JP2000078758A - Rechargeable battery charge status management device - Google Patents

Abstract

(57) [Problem] To provide a secondary battery charge state management device capable of accurately detecting a charge state of a secondary battery that is repeatedly charged and discharged at random from its terminal voltage. SOLUTION: A detecting means for detecting an open voltage of a secondary battery, a table storing a relation between a terminal voltage of the secondary battery and a state of charge thereof, and a storage means for storing a maximum state of charge of the secondary battery are provided. The charging state detecting means detects the terminal voltage after the charging is stopped (step S8), and obtains the charging state SOCx by referring to the table based on the open voltage (step S9). When the state of charge SOCx exceeds the maximum state of charge SOCmax stored in the storage means (step S10), the state of charge SOCx is output as the current state of charge SOC (step S12). The SOCmax is updated (step S11).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a secondary battery charge state management device capable of accurately detecting the charge state of a secondary battery such as a nickel metal hydride battery and managing the charge state.

[0002]

2. Description of the Related Art Battery voltage of a secondary battery such as a nickel-metal hydride battery exhibits different characteristics between charging and discharging, and generally has a hysteresis characteristic. In particular, changes in the charge voltage and the discharge voltage change depending on the state of charge at the start of charging and at the start of discharging. Therefore, when charging and discharging of the secondary battery are repeated at random, it is difficult to grasp the state of charge using the battery voltage.

[0003]

Therefore, in the prior art, for example, the charge / discharge current of the secondary battery is always detected, and the detected current amount is successively integrated with the initial value of the charge amount in the secondary battery. The state of charge is grasped. However, when the charge amount of the secondary battery is obtained by current integration, there is a problem in that the integration error is accumulated, so that the state of charge cannot be accurately grasped. For this reason, it has also been difficult to perform management such as preventing overcharge of the secondary battery or preventing deep discharge.

The present invention has been made in view of such circumstances, and has as its object to reduce the state of charge of a secondary battery even when charging and discharging of the secondary battery are repeated at random. An object of the present invention is to provide a secondary battery charge state management device that can accurately detect the charge state and effectively manage the charge state.

[0005]

In order to achieve the above-mentioned object, a secondary battery charge state management apparatus according to the present invention uses a diagram to show the relationship between the battery voltage and the state of charge during charge / discharge of the secondary battery. It is noted that the device has a predetermined hysteresis characteristic as shown in FIG. 1 and that the open-circuit voltage after charging is stopped without depending on the charging current as shown in FIG.

That is, according to the present invention, the change characteristic (charging curve) A of the charging voltage when the secondary battery is charged from a predetermined initial state of charge SOC0 to a state of charge SOC3, and the above-mentioned state of charge SOC3 from the initial state of charge SOC0. After the battery is charged to the state of charge SOC2 before reaching the state of charge, the secondary battery is once discharged to the state of charge SOC1, and then the charging voltage change characteristic (charge curve) B when the secondary battery is charged to the state of charge SOC2 again. However, it is noted that the change characteristic of the charging voltage when the battery is further charged beyond the state of charge SOC2 matches the change characteristic A described above.

In particular, as shown in FIG. 2, the open-circuit voltage of the secondary battery after the charging is stopped slightly decreases from the terminal voltage when the charging is stopped due to the impedance and the charging current, and then decreases. Dependent on the characteristic, as shown by the broken line in the figure, the voltage drops with a different characteristic. Therefore, paying attention to this open-circuit voltage, as shown by the broken line in FIG. 1, the charge / discharge characteristic C does not depend on the charging current, and accurately indicates the charging state at that time.

Therefore, a charge management device for a secondary battery according to the present invention, as described in claim 1, has an open-circuit voltage V
b, a table storing a relationship between the open-circuit voltage Vb of the secondary battery and its state of charge SOC, for example, as shown in FIG. 1, and a maximum state of charge SOCmax of the secondary battery. And a charge state SOCx of the secondary battery obtained by referring to the table based on the terminal voltage Vb detected by the detection means, and a charge state SOCx obtained from the table.
Exceeds the maximum state of charge SOCmax stored in the storage means, the state of charge SOCx is changed to the current state of charge SOx.
And a charge state detecting means for outputting as C and updating the maximum charge state SOCmax stored in the storage means in the state of charge SOC.

