery and the temperature of the battery pack, and these information are transmitted from the transceiver 32 to the battery controller 5.

The comparing section 33 compares the average no-load voltage of the cell battery sent from the battery controller 5 with a reference voltage. The reference voltage is set in accordance with the lower end of the linear portion of the capacity and terminal voltage of the lithium ion battery, and the lower limit of the calculation of the adjustment capacity. When the average no-load voltage is higher than the reference voltage in the comparison by the comparison unit 33, the correction unit 34 determines whether the cell battery having a large deviation in the positive direction with respect to the average no-load voltage has a predetermined current Ic.
And outputs an ON signal to the adjustment circuit of each cell battery so as to discharge. The timer 36 is set simultaneously with the output of the ON signal. The compensator 34 counts the timer time Ttm, sets a timing to discharge the cell battery with a capacity corresponding to the magnitude of the deviation, outputs an off signal, and turns off the adjustment circuit. The control unit 35 outputs the charging start signal to the battery controller 5 when the OFF signal is output from the correction unit 34 or the average no-load voltage is lower than the reference voltage in the comparison in the comparison unit 33.
Send to

On the battery controller 5 side, the no-load terminal voltage of the cell battery is received from the cell battery controller 3 and the average voltage calculating section 50 calculates the no-load average voltage.
When the charging start signal is sent, charging by the charging unit 53 is started. The power calculator 54 calculates the power that can be output by drawing a power table based on the relationship between the capacity and the power of the battery pack. The no-load voltage estimation unit 55 calculates the internal resistance of the battery pack based on the output power, calculates the increase in the terminal voltage due to the charging current, and calculates the average cell battery terminal voltage in the no-load state. Is estimated. The estimated value is further compared with a reference voltage by the control unit 52. If the voltage is higher than the reference voltage, the control unit 52 stops charging by the charging unit 53.

FIG. 3 is a flowchart showing the flow of operation in the above configuration. When charging is started, first, the cell battery controller 3 is started. The flowchart is executed with the battery controller 5 in a standby state. In step 101, the timer 36 is cleared, and the timer time Ttm becomes 0. In step 102, the no-load terminal voltage Vceln (n is the cell battery number in the module, which is used in the same manner in the following description) of each cell battery for each module is detected by the voltage detection unit 31, and the battery controller 5 is sent.

In step 103, the average voltage calculator 50 of the battery controller 5 calculates the sum of the terminal voltages of each cell battery, that is, the terminal voltage of the assembled battery, by the number of cell batteries (m ×
The average value VM of the no-load voltage is calculated by dividing by n) and transmitted to the cell battery controller 3. In step 104, the average value VM is compared with the reference voltage (the lower limit value of the operation) by the comparator 33.
VL. If VM ≧ VL, the process proceeds to step 105 because the variation correction can be performed. If VM <VL, the process proceeds to step 113 to perform charging.

In step 105, the correction unit 34 calculates the voltage deviation VDn (= Vcelln-VT) from the cell battery by using the average value VM as the virtual target voltage VT. In step 106, the adjustment capacity Cceln is obtained by interpolation calculation of the adjustment capacity table according to the magnitude of VDn so as to discharge the cell battery whose deviation is large in the positive direction.

In step 107, the correction section 34 outputs an ON signal for each cell battery having a deviation in the positive direction to turn on the respective adjustment circuits 2. Thereby, the cell battery is discharged with the adjustment current Ic. The timer 36 is set in synchronization with the output of the ON signal. In step 108, the correction unit 34 counts the timer time Ttm set for each cell battery, and calculates the remaining discharge amount Cc (Cceln-T
tm × Ic).

At step 109, it is checked whether or not the discharge remaining amount Cc of the cell battery has become zero. The cell battery having the remaining discharge amount of 0 is turned off by outputting an off signal to the adjustment circuit in step 110. In step 111, it is checked whether or not the adjustment circuits of all the cell batteries have been turned off. When the discharging is completed, the control unit 35 sends a charging signal to the battery controller 5, and charging is started in step 112.

FIG. 4 is a diagram showing changes in the average voltage VM during the charging process. Until the time t1, the no-load voltage is detected and the capacitance is adjusted, so that the terminal voltage does not increase. After the time t1, due to charging, the average voltage VM increases while showing a relationship with the capacity, reflecting the characteristics of the lithium ion battery. By the above processing, the capacity of the cell battery having a large capacity at the start of charging is adjusted to the virtual target voltage VL.

If it is determined in step 104 that the average voltage VM of the no-load voltage is lower than VL, step 11
At 3, the control unit 35 sends a charge signal to the battery controller 5, and in the battery controller 5, the charging unit 53 charges the assembled battery. In step 114, the power calculator 54 interpolates the power table storing data corresponding to the output power Pmax (the maximum output that the battery can output at that time) and the battery capacity shown in FIG. 5 from the battery capacity Cwh. An operation is performed to obtain Pmax.

In step 115, a deterioration correction coefficient Kr due to discharge is obtained, and the battery temperature Tmo detected by the temperature sensor 4 in communication with the cell battery controller 3 is determined.
d is requested, and the temperature coefficient table is interpolated to obtain the temperature coefficient Ktmod. In step 116, the output power Pmax is corrected based on equation (1) using the deterioration correction coefficient Kr and the temperature coefficient Ktmod. Pmax = (Pmax / Kr) / Ktmod) (1)

In step 117, the no-load voltage estimating unit 55 obtains the internal resistance R at that time by dividing Pmax calculated by the power calculating unit 54 by the charging current Ic. In step 118, a total voltage increase VUP of the battery pack due to charging given by Ic × R is obtained.

In step 119, the cell battery controller 3 is caused to transmit the terminal voltage of the cell detected by the voltage detector 31, and the total voltage Vtot (total voltage during charging) is subtracted from the total voltage Vtot to obtain the cell voltage increase VUP. The average estimated voltage VD of the cell voltage is calculated by dividing by the total number of batteries. In step 120, it is checked whether the average estimated voltage VD has become equal to or higher than the reference voltage VL. If not, the process returns to step 114, and the above calculation is newly performed. When it is determined that the average estimated voltage VD is higher than the reference voltage VL, the charging is stopped by the control of the control unit 52 in step 121, and the process returns to step 102. After that, the capacity is adjusted in the same manner as described above, and when the battery is adjusted to the virtual target voltage VT, the battery pack is charged again.

FIG. 6 is a diagram showing a change in the average voltage VM when the no-load voltage at the start of charging is lower than the reference voltage.
At time 0 to t1, a no-load voltage is detected. There is no voltage rise in this region. From t1 to t2, the capacity is recovered by charging, and the terminal voltage rises to a point where the voltage rise VUP due to charging is added from the reference voltage VL. t2-t
In No. 3, the non-negative voltage is detected and the capacity is adjusted, and the no-load terminal voltage falls from the time of charging and almost matches the reference voltage. From t3, charging is started, and the voltage increases while indicating the relationship between the capacity and the voltage.

This embodiment is configured as described above. When charging the assembled battery, the no-load terminal voltage of the cell battery is detected, and when the average no-load voltage VM is determined to be equal to or higher than the reference voltage, the terminal voltage is determined. The capacity of the cell battery having a large capacity can be adjusted to the virtual target voltage by the relation between the terminal voltage and the capacity. Also, when the average no-load voltage is determined to be equal to or lower than the reference voltage, charging is started, and when the no-load terminal voltage of the cell battery reaches the reference voltage, charging is stopped and capacity adjustment is performed. Even for a lithium ion battery having a non-linear capacity and terminal voltage, the capacity can be adjusted regardless of the terminal voltage at the start of charging, and the battery can be charged without damaging the assembled battery. Further, since the capacity recovery by charging is performed in accordance with the lower limit of the calculation of the terminal voltage, the adjustment is performed from the lowest possible voltage, so that the adjustment time becomes longer and the adjustment can be performed even when the variation is large.

In the above description, a method has been described in which one reference voltage is set, capacity is adjusted, and then charging is performed.
In addition, as shown in FIG. 7, the reference voltages are VL1, VL
A plurality of values such as 2, VL3, and VL4 can be set. When the terminal voltage due to charging becomes VL1, the capacity is adjusted and charging is started. Next, the reference voltage VL2 is applied, and when the estimated no-load terminal voltage reaches it,
The capacity adjustment is performed a plurality of times to perform the capacity adjustment again.
In this case, variations appearing at the time of charging and insufficient correction are corrected each time, so that more accurate correction can be performed.

The capacity discharged by the adjustment circuit is also Pma
Similarly to the case where x is corrected, the reciprocal of the value obtained by multiplying the deterioration coefficient and the temperature coefficient is set as the capacity adjustment gain Kg, and K is set as the adjustment capacity Cc.
It can also be corrected by multiplying by g. Further, when the present invention is applied to a hybrid vehicle, it is determined whether or not the battery pack is in a voltage region where the adjusted capacity can be calculated when the vehicle is stopped, and if possible, the capacity is adjusted and the vehicle is started. It is also possible to bring the battery into a chargeable state at the point of time.

Step 102 constitutes voltage means. Step 103 constitutes an average voltage calculating means. Step 104 constitutes voltage comparison means. Step 114 constitutes power calculation means. Step 117 constitutes an internal resistance calculating means. Step 119 constitutes voltage estimating means. Step 120
Constitutes an estimated voltage comparing means.

[0031]

As described above, according to the present invention, at the start of charging, in a range where the capacity of the battery pack can be calculated, the capacity is calculated and the variation is corrected. In the area where capacity calculation is not possible,
Since the variation is corrected after the capacity is restored to a range where the capacity can be calculated by charging, an effect is obtained that the variation can be corrected regardless of the no-load cell voltage.

If a plurality of the predetermined reference voltages are set, and the reference voltage is increased each time the variation is corrected by discharging the cell battery, the variation is corrected a plurality of times. The variation is also corrected each time, and an effect is obtained in which the variation can be corrected with high accuracy.

When the battery charger is used for charging a battery pack loaded in a hybrid vehicle, the average no-load voltage of the battery is compared with a predetermined reference voltage while the hybrid vehicle is stopped. If the correction is performed in an area where the variation can be corrected, the assembled battery can be charged when the hybrid vehicle is started.

[Brief description of the drawings]

FIG. 1 is a diagram showing an entire configuration of an embodiment.

FIG. 2 is a functional block diagram showing the functions of a cell battery controller 3 and a battery controller 5;

FIG. 3 is a flowchart showing a flow of operation of the embodiment.

FIG. 4 is a diagram showing a change in an average voltage VM during a charging process.

FIG. 5 is a table of a battery capacity Cwh and output power Pmax.

FIG. 6 is a diagram showing a change in average voltage VM when a no-load voltage at the start of charging is lower than a reference voltage.

FIG. 7 is a diagram illustrating a change in terminal voltage of a cell battery when performing a capacity adjustment calculation and adjustment a plurality of times.

FIG. 8 is a diagram showing a configuration of a conventional example.

FIG. 9 is a diagram showing characteristics of a lithium ion battery.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 module 2 adjustment circuit 3, 30 cell battery controller 4 temperature sensor 5 battery controller 21 resistor 22 transistor 31 voltage detection unit 32 transmission / reception unit 33 comparison unit 34 correction unit 35 control unit 36 timer 50 average voltage calculation unit 51 transmission / reception unit 52 control unit 53 charging unit 54 power calculation unit 55 no-load voltage estimation unit a cell battery E, F, D terminals

Claims (6)

[Claims] A voltage detecting means for detecting a terminal voltage of a cell battery of the battery pack; and an average voltage calculating means for calculating an average voltage of the cell battery. And, comprising a voltage comparison means for comparing the calculated average voltage with a predetermined reference voltage and an adjustment means for discharging the cell battery and adjusting the capacity, when starting charging,
The voltage detecting means detects a no-load terminal voltage of each cell battery, and compares the average no-load voltage of the cell battery calculated by the average voltage calculating means with a predetermined reference voltage, thereby obtaining a terminal of the cell battery. It is determined whether the voltage is in an area where the battery capacity can be calculated, and in the area where the capacity can be calculated,
In the battery charger for performing variation correction by discharging the cell battery having a large deviation in the positive direction with respect to the average no-load voltage by the adjusting means with a capacity corresponding to the deviation, the capacity of the assembled battery is Power calculating means for calculating the power that can be output from the battery, internal resistance calculating means for calculating the internal resistance of the battery pack based on the calculated value of the power calculating means, and charging with the charging current and the internal resistance of the charging means. A voltage estimating means for calculating the voltage drop in the internal resistance at times, and estimating a terminal voltage of the cell battery at no load, and an estimated voltage comparing means for comparing the terminal voltage estimated by the voltage estimating means with the reference voltage. A comparison between the average no-load voltage of the cell battery calculated by the average voltage calculation means and a predetermined reference voltage indicates that the terminal voltage of the cell battery cannot calculate the battery capacity. When it is determined that the charging by the charging means is started, the no-load terminal voltage estimated by the voltage estimating means is a region where the battery capacity can be calculated from the terminal voltage of the cell battery in comparison with the reference voltage. When the determination is made, the charging is stopped, the voltage detecting means detects the no-load terminal voltage of the cell battery, and performs variation correction based on the calculated deviation of the no-load average voltage of the cell battery and the cell battery. A battery charger for an assembled battery. 2. The power calculation means calculates a power that can be output from the battery pack using a power table that stores initial value data, and calculates a power calculation value using a deterioration coefficient indicating a decrease in capacity of the battery pack. The charging device for an assembled battery according to claim 1, wherein the charging device is modified. 3. The battery pack according to claim 2, wherein a temperature sensor is provided in the battery pack, and the power calculating means corrects the calculated output power value calculated by the detected temperature value. Charging device. 4. The method according to claim 1, wherein the adjusting means adjusts a capacity obtained by correcting a discharge capacity corresponding to a deviation between the average no-load voltage and a cell battery with a deterioration coefficient and a battery temperature of the assembled battery. The charging device for a battery pack according to claim 1. 5. The method according to claim 1, wherein a plurality of the predetermined reference voltages are set, and the reference voltage is increased each time the cell battery is discharged to perform the variation correction, and the variation correction is performed a plurality of times. The battery charger of the above-described battery pack. 6. The battery pack charging device is used for charging a battery pack loaded in a hybrid vehicle, and performs an average no-load of the battery so as to perform variation correction while the hybrid vehicle is stopped. 2. The battery charger according to claim 1, wherein the voltage is compared with a predetermined reference voltage, and correction is performed in a region where variation can be corrected.