JP5454027B2 - Charge control device and charge control method - Google Patents

Description

    The present invention relates to a charge control device and a charge control method.

By taking into account the voltage drop due to the internal resistance of the secondary battery, a threshold voltage higher than the fully charged voltage of the secondary battery is set as a fixed value, and charging is performed until the voltage between the terminals of the secondary battery reaches the threshold voltage. A charging method for a secondary battery that shortens the charging time is known (Patent Document 1).

JP-A-6-325794

  However, when the internal resistance of the secondary battery is low, the open voltage of the secondary battery becomes higher than the full charge voltage, which may cause the secondary battery to be overcharged. There was a possibility that the time would be longer.

  Therefore, the present invention provides a charge control device that prevents excessive and insufficient charging of a secondary battery.

The present invention solves the above-described problem by setting a predetermined threshold voltage according to the charging time, comparing the voltage between the terminals of the secondary battery with the predetermined threshold voltage, and controlling the charging power.

According to the present invention, a predetermined threshold voltage is set according to the charging time, and the voltage between the terminals of the secondary battery is compared with the predetermined threshold voltage to control the charging power. The predetermined threshold voltage can be set according to the magnitude of the internal resistance, and as a result, excessive or insufficient charging of the secondary battery can be prevented.

1 is a block diagram of a high-power system including a charge control device according to an embodiment of the invention. It is a graph which shows the characteristic of the internal resistance with respect to the charging time of the assembled battery shown in FIG. It is a graph which shows the characteristic of the voltage with respect to the internal resistance of the assembled battery shown in FIG. It is a graph which shows the characteristic of the internal resistance with respect to the battery temperature of the assembled battery shown in FIG. It is a flowchart which shows the control procedure in the high electric power system shown in FIG. It is a block diagram of a high-power system including a charge control device according to another embodiment of the present invention. It is a graph which shows the characteristic of internal resistance with respect to the deterioration degree of the assembled battery shown in FIG. It is a flowchart which shows the control procedure in the high electric power system shown in FIG.

  Hereinafter, embodiments of the invention will be described with reference to the drawings.

<< First Embodiment >>
A system including the charge control device of the present invention will be described by way of example in which it is used in an electric vehicle, for example. FIG. 1 shows a block diagram of a high voltage system including a charge control device of the present invention.

  In FIG. 1, a high-voltage system includes an assembled battery 101 including a plurality of secondary battery cells 100 connected in series, a charger 102 that supplies charging power to the assembled battery 101 and charges the assembled battery 101, and an assembled battery. 101, a voltage sensor 103 that detects a voltage between terminals, a current sensor 104 that detects a charging current supplied from the charger 102 to the assembled battery 101, a thermistor 105 that detects the temperature of the assembled battery 101, and each unit cell 100. A cell controller 106 for detecting the voltage of

  The positive electrode of the assembled battery 101 is connected to the charger 102 via the high-voltage harness 107 for positive electrode, and the negative electrode of the assembled battery 101 is connected to the charger 102 via the high-voltage harness 108 for negative electrode. Each unit cell 100 is connected to the cell controller 106 via the cell voltage detection line 109. The charger 102 connects a power plug 112 connected via a power harness 111 to a power outlet 113. The charger 102 has a timer 110 that measures the charging time of the assembled battery 1. The voltage sensor 103 is connected to both terminals of the assembled battery 3, and the voltage between the terminals of the assembled battery 101 detected by the sensor is transmitted to the charger 102 by a control signal. The current sensor 104 is connected to the high-voltage harness 107 for positive electrode, and the input / output current to the assembled battery 101 detected by the sensor is transmitted to the charger 102 by a control signal.

  The cell controller 106 detects the voltage of each cell 100 via the cell voltage detection line 109, and the detected voltage is transmitted to the charger 102 by a control signal. In addition, the cell controller 106 adjusts the capacity of the unit cell 100 by causing a capacity adjustment resistor (not shown) connected between the terminals of the unit cell 100 to be conducted under the control of a switching element (not shown).

  The charger 102 receives signals from the voltage sensor 103 and the current sensor 104, and samples the total voltage and input / output current of the assembled battery 101 at a predetermined sampling period. Further, the charger 102 detects the temperature of the assembled battery 101 based on a signal from the thermistor. The charger 102 is provided with a timer 110, and the timer 110 is a charging time from the time when the charging current is supplied from the charger 102 to the assembled battery 101, or the charging time from the time when charging / discharging is switched. Is detected.

