JP2000195567A - Battery pack - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a battery pack capable of improving measurement accuracy of a battery voltage when an output current is measured by using a shunt resistor for output current detection and capable of reducing power consumption in a shunt-resistor voltage measuring circuit for measuring the voltage. SOLUTION: A battery pack 18 is equipped with a rechargeable battery 23 made up by connecting a plurality of cells 23a to 23g, a battery-voltage measuring circuit 51 for measuring a voltage of the rechargeable battery 23, a shunt resistor 37 provided in a current output line from the rechargeable battery 23, a shunt-resistor voltage measuring circuit 40 for measuring a voltage across the shunt resistor 37, and an output-current value computing means 29 for finding the value of an output current from the detected shunt-resistor voltage. The shunt resistor 37 is insertedly connected to the minus side of the cell 23g in the lowest position of the plurality of cells 23a to 23g, and a point at which the shunt resistor is connected to the lowest-position cell 23g is used as a referential ground G for battery voltage measurement.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a battery pack provided with a rechargeable battery such as Ni-Cd, Ni-MH or lithium ion used as an energy source in, for example, electric bicycles, electric wheelchairs, electric scooters and the like.

[0002]

2. Description of the Related Art As a method of detecting an output current supplied from a battery to a driving device, a shunt resistor is conventionally inserted in a current output path, and the voltage across the shunt resistor is changed using the current value. It is common to measure and convert this voltage into a current value.

[0003]

However, when the above-described method of measuring the output current and the voltage measurement of the cell battery are used in combination,
Since the voltage between both ends of the shunt resistor always causes a variation error of the cell battery voltage, the accuracy of the battery voltage measurement decreases. In particular, since the load on the cell current increases as the large current flows, it is desirable that the voltage measurement be accurate. Also, the power consumption in the shunt resistance voltage measurement circuit cannot be ignored.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and can improve the measurement accuracy of a battery voltage when an output current value is measured using a shunt resistor for detecting an output current. An object of the present invention is to provide a battery pack that can reduce the power consumption of a shunt resistance voltage measurement circuit that measures the voltage.

[0005]

Means for Solving the Problems The first aspect of the present invention is shown in FIG.
, A rechargeable battery 23 connected to a plurality of cell batteries 23a to 23g, a battery voltage measuring circuit 51 for measuring the voltage of the rechargeable battery 23, and a current output path from the rechargeable battery 23 A shunt resistor 37, a shunt resistance voltage measuring circuit 40 for measuring a voltage across the shunt resistor 37, and an output current value calculating means for obtaining an output current value from the detected shunt resistance voltage. In the battery pack, the shunt resistor 37 is inserted and connected to the minus side of the lowermost cell battery 23g among the plurality of cell batteries 23a to 23g, and the connection point between the shunt resistor and the lowermost cell battery 23g is set to the battery voltage. It is characterized in that it is a reference ground G for measurement.

According to a second aspect of the present invention, in the first aspect, the resistance value of the shunt resistor 37 is adjusted so that the maximum reverse voltage of the shunt resistor 37 is equal to or less than the reverse breakdown voltage of the shunt resistance voltage measuring circuit 40. It is characterized by setting.

According to a third aspect of the present invention, in the first or second aspect, a switching element is provided in the shunt resistance voltage measuring circuit, and the switching element is provided only when the measuring circuit measures a shunt resistance voltage. 42 is turned on.

[0008]

According to the battery pack of the first aspect of the present invention, the lowermost cell battery 23g of the plurality of cell batteries is provided.
Since the shunt resistor 37 is inserted and connected to the negative side of the cell and the connection point is used as the reference ground G for measuring the battery voltage, the discharge current value is measured on the plus side when viewed from the reference ground G. A state unrelated to battery voltage measurement can be created. Accordingly, the voltage across the discharge current measuring shunt resistor 37 does not cause a variation error in the cell battery voltage, and the measurement accuracy of the cell battery voltage can be improved accordingly.

According to the battery pack of the second aspect of the present invention, the shunt resistance is set so that the maximum reverse voltage of the shunt resistor 37 is equal to or less than the reverse withstand voltage of the shunt resistance voltage measuring circuit 40. The shunt resistance voltage measurement circuit 40 can be protected.

According to the third aspect of the present invention, the switching element is provided in the shunt resistance voltage measuring circuit, and the switching element is turned on only when measurement is performed by the measuring circuit. Therefore, no current flows through the measurement circuit 40 during a period in which measurement is not performed, and power consumption can be reduced accordingly.

[0011]

Embodiments of the present invention will be described below with reference to the accompanying drawings. 1 to 6 are views for explaining a battery pack according to an embodiment of the present invention.
FIG. 1 is a side view of an electric assisted bicycle on which the battery pack is detachably mounted, FIG. 2 is a diagram mainly illustrating the configuration of the battery pack, and FIG. 3 is a diagram illustrating the configuration of the battery pack. FIG. 4 is a diagram showing a shunt resistor insertion portion in the battery pack. FIG. 5 is a characteristic diagram showing changes in discharge voltage, remaining battery capacity, and discharge capacity of the battery pack with time, and FIG. FIG. 3 is an explanatory diagram of functions of a CPU.

In FIG. 1, reference numeral 1 denotes an electric assist bicycle on which a battery pack 18 charged by a non-vehicle charging device 17 is detachably mounted. The body frame 2 of the electric assist bicycle 1 has a head pipe 3 and A down tube 4 extending obliquely downward from the head pipe 3 to the rear of the vehicle body, a seat tube 5 extending substantially upright from the rear end of the down tube 4, and a left side extending substantially horizontally rearward from the rear end of the down tube 4 A pair of right and left chain stays 6, a pair of left and right seat stays 7 connecting the rear ends of the two chain stays 6 and the upper end of the seat tube 5, and the head pipe 3 and the seat tube 5; And a top tube 11 to be connected.

A front fork 8 is pivotally supported on the head pipe 3 so as to be rotatable left and right. A front wheel 9 is pivotally supported at the lower end of the front fork 8, and a steering handle 10 is fixed at the upper end. A saddle 12 is attached to the upper end of the seat tube 5. Further, a rear wheel 13 is pivotally supported at the rear end of the chain stay 6. Although not shown, the steering handle 10
In the center of the instrument panel (not shown) equipped with a speed meter etc.
Is provided.

At the lower end of the body frame 2, a pedal depression force (manual force) input to a pedal 16b via a crank arm 16a attached to a projection at both ends of the crank shaft 16, and a built-in electric motor (not shown) ) Is mounted with a power unit 15 that outputs a resultant force with an auxiliary power proportional to the magnitude of the human power. That is, the magnitude of the pedal depression force is the motor drive command. This power unit 1
5 is transmitted to the rear wheel 13 via a chain 50.

The bicycle 1 of the present embodiment also includes a self-propelled lever 14 for inputting a motor drive command from the outside. By operating the self-propelled lever 14, the bicycle 1 can be driven without inputting to the pedal 16b. It is also possible to run only with the power from the motor.

The battery pack 18 serving as a power source for the electric motor or the like is arranged along the rear surface of the seat tube 5 so as to extend along the rear surface.
And it is detachably mounted on the vehicle body so as to be sandwiched between the left and right seat stays 7,7. The charging device 17 is inserted into a charging port 18a provided in the battery pack 18.
Of the charging plug 19 is connected to the connectors 22a and 22b provided in the charging port 18a. In addition, 20 is a plug connected to an outlet (not shown).

The battery pack 18 contains a rechargeable battery 23 formed by connecting a plurality of unit cells (cell batteries) 23a to 23g in series.
Is provided with a thermistor 24 for detecting the temperature of the cell battery and a thermal fuse 25 for stopping charging when the battery temperature rises abnormally.

In the battery pack 18, a charging path for connecting the charging device 17 to the rechargeable battery 23, specifically, as shown by a two-dot chain line in FIG. A path is provided from the connector 22a to the connector 22b via the rechargeable battery 23, and in the middle of the charging path, charging is performed for supplying and stopping the charging current from the charging device 17 to the rechargeable battery 23. FET 26 as switching element for rectifier diode 2
7 are provided. The driving of the FET 26 is performed by CP
This is performed by the output driver 28 controlled by U29.

The charging path includes a charging adapter connection voltage signal input circuit 30 for detecting that the charging device 17 is connected to the battery pack 18 and transmitting the charging signal to the CPU 29, and a charging current when the charging current is excessive. A charging fuse 31 for stopping current supply to the rechargeable battery 23 is provided.

The CPU 29 has a crystal oscillator 32 for setting a processing cycle of the CPU 29 and an LED (remaining capacity display section) 33 for displaying the remaining capacity of the rechargeable battery 23.
And a remaining amount display switch 34 for instructing the display of the remaining capacity by an external operation. G is a reference ground of the control circuit in the battery pack.

Between the positive electrode of the rechargeable battery 23 and the output connector 35a of the battery pack 18, the battery 23
There is provided a discharge fuse 36 for stopping the discharge when the discharge current value from is excessive. A power input connector (not shown) of the power unit 15 including the electric motor is connected to the output connectors 35a and 35b of the battery pack 18.

