JPH05290895A - Battery pack - Google Patents

Abstract

PURPOSE:To provide a battery pack which can be conveniently used by accurately displaying the capacity of the battery in three grades with a simple circuit, and reduce the manufacturing cost by reducing a component unit price. CONSTITUTION:A battery pack is equipped with a secondary battery and a capacity display means for detecting the voltage of the secondary battery and displaying the battery capacity in three grades in its casing. The capacity display means displays indicating as an intermediate capacity in a predetermined voltage range, which is lower than the fully charged left voltage and is higher than the empty capacity left voltage. Since the voltage of the battery is detected so that its capacity is displayed in three grades, its capacity can be displayed by means of a simple circuit without using costly components such as a microcomputer or an A/D converter.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a battery pack capable of displaying the capacity of a battery.

[0002]

2. Description of the Related Art A battery pack that can display capacity can be conveniently used. This is because the capacity can be checked before use. For example, when this type of battery pack is used in a video camera, the battery will not run out during use and cannot be used. The following battery packs are commercially available to display capacity.

The battery pack that most accurately displays the capacity is
The amount of charge and the amount of discharge of the battery are detected, and the capacity is calculated and displayed. This battery pack incorporates a microcomputer for calculating the amount of charge and the amount of discharge to calculate the battery capacity. Further, a current detection resistor is connected in series with the battery in order to detect the charge amount and the discharge amount of the battery. The current detection resistor generates a voltage proportional to the current of the battery. The voltage generated across the current detection resistor is opposite between charging and discharging. Therefore, the voltage of the current detection resistor is amplified, converted into a digital amount by the A / D converter, and the digital signal is calculated by the microcomputer to calculate the battery capacity.

[0004]

Since this battery pack displays the capacity of the battery from the difference between the charge amount and the discharge amount, it has a feature that the capacity can be displayed extremely accurately. However,
This battery pack has a drawback that the electronic circuit for displaying the capacity becomes extremely expensive. It has a complicated circuit structure and is an expensive component such as a microcomputer or A / D.
This is because it requires a converter. Batteries are consumables. It is discarded when used for an appropriate time. As described above, it is never preferable to equip the discarded consumables with expensive electronic circuits in order to effectively use the resources. Further, this kind of capacity display means built in the battery pack accounts for several tens of percent of the battery price, which causes the cost of parts of the battery pack to significantly increase. Furthermore, in the battery pack of this structure, it is necessary to connect a current detection resistor in series with the battery. This current detection resistor is designed to consume as little power as possible, but it has a drawback of always consuming power.

As a battery pack which solves this drawback, there is commercially available a battery pack equipped with a capacity display means for detecting a battery voltage and selectively turning on two light emitting diodes. In this battery pack, when the switch is pressed, the red light emitting diode is turned on when the voltage of the battery is above a certain level, and the green light emitting diode is turned on when the voltage of the battery is below a certain level. In this battery pack, since the light emitting diode is turned on by the voltage sensor, the circuit structure can be extremely simple. Therefore, it can be mass-produced at a very low cost, which is a fraction of that of the capacity display means incorporating the above-mentioned microcomputer. However, this battery pack can display the capacity of the battery only in two stages of "Yes" and "No", and cannot be conveniently used. When the capacitance is displayed in two levels of “present” and “not provided”, there is a problem as to what voltage is set as the boundary voltage for switching between “present” and “not provided”. If the boundary voltage is increased, the indication of "Yes" is displayed only when the battery is almost fully charged, and the indication of "None" is available. Conversely, if the boundary voltage is set low,
There is a drawback that the capacity of the battery that can be used only a little is displayed as “present” and the battery becomes empty during use.

Particularly, in secondary batteries such as nickel-cadmium batteries and nickel-hydrogen batteries, which are often used in battery packs, the terminal voltage drops very little during use, and it is extremely difficult to set the boundary voltage. For this reason, when the boundary voltage is increased, the batteries that can be used sufficiently are displayed as "none".
Further, when the boundary voltage is lowered, there is a drawback that the battery which is almost unusable is displayed as "present".

