JP3158898B2 - Low battery capacity detection device and low battery capacity alarm device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for detecting a decrease in battery capacity.
And to a low battery warning device, in particular, the combination battery
Decrease in capacity of at least one of a plurality of constituent batteries
Low battery detection device and combination battery
Of at least one of the batteries
The present invention relates to a low-battery warning device that issues a discharge warning .

[0002]

2. Description of the Related Art Among batteries commercially available today, there is a type in which a plurality of batteries are connected in series in a battery case in a commercially available state and generate a predetermined rated voltage. Here, such a battery is referred to as a “combination battery”.

[0003] First, the relationship between a combination battery and a battery constituting the combination battery (hereinafter, referred to as a "constituent battery") is as follows:
The meanings of these terms will be described with examples.

[Example 1] Relationship between cells (modules) / cells A combination battery is generally called a "cell" or a "module", for example, an automobile battery.
The constituent batteries in this case are called “cells”. That is, in general, in an automotive battery, there is a relation of cells (2 volts) × 6 cells → cells (12 volts).

[Example 2] Relationship between assembled battery (assembled battery) / unit cell (module) A combined battery is called an "assembled battery" or an "assembled battery". is there. The constituent battery in this case is the above-described unit cell (module). In other words, in an assembled battery for an electric vehicle, a unit cell (12 volts) x 25 → an assembled battery (300
Bolt). In this example, 25 component batteries are not combined in a commercially available state, but such a case is also included in the relationship between the combination battery and the component batteries.

[0006] As can be seen from the above two examples, the battery in a narrow sense for a collective battery is a unit cell, but since this unit cell is further composed of cells, this cell is also referred to as a battery in a broad sense for a collective battery. It is possible to call. In this specification, the constituent batteries are used in both narrow and broad senses as appropriate. It should be noted that the term “battery” may refer to either an assembled battery or a constituent battery.

In this specification, in addition to the above terms,
“Capacity” and “battery level” are used as important terms. Therefore, these terms are first defined.

[0008] "Capacity" means the maximum amount of charge that can be stored in a battery. It usually refers to the rated value indicated in the unit of amp-hour (Ah). Therefore, for example, a battery having a rating of 60 Ah has a capacity of 60 Ah regardless of the state of charge.

[0009] "Battery level" refers to the amount of charge actually remaining in the battery. That is, when a battery with a capacity of 60 Ah is used (discharged) from a fully charged state to half, the remaining battery capacity is 30 A
h.

As can be seen from these definitions, the capacity is constant for a particular battery, but the remaining battery capacity varies depending on the situation.

The prior art will be described according to the above definitions.

As is well known, rechargeable combination batteries are used in various industrial fields. This is due to the increasing demand for batteries and the demand for lower prices, rather than developing multiple types of batteries with the rated voltage desired by the user, rather than mass-producing several types of component batteries in accordance with standardized specifications. This is because it is more advantageous to assemble the combination battery so as to obtain a desired voltage. For this reason, the rated voltage of the constituent batteries is generally set to be relatively small. For example, in a battery of an automobile, six constituent batteries of 2 volts are connected in series. In the future, it is expected that the capacity of the constituent batteries will be increased, the size of the batteries will be reduced, and the price will be reduced.

Now, consider how such a combined battery is actually used in a device or the like. When a combination battery is used, the remaining amount of the battery naturally decreases due to discharging, and therefore, it is necessary to detect the timing of recharging by some method. Conventionally, such a timing has often been detected from a drop in the terminal voltage of the combination battery, and a warning display or the like has been issued to the user. Here, the method will be described.

FIG. 1 is a diagram showing the discharge characteristics of a combination battery (60 Ah automotive battery) using six constituent batteries rated at 2 volts. In the figure, the horizontal axis represents time t, and the vertical axis represents the terminal voltage V of the combined battery. It is assumed that the battery pack is fully charged at the start of discharging, and that only the discharging is performed at a constant current of 60 amps (that is, charging is not performed). In this example, the capacity of the six constituent batteries is assumed to be equal.