That is, if the state of charge SOCx of the secondary battery is temporarily determined from the open-circuit voltage Vb of the secondary battery by referring to the table, this state of charge SOCx is stored in the storage means. It is determined whether the state exceeds the state SOCmax. When the state of charge SOCx exceeds the maximum state of charge SOCmax, it is determined that the open circuit voltage Vb has changed in accordance with the characteristic A stored in the table, and the state of charge SOCx determined from the table is output as the current state of charge SOC. It is characterized by doing. At the same time, this state of charge SOC is changed to a new maximum state of charge S.
It is characterized in that the storage means is updated as OCmax.

The open-circuit voltage Vb is detected as a battery voltage after a lapse of a predetermined time after the charging of the secondary battery is stopped. Further, according to a preferred aspect of the present invention, as set forth in claim 3, an initial state detecting means for detecting that the secondary battery has reached the initial state of charge SOC0 and prohibiting discharging of the secondary battery is provided. It is further characterized by being provided. Claim 4
And a charging control unit for prohibiting charging of the secondary battery in accordance with the maximum state of charge SOCmax stored in the storage unit. And a discharge control unit for forcibly discharging the secondary battery according to the maximum state of charge SOCmax stored in the storage unit.

That is, by inhibiting excessive charging and excessive discharging of the secondary battery, the charging characteristic itself is prevented from changing, and the secondary battery is once forcibly discharged to the initial state. Thus, the state of charge SOC by the terminal voltage Vb
The detection accuracy is guaranteed.

[0012]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing a configuration of an apparatus for managing the state of charge of a secondary battery according to an embodiment of the present invention. FIG. 3 is a diagram showing a schematic configuration of the charging state management device according to the first embodiment, in which BAT is a secondary battery such as a nickel-metal hydride battery, PS is a charging power source for the secondary battery BAT,
RL is the load of the secondary battery BAT. Secondary battery B
When the AT is used as a drive source of a hybrid car using both an internal combustion engine and an electric motor, the charging power source PS is driven by a generator driven by an internal combustion engine or the like, and the load RL is driven by a secondary battery. Electric motor
It is realized as. It is needless to say that the electric motor can be used as a generator by being driven by an internal combustion engine. Thus, the secondary battery BAT is selectively connected to the charging power source PS or the load RL via the switches SW1 and SW2, and its charging and discharging are respectively controlled.

The secondary battery BAT has a voltage detector 1 for detecting its terminal voltage, particularly an open voltage Vb after charging is stopped, and a current detector 2 for detecting its charge / discharge current Ib.
A temperature detector 3 for detecting the battery temperature Tb is provided. The charge state detection unit 4 basically detects the stop of charging of the secondary battery BAT from the charge current detected by the current detection unit 2 and, after a lapse of a predetermined time from the stop of charge, the voltage detection unit 1 Based on the detected open-circuit voltage Vb of the secondary battery BAT, the secondary battery BAT is referred to in accordance with the maximum state of charge SOCmax stored in the maximum value storage section 6 by referring to a table 5 built in the state-of-charge detection section. And has a role of detecting the state of charge SOC.

By the way, the above-mentioned table 5 contains the secondary battery BA.
The relationship (change characteristic C) between the open circuit voltage Vb of T and the state of charge SOC thereof as shown in FIG. 1 is stored in advance in accordance with the battery characteristics unique to the secondary battery BAT. The relationship between the terminal voltage Vb and the state of charge SOC when the secondary battery BAT is fully charged from the predetermined initial state of charge SOC0 to the full state of charge SOC3 is indicated by the characteristics stored in the table 5. In Table 5, the terminal voltage Vb and the state of charge SO when the battery is continuously discharged from the fully charged state SOC3 to the state of charge (initial state of charge) SOC0 immediately before the deep discharge is reached.
The relationship with C may be stored together.
That is, the charge / discharge characteristics of the secondary battery BAT within the allowable maximum operation guarantee range may be stored in the table 5.

