JP2000356656A - Terminal voltage detector for battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a terminal voltage detector for battery which does not need an input line to an operational amplifier to be cut off, even if a control power source is in an off state. SOLUTION: The terminal voltage detector for battery 10 is provided with a battery pack 12 having a plurality of unit cells 12a-12c of a secondary battery connected in series with each other, an operational amplifier 18 detecting the terminal voltage accommodated in each cell, a control power source VCC providing a driving power source for the operational amplifier 18, and a bypass circuit 22 which consists of a resistance 14 with which a positive electrode end of each cell and a control power source line are connected so that a driving power source can be provided for an operational amplifier 18 when a control power source is off, and a diode 18, and moreover, is connected with a feedback resistor 26 between the input side negative electrode end and the output end side. For that reasons, since a switch part to cut off a voltage detection line from secondary battery cells, which a combination battery consists of, is unnecessary, a space-saving, low-cost terminal voltage detector for a battery can be provided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a terminal voltage detecting device for a battery, and more particularly to a terminal voltage detecting device for a rechargeable battery used in an electric vehicle or a portable electronic device.

[0002]

2. Description of the Related Art For example, an electric vehicle requires a driving battery (battery) as an energy source of a driving motor.
Generally, a rechargeable secondary battery is used. In that case,
The problem is accurate measurement of the remaining capacity of the battery.
That is, if the remaining discharge capacity is not known, the travelable distance of the electric vehicle cannot be determined, and in the worst case, the vehicle may stop at a place where there is no charging facility. In addition, portable electronic devices cannot be used if the battery capacity is insufficient during use. The remaining capacity of the battery is obtained by calculation based on the voltage between electrodes (voltage between terminals) when the battery is discharging a predetermined current.

[0003] Also, an assembled battery (pack battery or battery) in which a plurality of such secondary batteries (cells composed of a single battery or blocks composed of a plurality of cells) are connected in series or series-parallel by an amount corresponding to the required capacity (Also referred to as a pack). Since such a battery pack uses a large number of batteries, for example, about 100 to 250 cells in an electric vehicle, it is important to ensure the reliability of the battery system. That is,
If the function of any of the batteries constituting the assembled battery is reduced due to overdischarge, overcharge, or the like, the function of the entire assembled battery is reduced. 6A and 6B show general charging characteristics and discharging characteristics of a single cell.
Note that the terminal voltage differs depending on the charge / discharge current value in both the charge and discharge characteristics.

Further, in the case of such a battery pack, the degree of reduction in the discharge capacity (the amount of electricity that can be discharged) differs depending on the battery. Therefore, DOD (depth of discharge: 1 for all discharges)
The discharge capacity from 0% (00%, 0% at full charge) varies from battery to battery, thereby reducing the discharge capacity of the assembled battery. In other words, at the time of discharging, a battery having a reduced discharge capacity ends discharging quickly and enters an overdischarged state, and this overdischarged battery becomes a load of another battery, and all batteries do not reach a DOD of 100%. As a result, the voltage of the battery pack decreases, and the battery pack ends discharging.

On the other hand, during charging, DOD 100
%, The battery first reaches DOD 0% and the voltage rises, and charging ends. However, the battery that has been overdischarged during discharging ends charging without reaching DOD 0%. The difference widens, and the difference in the discharge capacity of each battery also widens. Therefore, when charging and discharging are repeated, the battery having a small discharge capacity is always insufficiently charged, so that the variation is large and the discharge capacity of the battery pack as a whole is reduced, and the specific battery is liable to be deteriorated. There is a problem, and there is a possibility that heat is generated more than necessary due to overdischarge or overcharge.

In order to solve such a problem, for example, zener diodes are connected in parallel for each cell constituting the battery pack, and the zener voltages of these zener diodes are set to the cell end-of-charge voltage. In this case, the charging proceeds and the terminal voltage of the cell rises, and when it reaches the charging end voltage, the Zener diode connected in parallel conducts and bypasses the charging current, so that further charging is performed. The cell in which the terminal voltage does not reach the charge end voltage is not charged and charging is continued. Therefore, charging is performed until each cell is fully charged, and variations can be reduced.

