JP5332559B2 - Charger - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To make sufficient use of a time until a secondary battery is used next and prevent a current value from becoming excessive even in secondary batteries different in capacity during charging. <P>SOLUTION: A charge controlling means gradually increases a charging current after start of charging and determines a charging current when the difference between terminal voltage and open voltage V<SB>o</SB>reaches a predetermined voltage difference set value &Delta;V<SB>a</SB>as maximum charging current I<SB>0</SB>. It carries out precharging with the maximum charging current. It determines a time t<SB>p0</SB>it takes for terminal voltage to reach an inflection-point voltage V<SB>p0</SB>by charging with the maximum charging current from a terminal voltage increment &Delta;V<SB>b</SB>relative to the precharging time t<SB>0</SB>. It calculates the earliest ending time T<SB>min</SB>at which charging is terminated based thereon and calculates a remaining amount of charge based thereon. When a target ending time T<SB>1</SB>is later than the earliest ending time, it determines a first current value and a second current value so that second constant-current charging is terminated at the target ending time. This determination is made based on the remaining amount of charge, a charging time relational expression between first constant-current charging and second constant-current charging, and a relational expression between the first current value I<SB>1</SB>and the second current value I<SB>2</SB>. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to a charging device that charges a secondary battery.

  In the process of charging the discharged secondary battery, the terminal voltage of the secondary battery increases, but an inflection point appears in the terminal voltage curve with respect to the charging time as it approaches full charge. If the terminal voltage exceeds this inflection point, the rate at which electrical energy supplied to the secondary battery is converted to thermal energy increases rapidly, resulting in poor charging efficiency and damage to the secondary battery due to heat generation. There is a risk of receiving. Therefore, conventionally, constant current charging is performed with a relatively large current value (hereinafter referred to as “current value Ia”) until the terminal voltage reaches the inflection point or until it reaches a voltage slightly lower than the inflection point. Therefore, the battery is kept as close to full charge as possible, and then charged with constant current with a relatively small current value (hereinafter referred to as “current value Ib”) until the battery is fully charged while suppressing heat generation. The charging method to be performed is performed.

  The inventor of the present invention has proposed a charging method in which the length of the total charging time is variable and the magnitude of the current value Ib can be set according to the length of the total charging time. (See Patent Document 1). According to this method, it is possible to cope with a change in time from the end of use of the secondary battery to the start of use of the secondary battery, and sufficiently charge the time to suppress the current value Ib to perform charging. Thus, heat generation can be suppressed and damage to the secondary battery can be reduced. In addition, since the charging can be terminated immediately before the use is started, the charged secondary battery is not left for a long time until the next use, and the charged state due to the spontaneous discharge of the secondary battery is prevented. A decrease in the chemical reaction activity due to a decrease in the temperature of the secondary battery can be prevented.

  However, the charging method of Patent Document 1 has room for improvement in that it is necessary to input the current value Ia according to the battery capacity of the secondary battery prior to charging. There has also been a demand for suppressing heat generation of the secondary battery in constant current charging with a relatively large current value Ia.

  Here, a charging device that adjusts a current value in constant current charging according to the battery capacity of the secondary battery has also been proposed (see Patent Document 2). Prior to constant current charging, the secondary battery's open circuit voltage is measured multiple times while flowing a constant current, and the battery capacity is determined by two or more open circuit voltages, the time between each measurement point, and the charge current value. The current value for performing constant current charging is determined based on the estimated battery capacity and a predetermined charging time.

JP 2005-20894 A JP 2008-61373 A

  However, in the charging device of Patent Document 2, since the total charging time is a predetermined fixed value, the time until the secondary battery is next used cannot be fully utilized, and the state of charge is caused by spontaneous discharge. There is a risk that the activity of the chemical reaction in the secondary battery may decrease due to a decrease in temperature. In addition, in the charging device of Patent Document 2, in order to measure the open circuit voltage a plurality of times, it is necessary to repeatedly turn on and off the electrical connection between the power supply unit and the secondary battery, and the control is complicated. . In addition, every time the electrical connection with the power supply unit is turned off multiple times, the terminal voltage of the secondary battery greatly decreases, so charging hardly proceeds during the process for estimating the battery capacity, and as a whole There was a problem of poor charging efficiency.