At this time, at t = 0, V is 12.3 to
At 12.4 volts. Thereafter, V gradually decreases with the discharge, and the rate of decrease gradually increases (such a decrease is hereinafter referred to as “gradual decrease”).

As the discharge continues, the remaining battery capacity of the combined battery naturally decreases, but as a characteristic of the battery, generally, the battery capacity gradually decreases until the remaining battery power is exhausted. Therefore, the voltage at both ends of the battery suddenly becomes zero at the same time when the remaining battery power is exhausted. In this figure, it is assumed that the moment arrives at t = T ₀ , and therefore T ₀
5 shows a state in which the discharge curve sharply drops and the discharge of the combination battery is completed. In this example, T ₀ is about one hour.

[0017] However, when using a combination battery with specific apparatus, usually not continue to discharge to T _0. This is because the continuation of the operation by the low terminal voltage at the end of the discharge causes inconvenience such as malfunction, and a warning is displayed when the terminal voltage V falls below a predetermined value, or the operation of the device is stopped. Action will be taken. In the case of this figure, the voltage to be detected to determine the vicinity of the end of the discharge is about 8.5 volts, and when the terminal voltage V decreases to this voltage, the user is warned.

In practice, the detection voltage is often set again according to the magnitude of the discharge current. In this example, the detection voltage is set assuming that the constant current discharge is performed at 60 amps. However, if this discharge is performed at 20 amps, it is necessary to increase the detection voltage to around 10 volts. This is because as the discharge current value decreases, the terminal voltage gradually decreases due to a gradual decrease, and the remaining battery level decreases while the terminal voltage remains high.

[0019]

According to the above method,
The timing of recharging can be known based on the discharge characteristics of the constituent batteries according to the discharge current value. However, when a combined battery is used, different considerations are required than when a constituent battery is used alone. This is because there is a slight deviation (variation) in the capacity of each constituent battery, and a reverse charge state occurs for the constituent battery whose battery level is quickly exhausted during discharging of the combined battery. This phenomenon will be described.

FIG. 2 is a discharge curve of a combined battery using six constituent batteries rated at 2 volts as in FIG. 1, but the capacity of one of the constituent batteries (battery A) is different from that of the other constituent batteries. FIG. 4 is a diagram showing discharge when the voltage is somewhat lower than that of a battery. Other conditions are the same as those in FIG.

Also in this case, V = 12.3 at t = 0.
〜12.4 volts, after which a gradual drop occurs. However, during the gradual decline, the remaining battery level of the battery A first becomes zero, and at this moment, the voltage across the battery A becomes almost zero. As a result, a step occurs in the discharge curve as shown in the figure.

That is, if this time is t = T ₁ , the terminal voltage V drops sharply at T ₁ , and this decrease corresponds to the voltage across the battery A immediately before T ₁ .

As described above, although the terminal voltage V drops to about 9 volts, the discharge of the remaining five constituent batteries continues, so that the terminal voltage V gradually decreases again from 9 volts, and the remaining battery levels of these five constituent batteries are reduced. At the same time runs out from t = T ₂ , the terminal voltage V drops sharply to around 0 volt, and the discharge ends. However, in reality, using traditional detection methods,
At t = T ₃ when the terminal voltage V becomes about 8.5 volts, a warning is displayed, and necessary measures such as recharging are taken.

The problem here is that the above T _{1 to} T ₃
During this period, the battery A is forcibly continuing to discharge while the remaining battery level is zero. If such a discharge is relatively captured at both ends of the battery A, the battery A is actually charged in a direction opposite to the normal direction, and as a result, the following inconvenience occurs.

1. Acceleration of Battery A Deterioration The internal resistance of Battery A increases, causing heat generation and the like, resulting in deterioration of characteristics. As a result, further decreases the capacity of the battery A, the next time the discharge is vicious cycle T ₁ of the 2 arrives more quickly occur.