The charge state detector 4 is, for example, shown in FIG.
, The state of charge SOC of the secondary battery BAT is detected. That is, the charging state detecting unit 4 first sets the secondary battery BAT in a predetermined initial state,
Is initially set to the state of charge SOC0 at the beginning of the charge indicated by the charge / discharge characteristics stored in [1] (step S1). Thereafter, in this initial state, the state of charge SOC0 at the start of charging is initially set in the maximum value storage unit 6 as the maximum state of charge SOCmax at that time [Step S].
2]. These processes are executed, for example, as pre-processes prior to the start of operation of the device.

Thereafter, the charging state detecting section 4 first initializes a counter for measuring a predetermined time after the charging is stopped to zero (0) [Step S3]. In this state, the charging current Ib obtained by the current detecting unit 2 is input [Step S
4], It is determined whether or not the charging current Ib has become zero (0), that is, whether or not charging has stopped [Step S5]. If the charging current Ib is not zero (0), it is determined that the charging of the secondary battery BAT is being continued, and the process returns to step S3 described above. Therefore, in this case, the counter is initialized to zero (0) again, and the detection of the charging current Ib is performed.

If it is detected that the charging current Ib has become zero (0), it is determined that the charging has stopped (step S5), and the counter is incremented to measure the time after the charging has stopped. [Step S6].
Then, it is determined whether or not the elapsed time after the stop of charging indicated by the value measured by the counter has reached a predetermined opening time (Step S7). Such increment of the counter and the determination thereof are repeatedly performed until the elapsed time after the charging is stopped reaches the opening time. However, if the charging current Ib is detected again in step S4 when the elapsed time is measured by the counter, it is determined that charging has been restarted before the predetermined time has elapsed after the charging was stopped, and the process is interrupted, and the above-described processing is interrupted. It returns to the processing from step S3.

If it is detected that a certain period of time has elapsed after charging of the secondary battery BAT is stopped (step S7),
Next, the open-circuit voltage Vb of the secondary battery BAT detected by the voltage detector 1 is input [Step S8]. Then, according to the input open-circuit voltage Vb, the state of charge SOC corresponding to the open-circuit voltage Vb is determined as a temporary state of charge SOCx by referring to the table 5 [Step S9].

Next, referring to the maximum state of charge SOCmax stored in the maximum value storage section 6, it is determined whether or not the state of charge SOCx is higher than the maximum state of charge SOCmax [step S10]. If it is determined by this determination that the state of charge SOCx has not reached the maximum state of charge SOCmax, the open voltage Vb at that time belongs to the change characteristic C shown in FIG. Since it is not known whether they belong, the maximum value storage unit 6
Since the charging voltage after discharging from the maximum state of charge SOCmax stored in is not known, this is ignored.
Then, the process returns to the step S4, and a series of processes from the input process of the charging current Ib is repeatedly executed again.

On the other hand, if it is detected in step S5 that the state of charge SOCx exceeds the maximum state of charge SOCmax, the open voltage Vb is stored in the table 5 regardless of the state of charge up to that time. It is determined that it has changed according to the charge / discharge characteristics C. That is, it is determined that the state of charge is higher than the previous maximum state of charge SOCmax. So in this case,
Next, it is assumed that the state of charge SOCx is the latest maximum state of charge, and the maximum value storage unit 6 is updated with the state of charge SOCx. That is, the state of charge SOCx is stored in the maximum value storage unit 6 as a new maximum state of charge SOCmax [Step S11]. At the same time, the state of charge SOCx is output as the current state of charge SOC (step S12). Thereafter, the process returns to the step 4, and a series of processes from the input process of the charging current Ib is repeatedly executed.

Thus, the charging state is determined from the open-circuit voltage Vb of the secondary battery BAT in accordance with the charging / discharging characteristics stored in the table 5 while referring to the maximum charging state SOCmax stored in the maximum value storage unit 6 as described above. According to this apparatus for calculating the SOC, even if the charging and discharging of the secondary battery BAT are repeated at random, the charging state SO of the secondary battery BAT is determined from the open voltage Vb at the time of charging.
C, especially its maximum state of charge SOCmax can be accurately detected. In addition, regardless of the charging / discharging current Ib, and irrespective of the change in the charging / discharging characteristics due to the temporary discharge, the charge state S
OC can be accurately grasped. In particular, since the state of charge SOC is obtained from the terminal voltage Vb after a lapse of a predetermined time after the charging is stopped, the state of charge SOC can be easily and accurately obtained without being affected by the charging current Ib. Practically significant effects can be achieved.

