JPH03225286A - Residual quantity display device - Google Patents

Abstract

PURPOSE:To accurately display residual quantity under the variation of load by providing the residual quantity display device with a timing circuit for generating a clock signal, a discharged current detecting means, a discharged charge quantity calculating means, a residual charge calculating means for subtracting the quantity of discharged charge from the initial charge value and the like. CONSTITUTION:A battery 11 such as a Ni-Cd battery is connected to a load 12 and a current detector 13 is inserted between the load 12 and the ground. A current value detected by the detector 13 is converted into a digital signal through an A/D converter 14 and the digital signal is supplied to a microcomputer system 15. The system 15 includes a CPU, a read-only memory(ROM), a random access memory(RAM), and the like. At the time of receiving a clock signal from the timing circuit 17, the converter 14 and the system 15 control their individual operation. Signals for controlling various equipments are supplied from the system 15, the residual quantity of accumulated electricity is calculated and a signal for displaying the residual quantity is sent to a display circuit 19.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a battery monitoring device, and particularly to a remaining charge display device capable of displaying the remaining charge of a battery.

Batteries such as dry batteries and storage batteries are widely used as DC power sources and portable power sources. When using a battery that is expected to consume a certain amount of electricity, the question is whether a battery that has been discharged to a certain extent can withstand use or not.

[Prior Art] Batteries are widely used in electrical and electronic devices. For dry batteries, the total amount of charge that can be used after that time is almost fixed at the time of manufacture, and for storage batteries, when it is fully charged.
In many electronic circuits such as radios, the consumption when on is t:
Since a is approximately constant, the usage time is proportional to the charge cap.

Taking advantage of this property, nickel cadmium (N1-C
d) A battery remaining capacity monitor is proposed that calculates the remaining capacity (remaining usage time) by measuring in advance the length of time that a constant voltage can be output from the storage battery, and accumulating the time from full charge to discharging. has been done.

However, the use of batteries is not limited to constant current use.

For example, Ni-Cd storage batteries and the like are used as power sources for motors in radio-controlled vehicles, boats, and the like.

In driving a motor, etc., a large torque is required at the time of starting, and therefore a large current is required, but the current value varies greatly depending on the usage mode, such as when driving a motor at a constant speed, a significantly reduced current is sufficient. For this reason, even if it is known how long the battery has been used since it was fully charged, it is difficult to judge whether or not a new charge is required when reusing these storage batteries.

Furthermore, in radio cassette players, etc., the current consumption is almost constant when using a radio, or when a cassette tape is used, the current consumption of the tape drive motor varies greatly in absolute value.

[Problems to be Solved by the Invention] As explained above, according to the conventional technology, it is difficult to use a battery while checking the remaining capacity of the battery, except when using a constant current.

An object of the present invention is to provide a remaining battery power display device that can accurately display the remaining battery power even when load fluctuations are large.

[Means for Solving the Problems] The battery remaining capacity display device of the present invention includes a timing circuit that generates a tarok signal, a current detection unit that detects discharge from the battery at the timing of the clock signal, and a current detection unit that detects discharge from the battery at the timing of the clock signal. The method includes means for calculating the amount of discharged charge from the time length and the detected discharge current value, means for subtracting the amount of discharged charge from the initial amount of charge to calculate the remaining amount of charge, and means for displaying the remaining amount of charge.

[Operation] The electrical energy that can be drawn from a battery that has a certain initial state has a certain value, but not only the electrical energy but also the amount of charge that can be drawn from a battery that has a certain initial state is constant. be. To measure the amount of charge, you only need to know the product of the current value and time.If the current value fluctuates, you can measure the consumed charge by knowing the constantly changing current value and the elapsed time. You can know the amount. By including a timing circuit that generates a clock signal and a current detection means that detects a discharge current from a battery at the timing of the clock signal, it becomes possible to monitor a current value that changes over time. By subtracting the amount of discharged charge from the total amount of charge that can be consumed, the remaining amount of charge is calculated, and by displaying this amount, the battery user can know how long the same battery can be used again. It becomes possible.

