JP2001178003A - Battery voltage compensating apparatus of set-battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce fluctuations of voltage of secondary battery, reduce the power consumption and also shorten the voltage compensating operation period, in a battery voltage compensating apparatus of a set-battery. SOLUTION: In a battery voltage compensating apparatus of a set-battery is connected in series, to both ends of the secondary battery 1, there are plural provided secondary batteries connect an on/off controllable discharging means 2 via a power feeding element 2b which turns off with the predetermined voltage, and a control unit 3 which detects a batter voltage to determine the secondary battery 1 which is required to conduct the discharge and cause the discharge means 2 to start the discharge by sending the on signal.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a battery voltage compensating device for an assembled battery, and more particularly to a mobile device such as an electric car and an electric cart, a portable device such as a video camera and a personal computer, a backup device in the event of a power failure, and The present invention is suitable for a battery voltage correction device for an assembled battery including a plurality of secondary batteries used as a power supply for products such as security devices.

[0002]

2. Description of the Related Art Generally, a secondary battery is a battery that can be used repeatedly by charging a battery in a discharged state. However, a secondary battery has a voltage limit for charging or discharging, respectively, depending on its composition.Charging or discharging beyond this limit not only causes performance degradation but also causes destruction. In some cases. Therefore, when charging or discharging the secondary battery, charging and discharging are performed while monitoring the battery voltage, and the charging or discharging is stopped before the voltage exceeds the limit voltage value.

However, when a plurality of secondary batteries are connected in series and used as an assembled battery, the current flowing through each of the secondary batteries may vary due to variations in various characteristics of each of the secondary batteries constituting the assembled battery. However, even if the time is the same, a difference occurs in the voltage of each secondary battery. Particularly, as the number of charge / discharge cycles increases, the difference between the voltages of the secondary batteries increases, and Because the charging of the assembled battery is terminated by the next battery, or the discharging of the assembled battery is terminated by the secondary battery with the lowest voltage,
There is a problem that the apparent capacity of the assembled battery is reduced.

Therefore, as a conventional voltage correction circuit for a secondary battery, for example, as described in Japanese Patent Application Laid-Open No. H11-150877, the charge and discharge amounts of a plurality of secondary batteries connected in series are disclosed. Connect a discharge circuit that can be turned on and off to each end of the secondary battery to correct the voltage difference due to the variation, and measure the individual terminal voltage of the battery with a microcontroller via the switching circuit and the differential amplifier. Based on the measurement result, the degree of variation in the terminal voltage and the degree of variation in the capacity of the battery are determined. The discharge circuit is turned on until the terminal voltage drops to the set value, and voltage correction is performed.
When the degree of variation in the capacity is large, a method has been devised in which the discharge circuit is kept in the off state and control for inhibiting voltage correction is performed irrespective of the degree of variation in the terminal voltage.

[0005]

However, according to the prior art, the microcontroller grasps the timing at which the discharge ends in the period during battery discharge for correcting the variation in the terminal voltage of each secondary battery. In addition, it is necessary to always perform an operation for monitoring the battery voltage and an operation for issuing a control signal for turning on the discharge circuit until the discharge is completed. For this reason, a large amount of power is consumed by the microcontroller and the battery voltage detection circuit until this discharge is completed, and the voltage correction circuit consumes a large amount of power.

In addition, since each secondary battery is sequentially discharged by the switching circuit, each battery cannot be discharged at the same time, so that the entire discharge time becomes longer.

SUMMARY OF THE INVENTION It is an object of the present invention to reduce the variation in terminal voltage of each secondary battery by discharging in a voltage correction operation, to reduce the power consumption in the voltage correction operation, and to shorten the operation time of a battery pack for an assembled battery. Is to get

[0008]

A first feature of the present invention to achieve the above object is that a discharge means which can be turned on / off connected to both ends of a secondary battery has an energizing element which turns off at a predetermined voltage. A control unit that controls the discharging unit determines a battery voltage detecting unit that detects a voltage of the secondary battery and the secondary battery that requires discharging based on the voltage detected by the battery voltage detecting unit. A battery voltage comparison / determination unit and a switch signal generation unit that sends an ON signal to the discharge unit connected to the secondary battery that needs to be discharged based on the determination result of the battery voltage comparison / determination unit It is in.

