JP2007181365A - Ac voltage applying circuit and method to battery group - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a circuit to apply an voltage for inspection to a battery group without making an impact on a load, in order to discriminate deteriorated batteries in the battery group in which a plurality of the batteries are connected in series. <P>SOLUTION: The ac voltage applying circuit to the battery group includes a first and a second capacitors connected in series between both electrodes of the battery group consisting of a plurality of the batteries connected in series, and an ac voltage source to apply an ac voltage to a connecting point which divides the battery group into a first portion battery group and a second portion battery group, an to a connecting point of the first and the second capacitors, wherein when the ac voltage is positive or negative, a current of a discharge direction or a current of a charge direction flows through the first portion battery group, respectively, and a current of a charge direction or a current of a discharge direction flows through the second portion battery group, respectively. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a circuit and method for applying an AC voltage to a battery group in order to check the internal resistance of each battery in a battery group in which a plurality of batteries are connected in series and determine the deterioration status of each battery. .

  There are electrical devices that cannot tolerate momentary interruptions or even short interruptions during commercial power outages. These devices are supplied with a large number of batteries connected in series for backup of commercial power, and these are installed in facilities having communication facilities, office buildings, and the like. The internal resistance of the battery increases with time, and as a result, problems such as a decrease in battery output and difficulty in starting an external load occur. In particular, when a plurality of batteries are connected in series, it is often seen that deterioration proceeds intensively in one of the batteries. Even if the internal resistance of any one of the batteries increases, it will have an adverse effect on the whole, and therefore an inspection means for determining which battery has deteriorated is required. Since this inspection is performed for each battery, a lot of operations are required.

Patent Document 1 describes a battery tester that measures the internal resistance of a battery by flowing an alternating current for measurement to the battery and detecting an alternating voltage generated between battery terminals.
Japanese Patent Laid-Open No. 9-297165

  Since the internal resistance of a battery is usually very small, it is advantageous to use alternating current when measuring the voltage drop due to the internal resistance. However, in the method of measuring internal resistance by applying an AC voltage for inspection between both electrodes of a battery and detecting only an AC component as in Patent Document 1, when a load is connected between both electrodes of the battery In some cases, an alternating voltage is applied to the load and an alternating current flows through the load, which adversely affects the operation of the device.

  In view of the above situation, the present invention is a state in which a load is connected in a circuit that applies a measurement AC voltage to a battery group in order to determine a deteriorated battery in a battery group in which a plurality of batteries are connected in series. However, an object is to provide a circuit that does not affect the load. Furthermore, even if the circuit of the present invention is connected and operated in a state where the battery is not floatingly charged, that is, the battery alone, the battery will not be completely discharged, and an AC voltage will be applied even if the battery is under floating charge. The purpose is to prevent the battery from being discharged due to the application of an alternating voltage.

(1) An AC voltage application circuit for a battery group according to claim 1 includes a first capacitor and a second capacitor connected in series between both electrodes of a battery group including a plurality of batteries connected in series;
A connection point that divides the battery group into a first partial battery group and a second partial battery group, and an AC voltage source that applies an AC voltage to the connection point of the first capacitor and the second capacitor,
During the positive or negative cycle of the AC voltage, a current in the discharge direction or a current in the charge direction flows through the first partial battery group, and a current in the charge direction or a current in the discharge direction flows through the second partial battery group, respectively. It is characterized by flowing.

(2) According to a second aspect of the present invention, there is provided an AC voltage application method in which a first capacitor and a second capacitor are connected in series between both electrodes of a battery group composed of a plurality of batteries connected in series.
An AC voltage is applied to a connection point that divides the battery group into a first partial battery group and a second partial battery group, and a connection point of the first capacitor and the second capacitor;
In the positive or negative cycle of the AC voltage, a current in the discharging direction or a current in the charging direction is supplied to the first partial battery group, and a current in the charging direction or a current in the discharging direction is supplied to the second partial battery group, respectively. It is characterized by flowing.