[Example 2] The present invention can be applied to batteries in general, but its effects are particularly noticeable when applied to storage batteries. Therefore, the case where the remaining amount of power stored in the storage battery is displayed will be explained below as an example.

FIG. 1 is a block diagram showing a power storage remaining amount display device according to an embodiment of the present invention.

A storage battery 11 such as a Ni-Cd battery is connected to a load 12. A current detector 13 is inserted between the load 12 and ground. That is, the current flowing through the load 12 is detected by the current detector 13.

The current value detected by the current detector 13 is transmitted to the A/D converter 1.
4, the signal is converted into a digital signal and supplied to the microcomputer system 15. The current detector 13 is composed of, for example, a resistor with a small resistance value connected in series with the load.

In addition, a device that detects current by induction may be used.

The voltage of the storage battery 11 is monitored by a voltmeter 22,
After being converted into a digital signal by the A/D converter 14, it is supplied to the microcomputer system 15. A/D converter 1
4 may have separate parts for current and voltage, but
It can also be used in time-sharing by changing the timing.

Here, the properties of the Ni-Cd1 battery will be explained in more detail. As shown in FIG. 4, the N1-CdW battery produces a nearly constant voltage within the area of use, as shown in the upper diagram. In this region, as shown in the lower diagram, the voltage value is approximately constant even if the value of the extinguishing gt current varies. However, after consuming a certain amount of electrical energy or charge, the properties of the Ni--Cd storage battery deteriorate rapidly. That is, as shown in FIG. 4, the voltage value begins to drop rapidly, and the current value that can be extracted accordingly also drops. The point at which this characteristic begins to deteriorate is called breakdown.

That is, l! When using a battery, the initial state is a fully charged state, and its power storage state is 100%. As a completely discharged state, it is also possible to take a state in which discharging is actually impossible, but in terms of battery usage, it is convenient to use the breaktown state as a completely discharged state and to set the remaining capacity to 0%.

As mentioned above, the current value detected by the current detector 13 is A
The signal is converted into a digital signal via the /D converter 14 and supplied to the microcomputer system 15. The microcomputer system 15 includes a central processing unit (CPU), a read-only memory (RO
M) The A/D converter 14 and the microcomputer system 15, including an arbitrary write/read memory (RAM), etc.
It receives a clock signal from the timing circuit 17 and controls its operation. The microcomputer system 15 supplies signals for controlling various devices. First, the remaining amount of electricity stored in the storage battery 11 is calculated, and the display 19 for displaying the remaining amount of electricity stored in the storage battery 11 is calculated.
In the case of 0, where a signal is sent to the battery and the remaining amount of electricity is displayed on a display such as an LCD, the remaining amount of electricity is displayed as a bar graph on the LCD.

Further, the voltage between the terminals of the storage battery 11 is monitored by a voltmeter 22, and the detected voltage is supplied to the microcomputer system 15 as a digital signal via the A/D converter 14. The A/D converter 14 converts the current value from the current detector 13 and the voltage value from the voltmeter 22 into digital signals, for example, by time division. The A/D converter 14, the timing circuit 17, the microcomputer system, etc. are powered by the storage battery 11.
Alternatively, when the remaining amount of charge in the storage battery 11 decreases, break town is detected and displayed, and the charging circuit 21 is switched to the switch 25. It is also possible to charge the storage battery 11 by connecting it to the storage battery 11 via the AC power source and supplying direct current obtained by rectifying a power source such as a commercial power source. Hereinafter, calculation of the amount of discharged charge will be explained in more detail.

In the circuit of FIG. 1, the current supplied from the storage battery 11 to the load 12 is constantly monitored by the current detector 13. This th current value is supplied from the current detector 13 to the microcomputer system 15 via the A/D converter 14 and recorded. The timing circuit 17, as shown in FIG.
Timing pulses are generated at regular intervals Δt. This timing signal is supplied to the A/D converter 14 and the microcomputer system 15 to start their operations. That is, the A/D converter and microcomputer system 15
takes in the current value detected by the current detector 13 every Δ.

