JPH10142301A - Apparatus for detecting residual capacity of battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an apparatus for correctly detecting the residual capacity of a battery so that battery-driven electric appliances are prevented from malfunctioning as a result of the decrease of a source voltage and the power of the battery can be utilized sufficiently. SOLUTION: A microcomputer 4 takes in an ON/OFF state of a presstalk switch 3 and, selects one of a voltage VS1 and a voltage VS2 (<VS1 ) stored in a ROM 5 in accordance with the taken in state. When the presstalk switch 3 is OFF, the voltage VS1 is used as a discharge termination detection voltage VS. When the presstalk switch 3 is ON, the voltage VS2 is used as the discharge termination detection voltage VS. The residual capacity of a battery is thus detected. While a consumed current is increased and a battery voltage VB is lowered when a portable radio 2 operates transmission, this is detected by the turning-ON of the presstalk switch 3, and consequently the discharge termination detection voltage VS is switched from the voltage VS1 to the voltage VS2 (<VS1 ). The residual capacity of the battery is accordingly correctly detected.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for preventing a malfunction of a battery-operated electric device due to a drop in power supply voltage, and more particularly to a device for detecting a remaining battery level suitable for a portable radio.

[0002]

2. Description of the Related Art In recent years, the spread of various portable radios has been remarkable, and the performance of batteries has been remarkably improved. However, the power capacity of batteries is limited and the remaining power is reduced. However, there is still no change in the point that the power supply voltage is reduced. Therefore, in such an electric device such as a portable wireless device that operates on a battery, the operation time of the battery can be extended as much as possible, while preventing malfunction of the device due to a decrease in the terminal voltage of the battery. It is desired to do.

Therefore, a battery remaining amount detecting device capable of detecting the remaining amount of the battery at any time as needed has been conventionally used. When the terminal voltage of the battery is reduced to the discharge end detection voltage, the operation of the electric device is stopped assuming that the remaining battery level has become zero. .

[0004]

However, the above-mentioned prior art does not take into consideration the accurate detection of the remaining battery level, and has a problem that the user is not satisfied with the sufficient use of the battery capacity. That is, although the terminal voltage of the battery is a factor that certainly indicates the remaining battery level, it also changes due to other factors, and does not always uniquely correspond to the remaining battery level. However, in the related art, as described above, the remaining battery level is simply determined based only on the terminal voltage of the battery, and thus the accuracy is lacking.

[0005] This will be described more specifically with reference to FIG. First, FIG. 3 shows that the terminal voltage V
_B is 12.6V (4.2 x 3) and recommended rated capacity is about 8
00mAh lithium-ion secondary battery recommended rated current
(For example, 150 mA). In this case, as shown in the figure, the terminal voltage decreases as the discharge proceeds, mainly due to a change in internal resistance due to the discharge of the battery. It is well known that this change in internal resistance is particularly remarkable in the case of a lithium ion secondary battery.

In this case, the discharge end detection voltage is
As shown in the figure, the voltage is set to 8.1 V. First, when the remaining amount is detected under the rated current, a zero battery level is detected at a point.
In this case, it can be used up to almost the rated capacity.

However, in the case of an electric device that receives power supply from the battery, the current greatly changes during use, such as a portable wireless device whose power consumption greatly changes between reception and transmission. Sometimes, for example, 1300 mA
In this case, a large voltage drop appears as shown in the figure due to the internal resistance of the battery.

Accordingly, at this time, as shown by the dots,
In spite of the fact that only about 700 mAh has been discharged, the battery remaining amount is determined to be zero here, and accurate remaining amount determination cannot be obtained.

SUMMARY OF THE INVENTION It is an object of the present invention to accurately determine the remaining amount of power in a battery and sufficiently reduce the power of the battery without causing a malfunction due to a decrease in the power supply voltage of an electric device operated by the battery. An object of the present invention is to provide a battery remaining amount detecting device that can be used.

[0010]

The object of the present invention is to provide means for correcting a discharge end detection voltage for battery remaining amount determination in accordance with a battery current at the time of the determination, and to provide the corrected discharge end detection voltage. This is achieved by determining the remaining battery power using the battery.

The above-mentioned means works so that the discharge end detection voltage for determining the remaining battery level is reduced as the battery current increases. As a result, the discharge end detection voltage for determining the remaining battery level can be reduced within a range where electrical equipment does not malfunction due to a temporary drop in power supply voltage, and the remaining power of the battery can be further used. The operation time can be extended by the battery.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a battery remaining amount detecting device according to the present invention will be described in detail with reference to the illustrated embodiments.
FIG. 1 shows an embodiment in which a battery level detecting device according to the present invention is applied to a portable wireless device. In the drawing, 1 is a secondary battery pack, 2 is a portable wireless device, 3 is a press talk switch, Is a microcomputer, and 5 is a ROM (read only memory).

The secondary battery pack 1 has a built-in lithium ion secondary battery B composed of, for example, three unit cells.
The terminal voltage V _B in the charged state and the open state is 12.6.
V, which is provided with a connection terminal so as to be freely attached to and detached from the portable wireless device 2 and packed.

Here, as is well known, a battery is equivalently represented by an electromotive force E and an internal resistance r as shown in the figure, and this internal resistance r has a minimum value when the battery is fully charged. And increases as the battery discharges. As described above, the increase in the internal resistance r is particularly remarkable in a lithium ion battery.

