JPH0310179A - Battery exhaustion detector - Google Patents

Abstract

PURPOSE:To enable accurate judgment of exhaustion of a battery by providing a resistor adapted to make a reference voltage by dividing a power source voltage with a thermistor to correct the reference voltage as criterion for exhaustion of the battery according to a temperature characteristic of an output voltage of the battery. CONSTITUTION:A power source is divided with a resistor 1 for making a reference voltage, a thermistor 22 and a resistor 2 to apply the reference voltage to a comparator 5. The reference voltage varies with a room temperature, as the thermistor 22 is connected in parallel with the resistor 1. Then, when a switch 3 is depressed, a backup battery 6 connected to a terminal 7 is connected to let current flow through a pseudo load resistor 4 and a voltage of the battery 6 is applied to the comparator 5 as detec tion voltage. The comparator 5 compares the detection voltage with the reference voltage and when the detection voltage is larger than the reference voltage, a transistor 8 is turned ON to light an LED 9, which indicates that the battery operates normally. When the detection voltage falls below the reference voltage with the battery consum ing, the transistor 8 will not be turned ON in response to the depression of the switch 3. Thus, exhaustion of the battery can be detected without the lighting of the LED 9.

Description

[Detailed Description of the Invention] Industrial Application Field The present invention operates using a commercial power source during normal use, such as an electronic hot water mixing device, and temporarily uses a battery when the power supply is interrupted, such as during a power outage. The present invention relates to a battery deadness detection device for a device that operates with backup.

, Conventional technology Among devices that operate by being powered by commercial power during normal operation, if the power is cut off due to a power outage or other cause, it would be in an inconvenient state if the device stopped in that state. For example, in the case of an electronic hot water mixing device with a flow rate adjustment function, if there is a power outage etc. during hot water supply and the 'r4# supply stops and the flow 111 control valve stops, the water cannot be stopped. become. In such devices, the power supply is backed up for a while after a power outage using rechargeable batteries or dry batteries, and during this time, for example, in the electronic hot water mixing device mentioned above, the valves are closed to ensure that no danger or inconvenience occurs. to stop state. Backup batteries built into devices for these purposes are prepared for situations that cannot be predicted at any time, such as power outages, as mentioned above, so when the above situation occurs, the battery can be used sufficiently. It is necessary to check the status from time to time. Generally, when a load current flows through a battery, its output voltage decreases due to internal resistance. Therefore, if you want to accurately detect whether or not the battery is usable, you can determine if the battery is dead by simulating the maximum possible load current when the backup battery is needed and measuring the voltage at that time. There is a need to.

FIG. 2 shows the configuration of a conventional battery exhaustion detection device.

A conventional dead battery detection device includes resistors 1 and 2 that are supplied with power and create a reference voltage for determining battery deadness, a switch 3 that is pressed by the user to measure dead battery, and switch 3.
A pseudo load resistor 4 is connected to the dummy load resistor 4, and the reference voltage from the resistor 1 and the resistor 2 is connected to the dummy load resistor 4, which flows the same current as the maximum load current that can be considered when the power supply is stopped due to a power outage, etc. a comparator 5 that compares and outputs the battery voltages of the
It consists of a terminal 7 to which a backup battery 6 is connected, and a dead battery indicator 10 consisting of a transistor 8 and a light emitting diode 9 to indicate when the battery is dead.

Next, the operation of the dead battery detection device configured as described above will be described.

The power supply is divided by resistors 1 and 2 to create a reference voltage, and provides a reference voltage Vref to the comparator 5.
ref is set to a voltage that can sufficiently drive the load when the maximum conceivable load current flows during a power outage. If the value is lower than V ref, it is determined that the battery is dead. When the user presses the switch 3, the backup battery 6 connected to the terminal 7 is connected. Then, a current flows through the pseudo load resistor 4, and the voltage of the backup battery 6 is applied to the comparator 5 as the detection voltage Vd. Comparator 5 receives reference voltage V re
f and the detection voltage Vd are compared and outputted. If the detected voltage Vd is higher than the reference voltage Vref, the transistor 8 turns ON and LP01 turns on, indicating that the battery is still usable. When the bank-up battery 6 is exhausted and the detection voltage Vd falls below the reference voltage, the switch 3
Even if you press , transistor 8 turns ON, so it's not LP01.
does not light up, allowing you to detect a dead battery.

Problems to be Solved by the Invention However, the dead battery detection device having the above configuration has the following problems because the reference voltage for determining whether the battery is dead is constant.

FIG. 3 shows an example of the temperature characteristics of the voltage when a load resistor is connected to a general dry battery and a current is passed through the battery.

The batteries used were eight common SUM-3 type dry batteries connected in series. In the figure, 11 is a new battery that was measured by passing a small current through it, and 12 was a 15Ω load resistor connected to this battery. These are the characteristics when connected and a current flows. 1
As the battery 2 becomes exhausted, the characteristics shift in the direction 14 as shown in FIG. 13, for example.

Now, for the purpose of explanation, this temperature characteristic is shown in the fourth diagram as a straight-line proximal diagram.
15 in the diagram shows the characteristics when the load resistor is set to RL in a new state, and as the battery wears down, the characteristics move in the direction of 16 in the diagram. In order to guarantee that this battery can be used in the entire temperature range, it is necessary to determine that the battery is dead if it is below the level of consumption shown in FIG. 17.