  Here, the internal resistance of the assembled battery 101, the temperature of the assembled battery 101, and the charging voltage of the assembled battery 101 will be described. 2 shows the characteristics of the internal resistance with respect to the charging time of the assembled battery 101, FIG. 3 shows the characteristics of the voltage with respect to the internal resistance of the assembled battery 101, and FIG. 4 shows the characteristics of the internal resistance with respect to the battery temperature of the assembled battery 101. It is. As shown in FIG. 2, the internal resistance of the assembled battery 101 has a characteristic of increasing with the charging time from the time when charging is started or the time when charging / discharging is switched (for example, see Japanese Patent Publication No. 2008-89447). reference). As shown in FIG. 3, when the internal resistance of the assembled battery 101 increases, the voltage across the terminals of the assembled battery 101 increases even when the open voltage of the assembled battery 101 is constant. . Further, the internal resistance of the assembled battery 101 has temperature dependency, and as shown in FIG. 4, the internal resistance of the assembled battery 101 has a characteristic of decreasing as the temperature increases.

  The charger 102 has the above-described characteristics relating to the battery to be charged set in advance as a parameter. The charger 102 estimates the internal resistance of the assembled battery 101 from the charging time measured by the timer 110, and A threshold voltage is set according to the charging time. Further, the charger 102 corrects the threshold voltage based on the temperature detected by the temperature sensor 105. When the detection voltage of the assembled battery 101 reaches the threshold voltage, the charging power supplied from the charger 102 to the assembled battery 101 is reduced.

  Hereinafter, the control procedure of the charge control apparatus of this example will be described with reference to FIG. FIG. 5 is a flowchart showing a control procedure of the charging control apparatus of this example.

  When the assembled battery 101 is connected to the charger 102 and charging is started, the timer 110 measures a charging time t, which is an elapsed time from the start of charging (step S1). Next, in step S <b> 2, the charger 102 detects the detected temperature of the assembled battery 101 detected by the thermometer 105.

  In step S3, charger 102 compares predetermined time tc set in advance with charging time t measured in step S1. The predetermined time tc is a value set in advance according to the characteristics of the battery of the assembled battery 1, and depending on whether the charging time t has passed the predetermined time tc, as will be described later. The resistance value of the internal resistance of the assembled battery 101 estimated by the charger 102 is different.

  If the charging time t is smaller than the predetermined time tc, the charger 102 sets the threshold voltage Vc as the voltage threshold V1 in step S41. Here, for the threshold voltage Vc, the charger 102 charges the assembled battery 101 with a constant charging current until the inter-terminal voltage Vs of the assembled battery 101 reaches the threshold voltage Vc, and the inter-terminal voltage Vs becomes the threshold voltage Vc. When it reaches, the charger 102 reduces the charging current and charges the assembled battery 101. Therefore, the threshold voltage Vc indicates a voltage that becomes a threshold for changing the control mode of the charging current. The voltage threshold Vc is set to the threshold voltage V1 or the threshold voltage V2, and the threshold voltage V2 is higher than the threshold voltage V1.

Threshold voltage V1, the full charge voltage V ₀ which the assembled battery 1, a voltage obtained by adding a voltage drop by the internal resistance of the battery pack 101. The full charge voltage V ₀ is a voltage when the assembled battery 101 is in a fully charged state, and is a voltage determined by setting at the time of designing the unit cell 100 included in the assembled battery 101. Since the internal resistance of the assembled battery 101 has a characteristic that varies with the charging time with reference to FIG. 2, the charger 102 of this example has a charging time t that has passed a predetermined time tc. The magnitude of the estimated internal resistance is changed depending on whether or not it is present. When the charging time t is longer than the predetermined charging time tc, the internal resistance r2 is estimated, and when the charging time t is shorter than the predetermined charging time tc, the internal resistance r1 is estimated. The internal resistance r2 is larger than the internal resistance r1.

  As shown in FIG. 4, since the internal resistance has temperature dependence, the charger 102 corrects the internal resistance by multiplying the internal resistance by a temperature correction coefficient α that changes according to the temperature. To do. When the temperature of the assembled battery 101 is high, the internal resistance is low, and when the temperature of the assembled battery 101 is low, the internal resistance is high (see FIG. 4). Therefore, for example, a threshold temperature is set in advance and stored in the charger 101. If the detected temperature detected in step S2 is higher than the threshold temperature, the charger 102 extracts the correction value α1, and the detected temperature is When the temperature is lower than the threshold temperature, a correction value α2 is extracted and used as a temperature correction coefficient. However, the correction value α1 is smaller than the correction value α2.

