JP2010175496A - Power supply apparatus equipped with device for determining deterioration of battery pack - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem, wherein when an emergency power supply is composed of a battery pack that uses a plurality of cells, the battery pack begins to be deteriorated with the lapse of time after the start of operation, mainly because of the change of internal resistance, but if the degree of change is small it is difficult to accurately determine the time for replacement; and to provide a power supply apparatus equipped with a device for determining deterioration which can accurately determine the time for replacement of the battery pack after the start of operation. <P>SOLUTION: The power supply apparatus that is constituted of a battery pack 6 charged from a system power supply 1 through an AC/DC converter 3 and a load 9, to which electric power is supplied from the battery pack 6 through a DC/AC converter 7 when the system power supply 1 fails and that is charged via the AC/DC converter 3, after the power recovery includes a device for determining the deterioration of the battery pack 6, which indicates the drooping characteristic of charging current from the time, when recharging is performed at a constant current and is then switched to constant-voltage charging. Furthermore, the device 15 has an ammeter 5 for measuring the charging current, indicating the drooping characteristic and a timer 11 for measuring the time indicating the drooping characteristic, and determines the deterioration of the battery pack, when the current value, after a lapse of a predetermined time period from the start of current drooping, exceeds a predetermined value by outputs of the ammeter and the timer 11. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an apparatus for determining deterioration when a long time has elapsed after the start of use of an assembled battery in which a plurality of storage batteries such as lead storage batteries used for emergency power supply equipment are connected, and further, a set whose deterioration state has been determined. The present invention relates to a power supply device including a device that determines a deteriorated cell as a secondary determination for each cell of a battery.

Normally, an assembled battery is used as an emergency power supply facility so that the load supplied with power from the system power supply can continue to be supplied even in the event of a power failure occurring in the system power supply. An assembled battery usually has a plurality of cells each composed of a control valve type lead storage battery connected in series and parallel. For this reason, after the start of the operation of the facility, a cell having deteriorated characteristics is generated after a long time. Since this type of power supply equipment normally keeps charging from the system power supply and maintains the voltage, the charging current is small and the total voltage of the assembled battery does not change, so it is easy to find a cell that has deteriorated. In addition, it was difficult to replace defective cells.
An example of a technique for improving such a defect is disclosed in Japanese Patent Laid-Open No. 2003-59544 cited as Patent Document 1. In Patent Document 1, the relationship between current and time during charging / discharging of a single secondary battery is shown by the curve in FIG. Also, the time when the normal battery starts to be charged with a constant current and the battery voltage reaches a predetermined voltage is indicated by t ₀ . After that, the charging current is suddenly decreased because of shifting to constant voltage charging. The charging current that changes with the passage of time changes along a curve indicating “normal”. Note that the sign of Q ₀ indicates the amount of electricity stored at the time of transition to constant voltage charging. The internal resistance of a storage battery that has been used for a long time increases. Therefore, as shown in FIG. 2, when shifting to constant current charging at the time of t ₀ ′ / D, the current change in this case changes more slowly than in the case of a normal battery, and in the point indicated by I _M in FIG. Crosses the current change curve in the case of a battery. After that, there is described an internal information detecting means for a secondary battery in which the current gradually decreases with time.
Another technique described in Japanese Patent Laid-Open No. 2002-343444 is cited as Patent Document 2 in order to improve the drawbacks of the prior art. In Patent Document 2, when the lead storage battery 4 connected to the assembled battery is fully charged as shown in FIG. 2, an alternating current of 20 Hz is applied once a day, and the internal resistance value is calculated in the calculation device 7. The internal resistance value is temperature-corrected by the measured temperature using a thermistor fixed to the side surface of the assembled battery 4, and the average value is obtained for the data for the past half year, and the time series is stored in the RAM 8 of the storage device. The state monitoring system of lead storage battery that displays the rate of change in comparison with the internal resistance average value for the previous half year, and displays the life on the display device 10 when the rate of change exceeds 110% Are listed.

