JP2007124750A - Charge control method of battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To charge a battery while the internal voltage of the battery is prevented from increasing, reduce the manufacturing cost and simplify maintenance, without having to provide a sensor and dedicated wiring for detecting the internal voltage to the battery. <P>SOLUTION: A charge control method of the battery detects a charging voltage and a charging current of the battery, and detects the internal voltage of the battery from the charging current and the charging voltage. The charge control method identifies the internal voltage increase voltage, at which the internal voltage of the battery starts increasing, based on the charging current. The charging current and the time are accumulated during an internal voltage increasing charge for charging the battery, excelling the internal voltage increasing voltage. The internal voltage of the battery is calculated from the accumulation values, and a charging state of the battery is controlled by the calculated internal voltage of the battery. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for controlling charging of a battery, and more particularly to a method for controlling charging of a battery that is suitable for controlling charging of a battery that is mounted on a vehicle and used as a power source of a motor that runs the vehicle.

  A power source that supplies electric power to a motor that drives a vehicle has a large number of batteries connected in series to increase the output voltage. The battery of this power source is discharged when the motor is driven, and is charged by regenerative braking by a brake. In the case of a hybrid car, it is charged by rotating a generator with an engine. The battery is charged when the remaining capacity is low, and is charged and used so as not to be overcharged. Depending on the charging conditions, the battery to be charged generates gas inside and the internal pressure rises. Since the battery may explode when the internal pressure becomes abnormally high, a safety valve is provided. The safety valve opens when the internal pressure of the battery becomes higher than the set pressure. The safety valve to be opened exhausts gas, electrolyte, etc. from the inside to prevent an increase in internal pressure and prevent destruction. The safety valve is opened to prevent the outer can from being ruptured. However, when the valve is opened, the electrolytic solution or the like is discharged, the electrical characteristics of the battery are lowered, and the life is shortened. Therefore, it is desirable for the battery to prevent the safety valve from opening by controlling charging so that the internal pressure does not rise abnormally.

In order to realize this, it is necessary to detect the internal pressure of the battery. This is because it is necessary to control the charging current based on the detected internal pressure. A technique for providing a strain gauge to detect the internal pressure of a battery is described in Patent Document 1.
Special table 2004-517440 gazette

  The battery is provided with a strain gauge to detect the internal pressure, and the charging current of the battery is controlled by the detected internal pressure so that the internal pressure does not increase. However, according to this method, it is necessary to provide the battery with a strain gauge for detecting the internal pressure, which complicates the battery structure. For this reason, the manufacturing cost of a battery becomes high. In addition, since the strain gauge occupies a predetermined volume inside the battery, there is a disadvantage that the capacity with respect to the outer shape is reduced. Furthermore, it is necessary to insulate the lead wires connected to the strain gauge from the outside of the battery, and this structure is further complicated. In addition, the lead wire drawn out of the battery needs to be connected to a control circuit that detects the internal pressure of the battery and controls charging, and there is a disadvantage that wiring is complicated. Moreover, the lead wire pulled out from the battery may cause a failure such as disconnection or short circuit. For this reason, there is a drawback that it takes time and labor for manufacturing and maintenance.

  The present invention has been developed for the purpose of solving this drawback. An important object of the present invention is to manufacture a battery by charging the battery while preventing an increase in the internal pressure of the battery without providing a sensor for detecting the internal pressure and without providing a dedicated wiring for detecting the internal pressure. An object of the present invention is to provide a battery charge control method capable of reducing cost and simplifying maintenance.

  The battery charge control method according to claim 1 of the present invention detects the voltage and charging current of the battery being charged, and detects the internal pressure of the battery from the charging current and voltage. In the charge control method, the internal voltage increase voltage at which the internal pressure of the battery starts to increase is specified based on the charge current, and in the internal pressure increase charge in which the charged battery voltage exceeds the internal pressure increase voltage, the charging current and time The internal pressure of the battery is calculated from the integrated value, and the state of charge of the battery is controlled by the calculated internal pressure of the battery.

  The battery charge control method according to claim 2 of the present invention detects the temperature, voltage and charge current of the battery being charged, and detects the internal pressure of the battery from the battery temperature, charge current and voltage. The charge control method specifies the internal pressure increase voltage at which the internal pressure of the battery starts to increase based on the temperature and the charge current, and in the internal pressure increase charge in which the charged battery voltage exceeds the internal pressure increase voltage, the charge current Then, the internal pressure of the battery is calculated from the integrated value, and the state of charge of the battery is controlled by the calculated internal pressure of the battery.

  The battery charge control method of the present invention calculates and detects the internal pressure of a battery equipped with a safety valve, and controls the state of charge of the battery so that the calculated internal pressure of the battery is lower than the valve opening pressure of the safety valve. Can do.