(3) An AC voltage application method for a battery group according to claim 3 is the method according to claim 2, wherein an initial value of an internal resistance of each battery present in the first partial battery group is set in each first partial battery group. The reciprocal of the value divided by the sum of the initial values of the internal resistance of the battery is used as a correction coefficient, the AC component voltage generated at both ends of each battery when the AC voltage is applied is measured, and the correction coefficient is set to a value proportional to the value. Multiply and / or
The reciprocal of the value obtained by dividing the initial value of the internal resistance of each battery existing in the second partial battery group by the sum of the initial values of the internal resistances of the batteries existing in the second partial battery group is used as the correction coefficient, and the AC Measure AC component voltage generated at both ends of each battery when applying voltage, multiply the value proportional to the value by the correction coefficient,
The change from the initial value of the internal resistance of each battery is determined based on the multiplied value.

The AC voltage application circuit for the battery group according to claim 1 is a series connection between a connection point dividing a battery group in which a plurality of batteries are connected in series into a first and a second partial battery group, and both electrodes of the battery group. An AC voltage source is provided between the connected first capacitor and the connection point of the second capacitor. As a result, alternating voltages having opposite polarities are applied to both connection points. Therefore, the current in the discharge direction and the current in the charge direction alternately flow in the first partial battery group by the positive / negative cycle of the AC voltage, and conversely, the current in the charge direction and the current in the discharge direction alternately flow in the second partial battery group. Flowing.
The “current in the discharge direction” or the “current in the charge direction” here refers to the current flowing with respect to the polarity of the battery regardless of whether or not the battery is substantially discharged or charged by the current. It is used for convenience to show the direction. That is, the current flowing into the negative electrode of the battery is referred to as “current in the discharging direction”, and the current flowing into the positive electrode is referred to as “current in the charging direction”.

  Accordingly, a voltage drop due to the internal resistance of each battery occurs due to the current in the discharging direction or the current in the charging direction of the first partial battery group and the second partial battery group due to the AC voltage. Since the voltage drops due to the internal resistances of the first and second partial battery groups have opposite polarities, the voltage fluctuations due to these voltage drops cancel each other, and the voltage across the entire battery group does not change. .

  In addition, the first capacitor and the second capacitor serve to block the direct current component of the current, and also allow measurement AC voltage to be applied to the batteries of the first partial battery group and the second partial battery group. Then, as the first capacitor and the second capacitor, by using a capacitor having a capacity necessary for substantially not changing the voltage between both ends, the voltage between both ends of the first and second capacitors connected in series also changes. do not do.

  As described above, this circuit can apply the AC voltage for measurement to each battery included in the battery group, and at the same time, does not change the voltage between both electrodes, that is, the output voltage of the entire battery group. This means that no AC voltage is applied to the load connected between the two electrodes of the battery group, and no current due to the AC voltage flows to the load. Therefore, an AC voltage for measurement can be applied to each battery without affecting the load.

  By measuring the AC component of the voltage between both electrodes of each battery due to the applied AC voltage, a change in the internal resistance of each battery can be detected, and a deteriorated battery can be determined based on the change.

  Further, since the current in the discharge direction and the current in the charge direction flow alternately in each of the first partial battery group and the second partial battery group, the entire battery group is not completely discharged or charged. That is, the capacity of the battery group does not change due to the application of the AC voltage. In this circuit, since the AC voltage applied to the battery group is supplied from an external AC voltage source, the energy stored in the battery group is not consumed.

  Furthermore, since this circuit does not affect the DC component, it is also possible to perform measurement using this circuit while floating charging the battery group with an external DC power supply. Therefore, each battery can be inspected even in applications where floating charging cannot be interrupted.

  The method for applying an alternating voltage to the battery group according to claim 2 is substantially the same as the invention according to claim 1 and has the same effect.

  The method for applying an alternating voltage to the battery group according to claim 3 is the method according to claim 2, wherein the initial value of the internal resistance of each battery included in the partial battery group is determined for each battery existing in the first partial battery group. The reciprocal of the value divided by the sum of the initial values of the internal resistance is used as the correction coefficient. Thereafter, the AC component of the voltage between both electrodes of each battery is measured with the AC voltage applied by the method of claim 2, and the corrected value obtained by multiplying the value proportional to the measured value by the correction coefficient is obtained. Based on this, it is determined whether or not the internal resistance of each battery has changed from its initial value. By multiplying the correction coefficient, even if the initial value of the internal resistance of each battery is different, it can be compared with the same reference value, so it is easy to determine whether the internal resistance has changed. Can do.