2. Shortening of Device Operating Time by Combination Battery When the internal resistance of Battery A becomes too large, current does not flow from the combination battery even though the remaining five constituent batteries have sufficient remaining battery power. Therefore, the capacity of the combination battery decreases.

3. Burnout of Battery A If discharge is continued in a state where the internal resistance of Battery A is large, Battery A will burn out in the worst case. Such burning is a major problem for the product safety of the combination battery and the device using the combination battery.

For example, as described in 2. T ₁ through T inconveniences in FIG
Consider the case that occurs in ₃ . If this time relying only on traditional methods, notices (which does not appear not equal T ₃₎
Without operation, the operation of the device suddenly stops. The significance of this situation can be easily understood by considering, for example, that the electric vehicle stops while traveling.

On the other hand, to prevent such a situation, a method of setting the detection voltage to a sufficiently high value in advance is conceivable. However, this method has no effect in the following case.

That is, a 12 volt battery is
When considering an electric vehicle to be used, a total of 150 2-volt cells are used. This is a problem when the above situation occurs. At this time, from the total terminal voltage of 300 volts to two for one cell
Although it is necessary to detect a drop in the bolt, it is difficult to distinguish the minute change from the change due to the gradual decrease. If the caution display is performed when the terminal voltage drops by 2 volts from the initial voltage, such a display will be displayed immediately after the start of traveling, which is far from the specification of the traveling distance. In other words, in order to avoid the above-described inconvenience, it means that the object cannot be achieved simply by detecting the terminal voltage with respect to time, that is, by detecting dV / dt.

On the other hand, in this example, for example, according to the conventional method, it is considered that the detection voltage is set at around 250 volts. Is also conceivable. That is, as the number of constituent batteries increases, undesirable situations are more likely to occur.

The present invention has been made to solve the above problems, and an object of the present invention is to measure the discharge current and the terminal voltage of a combined battery to detect that the remaining battery power of an arbitrary battery is exhausted. It is another object of the present invention to provide an improved low battery capacity alarm device that issues an alarm according to a situation as well as a caution display.

[0033]

SUMMARY OF THE INVENTION First battery capacity of the present invention
The drop detecting device includes a plurality of batteries constituting a combined battery.
Low battery capacity to detect at least one decrease in capacity
A detection device for measuring a discharge current of the combination battery.
Measuring the terminal voltage of the combined battery
The discharge current and the terminal voltage,
To calculate the terminal voltage drop per unit discharge current
Calculating means, and the terminal voltage drop amount exceeds a predetermined reference amount.
A detecting means for detecting a decrease in the capacity of any of the batteries.
And a step. Second battery of the present invention
The low-capacity detection device is composed of multiple batteries
Battery capacity for detecting a decrease in capacity of at least one of
A drop detection device, wherein a discharge current of the combination battery is measured.
Measuring the amount of current to be measured and the terminal voltage of the combination battery.
Voltage measuring means for measuring, the discharge current and the terminal voltage
And the rate of change of the terminal voltage drop per unit discharge current
Calculating means, and that the sign of the change rate is inverted
Detecting means for detecting a decrease in the capacity of any of the batteries
And the following.

The low battery capacity alarm device of the present invention is
Capacity of at least one of a plurality of batteries constituting the battery
Low battery warning device that detects a low battery level and issues an alarm.
Therefore, the first or second battery capacity drop detecting device of the present invention
And any one of the above-mentioned batteries by the battery capacity reduction detecting device.
The decrease in the amount is detected, and the terminal voltage of the combined battery is
Alarm generation method that issues an alarm when the voltage is higher than a predetermined reference voltage
And a step.

[0035]

In the apparatus for detecting a decrease in battery capacity according to the present invention, the calculation means first calculates the unit discharge current from the discharge current and the terminal voltage.
The amount of terminal voltage drop per unit is calculated. That is, this calculating means is a kind of differentiating circuit, and can detect the moment when the amount of decrease in the terminal voltage with respect to the discharge current becomes large. Here, since this moment corresponds to the moment when the battery capacity of any constituent battery is exhausted , any of the batteries
A reduction in capacity can be detected.