A second feature of the present invention is that the discharging means includes:
Once turned on, it has an energizing switch that does not turn off until current stops flowing regardless of the state of the subsequent switch control signal, and an energizing element that turns off at a predetermined voltage, and the control unit detects the voltage of the secondary battery. A battery voltage detection unit, a battery voltage comparison and determination unit that determines the secondary battery that needs to be discharged based on the voltage detected by the battery voltage detection unit, and a battery voltage comparison and determination unit based on the determination result of the battery voltage comparison and determination unit. A switch signal generating means for sending an ON signal to the discharging means connected to a secondary battery requiring discharging is provided.

[0010] A third feature of the present invention is that the discharging means includes:
Once turned on, there is a switch that continues to be on without an on signal, a constant voltage diode that turns off at a predetermined voltage, and a resistance element for discharging, and the control unit controls the voltage of the secondary battery. A battery voltage detecting unit for detecting, a battery voltage comparing and determining unit for determining the secondary battery that needs to be discharged based on the voltage detected by the battery voltage detecting unit, and Switch signal generating means for sending an ON signal to the discharge means connected to the secondary battery which needs to be discharged. These are configured by a microcontroller.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to FIGS.

First, the configuration of the battery voltage correction device for a battery pack according to the present invention will be described with reference to FIG. FIG. 1 is a schematic circuit diagram showing a configuration of a battery voltage correction device for an assembled battery according to one embodiment of the present invention.

The battery pack 2 is formed by connecting a plurality of secondary batteries 1, in this embodiment, N secondary batteries 1 in series.
The secondary battery 1 is a secondary battery, such as a lithium ion secondary battery, charged at a voltage lower than a predetermined low voltage. In this embodiment, the secondary battery 1 is a lithium ion secondary battery. In the battery pack 2, the plus side terminal 11 is connected to a plus terminal which is an external connection terminal, and the minus side terminal 12 is connected to a minus terminal which is an external connection terminal.

An energizing switch 2 controlled by a signal from a switch signal generator 3c is provided at both ends of each secondary battery 1.
a, a voltage compensating discharge circuit 2 comprising a constant voltage diode 2b operating as an arbitrary threshold voltage energizing element and a resistive element 2c for discharging. This voltage correction discharge circuit 2 constitutes a discharge means. The constant voltage diode 2 b has its energization threshold set to the discharge end voltage of the secondary battery 1.

A control unit 3 composed of a microcontroller has a battery voltage detecting unit 3a for detecting the voltage of each secondary battery 1, and comparing the detected battery voltages to determine the necessity of voltage correction. A battery voltage comparison / determination unit 3b and a switch signal generation unit 3c that outputs a signal for turning on the energizing switch 2a of the discharge circuit of each secondary battery when it is determined that voltage correction is necessary. The switch signal generator 3c outputs a switch control signal so that each energizing switch 2a is simultaneously turned on by one signal or an independent signal.

The switch control signal from the switch signal generator 3c to each energizing switch 2a uses a switch-on trigger signal. On the other hand, the energizing switch 2a is turned on once, as represented by a thyristor, and is energized. A switch that does not turn off until current stops flowing regardless of the state of the subsequent switch control signal is used. Note that an element having both functions of the energizing switch 2a and the constant voltage diode 2b may be used.

Further, although not shown, the battery pack is designed to charge and discharge the battery pack while monitoring the battery voltage of each secondary battery.