  Therefore, in view of the above circumstances, the present invention is a secondary battery having a different battery capacity by fully utilizing the time that may vary from the end of use of the secondary battery to the start of the next use. However, an object of the present invention is to provide a charging device that can efficiently charge while preventing the current value from becoming excessively large to suppress heat generation.

  In order to solve the above-described problems, the charging device according to the present invention includes a power supply unit that supplies DC power to a secondary battery, and a charging current detection unit that detects a charging current flowing from the power supply unit to the secondary battery. A terminal voltage detector for detecting a terminal voltage of the secondary battery; a clock means for outputting time; an output of the time by the clock means; a time measurement based on the time output from the clock means; and the charging current Based on detection of the charging current by the detection unit and detection of the terminal voltage by the terminal voltage detection unit, by controlling the supply of DC power from the power supply unit to the secondary battery, the first current value Charging control means for controlling execution of the first constant current charging by the second constant current charging by the second current value smaller than the first current value, and the charging control means comprises the secondary battery before charging. Open circuit voltage And gradually increasing the charging current while starting charging, determining the charging current when the difference between the terminal voltage and the open voltage reaches a predetermined voltage difference setting value as a maximum charging current, A precharge time for performing precharge with the maximum charge current and a value for increasing the terminal voltage associated with the precharge are determined in advance, the precharge is executed, the other value is calculated, and the precharge time is calculated. The time required for the terminal voltage to reach the inflection point voltage when it is assumed that charging with the maximum charging current is continued from the increase in the terminal voltage with respect to the shortest end time at which charging is terminated based on the required time And calculating the remaining charge amount from the end of the precharge to the shortest end time, and the end target time stored prior to the start of charge is after the shortest end time The remaining constant current charging is terminated at the end target time based on a predetermined distribution formula as a relational expression between the charging amount by the first constant current charging and the charging amount by the second constant current charging. The charge amount is distributed to the first constant current charge and the second constant current charge to determine the first current value and the second current value, and the first constant current charge according to the determined first current value And the second constant current charging with the second current value is performed.

  According to the charging device of the present invention having the above-described configuration, the maximum charging current is first obtained, the shortest end time is calculated from the precharge by the maximum charging current, and when the end target time is after the shortest end time, the end target time is set. The remaining charge amount is distributed to the first constant current charge and the second constant current charge so that the second constant current charge is completed. Therefore, it is possible to charge the secondary battery by making full use of the time until the target end time and keeping both the first current value and the second current value small.

  As a result, constant current charging is performed with a relatively large current value so that it is as close to full charge as possible, and then charging is performed compared to conventional charging in which constant current charging is performed with a relatively small current value. The risk of the secondary battery being damaged by heat generation can be greatly reduced. In addition, since the first current value and the second current value are determined so that the second constant current charging ends at the end target time, the charging of the secondary battery can be ended immediately before the start of use. As a result, it is possible to prevent a decrease in the state of charge due to spontaneous discharge, and it is possible to prevent a decrease in the activity of the chemical reaction due to a decrease in temperature of the secondary battery.

  Even if the voltage difference setting value is the same, if the battery capacity is different, the charging current when the terminal voltage is increased by the voltage difference, in other words, the maximum charging current is different. That is, the larger the battery capacity of the secondary battery, the smaller the internal impedance, so the amount of voltage increase when the same current flows is small. If the voltage difference setting value is the same, the larger the battery capacity, the larger the maximum charging current. Become. Therefore, according to the present invention, the difference in battery capacity can be reflected in the charging conditions without measuring the battery capacity itself of the secondary battery, and charging can be performed under conditions suitable for the battery capacity.

  Furthermore, since the secondary battery is charged even during the precharge performed for calculating the shortest end time, the entire battery can be charged efficiently.