By the way, the apparatus for managing the state of charge of a secondary battery according to the present invention can be configured to further include an initial state detector 7 as shown in FIG. 5, for example, in addition to the above-described configuration shown in FIG. . That is, the initial state detection unit 7 inputs the terminal voltage Vb, the charge / discharge current Ib, and the battery temperature Tb detected by the voltage detection unit 1, the current detection unit 2, and the temperature detection unit 3, respectively. The above-mentioned initial state SOC0 of the secondary battery BAT is detected based on each detection value. When the initial state SOC0 is detected, the maximum value storage unit 6 is reset, and the switch SW2 is opened to open the secondary battery BAT. It plays a role of inhibiting the discharge of the battery BAT. Incidentally, the detection of the initial state SOC0 is performed according to the terminal voltage Vb at the time of discharging the secondary battery BAT according to the above-described table 5.
And so on.

The provision of the initial state detector 7 which functions as described above prevents the secondary battery BAT from being deeply discharged, and maintains the initial state of charge SOC0 at the initial state of the charge / discharge characteristics stored in the above-mentioned table 5. Therefore, the actual charge / discharge characteristics of the secondary battery BAT do not change from the charge / discharge characteristics stored in the table 5. Therefore, it is possible to always stably guarantee the detection accuracy of the state of charge SOC based on the above-described open voltage Vb.

Further, as shown in FIG. 6, when the maximum state of charge SOCmax stored in the maximum value storage unit 6 is further compared with a predetermined judgment threshold value, when the maximum state of charge SOCmax reaches the full charge state, It is also effective to provide a charge control unit 8 that prohibits further charging of the secondary battery BAT. In this case, the charge control section 8 may forcibly turn off the switch SW1.

The provision of such a charge control section 8 prevents the rechargeable battery BAT from being overcharged, so that the battery characteristics of the rechargeable battery BAT do not deteriorate. In particular, the maximum charge state SOC3 of the charge / discharge characteristics stored in Table 5
Is set as the charge prohibition determination threshold, it is possible to prevent the actual charge / discharge characteristics of the secondary battery BAT from being changed from the charge / discharge characteristics stored in the table 5 due to further charging. .

When the switch SW1 is turned off to disable charging, for example, only the discharge of the secondary battery BAT is permitted. Therefore, the initial charging state SOC0 is changed by the initial state detecting unit 7 described above. At the time of detection, the above-described charging prohibition may be reset. Further, as shown in FIG. 7, the secondary battery BAT is forcibly discharged in parallel with the charge control unit 8 when the maximum charge state SOCmax stored in the maximum value storage unit 6 reaches the full charge state. It is also useful to provide the discharge control unit 9. In order to forcibly discharge the secondary battery BAT, for example, a dummy load DRL is provided to the secondary battery BAT via a switch SW3, and the secondary battery BAT is discharged via the dummy load DRL. Good. Note that the forced discharge of the secondary battery BAT is related to the operation of the above-described initial state detection unit 7 and the state of charge is changed to the above-described initial state SOC.
It is performed until it reaches 0.

With the provision of such a discharge control section 9, the secondary battery BAT can be quickly returned to the initial charge state without overcharging, so that the secondary battery BAT always operates in a stable operation region. It is possible to stably and accurately detect the state of charge from the terminal voltage Vb at the time of the charge described above. Note that the present invention is not limited to the above embodiments. For example, the state of charge SOC may be similarly obtained from the open voltage Vb at the time of discharging. However, in this case, for example, the maximum charge state of the charge / discharge characteristics stored in the table 5 is set as an initial state, and the discharge is managed. The state of charge at that time may be obtained from the discharge characteristics. Also, the above-mentioned secondary battery BAT
In controlling the forcible discharge, the initial state of charge may be detected from the integrated value of the charge / discharge current, for example. In addition, the present invention can be variously modified and implemented without departing from the gist thereof.