[0007]

However, the above-mentioned solutions have the following problems. In other words, since the bypass current flows when the terminal voltage of the cell reaches the charge end voltage, the bypass is performed so that the charging current from the charger does not completely flow to the cell to prevent overcharging. There is a need. Therefore, when the charging current is large as in the case of rapid charging or regenerative charging, it is necessary to use a zener diode and a resistor having a size corresponding to the charging current as a zener diode and a resistor constituting a bypass circuit. In addition, these diodes and resistors need to be arranged for each cell, and accordingly, a large space has to be taken and a rise in temperature has to be dealt with, resulting in problems such as an increase in cost.

When the remaining capacity of a battery is measured, the terminal voltage is detected when the battery is discharging at a predetermined current, as described above. However, the terminal voltage is not always detected, but is required. Is detected according to Therefore FIG.
As shown in FIG.
For example, the terminal of the battery 2 and the voltage detection circuit 3 are connected via a switching device 4. That is, the voltage detection circuit unit 3 supplies the terminal voltage VB1 (= 10
V) is included. In the operation when the control power supply VCC of the operational amplifier 3a is ON, the input INA
And INB are equalized, and the difference is the output. Operational amplifier output VOUT = INA-INB = VB1
(= 10V) at this time, the control power supply (circuit power supply) VCC
Is OFF, battery 2 goes to operational amplifier inputs INA and INB
May be directly applied to break the operational amplifier 3a.

[0009] Also, A is provided on the output side of the operational amplifier 3a.
Since the input voltage is applied to the input of the / D converter 5 via the feedback resistor Rf of the operational amplifier 3a, there is a possibility of destruction. Therefore, O of the control power supply VCC
At the time of FF, the above-described switch device 4 is required to disconnect the input line from the battery 2 to the operational amplifier 3a and the A / D converter 5.

The switching device 4 includes, for example, a mechanical switch such as a relay and a semiconductor switch such as an FET. However, the former switch has problems of opening / closing life and space, and the latter switch has a problem of voltage drop due to internal resistance.

Another conventional terminal voltage detecting device 1 shown in FIG. 5 is configured such that when the control power supply VCC is turned off, the input voltage to the operational amplifier 3a is controlled by the control power supply VCC via resistors RINA and RINB and diodes DA and DB, respectively. By bypassing to the line, the input / output voltage of the operational amplifier 3a can be reduced to zero. This is the control power supply V
When CC is OFF, the input voltage to the operational amplifier 3a is controlled by the control power supply VCC via the resistor RINA and the diode DA.
To the control power supply VCC line via the resistor RINB and the diode DB.
Apply voltage to CC.

At this time, since the power supply current of the operational amplifier 3a tends to flow, a voltage drop corresponding to the input voltage is generated by the resistors RINA and RINB.
Voltage becomes zero.

However, this configuration requires a sufficient resistance value to generate a voltage drop. On the other hand, if the resistance value is too large, line noise increases, which causes a malfunction. For example, to use a low-consumption operational amplifier,
It consumes only a few μA and the input resistance must be 1 MΩ or more to obtain a sufficient voltage drop.

[0014] Due to such a problem, the diodes DA and DB may not be completely clamped and the voltage may not become zero.

[0015] For this reason, the above-described switch device is required, and accordingly, a space for disposing the switch device is required, resulting in a problem that the cost is increased.

SUMMARY OF THE INVENTION Therefore, a main object of the present invention is to provide a battery terminal voltage detecting device in a battery terminal voltage detecting circuit which does not need to disconnect an input line to an operational amplifier even when a control power supply is OFF. .

[0017]

SUMMARY OF THE INVENTION The present invention provides an assembled battery in which a plurality of secondary battery cells are connected in series or in series / parallel, and a plurality of divided battery units each divided into one or more secondary battery cells. A differential amplifier that is provided for each block and connects a positive terminal and a negative terminal of each block to an input terminal to detect a voltage difference between the input terminals. A driving power supply is supplied to the differential amplifier via a control power line. Control power to be supplied, and comprising a bypass unit that connects a positive terminal of each of the blocks and a control power line to supply drive power to the differential amplifier when the control power is off,
It is a battery terminal voltage detection device.

[0018]

In order to supply drive power to the differential amplifier from each block when the control power supply is turned off, connection is made through, for example, bypass means composed of a series circuit of a resistor and a diode, so that only the operational amplifier constituting the differential amplifier is provided. The output voltage is reduced to zero by continuing operation at a low power supply voltage.

[0019]

According to the present invention, there is no need for a switch for separating the voltage detection line from each block of the secondary battery cell, so that a space-saving and low-cost battery terminal voltage detection device can be provided.