  The charging amount when the terminal voltage reaches the inflection point voltage in constant current charging is normally 80 to 90% of the full charge, and the increase characteristic of the terminal voltage after the inflection point is It differs depending on the type of secondary battery and the charging current value. Therefore, considering how long it takes to charge after reaching the inflection point voltage, charging can be completed in a state closer to full charge, and the time required to reach the inflection point voltage and the inflection The process of “calculating the shortest end time to end charging based on the required time” in the above configuration by predetermining a relational expression or table with the charging time after reaching the point voltage based on experience It can be performed.

  The charging device according to the present invention is described as follows. “The distribution formula is a charging time relationship in which a relationship between a time from the start of charging to the end of the first constant current charging and a time for performing the second constant current charging is determined in advance. The equation and the relationship between the first current value and the second current value are configured from a predetermined current value relational expression.

  With the above configuration, according to the charging device of the present invention, the first current value depends on the length of time from the shortest end time to the target end time, in other words, how much time is available until the shortest end time. The four factors of the second current value, the time until the first constant current charging is completed, and the time for performing the second constant current can be varied. This makes it easy to set the first current value and the second current value to appropriate values when allocating the remaining charge amount to the first constant current charge and the second constant current charge, and further reduces the damage received by the secondary battery. However, charging can be performed by fully utilizing the time until the end target time.

  In addition to the above-described configuration, the charging device according to the present invention further includes a “storage device that stores a table in which a voltage difference and an open circuit voltage are associated with each other, and the charge control unit includes a voltage difference associated with the acquired open circuit voltage. Is read out from the table and defined as a voltage difference set value, and a process for determining the maximum charging current is performed. "

  With the above configuration, according to the charging device of the present invention, the voltage difference set value is set with reference to the voltage difference-open voltage table, so that the larger the discharge is and the smaller the open voltage is, the larger the voltage difference set value is. It is possible to set to use. Thereby, it becomes possible to charge by determining an appropriate charging condition according to the discharge amount of the secondary battery.

  The charging device according to the present invention is described as follows: "The charging control means is a constant voltage charging or a variable voltage that decreases the charging current while continuing the charging between the first constant current charging and the second constant current charging. To charge ". Here, “constant voltage charging” is charging performed with a constant voltage value, whereas charging performed while changing the voltage value is referred to as “variable voltage charging”.

  If switching to the second constant current charging immediately after the end of the first constant current charging, the terminal voltage of the secondary battery may drop significantly due to the discontinuous decrease in the charging current. In contrast, in the present invention, the current value is gradually decreased while charging by performing constant voltage charging or variable voltage charging before the transition to the second constant current charging after the completion of the first constant current charging. Therefore, the secondary battery can be efficiently charged as a whole.

  As described above, as an effect of the present invention, a secondary battery having different battery capacities by fully utilizing the time that may vary from the end of use of the secondary battery to the start of the next use. However, it is possible to provide a charging device that can efficiently charge while preventing the current value from becoming excessively large in order to suppress heat generation.

Hereinafter, a charging apparatus according to an embodiment of the present invention will be described with reference to FIGS. Here, FIG. 1 is a block diagram showing the configuration of the charging device of the present embodiment, and FIGS. 2 to 4 are relationships between charging time, charging current, and terminal voltage for charging the secondary battery by the charging device of FIG. FIG. 5 is a graph illustrating the integration values A ₁ and A _{2 according} to the charging current time, respectively, when the end target times are T ₁ , T ₂ and T ₃ , respectively. FIG. 7 is a flowchart for explaining the flow of processing in the charging apparatus of FIG.

  As shown in FIG. 1, the charging device 1 of the present embodiment includes a power supply unit 5 that supplies DC power to the secondary battery 59 and a charging current detection unit that detects a charging current flowing from the power supply unit 5 to the secondary battery 59. 6, a terminal voltage detection unit 7 that detects a terminal voltage of the secondary battery 59, and a computer 9 that includes a control unit 10 that controls charging of the secondary battery 59 by the charging device 1 as a functional configuration. Has been.