JP 2003-59544 JP JP 2002-343444 A

However, the above invention disclosed in Patent Document 1 relates to internal information detection of a secondary battery. When cells are formed in an assembled battery, there is a difference in the degree of deterioration of each cell, and the degree of deterioration as an assembled battery tends to be diminished. Therefore, it becomes difficult to determine deterioration when the battery pack is configured.
In addition, the matter described in Patent Document 2 is an average value of data obtained by measuring and processing the internal resistance value of the assembled battery over a long period of time using the same method, and the average value data obtained in the past in the same manner. A cumbersome data process is required for making continuous comparisons.
An object of this invention is to provide the power supply device provided with the apparatus which can perform deterioration determination of an assembled battery easily.

The present invention, as described in claim 1, comprises an assembled battery that is charged from the system power supply via the AC / DC converter, and a load that is fed from the assembled battery via the orthogonal converter during a power failure of the system power supply. In the power supply device that is charged via the AC / DC converter after the power failure is restored, the assembled battery that shows the drooping characteristics of the charging current from when the recharging is performed at a constant current and then switched to the constant voltage charging And a device for measuring the charging current indicating the drooping characteristic, and a timer for measuring the time indicating the drooping characteristic, the output of the ammeter and the timer The battery pack power supply apparatus is characterized in that when the current value after a lapse of a predetermined time from the start of drooping of current exceeds a predetermined value, the battery pack is deteriorated.
Further, the present invention provides, as described in claim 2, a device for measuring the internal resistance of a cell constituting the assembled battery, and the internal resistance measured by the device with respect to the assembled battery for which occurrence of the deterioration state is determined. 2. The power supply device according to claim 1, wherein the deteriorated cell is determined as a secondary determination by a device that compares the value with an initial internal resistance value.

According to the first aspect of the present invention, it is possible to determine the occurrence of deterioration based on the magnitude of the charging current during the drooping using the drooping characteristics when the charging of the assembled battery is switched to the constant voltage charging. At that time, it is only necessary to use a simple device such as a timer, an ammeter, or a determination device.
According to the invention according to claim 2, for the cells constituting the assembled battery determined to be deteriorated, it is easily and quickly deteriorated by measuring with an internal resistance measuring device and comparing with the initial internal resistance value. A cell can be determined.

The figure which shows the structure of the power supply device provided with the deterioration determination apparatus of the battery which is the embodiment of this invention. Explanatory drawing which shows the drooping characteristic of the charging current of an assembled battery. FIG. 2 is a diagram showing a variation in variation in current after drooping in the assembled battery of the power supply device shown in FIG.

Embodiments of the present invention will be described with reference to the accompanying drawings.
FIG. 1 shows a power supply device for determining deterioration while charging / discharging an assembled battery 6 interposed between a system power supply 1 and a load. Reference numeral 2 denotes a switch, which is normally closed and supplies power from the system power supply 1 to the assembled battery 6 and the load 9. The system power supply 1 opens the switch 2 when a power failure occurs or when the charging to the assembled battery 6 is intended to be stopped. Reference numeral 3 denotes an AC / DC converter, which converts AC output from the system power supply 1 into DC. 4 indicates a changeover switch, which is closed to the AC / DC converter 3 side when the battery pack 6 is charged. When discharging the assembled battery 6, it is switched to the opposite side of the figure. 5 represents an ammeter, and 7 represents an orthogonal converter. 8 indicates a changeover switch. When power is supplied from the system power supply 1 to the load 9, the switch 8 is closed in the direction shown in the figure, and when the discharge power from the assembled battery 6 is supplied to the load 9, it is closed in the direction opposite to the direction shown in the figure. 10 is a voltmeter, 11 is a timer, 12 is a memory, and 13 is a deterioration determination device for an assembled battery.
Reference numeral 14 denotes a cell internal resistance measuring device, and 15 denotes a cell deterioration determining device.