Now, assume that the reference voltage Vref for determining battery exhaustion by the battery exhaustion detection device shown in FIG. 2 is set as shown in FIG. 418. At this time, when the battery with the degree of consumption shown in FIG. 19 is determined at a temperature of 20° C., it is determined that it can still be used because it exceeds V ref. However, if a power outage occurs when the temperature is 0° C., there will be an inconvenience that the load cannot be driven because the voltage is lower than the minimum voltage Vli- that can drive the load.

For example, if this device is installed indoors and the heating is turned on in the winter and the room temperature is 20"C, it will detect a dead battery and turn off the heating in the morning so that the user can go to bed. It is quite conceivable that a power outage would occur when the room temperature dropped to 0°C.

In order to avoid the above situation, it is conceivable to set the reference voltage Vref for determining whether the battery is dead to the maximum voltage within the guaranteed range based on the characteristics 17 in FIG. 4. In other words, the warranty range is from -20'C to 30''
When the voltage is set to C, the voltage shown in FIG. 20 is set to V ref. In this way, even if the determination is made at any temperature within the guaranteed range, the temperature difference from the time of determination will not make the device unusable during a power outage. However, in this example, if the determination is made at 5"C, all the batteries that are exhausted from 21 in the same figure will be dead.As is clear from the figure, batteries with a consumption level of 21 will not be able to handle the load sufficiently. The battery should be able to be driven, but the determination in this case is not accurate.In other words, it determines that the battery is dead even though it can still be used, so you have to replace the usable battery.Also, consider the battery life at that time. In this case, the battery life will be judged to be shorter than the actual life, so if you want to extend the life, you will have to increase the battery voltage.This is not only uneconomical due to the increase in the number of batteries, but also causes overvoltage on the load. In order to prevent this, it is necessary to provide a separate constant voltage circuit, which increases the cost of the equipment.

This invention was made in view of the above-mentioned problems, and provides a dead battery detection device that can accurately determine a dead battery by correcting a reference voltage that is a criterion for determining whether a battery is dead according to the temperature characteristics of the output voltage of the battery. It provides:

Means for Solving the Problems In order to solve the above problems, the dead battery detection device of the present invention is such that a thermistor as a room temperature sensor is provided in a resistor that divides the power supply voltage to create a reference voltage.

Effect The above configuration detects the room temperature and corrects the reference voltage, eliminating the influence of the temperature characteristics of the battery's output voltage on determining whether the battery is dead, so it is possible to accurately determine whether the battery is dead within the guaranteed temperature range. .

Embodiment FIG. 1 shows the configuration of a dead battery detection device of this embodiment. Components that are the same as those of the conventional example are given the same reference numerals, and detailed explanation thereof will be omitted. This dead battery detection device includes resistors 1 and 2 that generate a reference voltage, a thermistor 22 as a room temperature sensor connected in parallel with the resistor 1, a switch 3, a pseudo load resistor 4, a comparator 5, It consists of a terminal 7 and a dead battery indicator lO.

Next, the operation of the dead battery detection device configured as described above will be described.

The power supply consists of resistor 1 and thermistor 22 to create a reference voltage.
The voltage is divided by the resistor 2 and the reference voltage V ref is applied to the comparator 5. Here, since a thermistor is connected in parallel to the resistor 1, Vref changes depending on the room temperature. When the room temperature is high, the resistance value of the thermistor 22 is low, resulting in a high V ref; when the room temperature is low, the resistance value of the thermistor 22 is high, so V ref
f has a decreasing characteristic.

When the user presses the switch 3, the backup battery 6 connected to the terminal 7 is connected.

Then, a current flows through the pseudo load resistor 4, and the current flowing through the pseudo load resistor 4 causes the comparator 5 to receive a backup battery 6.
The voltage is given as the detection voltage Vd. The comparator 5 compares the reference voltage Vref and the detection voltage Vd, and if the detection voltage Vd is larger than the reference voltage Vref, the transistor 8 is turned on, and the light emitting diode 9 is turned on, indicating that the battery is still usable. Display something. When the battery 6 is exhausted and the detection voltage Vd is lower than the reference voltage, even if the switch 3 is pressed, the transistor 8 is not turned on, so the light emitting diode 9 does not light up, and the battery exhaustion can be detected.

That is, Vr
If the curve of ef is set to have the characteristics shown in FIG. 4, it is possible to accurately determine whether the battery is dead within the guaranteed temperature range.

Effects of the Invention As described above, the dead battery detection device of the present invention has an extremely simple configuration and corrects the reference voltage for determining dead battery according to the ambient temperature, so that dead battery can be detected accurately. can do.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of a dead battery detection device showing an embodiment of the present invention, FIG. 2 is a circuit diagram of a conventional battery dead detection device, FIG. 3 is a temperature characteristic diagram of dry battery output voltage, and FIG. The figure is a linear proximate diagram of the temperature characteristics of the battery's output voltage. 1...First resistor, 2...Second resistor, 4...Pseudo load resistor, 5...
Comparator, 22...Thermistor. Fig. 3 1/θ θ /θ 0 Jθ Fig.

Claims (1)

[Claims] A first resistor and a second resistor that divide the power supply voltage to create a reference voltage, a thermistor connected in parallel with the first resistor to detect room temperature, and a thermistor that is pressed by the user when measuring battery exhaustion. A switch whose contacts close when the load is applied, a pseudo load resistor that is connected in series with the switch and allows the same current to flow as the current at maximum load, and a voltage applied to the pseudo load resistor at the time of measurement with the reference voltage is compared and output. A battery depletion detection device, comprising: a comparator for detecting battery depletion; and a display section for displaying depletion of the battery according to the output of the comparator.