The portable wireless device 1 is of a so-called press-talk type, is controlled by a microcomputer 4, and becomes operable when a power switch (not shown) is turned on. In this state, the press-talk switch 3 is turned on. When the switch 3 is released, the receiving operation is performed, and only when the switch 3 is pressed, the transmitting operation is performed.

Normally, in a wireless device, the power consumption during transmission is considerably larger than the power consumption during reception standby or signal reception. For example, in the former, the battery current is 100%.
There is a considerable difference between the pre-stoke switch 3 and the off-state of the press-to-talk switch 3 in the portable wireless device 1.

The ROM 5 functions to store a discharge end detection voltage necessary for detecting the remaining battery level. In this embodiment, two types of discharge end detection voltages, that is, a voltage V _S1 (= 8.1 V) and a voltage V _S2 (= 7.5 V) are stored.

[0018] The microcomputer 4 controls the receiving unit and the transmitting unit of the mobile radio 2, with perform control necessary for communication by a press-talk system, captures the voltage V _B from the battery pack 1 is set to ROM5 compared to final discharge detection voltage in Te, when the terminal voltage V _B of the battery was reduced to final discharge detection voltage, as the battery level becomes zero, configured to stop the operation of the portable radio 2 Have been.

At this time, the microcomputer 4 further includes:
The ON / OFF state of the press talk switch 3 is captured,
According to the result of the capture, one of the two voltages V _S1 (= 8.1 V) and V _S2 (= 7.5 V) stored in the ROM 5 is selected, and the press-talk switch 3 is turned off. is when, using the voltage V _S1 as final discharge detection voltage V _S, when the press-talk switch 3 is on, the voltage V _S2
Is used as the discharge end detection voltage V _{S to} detect the remaining battery level.

Next, the operation of this embodiment will be described with reference to FIG. FIG. 2 shows a lithium ion secondary battery B having a recommended rated capacity of about 900 mAh. After the portable wireless device 2 is in a standby state until the capacity consumption becomes slightly less than 700 mAh, the press-talk switch 3 , The terminal voltage V _B when the pattern of transmission (ON) for about 1 minute, reception (OFF) for about 1 minute, and the standby state (OFF) for about 18 minutes is repeated four times
This shows the change of

[0021] In FIG. 2, now, similar to the case of the prior art described in FIG. 3, the discharge end detection voltage is the voltage V _S1
If it is fixed to (= V _S ), as is clear from the figure, when the capacity consumption of the battery B reaches about 700 mAh, the remaining battery level is determined to be zero.

However, in the embodiment of FIG. 1, as apparent from FIG. 2, the discharge end detection voltage V _S is
When the press talk switch 3 is off, that is, when receiving /
The voltage V between the standby state and the ON state, that is, the transmission state,
_{Since the} voltage is switched between _S1 and the voltage V _S2 , the battery remaining amount is determined to be zero because the capacity consumption of the battery B is indicated by a point 90.
This is a time when the battery B reaches a little less than 0 mAh, that is, near the recommended rated capacity of the battery B. Therefore, the above results are summarized as follows.

[0023]

[Table 1]

As is apparent from Table 1, according to the embodiment of FIG. 1, in the general use mode of the portable wireless device 2, it is possible to use the battery B almost up to the full rated capacity.
The use time of the portable wireless device 2 can be extended by 90 minutes at the maximum.

Therefore, according to the above-described embodiment, the effective use of the electric power remaining in the battery can be sufficiently achieved, and the operation time of the battery can be sufficiently extended.

By the way, in the embodiment of FIG. 1, on the press-to-talk switch 3, while switching the discharge termination detection voltage V _S according to off, instead of this, the press-talk switch 3 only when the off-cell The remaining battery level may be detected, and when ON, the battery remaining level detecting operation may be prohibited.

In this case, when the press talk switch 3 is turned on and the terminal voltage of the battery drops, the battery remaining amount detection operation is not performed. Since there is no detection, the power remaining in the battery can be effectively used, as in the embodiment of FIG. 1, and the operation time of the battery can be sufficiently extended.

In the embodiment of FIG. 1, since the portable wireless device 2 is an object to be applied, a change in the current of the battery B is detected by turning the press-talk switch 3 on and off. What is necessary is just to make it detect a current by the means of.

In the above embodiment, the case where the present invention is applied to a portable wireless device has been described. However, the present invention can be applied to any electric device powered by a battery. Needless to say.

[0030]

According to the present invention, it is possible to always use the electric equipment up to the full capacity of the battery, so that the operable time can be sufficiently extended by the effective use of the battery capacity.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of a battery remaining amount detecting device according to the present invention.

FIG. 2 is a characteristic diagram for explaining a battery remaining amount detecting operation according to an embodiment of the present invention.

FIG. 3 is a characteristic diagram for explaining a battery remaining amount detection operation according to the related art.

[Explanation of symbols]

 1 Secondary Battery Pack 2 Portable Radio 3 Press Talk Switch 4 Microcomputer (Microcomputer) 5 ROM (Read Only Memory)

Claims (2)

[Claims] 1. A battery remaining amount detecting device for detecting a remaining amount of a battery by comparing a terminal voltage of the battery with a preset discharging end detecting voltage, wherein the discharging end detecting voltage is changed. Means for detecting a remaining battery charge, wherein the discharge end detection voltage is reduced in accordance with an increase in a current value supplied to the load from the battery. 2. A battery remaining amount detecting apparatus for detecting a remaining amount of a battery by comparing a terminal voltage of the battery with a preset discharging end detecting voltage, wherein a means for detecting a discharge end detecting operation is provided. Wherein the prohibition process by the means is executed when the current value exceeds a predetermined value set in advance.