As shown in FIG. 2, if the sampling period Δt is made sufficiently small, the sampled current value can approximate the actual current value with sufficient accuracy.

In the graph of FIG. 2, when a current value I(t) is detected, that current value continues for a sampling period Δ. Therefore, by a bar graph as shown in Figure 2,
The total amount of current flowing is approximated. From a battery that initially has a charge of only QC, Qd=ΣI (t)・Δt during use
When the battery is discharged, the discharge charge is Qd, and the amount of charge remaining in the battery is QQc-Qd. By displaying this remaining power storage amount on the display 19, the user of the storage battery 11 can easily know the remaining power storage amount of the storage battery 11.

The remaining amount of power storage is shown in a graph obtained by dividing O to 10 into 10 equal parts, with full charge being 10.

FIG. 3 is a flowchart schematically showing the operation of the remaining power display device shown in FIG.

First, after the process starts, in step S1,
Initial settings of the microcomputer system are performed.

When the storage battery 11 is fully charged, the remaining power storage amount Q is set to QC.

Next, in step S2, the timing circuit 17 activates a real-time clock signal (clock interval Δt).

Next, in step S3, it is determined whether a new clock signal has been generated. When a new clock signal is generated, the current I flowing through the load 12 is read by the current detector 13 in step S4 according to the YES arrow. This current value 1 (t) is multiplied by the time difference Δt between the clock signals to approximate the amount of charge flowing during the time difference Δ (step S5). Using this amount of charge, the previous clock signal is The current amount of discharged charge Δt·I(t) is subtracted from the amount of charge Q at the time of generation to obtain the remaining amount of stored electricity Q=QC−Qd. Calculate the ratio between the remaining charge and the fully charged charge.

The remaining power storage amount obtained in this way is displayed on the display device 19 in step S7, and the process returns to step S3.

Incidentally, in step S3, if a new clock is not generated, the process returns to step S3 again and waits until a new clock is generated.

As described above, by constantly monitoring the discharge current at the timing of the time difference Δt, the discharge current value can be monitored,
It becomes possible to calculate the amount of discharged charge. In this way, even when load fluctuations are large, the remaining amount of power stored in the storage battery can always be accurately monitored and the remaining amount of stored power can be displayed on the display device 19.

Such a storage battery level display device can be used for storage batteries and batteries in general, but it is especially useful for storage batteries such as Ni-Cd, where the output voltage is constant and the remaining storage capacity cannot be determined from the voltage. big.

As shown in the Vt characteristic in the upper part of FIG. 4, the output voltage of the Ni--Cd storage battery hardly decreases with use, and maintains a constant output voltage. This property is an excellent property for a storage battery, but the remaining amount of charge cannot be determined from the voltage.
When the remaining amount of electricity in the storage battery is almost exhausted, the output voltage V suddenly decreases.
decreases.

When using a battery starter device, it is important to predict how long it will take to use the battery to reach the point at which the output voltage begins to drop.

It is convenient to set the remaining amount of stored power to 100% when fully charged and 0% at Break Town B.

When charging a storage battery, a current detector is installed in the charging circuit to monitor the current value and charging time to estimate the total charge amount and set the total charge amount taking into account variations between batteries. This also allows the total amount of charge available to be set. Thereafter, by monitoring the amount of discharged charge and subtracting the amount of discharged charge from the total amount of charge, the remaining amount of stored power can be calculated. By making the time difference Δt of the clock signals sufficiently small, it becomes possible to approximate the discharge current that actually flowed and the amount of discharge current that was measured with sufficient accuracy.

FIG. 2 is a diagram showing the amount of discharged charge approximated in the above embodiment. A discharge current value is detected at the timing of each timing signal, and the current value is approximated by continuing for the time difference Δ of the clock signals. Therefore, the total value of flowing current is approximated by the total area of the bar graph.

Another example of calculating the amount of discharged charge is shown in FIG. 5. In FIG. 5, the amount of discharged charge is approximated by a line graph instead of a bar graph. That is, the amount obtained by adding the previous detected current value and the current detected current value, multiplying by the time difference between them, dividing by 2, and averaging the amount is approximated as the amount of discharged charge.

In the circuit shown in FIG. 1, when the remaining amount of stored electricity becomes low, such as when a breakdown is detected, a command can be issued from the microcomputer system to activate charging port #121. The charging circuit 21 is supplied with power from a commercial AC power source or the like and generates a constant output voltage. In response to a command from the microcomputer system, the switch means 25 is closed, and current is supplied from the charging circuit 21 to the storage battery 11.

The inter-terminal voltage of the storage battery 11 is monitored by a voltmeter 22 and supplied to the microcomputer system 15 via the A/D converter 14. For example, a Ni-Cd storage battery has a -ΔV characteristic in which the voltage between its terminals once drops by -Δ■ when it is fully charged. By detecting this -Δ■ phenomenon by the charging cycle #121 or the microcomputer system 15, the storage battery 1
1 full charge is detected. When the storage battery 11 is fully charged, the switch 25 is released and the charging circuit 21 is connected to the storage battery 11.
Cut it ^ ``S.

In addition, when the voltmeter 22 detects a breakdown even though there is a remaining amount of stored power according to the calculation of the microcomputer system 14,
It is also possible to give priority to the detected breaktown and calibrate the total charge amount for future use.

The current detector 13 may be of any type as long as it detects the value of the flowing current; for example, it may be formed of a resistor and detect the voltage generated across the resistor to detect the value of the flowing current. .

Further, by connecting a constant voltage source 23 to the storage battery 11 and generating a constant voltage, it is possible to create a power source for the A/D converter 14, the microcomputer system 15, the timing circuit 17, etc. Note that it is of course possible to supply power to these circuits from separate power sources. Note that the constant voltage source 23 also supplies a reference voltage Vref for the A/D converter. Any load may be used as the load 12, and it is also possible to use a load with large load fluctuations, such as a motor, for which it was previously impossible to calculate the remaining amount of stored electricity.

The display circuit 19 may be any device capable of displaying the remaining amount of stored power.6 In the case shown in the figure, an LCD consisting of 10 segments is provided, and the remaining amount of stored power is displayed as a bar graph divided into ten equal parts.

FIG. 6 is a block diagram showing a remaining power display device according to another embodiment of the present invention. Parts labeled with the same reference numerals as in the embodiment of FIG. 1 perform equivalent functions.

In this embodiment, a constant current load 27 is connected to the storage battery 11 in parallel with a load 12, and either the load 12 or the constant current load 27 is selectively connected by a switch 28. The detected current value is converted into a digital signal by the A/D converter 14, and then sent to the microcomputer system 15.
The microcomputer system 15 sends a power storage remaining amount signal to the display circuit 19, and the remaining power storage amount is displayed.
In this embodiment, the remaining power storage amount is expressed as a numerical value as a percentage.

The constant current load 27 is for more accurately measuring the total amount of charge when the storage battery is fully charged by discharging the storage battery 11 at a constant current after the groove light.

In other words, when the identity of the storage battery 11 is unknown,
A constant current load 27, which determines the discharge state of the storage battery 11, is connected to the storage battery 11 via a switch 28, and first a constant current discharge is performed. The voltage across the terminals of the storage battery 11 is monitored with a voltmeter 22, and when a breakdown occurs, the discharge by the constant current load is stopped.Next, the charging cycle #121 is connected to the storage battery 11 via the switch 25,
Fully charge the storage battery 11. By detecting Δ■ with the pressure gauge 22, the microcomputer system 15 controls the charging cycle f#121 to terminate charging, discharge it again via the constant current load 27, and calculate the total amount of charge until breakdown. Qc is the total amount of charge charged to the storage battery 11 when it is fully charged.