[0028]

As described above, according to the present invention, according to the relationship (charge / discharge characteristics) between the charge terminal voltage stored in the table and the charge state, the charge state of the secondary battery is calculated from the open voltage after the stop of charging. When the charged state exceeds the stored maximum state of charge, this is output as the current state of charge, and the maximum state of charge is updated at the same time. The state can be easily and accurately detected. In particular, the state of charge can be determined with high accuracy without depending on the charging current. In addition, since the charging and discharging of the secondary battery is controlled in accordance with the detected state of charge, and the secondary battery is forcibly discharged, the charging and discharging characteristics of the secondary battery are stored in the table. Therefore, there is a great practical effect that the state of charge of the secondary battery can always be obtained stably from the open voltage when charging of the secondary battery is stopped.

[Brief description of the drawings]

FIG. 1 is a diagram showing a relationship (change characteristic) between a terminal voltage and a state of charge of a secondary battery as a basis of the present invention.

FIG. 2 is a diagram showing changes in terminal voltage during charging of a secondary battery and changes in open-circuit voltage after charging is stopped.

FIG. 3 is a block diagram showing a schematic configuration of a secondary battery charge state management device according to the first embodiment of the present invention.

FIG. 4 is a diagram showing a procedure of a processing operation in a charge state detection unit in the charge state management device according to the present invention.

FIG. 5 is a block diagram showing a schematic configuration of a secondary battery charge state management device according to a second embodiment of the present invention.

FIG. 6 is a block diagram showing a schematic configuration of a secondary battery charge state management device according to a third embodiment of the present invention.

FIG. 7 is a block diagram showing a schematic configuration of a secondary battery charge state management device according to a fourth embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Voltage detection part 2 Current detection part 3 Temperature detection part 4 Charge state detection part 5 Table 6 Maximum value storage part 7 Initial state detection part 8 Charge control part 9 Discharge control part BAT Secondary battery PS Charge power supply RL Load DRL Dummy load

Continuing from the front page (72) Inventor Norihito Kurisu 3-4-10 Minamishinagawa, Shinagawa-ku, Tokyo Toshiba Battery Corporation (72) Inventor Hirotaka Hayashida 72 Horikawa-cho, Saiwai-ku, Kawasaki-shi, Kanagawa Pref. (72) Inventor Yoshio Tobita 1-1-1, Shibaura, Minato-ku, Tokyo F-term (reference) 2G016 CA03 CB11 CB12 CB13 CB23 CB31 CB33 CC04 CC10 CC27 CC28 CD01 2G035 AB03 AC01 AC02 AC19 AD26 AD28 AD45 AD49 5G003 AA01 BA01 CA01 CA11 CB01 CC04 DA04 DA13 EA05 5H030 AA03 AA04 AA08 AS20 BB01 BB21 FF44 FF52

Claims (5)

[Claims] A detecting means for detecting an open-circuit voltage after charging the secondary battery; a table storing a relationship between the open-circuit voltage of the secondary battery and the state of charge; and a maximum charge state of the secondary battery. A storage unit for storing, and a charge state of the secondary battery is obtained by referring to the table based on the open-circuit voltage detected by the detection unit, and the charge state is a maximum charge state stored in the storage unit. A charging state detecting means for outputting the charging state as a current charging state when the charging state exceeds the current state and updating a maximum charging state stored in the storage means in the charging state. State management device. 2. The charging of a secondary battery according to claim 1, wherein the open-circuit voltage is obtained as a battery voltage of the secondary battery after a lapse of a predetermined time from when charging of the secondary battery is stopped. State management device. 3. The secondary battery charge state management device according to claim 1, further comprising detecting that the secondary battery has reached an initial state of charge start and prohibiting discharge of the secondary battery. An apparatus for managing a state of charge of a secondary battery, comprising a state detecting means. 4. The apparatus for managing the state of charge of a secondary battery according to claim 1, further comprising: charge control means for prohibiting charging of the secondary battery in accordance with the maximum charge state stored in the storage means. A charge state management device for a secondary battery. 5. The apparatus for managing a state of charge of a secondary battery according to claim 1, further comprising discharge control means for forcibly discharging said secondary battery according to a maximum charge state stored in said storage means. A charge state management device for a secondary battery, characterized in that: