JP3663886B2 - Battery charger - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an assembled battery charging apparatus capable of correcting variation regardless of the voltage of a cell battery when charging the assembled battery.
[0002]
[Prior art]
When charging the battery pack, it is necessary to adjust the capacity according to the variation of each cell battery. For example, a device as shown in FIG. 8 is used as a variation correcting device for adjusting the capacity.
An adjustment circuit 2 including 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 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 having a voltage higher than the average voltage, the transistor 22 in the adjustment circuit 2 is turned on and controlled to discharge with a capacity corresponding to the deviation from the average voltage. As a result, the capacity of the cell battery having the average voltage or higher is adjusted, and even if charging based on the average voltage is performed, it is possible to charge the battery without damaging the assembled battery without overcharging.
[0003]
[Problems to be solved by the invention]
However, the 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. In the case of a lithium ion battery, the relationship between the capacity and the open-circuit voltage is proportional, but as shown in FIG. 9, the proportional relationship changes as the open-circuit voltage changes. That is, if the open circuit voltage is equal to or higher than the predetermined calculation lower limit value, the capacity and the open circuit voltage have a linear relationship, but if the open circuit voltage is lower than the calculation lower limit value, the relationship between the capacity and the open circuit voltage becomes complicated. Therefore, in the case where the assembled battery is a lithium ion battery, if the terminal voltage at the start of charging is equal to or lower than the calculation lower limit value, the discharge capacity cannot be calculated easily, and there is a problem that variation correction cannot be performed accurately.
In view of the above problems, the present invention provides an assembled battery charging device capable of accurately correcting variation regardless of the terminal voltage at the start of charging even in a proportional relationship in which the terminal voltage and the capacity change. The goal is.
[0004]
[Means for Solving the Problems]
For this reason, the present invention has charging means for charging the assembled battery with a predetermined current,
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 cell battery;
Voltage comparison means for comparing the calculated average voltage with a predetermined reference voltage, and adjustment means for adjusting the capacity by discharging the cell battery,
When starting charging, the voltage detecting means detects the 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. It is determined whether the terminal voltage of the cell battery is in 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 In an assembled battery charging device that performs variation correction by discharging by the adjusting means with a capacity corresponding to a deviation, power computing means for computing power that can be output from the capacity of the assembled battery;
Internal resistance calculating means for calculating the internal resistance of the assembled battery based on the calculated value of the power calculating means;
With the charging current and internal resistance of the charging means, a voltage estimation means for calculating a voltage drop in the internal resistance at the time of charging, and estimating a terminal voltage at the time of no load of the cell battery,
Estimated voltage comparison means for comparing the terminal voltage estimated by the voltage estimation means and the reference voltage,
When the average no-load voltage of the cell battery calculated by the average voltage calculating means and a predetermined reference voltage are compared, and it is determined that the terminal voltage of the cell battery is an area where the battery capacity cannot be calculated, the charging by the charging means When the no-load terminal voltage estimated by the voltage estimation means is determined to be a region where the battery capacity can be calculated from the terminal voltage of the cell battery in comparison with the reference voltage, charging is stopped, The voltage detection means detects the no-load terminal voltage of the cell battery, and performs variation correction based on the calculated no-load average voltage of the cell battery and the deviation of the cell battery.
[0005]
The power calculation means can calculate the power that can be output from the assembled battery using a power table that stores initial value data, and can correct the calculated power value using a deterioration coefficient that indicates a decrease in the capacity of the assembled battery. It is.
A temperature sensor is installed in the assembled battery, and the power calculation means can correct the calculated power output value that can be output with the detected temperature value.
The adjusting means preferably 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 assembled battery and the battery temperature.
[0006]
It is possible to set a plurality of the predetermined reference voltages, increase the reference voltage each time the cell battery is discharged and perform the variation correction, and perform the variation correction a plurality of times.
[0007]
The battery pack charging device is used for charging a battery pack loaded in a hybrid vehicle, and the battery has an average no-load voltage and a predetermined reference voltage so that variation correction is performed while the hybrid vehicle is stopped. In the region where variation correction is possible, correction can be performed.
[0008]
[Action]
When 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 started first. The capacity is restored as the charging progresses. The power calculation means calculates the power that can be output from the capacity of the assembled battery, and calculates the internal resistance of the battery pack based on the output power. As a result, the voltage drop in the internal resistance is calculated during charging, and the terminal voltage at no load is estimated. By comparing the no-load estimated terminal voltage and the reference voltage, it can be determined whether or not the cell battery has recovered its capacity in 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 can be obtained in which variation correction can be performed regardless of the terminal voltage.
[0009]
If a plurality of the predetermined reference voltages are set, the cell voltage is discharged and the variation correction is performed every time the variation correction is performed, and the variation correction is performed a plurality of times, the variation that appears when the correction is insufficient or the charging progresses. It is corrected each time, and an effect that the variation can be corrected with high accuracy can be obtained.