  The battery charge control method of the present invention detects an internal pressure increase voltage specifying function for specifying an internal pressure increase voltage from current and voltage, compares the voltage and current of the battery being charged with the internal pressure increase specific function, and the voltage is When the voltage is higher than the rising voltage, charging current and time can be integrated as internal pressure rising charging.

  The battery charge control method of the present invention can reduce the detected internal pressure with a predetermined decrease rate as time elapses when the battery is not charged. The decreasing rate of the internal pressure can be changed with temperature.

  The battery charge control method of the present invention can prevent the calculated internal pressure of the battery from being added or subtracted when the battery is charged and does not exceed the internal pressure increase voltage.

  The battery charge control method of the present invention can change the internal pressure increase voltage as a function of time.

  The battery charge control method of the present invention calculates the remaining capacity from the charge / discharge current of the battery, controls the charge switch with a weighted average value of the remaining capacity and the calculated internal pressure, and also determines the remaining capacity by the value of the remaining capacity. The weight (weight) for weighted averaging of the calculated internal pressure can be changed.

  The battery charge control method of the present invention detects the voltage and charge current of a plurality of batteries that are charged and discharged simultaneously, and controls the charge current of all the batteries with an internal pressure calculated from the specific battery voltage and charge current. Can do.

  The battery charging control method of the present invention detects the voltage and charging current of a plurality of batteries that are charged and discharged simultaneously, calculates the internal pressure of each battery from each battery voltage and charging current, and calculates the battery from the calculated internal pressure. Can determine the lifetime.

  The battery charging control method of the present invention can correct the remaining capacity calculated by integrating the charging / discharging current with the integrated value of the charging current and time charged exceeding the internal pressure increase voltage.

Furthermore, the battery charge control method of the present invention can use the battery as a driving power source for the electric vehicle. Furthermore, the battery charge control method of the present invention can use a battery as a power source for driving an electric vehicle and a battery that generates gas during normal charging or overcharging.
However, in this specification, the electric vehicle is used in a broad sense including not only a vehicle such as an electric vehicle that runs on a motor but also a hybrid car that runs on both a motor and an engine.

  The present invention has an advantage that the battery can be charged while preventing an increase in the internal pressure of the battery without providing a sensor for detecting the internal pressure of the battery and without providing a dedicated wiring for detecting the internal pressure. This is because the charge control method of the present invention detects the internal pressure of the battery from the voltage and charge current of the battery being charged, or detects the internal pressure of the battery from the temperature, voltage and charge current of the battery being charged. It is. The charging control method according to the present invention specifies an internal pressure increase voltage at which the internal pressure of a battery starts to increase based on a charging current or a temperature and a charging current, and the charging battery voltage exceeds the internal pressure increase voltage. The charging time and charging current are integrated, and the internal pressure of the battery is calculated from this integrated value to control the state of charge of the battery. This charge control method calculates the internal pressure of the battery by measuring the voltage, current, and temperature of the battery, so that it does not require a sensor for detecting the internal pressure or a dedicated wiring as in the prior art. This makes it possible to ideally control charging while reducing the internal pressure of the battery and further simplifying the maintenance.

  Furthermore, the battery charge control method according to the twelfth aspect of the present invention is characterized in that the remaining battery capacity calculated by integrating the charge / discharge current can be calculated with higher accuracy. This is because this current control method corrects the remaining capacity of the battery with the integrated value of the charging current and time charged exceeding the internal pressure increase voltage. Normally, the remaining capacity of a battery is calculated by integrating the charging / discharging current.However, when the battery is nearly fully charged in the charging state of the battery, all the charging current is not used for charging the battery. Energy is consumed to generate gas inside the battery. As a result, an error occurs in the remaining capacity as charging and discharging are repeated. On the other hand, in the charging control method according to claim 12 of the present invention, a charging current charged exceeding the internal pressure increase voltage, that is, an integrated value of the charging current and time in a state where gas is generated inside the battery, is detected. Since the remaining capacity of the battery is corrected by the integrated value, the remaining capacity can be calculated with higher accuracy in consideration of the loss due to the current not used for charging.

  Embodiments of the present invention will be described below with reference to the drawings. However, the embodiment described below exemplifies a battery charge control method for embodying the technical idea of the present invention, and the present invention does not specify the battery charge control method as the following method.

  FIG. 1 shows a circuit diagram for controlling battery charging in the method of the present invention. In this circuit diagram, a plurality of batteries 1 are connected in series. The voltage, current and temperature of the battery 1 are detected by the control unit 2. The control unit 2 includes a voltage detection circuit 3 that detects the voltage of the battery 1, a current detection circuit 4 that detects charge / discharge current flowing through the battery 1, and a temperature detection circuit 5 that detects the temperature of the battery 1. Yes. Further, the control unit 2 includes an arithmetic circuit 6 that calculates the detected signal to calculate the internal pressure of the battery 1, and a charge switching circuit 8 that controls the charging current with the internal pressure calculated by the arithmetic circuit 6. A control circuit 7 for controlling is provided.