The present invention was developed for the purpose of solving the drawbacks of these conventional battery packs. An important object of the present invention is to simplify the circuit structure and reduce the cost of parts and to reduce the battery. It is to provide a battery pack that can display the capacity conveniently for use.

[0008]

The battery pack of the present invention comprises:
In order to achieve the above object, the following configuration is provided. That is, the battery pack of the present invention incorporates a secondary battery in the casing, detects the voltage of the secondary battery, and determines the battery capacity to 3
A capacity display means for displaying in stages is provided. The capacity display means has an "intermediate capacity" within a predetermined voltage range that is lower than the fully charged standing voltage and higher than the empty capacity standing voltage.
Is configured to display.

When the secondary battery is left as it is, the initial voltage change is large, the voltage change gradually decreases after about 10 to 15 hours, and the voltage change becomes very small after 25 hours. Therefore, in the present specification, the "full charge standing voltage" means a voltage at which the fully charged secondary battery is left for 25 hours after being charged at room temperature of 20 ° C, and the "vacant capacity standing voltage" is fully charged. Rechargeable secondary battery
It means the voltage of a secondary battery discharged for 10 hours at a current of 1 C and left for 25 hours. However, there is some variation in the fully charged standing voltage and the empty capacity standing voltage even for the same type of battery. For example, the fully charged standing voltage of a nickel-cadmium battery is 1.3 as shown by the broken line in FIG.
6V to 1.38V, empty capacity left voltage is 1.27V
It becomes ˜1.29V. For this reason, both the fully charged standing voltage and the empty capacity standing voltage have a variation of about 0.02 V between the maximum value and the minimum value. Therefore, in the present specification, the fully charged standing voltage and the empty capacity standing voltage mean the average value of 100 secondary batteries, and in the case of a nickel-cadmium battery, the fully charged standing voltage is 1.37V, The capacity leaving voltage is 1.28V, and the difference is 0.09V.

In the battery pack of the present invention, three light emitting diodes are turned on, or the light emitting color of one light emitting diode is changed to three, and the light emitting area of the EL light emitting element is changed, or the liquid crystal is also changed. Therefore, the capacity can be displayed in three levels. However, the battery pack of the present invention does not specify the mode for displaying the capacity.

[0011]

In the battery pack of the present invention, the capacity is changed in three steps by effectively utilizing the characteristic that the voltage of the charged and discharged secondary battery changes in a unique state. FIG. 1 shows the characteristic that the voltage of the nickel-cadmium battery changes. The voltage of the fully charged secondary battery decreases with time, and the voltage rises if the discharged battery is left until the capacity becomes empty. The voltage when a fully charged battery is left for a certain period of time does not become lower than the voltage when an empty battery is left, and there is a slight difference in voltage between the fully charged left voltage and the empty capacity left voltage. it can. In the case of nickel-cadmium batteries, the voltage difference is 0.
It becomes 09V. The battery pack of the present invention displays "intermediate capacity" when the battery voltage is in the hatched area in FIG. A battery that is fully charged and does not discharge never falls below the fully-charged standing voltage as shown by the chain line in FIG. However, the voltage of the battery discharged halfway drops as shown by the solid line, and falls to the range shown by the hatching between the full-charge standing voltage and the empty capacity standing voltage. Further, the voltage of the battery discharged to the empty does not rise to the hatched range even if it is slightly charged and left to stand, but the voltage rises to the hatched range when the capacity is increased by charging a predetermined amount. Therefore, by displaying the intermediate capacity in the voltage range indicated by hatching, the battery voltage can be detected and the capacity can be displayed in three levels.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. However, the examples described below exemplify a battery pack for embodying the technical idea of the present invention, and the battery pack of the present invention has different types, shapes, structures, circuits, and arrangements of components. Not specific to: The battery pack of the present invention can be modified in various ways within the scope of the claims.