The above objects, other objects, features and advantages of the present invention will become more apparent from the following detailed description of embodiments with reference to the drawings.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A battery terminal voltage detecting device 10 according to one embodiment of the present invention shown in FIG.
b, 12c,... connected in series for electric vehicle 1
2. Resistors 14 (RINA) and 16 (RIN) are provided at both ends (positive end and negative end) of the unit cell 12a of the battery pack 12, respectively.
B), an operational amplifier 18 as a differential amplifier for detecting a terminal voltage connected via the control amplifier VCC, a control power supply VCC for providing a driving power supply to the operational amplifier 18, and a positive-side input voltage of the operational amplifier 18 to the resistor 14 and the diode 20. A bypass circuit 22 for bypassing to the control power supply VCC line via a series circuit is included. Each of the unit cells 12a of the assembled battery 12 is a rechargeable battery such as a nickel cadmium battery, a nickel hydride battery, or a lithium ion secondary battery.

The assembled battery 12 includes single cells 12a and 12b.
And 12c may be configured by connecting a plurality of blocks connected in parallel.

Then, the terminal voltage of the single cell 12a is detected and amplified by the operational amplifier 18 and converted into an analog voltage output by the A / D converter.
The data is input to the converter 24 and converted into a digital value.
After that, for example, the state of the cell detected by the arithmetic processing by the microcomputer shown in the usage example described later via the driver is displayed on the display. A feedback resistor 26 (R) is connected between the input-side negative terminal and the output terminal of the operational amplifier 18.
B) is connected. Further, the input-side positive terminal of the operational amplifier 18 is grounded via a resistor 28 (RA), and the negative power supply of the operational amplifier 18 is also grounded.

As described above, the input voltage of the operational amplifier 18 is bypassed to the line of the control power supply VCC by the bypass circuit 22 configured by connecting the resistor 14 (RINA) and the diode 20 in series. The output voltage is maintained at zero by continuing operation at a low power supply voltage. This is operational amplifier 1
8, the output voltage VOUT = VINA-VINB, so that when the control power supply VCC is OFF, VINA = ICC
If the resistor 14 (RINA) is set so that VOUT = VINA-VINB <0 from × RINA, the output voltage is zero (a negative voltage is not output when used with a single power supply).
Becomes

The current consumption of the low-consumption type operational amplifier 18 is about 10 μA, which is almost negligible considering the self-discharge of the single cell 12a.

For example, RINA = RINB = 300k
Ω, RA = RB = 100 kΩ, VCC = 15 V, ICC
= 10μA, operation when VCC is ON, VINA
= VINB = 30V × 1/4 = 7.5V VOUT = 10 × 1/3 = 3.333V Operation when VCC is OFF, VINA = VINB = 7.5V-300kΩ × 10μA
= 4.5 V, VOUT = 0 V Here, originally, VINB = 20 V × １ ／ = 5 V, and VOUT = (VINA−VINB) × 4/3 − (− 0.5) = (4.5− 5) × 4/3 − (− 0.5) = − 0.5 V However, since it is a single power supply, a voltage less than zero voltage (negative voltage) cannot be output.

At this time, VCC = approximately 4 V (must be within the normal operation voltage range).

As described above, the terminal voltage detecting device 10 connected to the single cell 12a is provided in the other single cells 12b and 12c,.

Next, the terminal voltage detecting device 1 according to the present invention
A schematic configuration of a battery remaining amount estimation system using 0 will be described with reference to FIG.

A battery 30 as a storage battery composed of a plurality of secondary battery cells is connected to a load 30 and a generator 32 including, for example, a drive motor of an electric vehicle and a control circuit therefor. The power supply circuit (control power supply VCC) 36 in the remaining amount estimation system 34 is connected. A cable line 38 connecting the assembled battery 12 with the load 30 and the generator 32 is connected in series to a current detector 40 in the battery remaining amount estimation system 34.

The output voltage detected by the terminal voltage detecting device 10 in the battery remaining amount estimation system 34 connected to the battery pack 12 is converted into a digital value by the A / D converter 24, read by the microcomputer 42, and And the energizing time to calculate the energizing amount of the cable wire 38. The microcomputer 42 has a CPU (not shown)
(Central processing unit), ROM, RAM, and input / output I / O
F (interface).