Further, the output connector 35b and a lowermost cell battery 23g of the plurality of cell batteries 23a to 23g.
A shunt resistor 37 for obtaining an output current value is inserted and connected between the negative electrode and the negative electrode. A connection point between the shunt resistor 37 and the cell battery 23g is set to a reference ground G for monitoring the voltage of each of the cell batteries 23a to 23g described later.

A serial communication connector 38 is provided between the output connectors 35a and 35b, and the connector 38 is connected to the CPU 29. The CPU 29 is connected to the serial communication connector 38.
Outputs a predetermined instruction signal to the power unit 15 connected to the output connectors 35a and 35b via the power connector 35, thereby functioning as a discharge control means for controlling the output current value from the rechargeable battery 23 to the power unit 15. I have.

Between the rechargeable battery 23 and the intermediate voltage input switching control circuit 39, the cell batteries 23a to 23a are connected.
Cell partial pressure measuring circuit 5 for measuring each voltage (divided voltage) of 23 g
1 is provided. As shown in FIG. 3, the cell partial pressure measuring circuit 51 includes switching elements 52a to 52g between the cell batteries 23a to 23g and the reference ground G.
g, first voltage dividing resistors 53a to 53g, and second voltage dividing resistors 54a to 54g, and voltages (voltage division) Ea to Eg between the first and second voltage dividing resistors. Is input to the intermediate voltage input switching control circuit 39.

Each of the switching elements 52a to 52g employs an FET which is turned on and off by the CPU (switching element control means) 29, and is sequentially turned on only during the measurement of the partial pressure. For example, first, only the switching element 52a is turned on and all the cell batteries 23a to 23a to
The voltage Ea of the entire cell 23b to 23g is measured by measuring only the voltage Ea of the entire cell 23g and then turning on only the switching element 52b.
b, and then only the switching element 52c is sequentially
2d only is turned on, and finally the switching element 52
g alone is turned on, and the voltage Eg of one cell 23g is measured.

The above-mentioned input switching control circuit unit 3 for each cell battery.
Reference numeral 9 denotes the reference ground G and each of the cell batteries 23a to 23-2.
Detected voltages Ea to Eg between the first and second voltage dividing resistors interposed between the positive electrode and the 3 g positive electrode are input, and a predetermined one of the data (voltage value) is selected and output to the CPU 29. And a function as an analog multiplexer element, and a voltage for each cell battery selected by the CPU 29 is obtained based on the detected voltage.

A shunt resistor voltage detecting circuit 4 for detecting a voltage between both ends of the shunt resistor 37 is provided at both ends of the shunt resistor 37.
0 is connected, the detected voltage across the shunt resistor 37 is input to the CPU 29, and the CPU 29 obtains an output current value based on the change in the voltage across the shunt resistor 37.

Temperature information from the thermistor 24 is input into the battery pack 18 so that the CPU 2
9, a temperature input circuit 41 that outputs the battery temperature toward the power supply 9, an input signal circuit power supply control unit 42 that controls each power supply of the intermediate voltage input switching control circuit unit 39, the shunt resistance voltage detection circuit 40, and the temperature input circuit 41. 43 are provided.

The power supply current from the positive side of the cell battery 23a is supplied via the rectifier 44 to the cell batteries 23e and 23d.
A power supply current from between passes through a power supply stabilization circuit 45 via a power supply holding circuit 46 and a rectifying element 47 and is input to the input signal circuit power supply control units 42 and 43 and the CPU 29. The power supply current passes through the system reset circuit unit 48 and is input to the CPU 29 when a reset signal is output. The reset signal is also input to the power holding circuit 47 via the logic circuit 49.

The input signal circuit power supply control sections 42 and 43 are controlled by the multiplexer power supply control element control means 111 of the CPU 29 to function as switching elements, and the intermediate voltage input switching control circuit section 39, the shunt resistance voltage detection circuit 40 , The temperature input circuit 41 is intermittently turned on only at the time of performing the arithmetic processing.

Here, as shown in FIG. 4, a voltage in the shunt resistor 37 is generated at the time of charging in a direction opposite to that at the time of discharging. In the present embodiment, the shunt resistance voltage detection circuit 40
It is necessary to select a shunt resistor in accordance with the operating current range so as to be sufficiently tolerable against the reverse breakdown voltage of the semiconductor constituting the semiconductor device, and is set to 10 mΩ.