The operation of the degradation determination device shown in FIG. 1 will be described.
Initially, after charging the battery pack 6 and during normal operation, in order to prevent voltage drop due to self-discharge, float current (0.001 CA or less) (where C is battery capacity and A is amperage) Charged). Then, the operation of the present invention is started from the time of recharging after the assembled battery 6 is discharged due to a power failure or the like. Recharging starts charging at a predetermined constant current value. When the voltmeter 10 detects that the voltage across the assembled battery 6 has reached a predetermined value after a predetermined time, the voltmeter 10 starts a timer 11. At that time, charging of the assembled battery 6 is changed from constant current charging to rated voltage charging. Thereafter, the charging current for the assembled battery 6 that has been a substantially constant value until the timer 11 is started decreases rapidly. This is hereinafter referred to as “droop characteristics”.

FIG. 2 is a diagram showing a drooping characteristic of the charging current at this time. In FIG. 2, the vertical axis represents the charging current I, and the horizontal axis represents the elapsed charging time T. The solid line shows the change in the charging current I in the case of a new assembled battery immediately after the start of use, and the one-point difference line shows the change in the case of an assembled battery that has passed for a long time after the start of use.
The timer activation time when a predetermined voltage at which the constant current charging is switched to the constant voltage charging is reached is indicated as N ₁ for a new assembled battery and N _{2 for an} assembled battery after the start of use. After the timer starts N _1, N _2, to measure the time by the timer 11, when measuring the charging current I for each relatively short time, in the assembled battery of new after the start of use, N ₁ after initially drooping characteristics is It turns out to be extremely steep. The current at a point where a so-called quadratic curve changes after a considerable time has elapsed and the gradient switches to a substantially straight line is defined as I _1, and this charging current is defined as I ₁ . On the other hand, in an assembled battery that has been used for a long time after the start of use, the drooping characteristics are initially relatively moderate after N ₂ . Now, the time from N ₁ to when measuring the current I ₁ as T _1, the charging current has passed from the time T ₁ equal time T ₂ N ₂ inputs to the memory 12 as I _2. The charging current I ₂ at that time is larger than I ₁ . This is because, in the battery pack 6, when the number of cells having an increased internal resistance increases, the degree of decrease in the charging current after the drooping characteristics are generated becomes small. At this time, the value of the charging current I ₂ after a lapse of a predetermined time from the start of the current drooping is measured every predetermined period, and this value is compared with a predetermined value set in advance as a life determination value in the determination device 13 to be a larger value. If it is, it is determined that the assembled battery 6 has deteriorated.
Further, the change rate (increase rate) from the initial value can be used as a determination index so that it can be easily determined when the change amount of the current value is small.

  Next, in the invention according to claim 2, it is determined which cell is deteriorated in the assembled battery 6 determined to be deteriorated. Therefore, with respect to the assembled battery 6 determined to be deteriorated, the internal resistance of each cell is measured by the internal resistance measuring device 14. The degradation determination device 15 compares the result with the initial internal resistance data to determine whether the degradation has occurred. For those deteriorated by this determination, processing such as replacement is performed. Compared with the case where the assembled battery is entirely replaced immediately after the initial deterioration determination, the loss is reduced.

Example 1
In a power supply facility that supplies power from a storage battery to a load when a power failure occurs, the storage battery section is configured as an assembled battery consisting of 54 control valve type lead storage batteries (expected life 7 years) connected in series. The storage battery part of this facility is constantly charged at a constant voltage of 120.4V so that it becomes 2.23V per cell. When the storage battery is discharged due to a power failure or the like on the system side, the assembled battery voltage decreases, and charging is performed at the rated current value (20 A) of the AC / DC converter in the charging device until it reaches a predetermined 120.4 V after the power failure is restored. Since constant voltage control is performed after reaching the predetermined voltage, the current gradually decreases thereafter. Stabilizes after approximately 72 hours.
In such a power supply facility, the change in current during charging after the discharge was measured using a charging ammeter side device and a timer. A planned power outage was carried out once a year, and the change in storage battery charging current after the power outage and the internal resistance of each cell were measured and compared with the initial values.
The measurement results are shown in Table 1 below. The charging current was measured at the 10th and 20th hours from the start of the current droop as the time showing the drooping characteristics.