Assuming that the current flowing into the storage battery composed of the assembled battery 12, ie, the charging current, is positive and the current flowing out of the storage battery, ie, the discharge current, is negative, the amount of charge and the amount of discharge are calculated. Capacity is required.
This remaining capacity is displayed on the display 46 via the driver 44, for example, in a percentage such as%. In addition, this display may be displayed not only by the ratio but also by the remaining capacity (Ah) or, in the case of an electric vehicle, the possible travel distance or travel time.

The terminal voltage detecting device 10 detects a battery voltage when the battery 32 is being charged by the generator 32 such as regenerative braking, recognizes an overcharged state, does not accumulate the current at that time, and does not integrate the current at that time. It has a function of detecting battery voltage, recognizing an overdischarge state, and issuing a warning. Further, the temperature detection circuit 48 in the battery remaining amount estimation system 34 detects the temperature of the assembled battery 12 constituting the storage battery via the temperature sensor 50, and corrects the battery voltage.

Here, an outline of the operation after the detection of the terminal voltage will be described based on the flowchart shown in FIG.

First, in step S1, the terminal voltage detecting device 1
0, the terminal voltage of the assembled battery 12 is detected, and step S
At 3, the microcomputer 42 determines whether or not the terminal voltage of the battery pack is equal to or less than the overdischarge set value. As a result, "N
If "O", the process proceeds to step S5, and if "YES", the microcomputer 42 performs overdischarge in step S7.
An overcharge process is performed and the process proceeds to step S9. In step S5, the microcomputer 42 determines whether or not the terminal voltage of the battery pack is equal to or higher than the full charge set value. As a result, "YE
If “S”, the process proceeds to step S7, and if “NO”, the process proceeds to step S9.In step S9, the remaining capacity of the battery is estimated by the microcomputer 42, and the process returns to step S1.

After performing the overdischarge / overcharge process by the microcomputer 42 in step S7, a series of operations is terminated by a charge / discharge prohibition request in step S11.

[Brief description of the drawings]

FIG. 1 is a main part circuit diagram of a battery terminal voltage detecting device showing one embodiment of the present invention.

FIG. 2 is a block diagram showing a schematic configuration of a battery remaining amount estimation system using the battery terminal voltage detection device according to the present invention.

FIG. 3 is a flowchart showing an operation outline of the battery remaining amount estimation system shown in FIG. 2;

4 is a main part circuit diagram showing a conventional example of a battery terminal voltage detection device corresponding to FIG.

FIG. 5 is a main part circuit diagram showing another conventional example corresponding to FIG. 1;

FIGS. 6A and 6B are a discharge characteristic diagram and a charge characteristic diagram of a general single cell.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 ... Terminal voltage detection device 12 ... Battery pack (storage battery) 12a, 12b, 12c ... Single cell 14, 16 ... Resistance 18 ... Operational amplifier (differential amplifier) 20 ... Diode 22 ... Bypass circuit 24 ... A / D converter (A / D D converter) 26 Feedback resistance (feedback resistance) 30 Load (for example, drive motor) 34 Battery remaining amount estimation system 36 Power supply circuit (control power supply VCC) 40 Current detector 42 Microcomputer (CPU, ROM) , RA
48… Temperature detection circuit

Claims (5)

[Claims] 1. An assembled battery in which a plurality of secondary battery cells are connected in series or in series / parallel, wherein the assembled battery is provided for each of a plurality of blocks obtained by dividing one or a plurality of secondary battery cells as a unit, and A differential amplifier for connecting a positive terminal and a negative terminal to each input terminal to detect a voltage difference between the input terminals, a control power supply for supplying drive power to each of the differential amplifiers via a control power line, and A terminal voltage detecting device for a battery, comprising: bypass means for connecting a positive terminal of each of the blocks and the control power supply line to supply drive power to the differential amplifier when the control power supply is turned off. 2. The battery terminal voltage detecting device according to claim 1, wherein said differential amplifier includes an operational amplifier. 3. The battery terminal voltage detecting device according to claim 1, wherein said bypass means includes a series circuit of a resistor and a diode. 4. The battery terminal voltage detecting device according to claim 3, wherein a resistance of said bypass means is shared with a resistance connected to an input terminal of said operational amplifier. 5. The method according to claim 1, wherein the resistance value of the resistor is set to a value such that a current value flowing into the operational amplifier via the bypass means when the control power supply is turned off is within an allowable value of the operational amplifier. 5. The battery terminal voltage detection device according to 3 or 4.