  The control unit 2 shown in the figure detects the voltages of a plurality of batteries 1 with a voltage detection circuit 3. In the battery 1, a plurality of unit cells are connected in series to form a battery module, and a plurality of battery modules are connected in series to increase the output voltage. The voltage detection circuit 3 detects the voltage of each battery module. The control unit 2 that detects the voltage of each battery module by the voltage detection circuit 3 can detect the internal pressure of the battery 1 with each battery module as one unit. The control unit can detect all the batteries independently, and can detect the internal pressure of each battery independently. It is also possible to detect the total battery voltage and detect the internal pressure of the battery with all the batteries as one block.

  The current detection circuit 4 detects the current flowing through the battery 1. What connected the some battery 1 in series becomes the same electric current which flows into all the batteries 1. FIG. Therefore, the current of all the batteries can be detected by detecting the current of the batteries 1 connected in series. The current flowing through the battery 1 can be detected by connecting a current detection resistor in series with the battery 1 and the voltage across the current detection resistor. This is because the voltage induced across the current detection resistor is proportional to the current. Further, since the positive and negative directions of the voltage induced at both ends of the current detection resistor are reversed between the charging current and the discharging current, the charging current and the discharging current can be identified by the positive and negative directions of the voltage.

  The temperature detection circuit 5 can be detected by a temperature sensor 10 that is in contact with or close to the surface of the battery 1 and is thermally coupled to the battery. The temperature sensor 10 is a thermistor or PTC whose electric resistance changes with temperature. However, any temperature sensor that can detect the battery temperature, for example, a mechanism for detecting the battery temperature by detecting infrared rays radiated from the battery can be used. The temperature detection circuit 5 in the figure detects the temperature using one battery 1 as a representative battery, but can also detect the temperature of each battery or the temperature of each battery module. The control unit of the temperature detection circuit that detects each battery temperature uses the average value of each battery temperature as the battery temperature, or the maximum temperature as the battery temperature, or the weighted average of each battery temperature. It can be.

  The control unit 2 controls the charging switching circuit 8 so that the calculated internal pressure is lower than the valve opening pressure of the safety valve of the battery 1. That is, the control unit 2 compares the calculated internal pressure with the charge control internal pressure, and when the calculated internal pressure becomes higher than the charge control internal pressure, the control unit 2 controls the charge switching circuit 8 so as to inhibit charging, or sets the charge current. Control to make it smaller. The charge control internal pressure is stored in advance in a memory (not shown) of the control unit 2.

  The charge control internal pressure can be provided with a charge prohibition internal pressure that prohibits charging of the battery 1 and a charge limit internal pressure that limits the charge current of the battery 1 to a predetermined range. The charging prohibition internal pressure is a state in which charging of the battery 1 is prohibited, that is, a state in which the charging current is interrupted. The charge limiting internal pressure is a state in which the charging current of the battery 1 is not cut off, but the charging current is limited to a small current that does not increase the internal pressure of the battery 1. The charge limit internal pressure is set lower than the charge prohibition internal pressure. The charge limit internal pressure is, for example, 30 to 80%, preferably 40 to 70% of the charge prohibition internal pressure. Furthermore, the control unit 2 can store a plurality of charge limit internal pressures, and control the charge current to be smaller as the calculated internal pressure becomes higher than the stored large charge limit internal pressure. The control unit 2 can prevent the battery 1 from increasing in internal pressure by decreasing the charging current as the calculated internal pressure increases. Furthermore, the control unit 2 can store a function that specifies the maximum value of the charging current from the calculated internal pressure, and can control the maximum value of the current that allows the battery 1 to be charged based on this function.

  However, the control unit 2 can store only the charge prohibition internal pressure as the charge control internal pressure, and can control to prohibit charging when the calculated internal pressure exceeds the charge prohibition internal pressure. The control unit 2 can be charged with a simple circuit configuration while keeping the internal pressure of the battery 1 lower than the opening pressure of the safety valve.

  Furthermore, the control unit 2 shown in the figure also includes a remaining capacity detection circuit 9 that calculates the remaining capacity of the battery 1. The remaining capacity detection circuit 9 calculates the remaining capacity of the battery 1 from the charge / discharge current. The control circuit 7 of the control unit 2 controls the charging switching circuit 8 by the internal pressure of the battery 1 calculated by the arithmetic circuit 6, but the internal pressure calculated by the arithmetic circuit 6 and the remaining capacity detected by the remaining capacity detection circuit 9. The charge switching circuit 8 can be controlled by both of the capacities.

  The remaining capacity detection circuit 9 calculates the remaining capacity by integrating the current for charging and discharging the battery 1. The remaining capacity is corrected by the battery voltage, and the remaining capacity calculated by the output of the arithmetic circuit 6 that detects the internal pressure of the battery 1 is corrected. The remaining capacity is calculated by subtracting the discharge capacity from the charge capacity. The charge capacity is calculated by integrating the charge current, and the discharge capacity is calculated by integrating the discharge current. An error occurs in the remaining capacity calculated using the charge / discharge current as an integrated value as charge / discharge is repeated. This is because the entire charging current is not used for charging the battery, so that the charging efficiency cannot always be 100%. The charging efficiency of the battery gradually decreases when the battery is nearly fully charged. In this state, the internal pressure of the battery also increases. This is because when approaching full charge, the energy of the charging current is consumed to increase the internal pressure of the battery, in other words, it is consumed to generate gas inside the battery.

  A battery that is nearly fully charged consumes a part of the charging current internally for gas generation, and the rest is used for charging the battery. From this, in a state where the gas generation of the battery is increased, in other words, in a state where the internal pressure of the battery is increased, the proportion of the charging current energy used for the internal pressure increases and the proportion used for charging the battery Less. Therefore, the remaining value can be detected more accurately by detecting the integrated value of the charging current and time at which the battery is charged exceeding the internal pressure increase voltage, and correcting the charging efficiency to be lowered when this integrated value is increased.

  Further, the remaining capacity of the battery 1 can be corrected by the battery voltage. The battery is near the maximum voltage when fully charged and the minimum voltage when fully discharged. Therefore, when the battery reaches the maximum voltage, the battery is fully charged and the remaining capacity is 100%. This is because it can be determined that the remaining capacity is 0% even if the battery is discharged.

  A control circuit 7 that controls the charge switching circuit 8 with both the calculated internal pressure and the remaining capacity controls the charge switching circuit 8 with a weighted average value of the remaining capacity of the battery 1 and the calculated internal pressure. The control unit 2 changes the weight (weight) for weighted averaging of the remaining capacity and the calculated internal pressure with the value of the remaining capacity. FIG. 2 is a diagram showing the weight (weight) between the remaining capacity and the calculated internal pressure. As shown in this figure, the remaining capacity weight (weight) is increased in a large area where the remaining capacity exceeds a predetermined amount, and the remaining capacity weight (weight) is decreased in a small area where the remaining capacity is less than the predetermined amount. To do. The control unit 2 controls the state of charge by comparing the calculated internal pressure and the weighted average value of the remaining capacity with the charge control internal pressure.

  The battery 1 is connected to a generator 11 and a motor of a load 12 through a charge switching circuit 8. The charge switching circuit 8 is realized by a switch such as a switching element or a relay. However, since a hybrid car connects a generator and a motor to a battery via an inverter, a charge switching circuit is realized by the inverter. This is because the inverter is controlled to be in a state in which charging is prohibited, and can be controlled in a state in which charging of the battery is prohibited, substantially in a state in which the charge switching circuit is turned off.

  The battery 1 is charged by regenerative braking or by a generator 11 that is rotated by an engine. Further, electric power is supplied to the motor which is the load 12 to be discharged.

  When the battery 1 is charged under specific conditions, gas is generated inside and the internal pressure rises. That is, the charge control method of the present invention is not particularly limited as long as the battery is accompanied by gas generation during normal charging or overcharging. When the internal pressure of the battery 1 becomes higher than the set pressure, the safety valve built in the battery 1 is opened and gas and electrolyte are discharged. Therefore, the control unit 2 is charged so that the safety valve does not open. The switching circuit 8 is controlled.

  The control unit 2 detects the temperature, voltage, and charging current of the battery 1 being charged, and detects the internal pressure of the battery 1 from the charging current and voltage. The principle that the control unit 2 detects the internal pressure from the temperature, voltage and charging current of the battery 1 is shown in FIGS.

  FIG. 3 is a graph showing a curve in which the battery voltage and internal pressure rise when the battery is charged with a predetermined charging current. In this figure, the horizontal axis represents the battery voltage, and the vertical axis represents the internal pressure of the battery. This figure shows that when the battery is charged with a predetermined current, the internal pressure rapidly increases when the battery voltage becomes higher than a specific voltage. In this figure, the voltage at which the internal pressure of the battery starts to rise is defined as the internal pressure rise voltage.

  FIG. 4 is produced from FIG. 3, and is a graph in which the horizontal axis represents the charging current and the vertical axis represents the internal pressure increase voltage. This figure shows that the internal pressure increase voltage specifying function that specifies the internal pressure increase voltage can be expressed as a function of current. This figure shows that the internal pressure rising voltage specifying function approximates a linear function of current. In this figure, the internal pressure increase voltage specifying function A indicates the internal temperature increase voltage with the battery temperature of 40 ° C., the internal pressure increase voltage specific function B indicates the battery temperature of 20 ° C., and the internal pressure increase voltage specific function C indicates the battery temperature of 0 ° C. Yes. As shown in this figure, since the internal pressure increase voltage of the battery changes depending on the temperature, the internal pressure of the battery can be detected more accurately by detecting the internal pressure in consideration of the temperature. However, it is also possible to detect the internal pressure of the battery without detecting the temperature by setting the battery temperature to room temperature.