  More specifically, the power supply unit 5 includes a rectification unit 2 having a full-wave rectification circuit and a switching type DC-DC conversion unit 3, and the AC power supplied from the AC power supply 51 is all supplied by the rectification unit 2. After the wave rectification, the DC-DC conversion unit 3 converts the voltage into a different voltage and supplies it to the secondary battery 59. Further, the charging current detection unit 6 and the terminal voltage detection unit 7 output the detected charging current and the terminal voltage of the secondary battery 59 to the control unit 10, respectively.

  The computer 9 has a central processing unit, a main storage device, and an auxiliary storage device as hardware configurations, and a program that causes the computer 9 to function as the charge control means 20 is stored in the main storage device. The computer 9 also includes a clock unit 13 for outputting time, an operation input unit 11 such as a keyboard and a ponting device for inputting information such as an end target time and various commands to the control unit 10, and charging control. An output unit 12 such as a monitor for outputting the process and results of the processing by the means 20 via the display means 40 is provided.

  Further, the auxiliary storage device 30 includes an end target time storage unit 31 that stores the input end target time, and a charge start time storage unit 32 that stores a charge start time when charging is started, and a voltage difference and release. A voltage difference-open voltage table 35 associated with the voltage and a current-inflection voltage table 36 associated with the current value and the inflection point voltage at the current value are stored. The auxiliary storage device of this embodiment corresponds to the “storage device” of the present invention.

The charging control unit 20 includes a time measuring unit 21 that measures time based on the output of the clock unit, a charging current integrating unit 22 that integrates the charging current with time, and a voltage difference − a voltage difference setting value determining means 23 for determining reads from the open voltage table 35 as the voltage difference set value [Delta] V _a, the charging current when the difference between the terminal voltage and the open-circuit voltage reaches the voltage difference set value [Delta] V _a defined the maximum charging current determining means 24 for determining the maximum charging current I _0, and precharge time t ₀ executions predetermining precharge by the maximum charging current, the terminal voltage increment [Delta] V _b after the elapse of the precharge time t ₀ and precharge control means 25 for calculating, from the terminal voltage increment [Delta] V _b for precharge time t _0, varying terminal voltage at a current I ₀ when it is assumed to continue the charging with the maximum charge current I ₀ Calculates the time required to reach the point voltage V _po, the shortest end time calculation means 26 for calculating a remaining charge amount to calculate the shortest end time T _min based on the required time, the end target time and the shortest end time T _Based on the relationship with _min , the remaining charge amount, the charging time relational expression, and the current value relational expression, the first current value I ₁ , the second current value I ₂ , and the variable voltage charging are terminated and the second constant is determined. Current value calculating means 27 for determining the switching current value I ₂ ′ to be switched to current charging, and switching voltage calculating means for calculating the switching voltage V ₁ for switching from the first constant current charging to the variable voltage charging based on a predetermined arithmetic expression. 28, and a constant current charge / variable voltage charge control means 29 for controlling execution of the first constant current charge, variable voltage charge, and second constant current charge.

Next, the flow of processing in the charging device 1 will be described with reference to FIGS. First, when the process is started, the open-circuit voltage V ₀ of the secondary battery 59 is acquired based on the detection of the terminal voltage detector 7 prior to the start of energization of the secondary battery 59 (step S1). Also, an end target time is set (step S2). Here, if the end target time is input from the operation input unit 11, it is received and stored in the end target time storage unit 31. Alternatively, when the start time of use of the secondary battery 59 is constant every day as in the start work start time, for example, one hour before the start work start time is stored in the end target time storage unit 31 as a default value. If the end target time is not input from the operation input unit 11, the time already stored in the end target time storage unit 31 is used as the end target time as the default value or the end target time in the previous process. Can be set as

Then, the voltage difference - with reference to the open circuit voltage table 35, reads the voltage value associated with the open circuit voltage V ₀ obtained, and determines the value as a voltage difference setting value [Delta] V _a (step S3). Then, the current time is stored in the charging start time storage unit 32 as the charging start time by the output of the clock means, and the power source unit 5 is controlled to start charging the secondary battery 59 (step S4). Increase gradually (step S5). Then, the charging current is gradually increased at a constant rate until the difference between the terminal voltage and the open voltage reaches the voltage difference set value ΔV _a (No in step S6), and the difference between the terminal voltage and the open voltage is ΔV _a. upon reaching (Yes in step S6), and it determines the charging current at this time as the maximum charging current _{I 0} (step S7). The elapsed time is always measured by the time measuring means based on the output of the clock means. Further, the charge amount is always calculated by the charge current integration means as an integral value according to the time of the charge current.