(1) Circuit configuration FIG. 1 shows an AC voltage application circuit for a battery group according to the present invention. . It is the circuit diagram which showed the state connected to the battery group which consists of Bn. Such a battery group is used, for example, as a backup power source for commercial power in facilities or office buildings having communication facilities. This circuit can be basically configured as an independent circuit device that can be connected to and detached from the battery group. By connecting this circuit, an AC voltage for measurement can be applied to the battery group. The AC component of the voltage generated between the two electrodes of each battery by the applied AC voltage is measured by an appropriate measuring instrument, and the increase in internal resistance of each battery, that is, the presence or absence of deterioration of each battery is determined from the measured value. The battery inspection apparatus may be configured by integrating the circuit and the measuring instrument.

  In the circuit shown in FIG. 1, the transformer T is used as an AC voltage source, and the AC voltage Vin is obtained from the secondary side. An AC voltage ACV is input to the primary coil of the transformer T, and one output terminal of the secondary coil is connected to a connection point M in the battery group via an appropriate current limiting resistor R. The connection point M is a battery group B1. . This is a connection point that divides Bn into two partial battery groups. The two partial battery groups are the first partial battery group B1. . Bk and the second partial battery group Bk + 1. . Bn, each group including at least one battery. The number of batteries included in each of the two partial battery groups is preferably approximately the same, but in principle, the number may not necessarily be the same. Therefore, any connection point between adjacent batteries may be selected as the connection point M. In principle, the types of the batteries may not be the same type (capacity and other characteristics are the same).

  The other output terminal having a reverse polarity in the secondary coil of the transformer T is connected to a connection point between the first capacitor C1 and the second capacitor C2. The first capacitor C1 and the second capacitor C2 are connected in series with each other. Further, the other terminal 1 of the first capacitor C1 is connected to the positive side of the battery group, and the other terminal 2 of the second capacitor C2 is connected to the negative side of the battery group.

  As the first capacitor C1 and the second capacitor C2 are applied with a DC voltage between the two electrodes of the battery group and have a large capacity, an electrolytic capacitor is suitable as shown in FIG. Other types of capacitors may be used as long as they are obtained.

  Although not shown, the battery group may be subjected to floating charging by an external DC power source in a state where the circuit is connected to the battery group. Although not shown, this circuit may be connected in a state where a load is connected between both electrodes of the battery group.

  In the circuit of FIG. 1, the AC voltage source for obtaining the AC voltage Vin is not limited to the transformer.

(2) Circuit operation <Operation during positive cycle>
When the battery group side of the secondary coil of the transformer T is at a positive potential (indicated by + in a solid line circle in the figure), it is assumed as a positive cycle of the AC voltage Vin. At this time, the first partial battery group B1. . The current i1 flows through Bk, and the second partial battery group Bk + 1. . A current i2 flows through Bn. The current i1 is a current in the discharging direction that flows into the negative electrode side of the first partial battery group, while the current i2 is a current in the charging direction that flows into the positive electrode side of the second partial battery group.

Since the current i1 in the discharge direction flows through the first partial battery group, a voltage drop due to the internal resistance of each battery occurs. In this case, the voltage drop occurs in a direction opposite to the polarity of each battery. The voltage between both ends drops slightly.
On the other hand, since the current i2 in the charging direction flows through the second partial battery group, a voltage drop occurs due to the internal resistance of each battery. In this case, the voltage drop occurs in the same direction as the polarity of each battery. The voltage between both ends increases slightly.
Therefore, since the voltage drop in the first partial battery group and the voltage rise in the second partial battery group are offset, the voltage across the entire battery group does not change.

  Further, the first capacitor C1 and the second capacitor C2 block the direct current component of the current and allow only the alternating current component to pass therethrough, thereby applying the alternating voltage Vin to each battery of the first and second partial battery groups. And only an alternating current can be passed through the battery group. The first capacitor C1 and the second capacitor C2 are preferably ideal capacitors having large capacities, but may be capacitors having such a capacity that the voltage between both ends is not substantially varied. The voltage does not change.

  Thus, the voltage fluctuations of the two partial battery groups caused by the application of the alternating voltage Vin cancel each other out, and the voltage across the two capacitors is held constant, so the output voltage Vout of the battery group does not change. . According to this circuit, the AC voltage Vin for measurement can be applied to each battery without affecting the output voltage Vout of the battery group.

<Operation during negative cycle>
During the negative cycle, the capacitor side terminal of the secondary coil of the transformer T is at a positive potential (indicated by + in a broken line circle in the figure). The operation is exactly the same as in the normal cycle, except that the polarity of the current and voltage is reversed.