Next, the operation of the battery voltage correcting apparatus for a battery pack according to the present invention will be described with reference to FIG. FIG. 2 is a characteristic diagram of the battery voltage in the battery voltage correction device for an assembled battery according to the present invention. FIG. 2 shows representatively the discharge characteristics of the battery A having the lowest discharge voltage and the battery B having the highest discharge voltage among the secondary batteries 1 constituting the assembled battery.

In the battery pack in which N secondary batteries 1 are connected in series, when normal discharge starts at time 0, battery A having a low discharge voltage reaches the discharge end voltage at time t1, and discharge of the battery pack begins. Is completed. This time is the time shown as the normal discharge operation in FIG.

When the battery A having the lowest discharge voltage reaches the discharge end voltage, the respective voltages of the battery A and the battery B are read by the battery voltage detector 3a. Further, the battery voltage comparison determination unit 3
In step b, the voltage difference ΔV of the read voltage is calculated, and the voltage difference ΔV is compared with a voltage difference ΔVth that requires a preset battery voltage correction. In this comparison, if it is determined that △ V ≧ △ Vth, a switch-on trigger signal is sent from the switch signal generator 3c to the energizing switch 2a of the discharge circuit connected to the battery B.

When the energizing switch 2a is turned on in response to the switch-on trigger signal, the discharging circuit connected to the battery B starts discharging, and the operation shifts to the battery B voltage correction operation. This voltage correction operation of the battery B continues until the time t2 when the battery voltage reaches the discharge end voltage set by the constant voltage diode 2b. By this voltage correction operation,
The voltage of the battery requiring voltage correction can be the same as the voltage of battery A. As a result, it is possible to reduce the variation in the battery voltage of each of the secondary batteries 1 constituting the assembled battery.

In this case, the voltage correction operation in the battery B is terminated by using an energizing element that automatically turns off when the discharge end voltage is reached, such as the constant voltage diode 2b. It is not necessary to continuously monitor the battery voltage during the correction operation. For this reason, the battery voltage detection unit 3a of the control unit 3 constituted by a microcontroller
Need not be operated for monitoring the voltage correction operation, and the power consumption of the control unit 3 can be reduced.

Further, since the energizing switch 2a uses a switch such as a thyristor, which is turned on once and keeps on even if there is no on signal, the control unit 3 continues to perform the switch signal during the voltage correcting operation. There is no need to send a switch-on signal from the generator 3c. For this reason, the switch signal generation unit 3 of the control unit 3 configured by a microcontroller
It is not necessary to operate c during the voltage correction operation, and the power consumption of the control unit 3 can be reduced from this point as well.

In FIG. 2, the two batteries A and B are described as representatives. However, the battery voltages of all the secondary batteries 1 are detected, and the normal discharge operation is performed at the time when the discharge end voltage is reached the earliest. Rechargeable battery 1 that has finished and needs voltage correction operation
The operation shifts to the voltage correction operation of FIG. In this voltage correction operation, the respective voltages of all the remaining secondary batteries 1 are read by the battery voltage detection unit 3a, and the battery voltage comparison and determination unit 3b calculates the voltage difference ΔV between the read voltages. The difference ΔV is compared with a preset voltage difference ΔVth requiring battery voltage correction, and the switch signal generator 3c connects the battery B to the secondary battery 1 determined as ΔV ≧ △ Vth. The switch-on trigger signal is sent to the energizing switch 2a of the discharged circuit, and the secondary battery 1 requiring the voltage correction operation is simultaneously discharged. Each secondary battery 1
Is automatically terminated when the voltage of each secondary battery 1 reaches the discharge end voltage. As described above, since the secondary batteries 1 requiring the voltage correction operation are simultaneously discharged,
Voltage correction operation time can be reduced.

A method for restarting the voltage correction operation of the control unit 3 constituted by the microcontroller after the end of the voltage correction operation is to operate only the timer in the microcontroller.
A preset time from the end time of the normal discharge operation.
After t, restart the microcontroller. The set time Δt is set slightly longer than the maximum time, assuming the operation time of the voltage correction in advance. Note that a circuit that outputs a signal only when the battery voltage reaches the discharge end voltage may be provided in the battery voltage detection unit 3a, and the microcontroller may be restarted by this signal.