FIG. 3 shows the external appearance of the battery pack, and FIG. 4 shows a block diagram of the circuit of the battery pack. The battery pack 1 shown in FIG. 3 has a casing 2 in which a secondary battery such as a nickel-cadmium battery, a nickel-hydrogen battery, and a lithium battery, and a capacity display unit are incorporated. Casing 2
In order to take out electric power from the battery pack 1 and charge the secondary battery 7, the contact 3 connected to the + -electrode of the secondary battery 7 is exposed. Further, a switch 4 that is pushed when displaying the capacity is projected on the casing, and a light emitting diode 5 of the capacity display means is exposed.

The capacity display means is connected to the secondary battery 7 via the switch 4, as shown in FIG. The capacity display means 6 includes a voltage detection circuit 8 that detects the voltage of the battery and turns on the light emitting diode 5, and a light emitting diode 5 that displays the capacity of the battery 7 in three stages.

The light emitting diode 5 has two light emitting elements 5A and 5B which emit red and green lights in one case,
It has three lead wires with a common ground. The voltage detection circuit 8 causes the light emitting diode 5 to emit light in one of the following states, and displays the battery capacity in three levels of "capacity", "intermediate capacity", and "no capacity". … “Capacity” …… Lights red light-emitting element 5A… “Intermediate capacity” …… Lights red and green light-emitting elements 5A, 5B… “No capacity” …… Lights green light-emitting element 5B

FIG. 5 shows a voltage setting range in which the voltage detection circuit 8 lights the red and green light emitting elements 5A and 5B of the light emitting diode 5. In the voltage detection circuit shown in this figure, the red light emitting element is turned on when the voltage per cell of the secondary battery is 1.30 V or more, and the green light emitting element is turned on at 1.34 V or less. The fully charged standing voltage per cell of the nickel-cadmium battery is 1.37V, and the empty capacity standing voltage is 1.28V.
Therefore, by displaying "intermediate capacity" in the voltage range of 1.30 to 1.34 V, a fully charged battery and an empty capacity battery are not displayed as "intermediate capacity".

FIG. 6 shows a circuit for detecting the voltage of the battery and lighting the light emitting diode. The circuit shown in this figure is
Two sets of comparators 9A and 9B composed of operational amplifiers
Is equipped with. The comparators 9A and 9B have
The red light emitting element 5A and the green light emitting element 5B are connected via the diode 10 and the current adjusting resistor 11. The comparator 9A is connected to the + input terminal, and the comparator 9B is connected to the − input terminal, and the + side of the battery 7 is connected via the switch 4.
The − side input terminal of the comparator 9A for lighting the red light emitting element supplies the reference voltage of 1.30V, and the + side input terminal of the comparator 9B for lighting the green light emitting element is connected to the reference voltage of 1.34V. .. This circuit has a battery voltage of 1.3
When it is 0 V or more, the output terminal of the comparator 9A to which the red light emitting element is connected becomes +, and the red light emitting element 5A is turned on. When the battery voltage is 1.34 V or less, the output terminal of the comparator 9B becomes +, and the green light emitting element 5B is turned on. When the battery voltage is in the range of 1.30 to 1.34V, the output terminals of the comparators 9A and 9B become +, and both the red light emitting element 5A and the green light emitting element 5B are turned on.

The comparators 9A and 9B can be switched on and off without lighting the light emitting elements 5A and 5B in the vicinity of the reference voltage with intermediate brightness.
As shown in FIG. 5, there is a feature that the capacity of the battery can be displayed more accurately by gradually lighting up brightly in the vicinity of the reference voltage. This is because the capacity of the battery can be displayed more finely by changing the brightness of the red and green light emitting elements.