  As shown in Table 1, it can be confirmed that the variation in internal resistance between cells increases as the operation years after installation become longer. In particular, since the expected life of 7 years has passed, it has been observed that the internal resistance of this cell exceeds 1.5 times, which is the level that requires replacement. This means that the deterioration of the cell has progressed and the difference in the degree of deterioration has increased, indicating that the performance of the assembled battery as a whole has been reduced.

FIG. 3 shows changes in current values and internal resistance values after a predetermined time with the passage of years after the start of operation, and is a graph of the numerical values in Table 1.
As is clear from the figure, there is an increasing trend in the values at the 10th and 20th hours after the drooping of the charging current of the assembled battery, and it can be seen that there is a correlation with the variation in the internal resistance value of the cell. . In particular, since the current at the 10th hour showing the drooping characteristics varies greatly, it is preferable for the determination of deterioration to examine the current value change at regular intervals with this time as a target.
Still further, an example of the operation of the power supply device of the present invention will be described in detail. After discharging the assembled battery and supplying power to the load, the system power supply is restored to supply power to the load, and The battery pack is charged by the converter. In this charging, the battery is first charged with a constant current of 20A, which is the rated current, and when the voltage reaches 120.4V, it switches to constant voltage charging with this voltage, and the voltmeter measures this value and signals the timer. And the timer starts. When the measurement by the timer reaches 10 hours, the measured value of the ammeter is sent to the battery pack deterioration judgment device. If the value is 3.6A or more, the battery pack deterioration judgment device issues an alarm, and the battery pack Lets know that is in a degraded state. Alternatively, the battery pack deterioration determination device emits a signal, activates the internal resistance measurement device, measures the internal resistance of each cell constituting the battery pack, and transmits the value to the cell deterioration determination device. In the cell deterioration determination device, the value of the sent internal resistance is compared with the internal resistance of the new cell that is measured in advance, and if there is something that exceeds 1.5 times, an alarm is issued, The cell was displayed.
In the figure, the case of a group of assembled batteries in which cells are connected in series is shown. However, a plurality of groups of assembled batteries may be connected in parallel to form an assembled battery. In this case, it may be possible to determine the deterioration of the entire assembled battery connected in series and parallel, but a device for determining deterioration is provided for each group of assembled batteries connected in series. If the deterioration is determined and cell deterioration is determined only for a group of assembled batteries that are determined to be deteriorated, the number of steps can be reduced.

Single power supply
2 switch
3 AC / DC converter
4 selector switch
5 Ammeter
6 batteries
7 Orthogonal transformer
8 selector switch
9 Load
10 Voltmeter
11 Timer
12 memory
13 Battery deterioration assessment device
14 Internal resistance measuring device
15 Cell degradation assessment device

Claims (2)

  Consists of an assembled battery that is charged from the system power supply via the AC / DC converter, and a load that is fed from the assembled battery via the orthogonal converter at the time of a power failure of the system power supply. A power supply device to be charged is provided with a device for determining deterioration of an assembled battery showing drooping characteristics of charging current from the time when recharging is performed at a constant current and then switching to constant voltage charging, and The apparatus has an ammeter for measuring the charging current indicating the drooping characteristic, and a timer for measuring the time indicating the drooping characteristic, and the output of the ammeter and the output of the timer are used after a predetermined time has elapsed from the start of the current drooping. A battery pack power supply apparatus, characterized in that when the current value exceeds a predetermined value, the battery pack deterioration is determined.   For an assembled battery that has been determined to have a deteriorated state, a device that measures the internal resistance of the cells that make up the assembled battery and a device that compares the internal resistance value measured by the device with the initial internal resistance value 2. The power supply device according to claim 1, wherein a deteriorated cell is determined as the determination.

Images