On the other hand, when the battery pack 18 is mounted on the battery-assisted bicycle 1 and used for traveling, the battery type of the rechargeable battery 23, the maker name of the charging device 17, the charging capacity (4 to 9) 4Ah) is the CP of the battery pack 18.
It is input to U29. At the time of discharging, the remaining amount warning time and its determination time, the final discharge voltage and its determination time, unbalanced voltage, discharge overcurrent, self-discharge amount, and the like are monitored.
Furthermore, at the time of charging, the minimum chargeable voltage, the minimum charge time, the chargeable temperature range, the unbalanced voltage, the charge overcurrent and its determination time, the charge end capacity, and the like are monitored.

When charging using the charging device 17, first, when the rising of the DC power supply is detected by the charging adapter connection voltage signal input circuit 30, the charging device 17 is charged.
Is determined to be connected. Then, it is determined whether or not the charging start condition is satisfied. If the battery temperature ta is within an appropriate range, charging is started. If the predetermined current value Ich0 is within an appropriate range, it is determined that the effective charge is being performed.
3 displays the remaining capacity. In addition, as the charge measurement, the remaining capacity of the remaining amount register is incremented by one until the learning capacity reaches the effective capacity. Note that the charging counter is +150
Values greater than zero are not counted. And
When the remaining capacity of the remaining amount register reaches the effective capacity of the learning capacity, charging is stopped.

When the discharge of the rechargeable battery 23 is started and the output current flows, the discharge register is incremented by 1, the remaining amount register is decreased by 1, and the discharging register is reset when the remaining amount register = learning capacity. . Note that the discharge register is incremented by one even if the remaining amount register = 0.

When the final discharge voltage and the unbalanced voltage are detected, the discharge suppression data is used, the LED 33 is not displayed, and the discharge rate is adjusted with reference to the temperature. Further, as time passes, the remaining amount register is decremented by -1 and the discharge register is incremented by +1 according to the discharge rate. The LED 33 is turned on and off when the discharge end voltage is detected, and is turned off when the final discharge voltage is detected.

Next, the operation of measuring the remaining capacity of the battery in the battery pack 18 of the present embodiment, that is, the operation of learning the charge capacity to be supplied until the battery is fully charged will be described with reference to FIG.

When the charging (1) is started, the remaining battery capacity increases as shown by a remaining capacity characteristic line b, and when the battery reaches the initial capacity at time t1, the battery is fully charged, and the stored discharge capacity is reset. Then, the charging (1) is completed.

When the battery pack 18 is started to be used at time t3 and discharge (1) is started, the remaining capacity characteristic line b
, The remaining battery capacity starts to decrease from the initial capacity, and the discharge capacity starts to increase as shown by the discharge capacity characteristic line c. At time t4, as shown by the voltage characteristic line a, when the battery voltage decreases to the discharge end voltage, the learning of the discharge capacity A is performed from the time of full charge at the time t1 to the time of detection of the discharge end voltage.

Next, when charging (2) is started at time t5, the battery voltage rises as shown by the voltage characteristic line a, and the battery remaining capacity increases as shown by the remaining capacity characteristic line b. As shown by the discharge capacity characteristic line c, the stored discharge capacity value is reset to 0, and the full charge capacity value in charge (2) is updated to A 'by the discharge capacity A in discharge (1).

When the remaining battery capacity reaches A 'at time t6, the charging (2) is stopped. Thus, at time t6
The remaining battery capacity A 'set by updating the remaining learning capacity at the time t5 as the remaining battery capacity at the time of full charge in.
Is used.

Even when the battery pack 18 is not used for traveling, the rechargeable battery 23 is capable of self-discharging (1).
Then, the voltage decreases as indicated by the voltage characteristic line a, the remaining battery capacity decreases as indicated by the remaining capacity characteristic line b, and the discharge capacity increases as indicated by the discharge capacity characteristic line c.

As described above, at the time t5, the stored remaining capacity value is reset and the discharge (1) is performed.
The learning capacity is updated after discharging to the discharge end voltage in the processing of (1), and the discharge capacity A in the processing of the discharge (1) shown by the characteristic line c is changed to the full charge in the next charging (2) processing shown by the characteristic line b. Since the charging capacity A ′ is set up to this, an appropriate charging capacity can be set, and overcharging can be prevented.

In the above charging, the charging device 17
The supply and the stop of the charging current from the battery to the rechargeable battery 23 are performed by the switching element 26 disposed in the battery pack 18, so that whether or not the charging is possible is not affected by the capacity of the charging device. Thus, restrictions on usable charging devices can be reduced.

Further, by controlling the switching element 26 based on the remaining capacity of the rechargeable battery 23 stored in the CPU 29, in other words, on the basis of the discharge capacity, the amount of charge, the charging time and the like are managed. Charging according to the capacity can be performed, overcharging can be avoided as in the case where charge management is performed based on changes in the physical state such as battery temperature and voltage, and the battery is not overloaded and the battery life can be extended.