In the above-described embodiment, the voltage correction discharge circuit is provided for each secondary battery. However, when the number of secondary batteries is large, for example, for each module battery, a plurality of secondary batteries are used as a unit. A voltage correction discharge circuit may be provided. With this arrangement, the number of voltage correction discharge circuits can be reduced,
The control is also simplified and the cost can be reduced.

[0027]

According to the present invention, the variation in the terminal voltage of each secondary battery can be reduced by the discharge in the voltage correction operation, the power consumption in the voltage correction operation is small, and the battery voltage of the assembled battery is short. A correction device can be obtained.

[Brief description of the drawings]

FIG. 1 is a schematic circuit diagram showing a configuration of a battery voltage correction device for a battery pack according to one embodiment of the present invention.

FIG. 2 is a characteristic diagram of a battery voltage in the battery voltage correction device of FIG.

[Explanation of symbols]

1 secondary battery, 2 discharge means (discharge circuit for voltage correction),
2a ... energizing switch, 2b ... constant voltage diode, 2c ...
Resistance element, 3 ... Control section, 3a ... Battery voltage detection section, 3b ...
Battery voltage comparison / determination section, 3c... Switch signal generation section.

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Yoshimi Miyamoto 800 F, Tomita, Oita-machi, Ohira-machi, Shimotsuga-gun, Tochigi F-term (Ref.) 5C003 AA01 BA03 CA11 CC02 FA08 GC05 5H030 AA01 AS06 AS08 AS11 BB21 FF44

Claims (3)

[Claims] An assembled battery in which a plurality of secondary batteries are connected in series;
On / off discharging means connected to both ends of the secondary battery, and a control unit for controlling the discharging means, the discharging means has an energizing element to turn off at a predetermined voltage, the control unit, A battery voltage detection unit for detecting a voltage of the secondary battery, a battery voltage comparison and determination unit for determining the secondary battery that needs to be discharged based on the voltage detected by the battery voltage detection unit, and a battery voltage comparison and determination unit And a switch signal generating means for transmitting an ON signal to the discharging means connected to the secondary battery which needs to be discharged based on the determination result of the unit. 2. An assembled battery in which a plurality of secondary batteries are connected in series;
A discharge unit connected to both ends of the secondary battery and capable of turning on and off, and a control unit for controlling the discharge unit, wherein once the discharge unit is turned on, a current flows regardless of the state of a subsequent switch control signal. An energizing switch that does not turn off until it disappears, an energizing element that turns off at a predetermined voltage, the control unit includes a battery voltage detecting unit that detects a voltage of the secondary battery, and a voltage detected by the battery voltage detecting unit. A battery voltage comparison / determination unit that determines the secondary battery that requires discharge based on the battery voltage comparison / determination unit, and the discharging unit that is connected to the secondary battery that requires discharge based on the determination result of the battery voltage comparison / determination unit. A battery voltage correction device for an assembled battery, comprising: a switch signal generating means for sending an ON signal. 3. An assembled battery in which a plurality of secondary batteries are connected in series;
On-off discharge means connected to both ends of the secondary battery, comprising a control unit for controlling the discharge means, the discharge means, once turned on, a switch that continues to turn on without an ON signal, A constant voltage diode that is turned off at a predetermined voltage, and a resistance element for discharging, the control unit detects a voltage of the secondary battery, a battery voltage detection unit,
A battery voltage comparison and determination unit that determines the secondary battery that requires discharge based on the voltage detected by the battery voltage detection unit; and a secondary battery that requires discharge based on the determination result of the battery voltage comparison determination unit. A switch signal generating means for sending an on signal to the discharging means connected to the battery; and a microcontroller comprising these means.