  That is, the first partial battery group B1. . The current i3 flows through Bk, and the second partial battery group Bk + 1. . A current i4 flows through Bn. The current i3 is a charging direction current flowing into the positive side of the first partial battery group, while the current i4 is a discharging direction current flowing into the negative side of the second partial battery group.

  As in the positive cycle, the voltage drop due to the internal resistance generated in each of the two partial battery groups by the application of the alternating voltage Vin cancels each other, and the voltage across the two capacitors does not change, so the output voltage of the battery group does not change. Vout does not change.

<Description by current equivalent circuit>
2A and 2B are equivalent circuits representing currents i1 and i2 in the positive cycle, respectively. The symbols + and-in circles in the figure indicate the polarity of the voltage.
In the equivalent circuit of FIG. 2A, the first partial battery group B1. . The voltage between both electrodes Bk (DC component) and the voltage across the first capacitor C1 are balanced. A voltage drop (i1 × R1 = Vin) occurs in the sum R1 of the internal resistances of the batteries of the first partial battery group due to the current i1 flowing by the AC voltage Vin. The direction of this voltage drop is opposite to the polarity of the first partial battery group. Therefore, the actual voltage between both ends of the first partial battery group is reduced by the amount of voltage drop due to the internal resistance R1.

  Similarly, in the equivalent circuit of FIG. 2B, the second partial battery group Bk + 1. . The voltage between both electrodes Bn (DC component) and the voltage across the second capacitor C2 are balanced. A voltage drop (i2 × R2 = Vin) occurs in the total internal resistance R2 of the batteries of the second partial battery group due to the current i2 flowing by the alternating voltage Vin. The direction of this voltage drop is the same as the polarity of the second partial battery group. Thus, the actual voltage across the second partial battery group is increased by the amount of voltage drop due to the internal resistance R2.

  The voltage drop due to the internal resistance in each equivalent circuit of FIGS. 2A and 2B cancels each other, so that the voltage across the entire electrode including the first and second partial battery groups does not change.

When the first partial battery group and the second partial battery group include the same number of batteries of the same type, the sum of the internal resistances is equal (R1 = R2) to i1 = i2.
Even in the negative cycle, the polarity is opposite, but the equivalent circuit is exactly the same.

  As shown in FIG. 2, the voltage between both electrodes (DC component) of each partial battery group and the voltage across each capacitor are balanced, which is sufficient for measuring the internal resistance due to the AC component even if the AC voltage Vin is low. It is. The magnitudes of the appropriate currents i1 to i4 are set according to demands such as the scale of the battery group and the measurement accuracy, and the magnitude of the necessary AC voltage Vin is determined based on the magnitudes. In practice, power loss is caused by the current limiting resistor R shown in FIG. 1, and it is desirable to reduce the AC voltage Vin to reduce this.

  In addition, since the voltages at both ends of each partial battery group and each capacitor are always balanced, the number of batteries included in the first and second partial battery groups may be different, and the types of each battery are not the same. Also good. This is because the balance with the voltage across the capacitor is maintained even if the sum of the internal resistances of the partial battery groups changes.

<Description by equivalent internal impedance circuit>
FIG. 3 is an equivalent circuit showing the internal resistances R11 and R12 of each battery in the first partial battery group and the internal resistances R21 and R22 of each battery in the second partial battery group.
Measuring the AC component of the voltage across each battery with the AC voltage Vin applied means measuring the voltage Vr11, Vr12, Vr21, Vr22 across the internal resistances R11, R12, R21, R22 of each battery. become.

  If R11> R12 = R21 = R22 in FIG. 3 and the AC component of the voltage across each battery is measured, the voltage across the battery having the internal resistance R11 is greater than the voltage across the other batteries. Measured with large values. When the value rises beyond a predetermined range that is normal in design compared to the measured average value for all batteries, it is determined that the battery is deteriorated. However, in this example, each partial battery group includes the same number of batteries of the same type.

(3) Measurement example for determining battery deterioration When the batteries included in the battery group are not of the same type, the initial value of the internal resistance of each battery is different. In such a case, it becomes complicated to evaluate the change from the initial value of the internal resistance of each battery based on the measured value of the voltage between both electrodes of each battery measured using the circuit of FIG. Therefore, if the following method is used, analysis of the measured value is facilitated, and efficient deterioration determination is possible.