In the second battery capacity drop detecting device of the present invention,
Is calculated from the discharge current and terminal voltage per unit discharge current
Calculation means for calculating the rate of change of the terminal voltage drop
Have been. Therefore, this calculation means is a kind of second-order differentiation circuit
And the amount of decrease in the terminal voltage with respect to the discharge current is large.
At the moment when it returns to its original state, that is, the inflection point of the terminal voltage.
Can be detected. Therefore, any capacity of the battery
Can be detected.

In the low battery warning device of the present invention,
1st or 2nd low battery detection device
Any decrease in capacity is detected, and the terminal voltage of
If it is higher than the predetermined voltage, an alarm can be issued
You.

[0038]

【Example】

Embodiment 1 FIG. Here, an embodiment of the battery capacity reduction alarm device according to the present invention will be described with reference to the drawings. FIG. 3 is a schematic configuration diagram of the present embodiment.

In the figure, the combination battery 2 is composed of a plurality of constituent batteries 2a, 2b... 2n, and the load circuit 4 of the combination battery 2 is connected between the terminals P and Q of the combination battery 2. A voltage measurement circuit 6 for measuring the terminal voltage V of the combination battery 2 is similarly connected between the terminals P and Q.
On the other hand, the current measuring circuit 8 measures a discharge current I flowing through a closed circuit formed by the combination battery 2 and the load circuit 4.
The terminal voltage V measured by the voltage measuring circuit 6 and the discharge current I measured by the current measuring circuit 8 are both input to the arithmetic circuit 10 at the subsequent stage.

FIG. 4 is a diagram showing the internal configuration of the arithmetic circuit 10.

In the figure, a discharge current I is input to an integrating circuit 12, while a terminal voltage V is a terminal voltage drop amount detecting circuit 1.
4 is input. Here, the integrating circuit 12 generates the inspection timing signal 16 every time the discharge amount reaches a certain unit amount, and inputs this to the terminal voltage drop amount detection circuit 14.

On the other hand, the terminal voltage drop amount detection circuit 14 captures the value of the terminal voltage V every time the inspection timing signal 16 is generated, and subtracts the previously captured value from this value. The amount of decrease in the terminal voltage is detected by multiplying the numerical value by (−1). In other words, the terminal voltage drop amount detection circuit 14 is a differentiating circuit, and calculates a terminal voltage drop amount per unit discharge amount, that is, a numerical value R defined by the following equation.

R = -dV / dI Multiplying by (-1) is a convenience for treating the decrease amount as a positive value.

The R thus obtained is input to a comparator 18, and when this value becomes larger than a predetermined reference value Rref, an alarm preparation signal 20 is generated. On the other hand, the terminal voltage V is also input to another comparator 22, and the alarm permit signal 24 is output as long as the terminal voltage is higher than the predetermined reference voltage Vref.

The AND gate 2 is provided at the last stage of the arithmetic circuit 10.
6 are provided. Here, the alarm preparation signal 20
And an alarm permission signal 24 are input, and when both these signals are true, an alarm signal 28 is output to the outside. Here, returning to FIG. 3, the alarm signal 28 is input to an alarm generator 30 composed of, for example, a light emitter or a loudspeaker, and an alarm is actually issued.

This alarm indicates that the capacity of a certain battery is considerably reduced, and that the inconveniences 1 to 3 described as a conventional problem are likely to occur. Instead, it is to identify and replace the component battery in question. This is because despite the fact that the terminal voltage V is somewhat high (V> Vref), the remaining battery power of a certain constituent battery has run out (R> Rref). Based.