Next, the pre-charge at a predetermined precharge time t ₀ by the constant current at a maximum charging current I ₀ which is determined (step S8). After the elapse of time t ₀ , the terminal voltage increase ΔV _b = V _t0 −ΔV _a −V ₀ in precharging is calculated based on the detection of the terminal voltage V _t0 (step S9). The current - reading the inflection point voltage Vp ₀ when the current I ₀ from the inflection point voltage table 36. When it is assumed that charging with the maximum charging current I ₀ is continued from the slope (ΔV _b / t ₀ ) of the charging time-terminal voltage curve in precharging, the terminal voltage becomes the inflection point voltage V _p0 from the start of precharging. The time t _p0 to reach is known. Normally, the charge amount when the terminal voltage reaches the inflection point voltage _Vp0 in constant current charging is 80 to 90% of full charge, and a relational expression (e.g., t _f = αt _po + β), a time t _f until it is determined that the battery has almost fully charged since the start of precharging and the charging is finished is calculated.

Since the time that started the precharge can be grasped on the basis of the output by the clock means, determine the time T _min after the lapse of time t _f from the time of precharge started, the time and the shortest end time T _min (step S10 ). Further, the amount of charge from the end of precharge to the shortest end time T _min that reaches almost full charge is calculated and set as the remaining amount of charge (step S11).

Further, the shortest end time _Tmin is compared with the target end time, and when the target end time is after the shortest end time (Yes in step S12), the remaining charge amount, from the start of charging to the end of the first constant current charging. A charging time relational expression (for example, t ₂ = 0.4 × t ₁ +0.4 (h)) that predetermines the relationship between the time t ₁ and the time t ₂ for performing the second constant current charging, and the first current Based on a current value relational expression (for example, I ₂ = k × I ₁ , 0 <k <1) that predetermines the relationship between the value I ₁ and the second current value I ₂ , the first current value I ₁ and the second current value I ₂ determining a second current value _{I 2} (step S13). At this time, based on the determined second current value I ₂ , the switching current value I ₂ ′ for switching to the second constant current charging can also be determined by the relational expression described later.

Thus, after the precharge, the first constant current charging with a first current value I _1, performed from the time of start of charging to the point where time t ₁ has elapsed, the second current value I ₂ according to the second constant-current charging time t ₂ , the second constant current charging is almost completed at the target end time, but in this embodiment, the first constant current charging and the second constant current charging are not managed by time, The constant current charging is managed by the actual terminal voltage of the secondary battery 59, and the second constant current charging is managed by the charge amount as described later. Specifically, the switching voltage V ₁ for ending the first constant current charging is determined by the arithmetic expression V ₁ = (I ₁ / I ₀ ) m + V _p0 (step S14). Here, m is a negative factor, switching voltages V ₁ is slightly smaller than the inflection point voltage V _p0 in the case of charging with the maximum charge current I _0.

Then, until it reaches the switching voltages _{V 1} the terminal voltage has been determined, the first constant current charging performed by the first current value _{I 1} (No in step S15, step S16). When the terminal voltage reaches the switching voltage V ₁ (in step S16 Yes), and terminates the first constant current charging, the integrated value A ₁ to grasp the charging amount up to this point as the integrated value A ₁ with time of the charging current calculates _{a 2} to be described later from (step S17), and proceeds to the variable voltage charge (step S18).