After that, the storage battery 11 is fully charged, and the load 12 is transferred to the storage battery 11.
The charge amount used at that time is monitored by the current detector 13.

According to the remaining power display device shown in FIG. 6, it is possible to always accurately measure the remaining amount of power regardless of variations in the characteristics of the storage battery. The characteristics of a storage battery using such a constant current load 27 can be measured, for example, on a manufacturer's production line, at any time by a user, or when the remaining amount of storage battery reaches 0% while driving a load device. You can start it.

FIG. 7 is a graph conceptually showing measurement of characteristics of such a storage battery. When the storage battery 11 is fully charged, it is in the state for time t=o (100%) shown in FIG. 7, and then generates a substantially constant output voltage until it reaches breakdown. When the constant current load 27 is connected at time A when the battery has been discharged to a certain extent and measurement of the characteristics of the storage battery is started, first
The characteristics move from 0% to breakdown (0%).

After that, by performing a quick charge, it will go from 0% to 100%.
move to the state of After being fully charged, the storage battery 11 is discharged via the constant current load 27, the discharge current at that time is detected by the current detector 13, and the amount of discharged charge 1 (t)·Δ
t is detected and the amount of discharged charge up to break town is measured. When breakdown occurs, the amount of discharged charge up to that point is integrated to determine the total amount of accumulated charge. After that, the storage battery 11 is fully charged again, and the remaining amount of stored power is calculated by subtracting the discharged charge amount from the measured total charge amount at full charge.

Note that such characteristic measurements can be carried out at any time, but when carried out at the time of breakdown, the first discharging process can be omitted, so charging and discharging can be carried out once, and it is also possible to If this characteristic measurement is started when the battery is charged, the characteristic will be measured through - times of discharging steps.

In addition, even though there should be some charge remaining, by the time we head to Breaktown, the characteristics of the storage battery 11 are thought to have changed, so we set a new total charge amount at full charge. This allows you to calibrate the remaining power display from next time onwards.

Although the present invention has been described above in accordance with the examples, the present invention is not limited to these examples. For example, various modifications,
It will be obvious to those skilled in the art that improvements, combinations, etc. are possible.

[Effects of the Invention] As explained above, according to the present invention, even when load fluctuations are severe, the remaining charge of the battery can be measured with high accuracy,
Can be displayed.

Since the battery user can always know the remaining charge level of the battery and decide on its subsequent use, the battery can be used safely.

Further, in the case of a storage battery, it is possible to prevent erroneous operation due to breakout of the storage battery, and unnecessary charging can be omitted by knowing the remaining amount of stored power.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing a remaining power display device according to an embodiment of the present invention. FIG. 2 is a graph showing an example of calculating the amount of discharged charge of a storage battery. A flowchart of the software of basic functions to explain the operation of the quantity display device, Fig. 4 is a graph showing the properties of the Ni-Cd1 battery, and Fig. 5 shows another example of calculating the amount of discharged charge. Graph, FIG. 6 is a block diagram showing a remaining power display device according to another embodiment of the present invention, and FIG. 7 is a graph for explaining the concept of operation of the remaining power display device shown in FIG. It is. In the figure, 11 storage battery 12 load 3 4 5 7 9 1 2 3 25, 7 8 current detector A/D converter microcomputer system timing circuit display circuit/charging circuit voltmeter constant voltage source switch constant current load

Claims (2)

[Claims] (1) A remaining capacity display device for a battery, which includes: a timing circuit that generates a clock signal; a current detection means that detects discharge from the battery at the timing of the clock signal; and a time length between the clock signals and the detected discharge. A remaining amount display device comprising: means for calculating the amount of discharged charge from a current value; means for calculating the remaining amount of charge by subtracting the amount of discharged charge from the initial amount of charge; and means for displaying the remaining amount of charge. (2) In the remaining capacity display device according to claim 1, the battery is a storage battery, further comprising a constant current load capable of discharging a constant current from the storage battery, and a voltage detection capable of detecting a voltage between terminals of the storage battery. and a remaining amount display device.