It should be noted that the terminal voltage V is different from that of another comparator 32.
When the terminal voltage V becomes lower than the predetermined reference voltage Vref2, the caution generator 34 issues a normal caution. That is, the comparator 32 is provided to detect a decrease in the remaining battery level of the combination battery 2 from the decrease in the terminal voltage V itself as in the related art. If the capacities of all the constituent batteries match, the comparator 32 Battery 2
Follows the discharge curve of FIG. 1 and normal attention is given at T ₀ in FIG. In such a case, no alarm is issued because a state in which the remaining battery power of one of the constituent batteries runs out quickly does not occur, and a warning indicating that the remaining battery power of the entire combined battery is low is simply displayed. Therefore, when this caution display appears, the combination battery 2 may be simply charged, and the meaning of this display is fundamentally different from the meaning of the alarm display requiring repair. That is, the warning display is displayed, for example, "Please recharge", while the alarm display is displayed, "Replace the battery".

The operation of this embodiment having the above configuration will be described.

First, also in this embodiment, it is assumed that one constituent battery has a small capacity, and this battery is referred to as a battery A. At this time, the combination battery 2 draws the discharge curve described with reference to FIG. Therefore, by differentiating this discharge curve and multiplying by (−1), R draws a curve as shown in FIG. Here, the behavior of R in FIG. 5 will be described.

At t = 0 to T ₁ in FIG. 1, the terminal voltage V gradually decreases, and the rate of decrease gradually increases, so that R increases almost linearly in the positive range. But the value of R for voltage of descent of the terminal voltage V battery A when reached T ₁ takes a maximum value Rmax rapidly increased. T ₁ and later, since the terminal voltage V gradually returning to decrease the value of R also returns to the original straight line.

Therefore, in this embodiment, the reference value Rref
As shown in FIG. 5, a value slightly lower than the maximum value Rmax is set. Rmax Since determined from the slope of the terminal voltage V when the one battery remaining amount of the assembled battery becomes 0, is considered to be substantially the same value even when occurring at a location other than T _1, to determine the Rref It becomes possible.
In this manner T _1, warning preparation signal 20 from the comparator 18 is output.

On the other hand, the reason for generating the alarm permission signal 24 using the comparator 22 is as follows. That is,
No matter how much the capacity of the constituent batteries is uniform, there is always some deviation, so that the ideal state as shown in FIG. 1 does not actually exist. Therefore, the discharge curve of the combination battery 2 should always be stepwise as shown in FIG. It is an object of the present invention to provide an alarm for replacing and repairing a battery whose capacity has been considerably reduced, so that an alarm display should not be issued for a normal deviation. The determination as to whether or not this is a normal deviation is obtained at the time when Rmax occurs. That is, if Rmax is generated while the entire terminal voltage V is still high, an alarm is issued, and if the terminal voltage V is sufficiently low, Rmax is generated.
Should occur and should not be alerted as a normal deviation. Vref is a judgment reference voltage provided for this purpose.

If Rmax occurs after the terminal voltage V has already fallen below Vref, it is considered that the terminal voltage V reaches Vref2 relatively soon after that point. Will be done.

In this embodiment, the alarm timing is detected purely from the discharge current and the terminal voltage. However, depending on the case, the following configuration can be added.
That is, since the temperature of a component battery which has been exhausted quickly and is placed in a reverse charge state rises due to an increase in the internal resistance, the above-described alarm signal 28 is limited only when the temperature of any component battery is equal to or higher than a certain value. And an AND gate is added to generate. This is an effective means when it is known that there is no possibility of battery deterioration if the internal temperature rises within a certain range even in the reverse charge state.

Embodiment 2 FIG. In the first embodiment, Rmax is equal to Rref.
In the second embodiment, the alarm preparation signal 20 is output when the signal exceeds the threshold voltage. However, in the second embodiment, the change rate detection circuit 4 for detecting the change rate of the terminal voltage drop amount
0 is introduced. That is, the terminal voltage drop amount detection circuit 14 calculates R = −dV / dI, but the change rate detection circuit 40 of the present embodiment calculates X = dR / dI = −d ² V / dI ^2. Is calculated. After this X becomes 0 (or when the sign of X changes), an alarm preparation signal 20 is output. Therefore, in the second embodiment, the comparator 18 of the first embodiment is deleted, and the output of the change rate detection circuit 40 is directly input to the AND gate 26. Other configurations are the same as those of the first embodiment.