In variable voltage charging, a predetermined arithmetic expression V _x = K × I _x + n to V _{x is} set so that the charging current I _x detected by the charging current detector 6 and the terminal voltage V _x have a proportional relationship. look, the voltage applied to the control unit 10 to control to the secondary battery 59 is adjusted to be V _x. Then, until the switching current value I ₂ ′ is slightly larger than the second current value I ₂ , the charging current is gradually reduced by the above process (No in step S19). In this embodiment, the relational expression I ₂ ′ = k ′ × I ₁ (0 <k <k ′ <1) is used, and the switching current value I ₂ ′ is a value slightly larger than the second current value I _2. It is set to be.

When the charging current reaches the switching current I ₂ ′ (Yes in Step S19), the charging current is switched to the second current value I ₂ and the second constant current charging is performed (Step S20). The second constant-current charging, as shown in FIG. 5, on the basis of the calculation by the charging current integrating means, carried out until the integrated value by the time of the constant current charging at the end after the charging current reaches A ₂ ( No in step S21). Here, A ₂ is determined by predetermining a ratio to the integrated value A ₁ obtained by integrating the charging current with time from the start of charging to the end of the first constant current charging, or the relationship between A ₁ and A _2. It can be calculated by predetermining the formula. Then, the integration value by the time of the constant current charging at the end after the charging current reaches the A ₂ (Yes in step S21), and terminates the charging of the secondary battery 59. Note that V _p2 in FIG. 5 is the inflection point voltage V _p2 at the second current value I ₂ . Normally, the charging amount when the terminal voltage reaches the inflection point voltage in constant current charging is 80 to 90% of full charging, but in this embodiment, the integral value depending on the charging current time is A _{2. Therefore} , even after the terminal voltage reaches V _p2 , charging is continuously performed at the second current value I ₂ that is a small current value.

By the above processing, when the end target time is after the shortest end time T _min , the secondary current is charged as shown in the charging current curve and the terminal voltage curve with respect to the charging time in FIGS. Here, FIG. 2 shows a case end mark time is T _1, FIG. 3 shows the case end mark time is earlier time T _2, from T _1. As is apparent from these graphs, the remaining charge amount is distributed to the first constant current charge and the second constant current charge according to the length of time from the shortest end time _Tmin to the end target time. Charging can be performed while the first current value I ₁ and the second current value I ₂ are both reduced to a smaller value as the time is increased.

On the other hand, as shown in FIG. 4, the end mark time _{T 3} in the case of prior shortest end time _{T min} and by performing (No in step S12), the first constant current charging at the maximum charging current _{I 0 (I 1} = I ₀ ), I ₂ and I ₂ ′ are calculated from the current value relational expression (step P1), and V ₁ is calculated in the same manner as described above (step P2).

Although subsequent processing is the same as the above-described processing (step P3～P9), in the example of FIG. 4, the integrated value over time of the charging current is terminated target time T ₃ arrives before reaching the A _2. Therefore, in the present embodiment, even when the second constant current charging is in progress, if a termination command is input by a manual input by the user (Yes in Step P10), the charging is terminated.

As described above, according to the charging device 1 of the present embodiment, fully utilize the time to the end target time, both suppressed the first current value I ₁ and the second current value I _2, the secondary battery 59 The secondary battery 59 can be charged by reducing the risk of damage.

Even if the voltage difference setting value ΔV _a is the same, the maximum charging current I ₀ differs if the battery capacity is different. Therefore, the difference in battery capacity is not measured without measuring the battery capacity itself of the secondary battery 59. Can be reflected in the charging conditions, and charging can be performed under conditions suitable for the battery capacity.

In addition, in this embodiment, ΔV _a is determined based on the open voltage of the secondary battery 59 by referring to the voltage difference-open voltage table 35. Thus, for example, ΔV _a can be set large when the discharge is deep, and ΔV _a can be set small when the discharge is shallow, and charging is performed by setting appropriate charging conditions according to the discharge amount. Can do.

Moreover, since during the precharge secondary batteries 59 performed to calculate the shortest end time T _min is charged, it is possible to perform efficiently charge as a whole. Further, before the transition to the second constant current charging after the completion of the first constant current charging, the current value is gradually decreased while continuing the charging to the current value I ₂ ′ close to the second current value I _2. Therefore, unlike the case of directly switching from the first constant current charge to the second constant current charge, the terminal voltage does not drop greatly, and the secondary battery 59 can be efficiently charged as a whole.