  Furthermore, the internal pressure rise voltage can be changed as a function of time. The time here refers to the lifetime of the battery. The battery tends to generate gas inside at the end of life compared to the beginning of life, and the internal pressure rises more easily. That is, the internal pressure increase voltage of the battery also changes depending on the battery life. Therefore, the control unit can store the conversion table or conversion formula corresponding to the battery life in a memory (not shown) and change the internal pressure increase voltage as a function of time. For example, the control unit can store conversion rates for the initial life, middle life, and last life in a table, and change the internal pressure increase voltage in accordance with the battery life. In this case, the conversion rates from the initial life stage to the middle life stage and from the middle life stage to the last life stage can be obtained by linearly interpolating the conversion ratios corresponding to the early life stage, the middle life stage, and the last life stage. The time for determining the life of the battery can be the total usage time after shipment. However, the time for determining the battery life can be the total time charged and discharged. As described above, the method of calculating the internal pressure increase voltage as a function of time can calculate the internal pressure of the battery more accurately.

  FIG. 4 shows an internal pressure increase voltage at which the internal pressure of the battery to be charged starts to increase. When the battery is charged at a voltage higher than the internal pressure increase voltage, the internal pressure increases and is lower than the internal pressure increase voltage. When charged with voltage, the internal pressure does not increase.

The degree to which the internal pressure of the battery increases varies depending on the integrated value of the charging current of the battery charged exceeding the internal pressure increasing voltage. As the integrated value increases, the internal pressure of the battery gradually increases. FIG. 5 is a graph showing a state in which the internal pressure of the battery increases due to this integrated value. In this figure, the horizontal axis represents time, and the vertical axis represents the current for charging / discharging the battery, the voltage of the battery, and the internal pressure of the battery. In this figure, curve A shows the current for charging / discharging the battery, curve B shows the voltage of the battery, and curve C shows the internal pressure of the battery calculated from the integrated value of the current charged exceeding the internal pressure increase voltage. Show. Further, in this figure, a chain line D indicates an internal pressure increase voltage. The internal pressure of the battery is calculated by the product of the integrated value of the current charged exceeding the internal pressure increase voltage and the conversion coefficient. The conversion coefficient is a battery internal pressure measuring device with a built-in strain gauge and pressure sensor that detects internal pressure. The internal pressure of the prototype battery is detected by the pressure sensor, and the integrated value of the current charged exceeding the internal pressure rise voltage is detected. Then, it is identified from the detected integrated value and the detected pressure of the pressure sensor. If the charge control internal pressure is several MPa, the conversion coefficient is, for example, 1 to 9 × 10 ⁻⁴ MPa / As.

  The internal pressure of the battery gradually increases when charging exceeds the internal pressure increase voltage, and gradually decreases when charging of the battery is stopped or discharged. Therefore, when the charging of the battery is stopped or discharged, the calculated internal pressure is gradually reduced.

FIG. 6 shows an example of the characteristic that the internal pressure of the battery decreases. The rate at which the internal pressure decreases depends on the temperature. In this figure, curves A, B, and C show an internal pressure lowering function in which the internal pressure of a battery having temperatures of −20 ° C., 0 ° C., and 50 ° C. decreases. From the internal pressure decreasing function shown in this figure, the state in which the internal pressure of the battery decreases can be calculated as a function of the battery temperature and time. Since the rate at which the internal pressure of the battery decreases varies depending on the temperature of the battery, the internal pressure decreasing function is a function of the battery temperature and time. The internal pressure lowering function is specified by measuring with an actual battery. For example, the internal pressure lowering function (y) of the battery decreases by approximating with the following function.
y = a * Ln (t + b) + c
In this formula, a, b, and c are constants specified by temperature.

  As shown in FIG. 6, the amount of decrease in internal pressure of the battery is specified by temperature. Accordingly, the internal pressure of the battery calculated from the integrated value of the current charged exceeding the internal pressure increase voltage is gradually reduced in a state where the battery is not charged or discharged (= the battery is not charged). The Since the rate at which the internal pressure decreases is calculated as a function of temperature, the internal pressure is decreased based on the battery temperature.

  The above charging control method is not limited to constant current charging, constant current-constant voltage charging, and constant power charging, which are often used in consumer batteries. It can also be used in pulse charge / discharge patterns where the current value is variable.