The operation of this embodiment having the above configuration will be described. FIG. 6 is a diagram showing the behavior of X obtained by differentiating R of FIG. 5 with I.

As is clear from the figure, X becomes 0 at t = T ₁ and the sign is inverted. Therefore, the alarm preparation signal 20 is issued thereafter, and the operation returns to the same operation as in the first embodiment.

In the present embodiment, although the scale of the configuration is slightly larger than that of the first embodiment in obtaining the second order differentiation, it is advantageous in that it is not necessary to grasp the value of Rmax in advance as in the first embodiment. is there.

[0059]

As explained in detail above, the battery capacity drop detecting device of the present invention detects the moment when the amount of decrease in the terminal voltage becomes large with respect to the discharge current. The moment when it disappears can be detected .
Further, in the battery capacity reduction detecting device of the present invention, the discharge current and the
Terminal voltage per unit discharge current from terminal and terminal voltage
Since the desired detection is possible from the rate of change of the amount,
It is possible to improve the accuracy of detection. As a result ,
It is now possible to detect a decrease in the capacity of each constituent battery, which was not possible by simply monitoring the decrease in the overall terminal voltage as in the past. And the burning of the constituent batteries can be solved.

Further, in the low battery capacity alarm device of the present invention,
Refers to the terminal voltage level.
Some batteries have lost their battery capacity despite their high
Sometimes undesired situations such as a long reverse charge state
An alarm can be issued as possible.

[Brief description of the drawings]

FIG. 1 is a diagram showing discharge characteristics of a combination battery using six constituent batteries rated at 2 volts.

FIG. 2 is a diagram showing a discharge curve of a combination battery using six component batteries rated at 2 volts when the capacity of battery A is somewhat lower than other component batteries.

FIG. 3 is a schematic configuration diagram of a first embodiment.

FIG. 4 is a diagram showing an internal configuration of the arithmetic circuit 10.

FIG. 5 is a diagram illustrating characteristics of R in the first embodiment.

FIG. 6 is a diagram showing characteristics of X obtained by differentiating R of FIG. 5 with I.

[Explanation of symbols]

 6 Voltage measurement circuit 8 Current measurement circuit 10 Operation circuit 12 Integration circuit 14 Terminal voltage drop detection circuit 18, 22 Comparator 26 AND gate 30 Alarm generator 40 Change rate detection circuit

Claims (3)

(57) [Claims] An apparatus for detecting a decrease in the capacity of at least one of a plurality of batteries constituting a combination battery, comprising: a current amount measuring means for measuring a discharge current of the combination battery; Voltage measuring means for measuring a terminal voltage of a battery; calculating means for calculating a terminal voltage decrease amount per unit discharge current amount from the discharge current and the terminal voltage; and the terminal voltage decrease amount exceeds a predetermined reference amount. Detecting means for detecting a drop in the capacity of any of the batteries when the battery has dropped. 2. A battery capacity decrease detection device for detecting a decrease in capacity of at least one of a plurality of batteries constituting a combination battery, comprising: a current amount measuring means for measuring a discharge current of the combination battery; Voltage measuring means for measuring the terminal voltage of the battery; calculating means for calculating the rate of change of the terminal voltage drop per unit discharge current amount from the discharge current and the terminal voltage; and when the sign of the rate of change is reversed. Detecting means for detecting a decrease in the capacity of any one of the batteries; 3. A low-battery alarm device that detects a reduction in the capacity of at least one of a plurality of batteries constituting a combination battery and issues an alarm, wherein the low-battery detection device according to claim 1 or 2 is provided. Alarm detection means for detecting a decrease in the capacity of any of the batteries with the battery capacity decrease detection device, and issuing an alarm when the terminal voltage of the combination battery is higher than a predetermined reference voltage. Characteristic low battery warning device.