Furthermore, in this embodiment, after the completion of the first constant current charging, as charging that gradually decreases the current value while charging, a variable voltage that decreases the voltage so as to be proportional to the charging current that changes and decreases every moment. Charging is in progress. Conventionally, when charging is performed by changing the current value to the current value of constant current charging performed later between two constant current charging, constant voltage charging is performed at a voltage value corresponding to the current value of constant current charging performed later. In this case, it takes time to reach the current value of constant current charging to be performed later. On the other hand, in this embodiment, since the voltage value is gradually decreased from a high voltage value, the charging efficiency is high, and the current can be dropped earlier until the switching current value I ₂ ′ is reached.

In addition, in the present embodiment, the variable voltage charging is terminated with a switching current value I ₂ ′ slightly larger than the second current value I ₂ . Therefore, the terminal voltage slightly decreases discontinuously at the start of the second constant current charging, and the terminal voltage increases with the second constant current charging. Accordingly, even when reaching the inflection point voltage V _p2 soon at a current value I ₂ after switching to the second constant-current charging, easy to grasp it.

In addition, the charge amount when the terminal voltage reaches the inflection point voltage is normally 80 to 90% of the full charge, but in this embodiment, the charge current time in the first constant current charge Since the second constant current charging is performed until the integration value according to the charging current time after the completion of the first constant current charging becomes A ₂ based on the integration value A ₁ by the terminal current, the terminal voltage is equal to the second current value I ₂ . Even after reaching the inflection point voltage _Vp2 , the charging is continued. Therefore, it is possible to charge the secondary battery 59 to a state closer to full charge while suppressing the heat generation of the secondary battery 59 with the current value I ₂ which is a small current value.

In addition, in the present embodiment, when the first current value I ₁ and the second current value I ₂ are determined, a relational expression between the charging times t ₂ and t ₁ is used. Switching to voltage charging, switching from variable voltage charging to second constant current charging, and termination of second constant current charging are not time-based control, but include switching voltage V ₁ , switching current I ₂ ′, charging current It is controlled by the integral value A ₂ with time. As described above, since the charging control is performed reflecting the actual charging state of the secondary battery 59, the charging can be performed more appropriately.

  The present invention has been described with reference to the preferred embodiments. However, the present invention is not limited to the above-described embodiments, and various improvements can be made without departing from the scope of the present invention as described below. And design changes are possible.

For example, in the above, the precharge time t ₀ is set in advance in the precharge, and the terminal voltage curve slope with respect to the charge time is obtained by detecting the terminal voltage increase ΔV _b after the precharge time t _{0 has} elapsed. On the contrary, ΔV _b may be set to a predetermined value, and the time t ₀ required for the terminal voltage to rise by ΔV _b may be measured. In the case of the former, by the terminal voltage it takes a long time to increase by [Delta] V _b, there is a merit that it is possible to avoid the risk that the rate of pre-charge the entire charging time increases.

  Moreover, although the case where the inflection point voltage in a certain current value is read from the current-inflection point voltage table is illustrated, the present invention is not limited to this, and an arithmetic expression in which the relationship between the current value and the inflection point voltage is determined in advance is used. Thus, the inflection point voltage can be calculated.

Further, in the process of obtaining the maximum charging current, the case where the voltage difference-open voltage table is used when ΔV _a is determined based on the open voltage has been illustrated. A table to which a temperature element is added is provided, and a temperature detection unit that detects the temperature of the secondary battery is provided, and ΔV _a can be determined based on the temperature and open circuit voltage of the secondary battery.

  Moreover, although the case where the charging time relational expression was preset was illustrated above, it is not limited to this, It can also be set as the structure which a user can select from several charging time relational expressions. For example, when precharging is completed, the charging current curve and the terminal voltage curve with respect to the charging time when the first current value and the second current value calculated based on different charging time relational expressions are used, such as a monitor It is possible to set a charging time relational expression by displaying a plurality of items on the output unit 12 and selecting a desired charging current curve and terminal voltage curve from among them and inputting them from the operation input unit 11.