[0010]
When the assembled battery charging device is used for charging an assembled battery 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 correction is performed in the area where correction is possible, the assembled battery can be charged when the hybrid vehicle is started.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the invention will be described by way of examples.
FIG. 1 is a diagram showing a configuration of an embodiment of the present invention. m module batteries 1 having n cell batteries a are connected in series, and an assembled battery is constituted by a total of m × n cell batteries. The cell battery is a lithium ion battery, and an adjustment circuit 2 as an adjustment means for adjusting the capacity is connected to both terminals of each cell battery. The adjustment circuit 2 includes a discharge resistor 21 and a transistor 22 forming a switching circuit.
[0012]
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 so as to communicate with the battery controller 5 that performs charging, and the control terminal D is connected to the base of the transistor 22 between the adjustment circuit 2.
In FIG. 1, only one adjustment circuit 2 is representatively 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 temperature information of the assembled battery is output to the cell battery controller 3.
The battery controller 5 has a charging unit as a charging means, and manages many pieces of information related to the assembled battery such as charging / discharging information of the assembled battery.
[0013]
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.
In the cell battery controller 3, the voltage detection unit 31 and the temperature sensor 4 detect the terminal voltage of each cell battery and the temperature of the assembled battery, and the information is transmitted from the transmission / reception unit 32 to the battery controller 5.
[0014]
The comparison unit 33 compares the average no-load voltage of the cell battery sent from the battery controller 5 with the reference voltage. The reference voltage is set according to the lower limit of the linear portion of the capacity of the lithium ion battery and the terminal voltage, and the calculation lower limit value of the adjustment capacity. When the average no-load voltage is higher than the reference voltage in the comparison in the comparison unit 33, the correction unit 34 discharges each cell battery having a large deviation in the positive direction with respect to the average no-load voltage with a predetermined current Ic. An ON signal is output to the adjustment circuit of the cell battery. The timer 36 is set simultaneously with the output of the on signal. The correction unit 34 counts the timer time Ttm to time the cell battery to be discharged with a capacity corresponding to the magnitude of the deviation, and outputs an off signal to turn off the adjustment circuit. 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 by the comparison unit 33, the control unit 35 transmits a charge start signal to the battery controller 5.
[0015]
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 calculation unit 50 calculates the no-load average voltage. When the charging start signal is sent, charging by the charging unit 53 is started. The power calculation unit 54 calculates the power that can be output by drawing a power table based on the relationship between the capacity and power of the assembled battery. Based on the power that can be output, the no-load voltage estimation unit 55 calculates the internal resistance of the assembled battery, 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. When the voltage is higher than the reference voltage, the control unit 52 stops charging by the charging unit 53.
[0016]
FIG. 3 is a flowchart showing the flow of operation in the above configuration.
When starting charging, the cell battery controller 3 is first activated. The battery controller 5 enters a standby state and the flowchart is executed.
In step 101, the timer 36 is cleared and the timer time Ttm becomes zero.
In step 102, the no-load terminal voltage Vceln of each cell battery for each module (n is a cell battery number in the module, which is used in the same meaning in the following description) is detected by the voltage detection unit 31, and the battery controller 5 is transmitted.
[0017]
In step 103, the average voltage calculation unit 50 of the battery controller 5 calculates the average value VM of the no-load voltage by dividing 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 × n). And transmitted to the cell battery controller 3.
In step 104, the average value VM is compared with the reference voltage (calculation lower limit value) VL by the comparison unit 33. If VM ≧ VL, variation correction can be performed, and the process proceeds to step 105. If VM <VL, the process proceeds to step 113 to charge.
[0018]
In step 105, the correction unit 34 sets the average value VM as the virtual target voltage VT, and calculates a voltage deviation VDn (= Vceln−VT) from the cell battery.
In step 106, the adjustment capacity Cceln is obtained by interpolation calculation of the adjustment capacity table in accordance with the magnitude of VDn so as to discharge the cell battery whose deviation is large in the positive direction.
[0019]
In step 107, the correction unit 34 outputs an ON signal for each cell battery having a deviation in the positive direction to turn on each adjustment circuit 2. As a result, 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 monitors the remaining discharge amount Cc (Cceln−Ttm × Ic).
[0020]
In step 109, it is checked whether or not the remaining discharge capacity Cc of the cell battery has become zero. For the cell battery whose remaining discharge amount is 0, an off signal is output to the adjustment circuit in step 110 to turn it off.
In step 111, it is checked whether the adjustment circuits of all the cell batteries are turned off. When the discharge is completed, the control unit 35 sends a charge signal to the battery controller 5, and charging is started in step 112.
[0021]
FIG. 4 is a diagram illustrating changes in the average voltage VM during the charging process. Until the time t1, no-load voltage is detected and capacity adjustment is performed, so that the terminal voltage does not increase. After t1, after charging, the average voltage VM rises while showing the relationship with the capacity, reflecting the characteristics of the lithium ion battery.
Through the above process, the capacity of the cell battery having a large capacity at the start of charging is adjusted to the virtual target voltage VL.
[0022]
When it is determined in step 104 that the average voltage VM of the no-load voltage is less than VL, in step 113, the control unit 35 sends a charge signal to the battery controller 5, and in the battery controller 5, the charging unit 53 becomes an assembled battery. Charge the battery.
In step 114, the power calculation unit 54 interpolates a power table storing data corresponding to the battery capacity corresponding to the power Pmax (the maximum output that the battery can output at that time) shown in FIG. 5 from the battery capacity Cwh. Calculate Pmax.
[0023]
In step 115, the deterioration correction coefficient Kr due to discharge is obtained, the battery temperature Tmod detected by the temperature sensor 4 through communication with the cell battery controller 3 is requested, and the temperature coefficient Ktmod is obtained by interpolating the temperature coefficient table.
In step 116, the output power Pmax is corrected based on the equation (1) using the deterioration correction coefficient Kr and the temperature coefficient Ktmod.
Pmax = (Pmax / Kr) / Ktmod) (1)
[0024]
In step 117, the no-load voltage estimation unit 55 obtains the internal resistance R at that time by dividing Pmax calculated by the power calculation unit 54 by the charging current Ic.
In step 118, the total voltage increase VUP of the assembled battery due to charging given by Ic × R is obtained.
[0025]
In step 119, the cell battery controller 3 is caused to transmit the terminal voltage of the cell detected by the voltage detection unit 31, and the total voltage increase VUP due to charging is subtracted from the total voltage Vtot (total voltage during charging). The average estimated voltage VD of the cell voltage is calculated.
In step 120, it is checked whether the average estimated voltage VD is equal to or higher than the reference voltage VL. If not, the process returns to step 114 and the above calculation is newly performed. If it is determined that the average estimated voltage VD is greater than the reference voltage VL, charging is stopped under the control of the control unit 52 in step 121 and the process returns to step 102. Thereafter, the capacity is adjusted in the same manner as described above, and when the virtual target voltage VT is adjusted, the assembled battery is charged again.
[0026]
FIG. 6 is a diagram illustrating a change in the average voltage VM when the no-load voltage at the start of charging is lower than the reference voltage. A no-load voltage is detected from time 0 to t1. There is no voltage rise in this region. From t1 to t2, the capacity is recovered by charging, and the terminal voltage increases from the reference voltage VL to the point where the voltage increase VUP due to charging is added. From t2 to t3, the no-negative voltage is detected and the capacity is adjusted, and the no-load terminal voltage decreases from the time of charging and substantially matches the reference voltage. From t3, charging is started, and the voltage rises while showing the relationship between the capacity and the voltage.
[0027]
The present 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 capacity calculation is performed from the terminal voltage. The cell battery having a large capacity is adjusted to the virtual target voltage based on the relationship between the terminal voltage and the capacity. In addition, when it is determined that the average no-load voltage is equal to or lower than the reference voltage, charging is started, and when the reference voltage is reached by estimating the no-load terminal voltage of the cell battery, charging is stopped and capacity adjustment is performed. Even if the capacity and terminal voltage of the lithium ion battery are not linear, the capacity can be adjusted regardless of the terminal voltage at the start of charging, and charging can be performed without damaging the assembled battery.
Further, since the capacity recovery by charging is performed in accordance with the calculation lower limit value of the terminal voltage, the adjustment is performed from the lowest possible voltage, the adjustment time becomes long, and the adjustment can be performed even when the variation is large.
[0028]
In the above description, a method is shown in which one reference voltage is set, capacity adjustment is performed, and then charging is performed. In addition to this, reference voltages are set as VL1, VL2, VL3, and VL4 as shown in FIG. Multiple settings can be made. When the terminal voltage due to charging becomes VL1, capacity adjustment is performed 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 so that the capacity adjustment is performed again. In this case, variations and insufficient correction appearing at the time of charging are corrected each time, and correction with higher accuracy becomes possible.
[0029]
As in the case where Pmax is corrected, the capacity discharged by the adjustment circuit can also be corrected by multiplying the adjustment capacity Cc by Kg, with the inverse of the value obtained by multiplying the deterioration coefficient and the temperature coefficient being Kg.
Further, when the present invention is used for a hybrid vehicle, it is determined whether the assembled battery is in a voltage region where the adjustment 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 make it possible to charge the battery at that time.
[0030]
Step 102 constitutes voltage means.
Step 103 constitutes an average voltage calculation means.
Step 104 constitutes voltage comparison means.
Step 114 constitutes a power calculation means.
Step 117 constitutes internal resistance calculation means.
Step 119 constitutes voltage estimation means.
Step 120 constitutes an estimated voltage comparison means.
[0031]
【The invention's effect】
As described above, according to the present invention, at the start of charging, in a region where the assembled battery can calculate the capacity, the capacity is calculated and the variation correction is performed. In a region where capacity calculation cannot be performed, variation correction is performed after the capacity is restored to a region where capacity calculation can be performed by charging, so that an effect that variation correction is possible regardless of the no-load cell voltage is obtained.
[0032]
If a plurality of the predetermined reference voltages are set, the cell voltage is discharged and the variation correction is performed every time the variation correction is performed, and the variation correction is performed a plurality of times, the variation that appears when the correction is insufficient or the charging progresses. It is corrected each time, and an effect that the variation can be corrected with high accuracy can be obtained.
[0033]
When the assembled battery charging device is used for charging an assembled battery 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 correction is performed in the area where correction is possible, the assembled battery can be charged when the hybrid vehicle is started.
[Brief description of the drawings]
FIG. 1 is a diagram showing an overall configuration of an embodiment.
FIG. 2 is a diagram showing the functions of the cell battery controller 3 and the battery controller 5 in function blocks.
FIG. 3 is a flowchart showing a flow of operation of the embodiment.
FIG. 4 is a diagram showing a change in average voltage VM in a charging process.
FIG. 5 is a table of battery capacity Cwh and output power Pmax.
FIG. 6 is a diagram showing a change in average voltage VM when the no-load voltage at the start of charging is lower than the reference voltage.
FIG. 7 is a diagram showing a change in the terminal voltage of the cell battery when performing 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]
DESCRIPTION OF SYMBOLS 1 Module 2 Adjustment circuit 3, 30 Cell battery controller 4 Temperature sensor 5 Battery controller 21 Resistance 22 Transistor 31 Voltage detection part 32 Transmission / reception part 33 Comparison part 34 Correction part 35 Control part 36 Timer 50 Average voltage calculation part 51 Transmission / reception part 52 Control part 53 Charging unit 54 Power calculation unit 55 No-load voltage estimation unit a Cell battery E, F, D terminal

Claims (6)

Having charging means for charging the battery pack with a predetermined current;
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 cell battery;
Voltage comparison means for comparing the calculated average voltage with a predetermined reference voltage, and adjustment means for adjusting the capacity by discharging the cell battery,
When starting charging, the voltage detecting means detects the 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. It is determined whether the terminal voltage of the cell battery is in 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 In an assembled battery charging device that performs variation correction by discharging by the adjusting means with a capacity corresponding to a deviation, power computing means for computing power that can be output from the capacity of the assembled battery;
Internal resistance calculating means for calculating the internal resistance of the assembled battery based on the calculated value of the power calculating means;
With the charging current and internal resistance of the charging means, a voltage estimation means for calculating a voltage drop in the internal resistance at the time of charging, and estimating a terminal voltage at the time of no load of the cell battery,
Estimated voltage comparison means for comparing the terminal voltage estimated by the voltage estimation means and the reference voltage,
When the average no-load voltage of the cell battery calculated by the average voltage calculating means and a predetermined reference voltage are compared, and it is determined that the terminal voltage of the cell battery is an area where the battery capacity cannot be calculated, the charging by the charging means When the no-load terminal voltage estimated by the voltage estimation means is determined to be a region where the battery capacity can be calculated from the terminal voltage of the cell battery in comparison with the reference voltage, charging is stopped, An assembled battery charging device, wherein the voltage detecting means detects a no-load terminal voltage of a cell battery and corrects variation based on the calculated no-load average voltage of the cell battery and the deviation of the cell battery. The power calculation means calculates a power that can be output from the assembled battery by using a power table that stores initial value data, and corrects the calculated power value by using a deterioration coefficient that indicates a decrease in the capacity of the assembled battery. The battery charger for an assembled battery according to claim 1. 3. The assembled battery charging device according to claim 2, wherein a temperature sensor is installed in the assembled battery, and the power calculation means corrects the calculated output power calculation value with a detected temperature value. 2. The adjustment unit according to claim 1, wherein the adjustment unit 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 by the deterioration coefficient of the assembled battery and the battery temperature. Battery charger. 2. The assembled battery according to claim 1, wherein a plurality of the predetermined reference voltages are set, the reference voltage is increased each time the variation correction is performed by discharging the cell battery, and the variation correction is performed a plurality of times. Charging device. The battery pack charging device is used for charging a battery pack loaded in a hybrid vehicle, and the battery is subjected to an average no-load voltage and a predetermined reference so that variation correction is performed while the hybrid vehicle is stopped. 2. The assembled battery charging device according to claim 1, wherein the voltage is compared and correction is performed in a region where variation correction is possible.

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