In the charger 102, the threshold voltage is calculated by the following formula: threshold voltage (V1) = full charge voltage (V ₀ ) + temperature correction coefficient (α1) · internal resistance (r1) × charge current.

On the other hand, when the charging time t is longer than the predetermined time tc, the charger 102 sets the threshold voltage Vc as the voltage threshold V2 in step S42. The internal resistance is estimated as the internal resistance r2 because the charging time t is longer than the predetermined time tc. Further, the charger 102 extracts a temperature correction coefficient α that changes according to the temperature. The threshold voltage is calculated by the following formula: threshold voltage (V2) = full charge voltage (V ₀ ) + temperature correction coefficient (α2) · internal resistance (r2) × charge current.

  Next, in step S <b> 5, the charger 102 detects the current inter-terminal voltage Vs of the assembled battery from the voltage sensor 103. In step S6, the charger 102 compares the inter-terminal voltage Vs with the threshold voltage Vc set in step S41 or S42.

  When the inter-terminal voltage Vs is lower than the threshold voltage Vc, the charger 102 continues charging while maintaining the current charging current, returns to step S1, and repeats the above steps. On the other hand, when the inter-terminal voltage Vs is higher than the threshold voltage Vc, the charger 102 reduces the current charging current and reduces the output current to the assembled battery 101 for charging (step S8). When the magnitude of the charging current supplied to the assembled battery 101 approaches zero and it is determined that the assembled battery 101 is fully charged (step S8), the charger 102 ends the charging.

  As described above, the present invention pays attention to the change in internal resistance due to the charging time, and the charging control device of this example is a threshold voltage that is a threshold for controlling the charging power according to the charging time measured by the timer 110. Set Vc. Thereby, this example can aim at shortening of charge time, preventing the overcharge and shortage of charge of the assembled battery 101. FIG.

  That is, in this example, the threshold voltage is set in accordance with the amount of decrease in the internal resistance according to the state of the internal resistance of the assembled battery. Thereby, since this example suppresses that an excessive voltage is added with respect to the assembled battery 101 when the internal resistance of the assembled battery 101 is low, the overcharge of the assembled battery 101 can be prevented. Further, when the internal resistance of the assembled battery 101 is high, the threshold voltage V2 (> V1) is set in accordance with the drop in the internal resistance, so that the charging time is shortened while preventing the assembled battery from being insufficiently charged. Can be achieved. Further, in this example, even if the internal resistance of the assembled battery 101 is not directly calculated, the voltage threshold is changed according to the change of the internal resistance, so that the calculation load of the control part can be reduced.

  In the present invention, the threshold voltage V2 that is set when the charging time t is longer than the predetermined time tc is higher than the threshold voltage V1 that is set when the charging time t is shorter than the predetermined time tc. Is set. As a result, the threshold voltage is set in accordance with the fluctuation of the voltage drop of the internal resistance that changes depending on the charging time, so that overcharging or undercharging of the assembled battery 101 can be prevented.

  The present invention also includes a thermistor 105 that detects the temperature of the assembled battery 101 and sets a threshold voltage according to the detected temperature. Further, the temperature correction coefficient is set so that the threshold voltage set when the detected temperature is higher than the predetermined temperature is lower than the threshold voltage set when the detected temperature is lower than the predetermined temperature. Thus, in this example, the threshold voltage Vc is corrected in accordance with the temperature state of the assembled battery 101. Therefore, a threshold voltage suitable for the temperature state can be set, and charging time can be reduced while preventing excessive or insufficient charging. Shortening can be achieved.

  In the present invention, the threshold voltage V1 or V2 is set and the charge control is performed using the predetermined time tc as the time threshold value. However, the time threshold value is not necessarily limited to one and may be a plurality. Alternatively, a threshold voltage linked to the charging time may be set.

  In this example, the threshold voltage is corrected by multiplying the internal resistance by the temperature correction coefficient α. However, the threshold voltage Vc may be set by correcting by adding or subtracting the temperature correction coefficient.

Further, as shown in FIG. 2, the internal resistance of the assembled battery 101 has a characteristic of gradually increasing from the start of the charging time and saturating from a certain point in time. Here, the saturated internal resistance is defined as saturated internal resistance (r _f ), and the corresponding time is defined as saturation time (t _f ). The charger 101, until saturation time t _f from the time of start of charging increases in conjunction with the threshold voltage Vc respect charging time t. Then, since the charging time t has reached the saturation time t _f, the charger 102 maintains to fix the threshold voltage.