7 and 8 show a flowchart in which the control unit 2 of FIG. 1 calculates the internal pressure from the temperature, voltage and charging current of the battery 1 to control the charging switching circuit 8.
The flowchart of FIG. 7 controls the charging current of the battery 1 in the following steps to control the internal pressure of the battery 1 lower than the valve opening pressure of the safety valve.
[Step of n = 1]
The control unit 2 determines whether or not the battery 1 is charged in this step. Whether or not the battery 1 is charged can be detected by detecting the direction of the current flowing through the battery 1 with the current detection circuit 4.

[Steps n = 2, 3]
When it is determined that the battery 1 is not charged, the time during which the battery 1 is not charged, that is, the time when the battery 1 is discharged or the time when the battery 1 is not charged is detected, and the internal pressure of the battery 1 is determined. Reduce. When the internal pressure of the battery 1 is 0, the internal pressure is not reduced. As shown in FIG. 6, the rate at which the internal pressure of the battery 1 decreases varies depending on the battery temperature. Therefore, the temperature of the battery 1 is measured in this step or in the step before this step. Based on the measured temperature of the battery 1, a decrease in the internal pressure is calculated based on an internal pressure decrease function indicating a rate at which the internal pressure of the battery 1 decreases with time. The internal pressure decreasing function for decreasing the internal pressure is stored in a memory (not shown) of the control unit 2 by measuring a state in which the actual internal pressure of the battery decreases in advance. The decrease in the internal pressure of the battery 1 can be stored in the table as the internal pressure specified from the temperature and time regardless of the internal pressure decrease function, and the decrease in the internal pressure can be detected from the table.

[Step n = 4]
If it is determined that the battery 1 is charged, it is determined whether the voltage of the battery 1 charged in this step is higher than the internal pressure increase voltage. As shown in FIG. 3, the internal pressure increase voltage varies depending on the temperature and current of the battery 1. Therefore, the control unit 2 stores in the memory an internal pressure increase voltage specifying function for calculating the internal pressure increase voltage as a function of temperature and current, and from this internal pressure increase voltage specification function, the voltage of the battery 1 becomes the internal pressure increase voltage. To determine if it is higher. However, the control unit can also store in the memory a table for specifying the internal pressure increase voltage from the temperature and current, and determine whether or not the battery voltage is higher than the internal pressure increase voltage based on this table.
[Step n = 5]
If the voltage of the battery 1 being charged is not higher than the internal pressure increase voltage, in other words, below the internal pressure increase voltage, the charging current is not integrated in this step.

[Step n = 6]
If the voltage of the battery 1 being charged is higher than the internal pressure increase voltage, the current and time charged exceeding the internal pressure increase voltage are integrated in this step. That is, the product of the time over which the internal pressure rise voltage is exceeded and the charging current is calculated. The calculated integrated value is added to any previous integrated value.
[Step n = 7]
The internal pressure of the battery is calculated by multiplying the calculated integrated value by the conversion coefficient, that is, from the product of the integrated value and the conversion coefficient.

[Step n = 8]
The calculated internal pressure is compared with the charge prohibition internal pressure. The charge prohibition internal pressure is a pressure set lower than the valve opening pressure of the safety valve, and is stored in the memory of the control unit 2 in advance. For example, the charging prohibition internal pressure is set to 30 to 90%, preferably 40 to 80%, more preferably 40 to 70% of the valve opening pressure of the safety valve. If the calculated internal pressure is lower than the charge-prohibited internal pressure, the process loops to a step of n = 1.

  In this step, a weighted average value can be detected from both the calculated internal pressure and the remaining capacity of the battery 1, and the weighted average value can be compared with the charge control internal pressure.

[Step n = 9]
When the calculated internal pressure or the weighted average value is higher than the charge prohibition internal pressure, the control unit 2 sets the charge switching circuit 8 in a state in which charging is prohibited, pauses charging, and allows only discharge. The charging switching circuit 8 is a switch such as a switching element or a relay, and can be turned off to prohibit charging. However, since the hybrid car has an inverter connected between the battery and the generator, the inverter can be controlled to a state in which charging is prohibited, and charging of the battery can be suspended. The inverter in a state where charging is prohibited interrupts the charging current, but is controlled so that it can be discharged.

In the flowchart of FIG. 8, the charging current of the battery 1 is controlled by the following steps to control the internal pressure of the battery 1 lower than the valve opening pressure of the safety valve.
[Step of n = 1]
The control unit 2 determines whether or not the battery 1 is charged in this step. Whether or not the battery 1 is charged can be detected by detecting the direction of the current flowing through the battery 1 with the current detection circuit 4.