It is a block diagram which shows the structure of the charging device of this embodiment. Is a graph for charging the secondary battery by the charging device of FIG. 1 shows the relationship between the charging time and the charging current and the terminal voltage (If the end goal time is T _1). It is a graph for charging the secondary battery by the charging device of FIG. 1 shows the relationship between the charging time and the charging current and the terminal voltage (If the end goal time is earlier time T _2, from T _1). Is a graph for charging the secondary battery by the charging device of FIG. 1 shows the relationship between the charging time and the charging current and the terminal voltage (If the end target time T ₃ is earlier than the shortest end time T _min). Is a graph illustrating the integral value A ₁ and A ₂ is calculated by integrating the charge current time. 3 is a flowchart for explaining a processing flow in the charging apparatus of FIG. 1. 7 is a flowchart for explaining the flow of processing in the charging device of FIG. 1 following FIG. 6.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Charging apparatus 5 Power supply part 6 Charging current detection part 7 Terminal voltage detection part 13 Clock means 20 Charging control means 30 Auxiliary storage device (storage device)
35 Voltage difference-open voltage table 59 Secondary battery I ₁ First current value I ₂ Second current value I ₀ Maximum charging current V ₀ Open voltage V _p0 Current I _{0 Inflection} point voltage ΔV _a Voltage difference set value Δ V _b terminal voltage increase t ₀ precharge time t _p0 Precharge time required time until terminal voltage reaches inflection point voltage V _p0 T _min shortest end time T ₁ , T ₂ , T ₃ target end time

Claims (4)

A power supply unit for supplying DC power to the secondary battery;
A charging current detector for detecting a charging current flowing from the power source to the secondary battery;
A terminal voltage detector for detecting a terminal voltage of the secondary battery;
Clock means for outputting time;
Based on the output of the time by the timepiece means, the measurement of the time based on the time output from the timepiece means, the detection of the charging current by the charging current detection section, and the detection of the terminal voltage by the terminal voltage detection section , By controlling the supply of DC power from the power supply unit to the secondary battery, the first constant current charging by the first current value and the second constant current charging by the second current value smaller than the first current value Charging control means for controlling execution,
The charge control means includes
Obtain the open voltage of the secondary battery before charging,
Starting charging and gradually increasing the charging current, determining the charging current when the difference between the terminal voltage and the open voltage reaches a predetermined voltage difference set value as a maximum charging current,
Predetermining either one of the precharge time for precharging with the maximum charging current and the terminal voltage increase associated with the precharge, and performing the precharge to calculate the other value,
When it is assumed that the charging with the maximum charging current is continued from the increase in the terminal voltage with respect to the precharge time, the time required for the terminal voltage to reach the inflection point voltage is calculated, and charging is terminated based on the time required. Calculating the shortest end time to be calculated, and calculating the remaining charge amount from the end time of the precharge to the shortest end time,
When the end target time stored prior to the start of charging is after the shortest end time, a predetermined distribution formula is used as a relational expression between the charge amount by the first constant current charge and the charge amount by the second constant current charge. Based on the first current value and the second current, the remaining charge amount is distributed to the first constant current charge and the second constant current charge so that the second constant current charge ends at the target end time. A charging device that determines a value and executes the first constant current charging with the determined first current value and the second constant current charging with the second current value, respectively. The distribution formula is
A charging time relational expression that predetermines the relationship between the time from the start of charging to the end of the first constant current charging and the time for performing the second constant current charging, and the first current value and the second current The charging device according to claim 1, wherein the charging device is configured by a current value relational expression that has a predetermined relationship with a value. A storage device for storing a table associating the voltage difference with the open circuit voltage;
3. The charging device according to claim 1, wherein the charging control unit reads a voltage difference associated with the acquired open-circuit voltage from the table and sets the voltage difference as a voltage difference setting value. The charge control means includes
The constant voltage charging or the variable voltage charging for reducing the charging current while controlling the charging is controlled between the first constant current charging and the second constant current charging. The charging device according to claim 3.

Images