Thus, this example, in accordance with the charging time that the internal resistance is saturated, for setting the threshold voltage Vc, the internal resistance higher than the saturated internal resistance r _f is not estimated. Therefore, since the voltage that may cause overcharging is not set as the threshold voltage while shortening the charging time, overcharging of the assembled battery 101 can be prevented.

In this example, the threshold voltage Vc is increased in conjunction with the charging time t from the start of charging to the saturation time t _f . However, the threshold voltage having a stepwise magnitude is set to control charging. May be.

  Further, in this example, when the inter-terminal voltage Vs reaches a predetermined threshold voltage Vc, the charging current to the assembled battery 101 is reduced. Thereby, the voltage rise by the product of internal resistance and charging current can be suppressed, and it can charge to full charge accurately.

  In this example, the voltage sensor 103 detects the voltage between the terminals of the assembled battery 101 and performs the above control. However, even if the above control is performed using the detection voltage of the cell 100 detected by the cell controller 106. Good.

  In this example, the internal resistance of the assembled battery 101 is estimated based on the charging time. However, the internal resistance may be directly measured, the threshold voltage may be set, and the charging power may be controlled. Thereby, it can be made to charge to full charge accurately, and the excess and deficiency of charge can be prevented.

  In this example, the charging power source for charging the assembled battery 101 by the charger 102 is the outlet 113. However, for example, regenerative charging of a motor mounted on the vehicle may be used as the generating power source. In the present system, the assembled battery 101 can be removed from the assembled battery 101 and replaced with another assembled battery 101.

  The voltage sensor 103 in this example corresponds to “voltage detection means”, the timer 110 corresponds to “charging time measurement means”, and the thermistor 105 corresponds to “temperature detection means”.

<< Second Embodiment >>
FIG. 6 is a block diagram of a high voltage system including a charge control device according to another embodiment of the invention. This example is different from the first embodiment described above in that a deterioration degree measuring unit 201 is provided instead of the thermistor 105. The description of the same structure as 1st Embodiment mentioned above by the structure except this is used.

  As shown in FIG. 6, the charger 102 includes a deterioration degree measuring unit 201, and the deterioration degree measuring unit 201 measures the degree of deterioration based on the detected voltage by the voltage sensor 103 and the detected current by the current sensor 104.

  The degree of deterioration is calculated, for example, by the ratio of the current (after deterioration) battery capacity to the initial (before deterioration) battery capacity in a predetermined SOC (State of Charge). The initial battery capacity is determined in advance at the design stage of the unit cells included in the assembled battery 101. The battery capacity after deterioration can be obtained by calculating the integrated current value from the start of charging to a certain point. As shown in FIG. 7, the assembled battery 101 has a characteristic that the internal resistance increases as the deterioration progresses. FIG. 7 is a graph showing the characteristic of the internal resistance with respect to the degree of deterioration of the assembled battery 101.

  Next, the control procedure of the charging control apparatus of this example will be described with reference to FIG. FIG. 8 is a flowchart showing a control procedure of the charge control device of this example. In the charge control device of this example, the control process of Step S1, Step S3, Step S5 to Step S9 is the same as the control process of the charge control device according to the first embodiment, and thus the description thereof is omitted and different control steps are performed. This will be described below.

  In step S <b> 21, the charger 101 uses the deterioration level measurement unit 201 to measure the deterioration level during the charging time t. If the charging time t is smaller than the predetermined time tc, the charger 102 sets the threshold voltage Vc as the voltage threshold V1 in step S241.

  As shown in FIG. 7, since the internal resistance depends on the degree of deterioration, the charger 102 corrects the internal resistance by multiplying the internal resistance by a deterioration degree correction coefficient β that changes according to the degree of deterioration. When the deterioration degree of the assembled battery 101 is high, the internal resistance is high, and when the deterioration degree of the assembled battery 101 is low, the internal resistance is low (see FIG. 4). Therefore, for example, the threshold deterioration degree is set in advance and stored in the charger 101. When the deterioration degree measured in step S21 is higher than the threshold deterioration degree, the charger 102 extracts the correction value β1 and deteriorates the deterioration degree. When the degree is lower than the threshold deterioration degree, the deterioration degree correction coefficient β2 is extracted and used as the deterioration degree correction coefficient. However, the correction value β1 is larger than the correction value β2.

In the charger 102, the threshold voltage is calculated by the following formula: threshold voltage (V1) = full charge voltage (V ₀ ) + deterioration degree correction coefficient (β1) · internal resistance (r1) × charge current.

On the other hand, when the charging time t is longer than the predetermined time tc, the charger 102 sets the threshold voltage Vc as the voltage threshold V2 in step S242. The internal resistance is estimated as the internal resistance r2 because the charging time t is longer than the predetermined time tc. Further, the charger 102 extracts a deterioration degree correction coefficient β2 that changes according to the deterioration degree. The threshold voltage is calculated by the following formula: threshold voltage (V2) = full charge voltage (V ₀ ) + deterioration degree correction coefficient (β2) · internal resistance (r2) × charge current.

  As described above, the present example includes the deterioration degree measuring unit 201 that measures the deterioration degree of the assembled battery 101, and sets the threshold voltage according to the deterioration degree. Further, the deterioration degree correction coefficient is set so that the threshold voltage set when the deterioration degree is higher than the predetermined deterioration degree is higher than the threshold voltage set when the deterioration degree is lower than the predetermined deterioration degree. Thereby, since the threshold voltage Vc is corrected according to the deterioration state of the assembled battery 1, a threshold voltage suitable for the deterioration state can be set, and the charging time can be shortened while preventing excessive or insufficient charging. be able to.

  In this example, correction is performed by multiplying the deterioration degree correction coefficient β by the internal resistance. However, the threshold voltage Vc may be set by performing correction by adding or subtracting the deterioration degree correction coefficient.

  Note that the degradation level measurement unit 201 of this example corresponds to “a degradation level measurement unit”.

DESCRIPTION OF SYMBOLS 100 ... Single cell 101 ... Battery pack 102 ... Charger 103 ... Voltage sensor 104 ... Current sensor 105 ... Thermistor 106 ... Cell controller 107 ... Positive electrode harness 108 ... Negative electrode harness 109 ... Cell voltage detection wire 110 ... Timer 111 ... Power supply harness 112 ... Power plug 113 ... Outlet 201 ... Deterioration degree measuring unit

Claims (8)

Voltage detecting means for detecting a voltage between terminals of the secondary battery;
Charging time measuring means for measuring the charging time of the secondary battery;
A charger that controls the charging power to the secondary battery by comparing the voltage between the terminals and a predetermined threshold voltage;
The charger is
Charging characterized in that the predetermined threshold voltage set when the charging time is longer than a predetermined time is higher than the predetermined threshold voltage set when the charging time is shorter than the predetermined time. Control device. A temperature detecting means for detecting the temperature of the secondary battery;
2. The charging control apparatus according to claim 1 , wherein the charger sets the predetermined threshold voltage according to a temperature detected by the temperature detecting means. The charger is
3. The predetermined threshold voltage that is set when the temperature is higher than a predetermined temperature is set lower than the predetermined threshold voltage that is set when the temperature is lower than the predetermined temperature. The charging control device described. A deterioration degree measuring means for measuring a deterioration degree of the secondary battery;
The charger, in accordance with the deterioration degree as measured by the deterioration degree measurement device, the charge control device according to any one of claims 1 to 3, setting the predetermined threshold voltage. The charger is
The predetermined threshold voltage that is set when the degree of deterioration is higher than a predetermined degree of deterioration is higher than the predetermined threshold voltage that is set when the degree of deterioration is lower than a predetermined degree of deterioration. The charge control apparatus according to claim 4 . The charger, in accordance with the charging time internal resistance of the secondary battery is saturated, the charging control apparatus according to any one of claims 1 to 5 for setting the predetermined threshold voltage. The charger, if the voltage between the terminals reaches the predetermined threshold voltage, set forth in any one of claims 1 to 6, characterized in that to reduce the charging current to the secondary battery charging Control device. Measuring the voltage across the terminals of the secondary battery;
A charging time measuring step for measuring a charging time of the secondary battery;
A setting step for setting a predetermined threshold voltage according to the charging time measured by the charging time measuring step;
Comparing the inter-terminal voltage and the predetermined threshold voltage, controlling the charging power to the secondary battery, and charging the secondary battery,
The setting step includes
The predetermined threshold voltage that is set when the charging time is longer than the predetermined time is set higher than the predetermined threshold voltage that is set when the charging time is shorter than the predetermined time. Method.

Images