[Steps n = 2, 3]
When it is determined that the battery 1 is not charged, the time during which the battery 1 is not charged, that is, the time when the battery 1 is discharged or the time when the battery 1 is not charged is detected, and the internal pressure of the battery 1 is determined. Reduce. When the internal pressure of the battery 1 is 0, the internal pressure is not reduced. As described above, the decrease in the internal pressure of the battery 1 is calculated from the measured temperature of the battery 1 based on the internal pressure decrease function indicating the rate at which the internal pressure of the battery 1 decreases with time. The decrease in the internal pressure of the battery 1 can also be detected from a table stored as the internal pressure specified from the temperature and time, regardless of the internal pressure decrease function.

[Steps n = 4, 5]
If it is determined that the battery 1 is charged, the voltage, charging current, and temperature of the battery being charged are detected in n = 4 steps. Further, in step n = 5, the voltage X at 0 A is calculated from the detected battery voltage, charging current, and temperature.
As shown in FIG. 4, the relationship between the internal pressure increase voltage and the charging current can be expressed as a linear function whose gradient is determined by temperature. That is, when the temperature is detected, a gradient of a linear function that specifies the relationship between the internal pressure increase voltage and the charging current can be obtained. The control unit 2 stores in a memory a function or table that specifies a gradient of a linear function indicating the relationship between the internal pressure increase voltage and the charging current from the temperature, and based on this function or table, the internal pressure increase voltage and the charge are detected from the detected temperature. The gradient of a linear function that specifies the current relationship is specified.
The detected battery voltage and charging current are substituted into the linear function for which the gradient is determined, and the intercept of this linear function is calculated. In the graph shown in FIG. 4, the horizontal axis represents the charging current, and thus the calculated intercept value corresponds to the voltage at 0 A. As described above, the voltage X at 0 A is calculated from the detected battery voltage, charging current, and temperature.

[Step n = 6]
It is determined whether or not the voltage X at 0A obtained in the step of n = 5 is higher than the internal pressure increase voltage at 0A. The internal pressure increase voltage at 0 A can be obtained from an internal pressure increase voltage specifying function, which is a function of temperature and current, stored in the memory of the control unit 2. However, the control unit stores in the memory a table that specifies the internal pressure increase voltage at 0A from the temperature and current, and based on this table, determines whether the voltage at 0A is higher than the internal pressure increase voltage at 0A. It can also be determined.
[Step n = 7]
If the voltage X at 0A is not higher than the internal pressure increase voltage at 0A, in other words, below the internal pressure increase voltage at 0A, the charging current is not integrated in this step.

[Step n = 8]
If the voltage X at 0A of the battery 1 being charged is higher than the internal pressure increase voltage at 0A, in this step, the current and time charged exceeding the internal pressure increase voltage are integrated. That is, the product of the time over which the internal pressure rise voltage is exceeded and the charging current is calculated. The calculated integrated value is added to any previous integrated value.
[Step n = 9]
The internal pressure of the battery is calculated by multiplying the calculated integrated value by the conversion coefficient, that is, from the product of the integrated value and the conversion coefficient.

[Step n = 10]
The calculated internal pressure is compared with the charge prohibition internal pressure. The charge prohibition internal pressure is a pressure set lower than the valve opening pressure of the safety valve, and is stored in the memory of the control unit 2 in advance. For example, the charging prohibition internal pressure is set to 30 to 90%, preferably 40 to 80%, more preferably 40 to 70% of the valve opening pressure of the safety valve. If the calculated internal pressure is lower than the charge-prohibited internal pressure, the process loops to a step of n = 1.

  In this step, a weighted average value can be detected from both the calculated internal pressure and the remaining capacity of the battery 1, and the weighted average value can be compared with the charge control internal pressure.

[Step n = 11]
When the calculated internal pressure or the weighted average value is higher than the charge prohibition internal pressure, the control unit 2 sets the charge switching circuit 8 in a state in which charging is prohibited, stops charging, and sets in a state in which only discharge is possible. The charging switching circuit 8 is a switch such as a switching element or a relay, and can be turned off to prohibit charging. However, since the hybrid car has an inverter connected between the battery and the generator, the inverter can be controlled to a state in which charging is prohibited, and charging of the battery can be suspended. The inverter in a state where charging is prohibited interrupts the charging current, but is controlled so that it can be discharged.

  In the above battery charge control method, the battery internal pressure is calculated for each battery module unit, or the internal pressure is calculated for each battery unit, the calculated maximum internal pressure is compared with the charge control internal pressure, and the maximum internal pressure is calculated. When the internal pressure becomes higher than the charging control internal pressure, the charging of the battery is prohibited or the charging current is controlled to be small. It is also possible to calculate and detect the internal pressure of the battery with all the batteries as one block, and control the charging current by comparing the calculated internal pressure with the charge control internal pressure.