In this embodiment, a plurality of rechargeable batteries 2
First voltage dividing resistors 53a to 53g and second voltage dividing resistors 54a to 54g are provided for every 3a to 23g.
3g, switching elements 52a-5 every 54a-54g
Since 2 g is provided and the switching element for the cell battery is turned on only while measuring the partial pressure of the cell battery, the consumption of the battery by the partial pressure measuring unit 51 can be reduced.

Further, since the measured cell voltage is output by the intermediate voltage input switching control circuit section 39 by time division processing, one circuit section 39 can measure a large number of cell voltage divisions. .

The intermediate voltage input switching control circuit 3
9 is turned ON only by the input signal circuit power supply control unit (1) 42 at the time of measuring the divided voltage, so that the power consumption can be further reduced.

In this embodiment, the shunt resistor 37 is inserted on the minus side of the lowest battery 23g, and this insertion point is used as the reference ground G for voltage monitoring. Therefore, as shown in FIGS. Since the value is measured on the plus side when viewed from the reference ground G, the measurement accuracy of the cell voltage in the cell voltage measurement circuit 51 can be improved.

That is, when the plus side of the shunt resistor 37 for calculating the discharge current value is used as the reference ground, a fluctuation error always occurs by the voltage between both ends of the shunt resistor 37, and the cell voltage measurement accuracy is reduced. In particular, when a large current is output, the load on the cell battery increases. Therefore, it is desirable to accurately measure the voltage. In the present embodiment, the large discharge current value is measured in a configuration separated from the measurement of the cell voltage, and has no effect on the measurement of the cell voltage, so that the measurement accuracy of the cell voltage can be improved.

Since the shunt resistance value is set so that the current value of the shunt resistor 37 is equal to or less than the reverse breakdown voltage of the shunt voltage measurement circuit 51, the shunt voltage measurement circuit 51 can be protected.

The shunt resistance voltage detection circuit 40
Are intermittently turned on only when the shunt voltage is measured, so that the power consumption can be reduced accordingly.

[Brief description of the drawings]

FIG. 1 is a side view of an electric assisted bicycle on which a battery pack of the present invention is mounted.

FIG. 2 is a diagram for explaining a configuration of the battery pack.

FIG. 3 is a diagram illustrating a configuration of the battery pack.

FIG. 4 is a view showing a shunt resistor insertion portion in the battery pack.

FIG. 5 is a characteristic diagram showing changes in battery voltage, remaining battery capacity, and discharge capacity over time due to charging and discharging in the battery pack.

FIG. 6 is a diagram showing functions of a CPU in the battery pack.

FIG. 7 is a diagram showing the configuration of the claims of the present invention.

[Description of Signs] 18 Battery packs 23a to 23g Cell battery 23g Lowest cell battery 23 Rechargeable battery 29 CPU (output current value calculation means) 37 Shunt resistor 40 Shunt resistance voltage measurement circuit 42 Input signal circuit 51 Battery voltage measurement circuit G Reference ground

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H02J 7/10 H02J 7/10 H // B62M 23/02 B62M 23/02 PF term (Reference) 2G016 CA00 CB12 CB13 CB21 CB31 CC01 CC04 CC06 CC07 CC14 CC15 CC27 CC28 CD02 CD14 CE02 5G003 AA01 BA03 CA06 CA11 CB01 CC02 DA07 EA05 GA01 GC05 5H030 AA04 AS06 AS08 BB21 FF42

Claims (3)

[Claims] 1. A rechargeable battery having a plurality of cell batteries connected thereto, a battery voltage measuring circuit for measuring a voltage of the rechargeable battery, and a shunt resistor provided in a current output path from the rechargeable battery. And a shunt resistance voltage measurement circuit for measuring a voltage across the shunt resistor, and an output current value calculation means for obtaining an output current value from the detected shunt resistance voltage. A battery pack wherein the shunt resistor is inserted and connected to the minus side of the lowest cell battery, and a connection point between the shunt resistor and the lowest cell battery is used as a reference ground for the battery voltage measurement. 2. The battery according to claim 1, wherein the resistance value of the shunt resistor is set so that the maximum reverse voltage of the shunt resistor is equal to or less than the reverse breakdown voltage of the shunt resistance voltage measurement circuit. pack. 3. The shunt resistance voltage measuring circuit according to claim 1, wherein a switching element is provided in the shunt resistance voltage measuring circuit, and the switching element is turned on only when the measuring circuit measures the shunt resistance voltage. Battery pack.