  Reference is now made to FIG. For example, the total internal resistance R1 of the first partial battery group is constituted by R11, R12 and R13 (R1 = R11 + R12 + R13), and the total internal resistance R2 of the second partial battery group is constituted by R21 and R22. (R2 = R21 + R22). These values are initial values or values in a state where no deterioration has occurred. At this time, the voltage coefficients indicating the ratio by which the AC voltage Vin is divided into the internal resistors are R11 / R1, R12 / R1, R13 / R1, R21 / R2, and R22 / R2, respectively. The reciprocal of these voltage coefficients will be used as the “correction coefficient” for each battery having its own internal resistance. In other words, the correction coefficient is the reciprocal of the value obtained by dividing the internal resistance (initial value) of each battery by the sum (initial value) of the internal resistances of all the batteries existing in the partial battery group. That is, the correction coefficients in this example are R1 / R11, R1 / R12, R1 / R13, R2 / R21, and R2 / R22.

  Thereafter, an AC voltage Vin is applied to each battery using the circuit of FIG. 1, and an AC component of the voltage between both electrodes of each battery is measured by a measuring instrument. Each measurement value obtained is corrected by multiplying the respective correction coefficient. More generally, it is not necessary to use each obtained measurement value as it is, convert each obtained measurement value to a proportional value, and multiply the proportional value by the respective correction coefficient to correct it. Also good. Such calculation may be performed automatically using an appropriate calculation circuit or the like built in the measuring instrument, and the result may be output. By correcting the raw measurement values in this way, even if the initial values of the internal resistances of the batteries are different from each other, all the corrected values may be compared with the same reference value. When the internal resistance increases and the measured value changes from the initial value, the corrected value changes from the reference value, so that deterioration can be determined based on that.

FIG. 3 is a circuit diagram illustrating a state in which an AC voltage application circuit for testing a battery group according to the present invention is connected to a battery group including a plurality of batteries connected in series. (A) and (B) are equivalent circuits representing the currents i1 and i2 during the positive cycle, respectively. It is an equivalent circuit showing internal resistance R11, R12 of each battery of a 1st partial battery group, and internal resistance R21, R22 of each battery of a 2nd partial battery group.

Explanation of symbols

T transformer C1 first capacitor C2 second capacitor R current limiting resistor B1. . Bk first partial battery group Bk + 1. . Bn second part battery group

Claims (3)

A first capacitor and a second capacitor connected in series between both electrodes of a battery group consisting of a plurality of batteries connected in series;
A connection point that divides the battery group into a first partial battery group and a second partial battery group, and an AC voltage source that applies an AC voltage to the connection point of the first capacitor and the second capacitor,
During the positive or negative cycle of the AC voltage, a current in the discharge direction or a current in the charge direction flows through the first partial battery group, and a current in the charge direction or a current in the discharge direction flows through the second partial battery group, respectively. An alternating voltage application circuit for a battery group, wherein A first capacitor and a second capacitor are connected in series between both poles of a battery group composed of a plurality of batteries connected in series,
An AC voltage is applied to a connection point that divides the battery group into a first partial battery group and a second partial battery group, and a connection point of the first capacitor and the second capacitor;
In the positive or negative cycle of the AC voltage, a current in the discharging direction or a current in the charging direction is supplied to the first partial battery group, and a current in the charging direction or a current in the discharging direction is supplied to the second partial battery group, respectively. A method of applying an alternating voltage to a battery group, wherein The reciprocal of a value obtained by dividing the initial value of the internal resistance of each battery existing in the first partial battery group by the sum of the initial values of the internal resistances of the batteries existing in the first partial battery group is used as the correction coefficient, and the AC Measure AC component voltage generated at both ends of each battery when voltage is applied, multiply the value proportional to the value by the correction coefficient, and / or
The reciprocal of the value obtained by dividing the initial value of the internal resistance of each battery existing in the second partial battery group by the sum of the initial values of the internal resistances of the batteries existing in the second partial battery group is used as the correction coefficient, and the AC Measure AC component voltage generated at both ends of each battery when applying voltage, multiply the value proportional to the value by the correction coefficient,
3. The method of applying an alternating voltage to a battery group according to claim 2, wherein a change from the initial value of the internal resistance of each battery is determined based on the multiplied value.

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