  In the method of detecting the internal pressure of each battery or battery module, the battery life can be determined from the calculated internal pressure. It is easy to increase the internal pressure of a battery whose lifetime has expired and whose electrical characteristics have deteriorated compared to other batteries. Therefore, even if a battery whose lifetime has expired is charged and discharged with the same current, the calculated internal pressure is charged. This is because the probability of exceeding the control internal pressure increases. Therefore, it can be determined that the battery or battery module whose calculated internal pressure exceeds the charge control internal pressure for a specific number of times or more in a specific period has expired.

It is a circuit diagram which shows an example of the circuit which controls charge of a battery with the charge control method of the battery concerning one Example of this invention. It is a figure which shows the weight which a control circuit controls a charge switching circuit. It is a graph which shows the characteristic of a battery voltage and an internal pressure rise. It is a graph which shows the characteristic of a charging current and an internal pressure rise voltage. It is a graph which shows the state which the internal pressure of the battery charged exceeding internal pressure rise voltage rises. It is a graph which shows the characteristic that the internal pressure of a battery falls. It is a flowchart which shows an example which calculates internal pressure from the temperature of a battery, a voltage, and a charging current, and controls charge of a battery. It is a flowchart which shows another example which calculates internal pressure from the temperature of a battery, a voltage, and a charging current, and controls charging of a battery.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Battery 2 ... Control unit 3 ... Voltage detection circuit 4 ... Current detection circuit 5 ... Temperature detection circuit 6 ... Arithmetic circuit 7 ... Control circuit 8 ... Charge switching circuit 9 ... Remaining capacity detection circuit 10 ... Temperature sensor 11 ... Generator 12 ... Load R

Claims (14)

A method for detecting a voltage and a charging current of a battery being charged, and detecting an internal pressure of the battery from the charging current and the voltage,
The internal voltage rise voltage at which the internal pressure of the battery starts to rise is specified based on the charge current, and the charge current and time are integrated in the internal pressure rise charge in which the charged battery voltage exceeds the internal pressure rise voltage. A battery charge control method that calculates the internal pressure of a battery from an integrated value and controls the state of charge of the battery by the calculated internal pressure of the battery. A method for detecting the internal pressure of the battery from the battery temperature, charging current and voltage by detecting the temperature, voltage and charging current of the battery being charged,
The internal voltage rise voltage at which the internal pressure of the battery starts to rise is specified based on the temperature and the charge current, and the charge current and time are integrated in the internal pressure rise charge where the charged battery voltage exceeds the internal pressure rise voltage. A battery charge control method that calculates the internal pressure of the battery from the integrated value and controls the state of charge of the battery by the calculated internal pressure of the battery.   The battery according to claim 1 or 2, wherein the internal pressure of the battery including the safety valve is calculated and detected, and the state of charge of the battery is controlled so that the calculated internal pressure of the battery is lower than the opening pressure of the safety valve. Charge control method.   An internal pressure increase voltage specifying function that identifies the internal pressure increase voltage from the current and voltage is detected, the voltage and current of the battery being charged are compared with the internal pressure increase specific function, and the internal pressure increases when the voltage is higher than the internal pressure increase voltage The battery charging control method according to claim 1 or 2, wherein the charging current and time are integrated as charging.   3. The battery charge control method according to claim 1, wherein in a state where the battery is not charged, the detected internal pressure is decreased at a predetermined decrease rate as time elapses.   The battery charge control method according to claim 5, wherein the rate of decrease of the internal pressure is changed with temperature.   3. The battery charge control method according to claim 1 or 2, wherein the calculated internal pressure of the battery is neither added nor subtracted in a state where the battery is charged and does not exceed the internal pressure increase voltage.   The battery charge control method according to claim 1 or 2, wherein the internal pressure increase voltage is changed as a function of time.   Calculates the remaining capacity from the charge / discharge current of the battery, controls the charge switch with the weighted average value of the remaining capacity and the calculated internal pressure, and weights the weighted average of the remaining capacity and the calculated internal pressure with the remaining capacity value. The battery charge control method according to claim 1 or 2, wherein (weight) is changed.   The battery according to claim 1 or 2, wherein the voltage and charging current of a plurality of batteries charged and discharged simultaneously are detected, and the charging current of all the batteries is controlled by an internal pressure calculated from the specific battery voltage and charging current. Charge control method.   3. The voltage and charging current of a plurality of batteries that are charged and discharged simultaneously are detected, the internal pressure of each battery is calculated from each battery voltage and charging current, and the battery life is determined from the calculated internal pressure. The charge control method of the battery described in 2.   The charge control method for a battery according to claim 1 or 2, wherein the remaining capacity calculated by integrating the charge / discharge current is corrected by an integration value of the charge current and time charged exceeding the internal pressure increase voltage.   The battery charging control method according to claim 1, wherein the battery is a power source for driving an electric vehicle. The battery charge control method according to any one of claims 1 to 12, wherein the battery is a power source for driving an electric vehicle and is a battery accompanied by gas generation during normal charging or overcharging.

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