Further, as shown in FIG. 7, the capacity display means has three light emitting diodes, EL, depending on the capacity of the battery.
It is also possible to display the battery capacity in three stages by turning on the light emitting element or the like or by changing the display of the liquid crystal or the like.

[0020]

The battery pack of the present invention detects the voltage of the battery and displays the "intermediate capacity" in a predetermined voltage range that is lower than the fully charged standing voltage and higher than the empty capacity standing voltage. It has a capacity display means. That is, the battery pack of the present invention displays the "intermediate capacity" by effectively utilizing the characteristic that the voltage of a fully charged battery changes and the characteristic that the voltage of a discharged and empty battery changes. There is. The battery pack of the present invention cannot be put into practical use if the voltage when the fully charged secondary battery is left as it is and the voltage when the discharged secondary battery is left as substantially equal are left. Secondary batteries such as nickel-cadmium batteries and nickel-hydrogen batteries have an excellent property that the voltage drop in use is extremely small. Therefore, the present inventor believed that the voltage of the secondary battery left fully charged and left almost equal to the voltage when the discharged secondary battery was left unattended.
However, as a result of actually measuring the characteristics of the voltage of these batteries changing with time, it was found that the characteristics show extremely unique characteristics. That is, the fully charged standing voltage when the fully charged battery was left was higher than the empty capacity standing voltage when the secondary battery was left by discharging and the voltage dropped. Therefore, the secondary battery has a characteristic that a constant voltage width can be provided between the fully charged standing voltage and the empty capacity standing voltage. FIG. 1 shows the characteristic that the voltage of a nickel-cadmium battery changes with time. The nickel-cadmium battery shown in this figure has 1
The fully charged standing voltage per cell is 1.37V, and the empty capacity standing voltage is 1.28V. Therefore, a voltage difference of 0.09 V is generated between the fully charged standing voltage and the empty capacity standing voltage. Therefore, by displaying “intermediate capacity” in the range of 1.32 ± 0.02 V, it is possible to display the middle of the fully charged state and the empty battery state.

Therefore, the battery pack of the present invention can display the most important "intermediate capacity" from the simple display of "Yes" and "No" and can be used very conveniently. There is.

Further, a remarkable feature of the battery pack of the present invention is that the battery capacity can be conveniently detected by displaying the intermediate capacity, but the capacity of the battery pack can be displayed in three levels, so that the microcomputer and the There is no need to use expensive and complicated elements such as an A / D converter, and there is no needless consumption of power by the current detection resistor, so that a very simple circuit can be mass-produced at low cost. Therefore, the battery pack of the present invention also realizes a feature that the capacity indicating means to be discarded together with the battery as a consumable item can be prevented from being wastefully discarded with a small number of parts.

[Brief description of drawings]

FIG. 1 is a graph showing the voltage change of a nickel-cadmium battery.

FIG. 2 is a graph showing changes in voltage of a charged and discharged nickel-cadmium battery.

FIG. 3 is a perspective view of a battery pack showing an embodiment of the present invention.

FIG. 4 is a block diagram showing an example of capacity display means.

FIG. 5 is a graph showing a voltage at which a voltage detection circuit lights a light emitting diode.

FIG. 6 is a circuit diagram showing an example of a voltage detection circuit.

FIG. 7 is a block diagram of a capacitance display means showing another embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Battery pack 2 ... Casing 3 ... Contact point 4 ... Switch 5 ... Light emitting diode 6 ... Capacity display means 7 ... Secondary battery 8 ... Voltage detection circuit 9A ... Comparator 9B ... Comparator 10 ... Diode 11 ... Current adjustment resistance

Claims (1)

[Claims] 1. A battery pack comprising a secondary battery built in a casing, and having a capacity display means for detecting the voltage of the secondary battery and displaying the battery capacity in three stages, wherein the capacity display means is left fully charged. A battery pack characterized in that it is configured to display an intermediate capacity in a predetermined voltage range that is lower than the voltage and higher than the empty capacity standing voltage.