JP2008005616A - Backup power-supply unit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a technology for improving the charging efficiency, especially at high temperatures, in a backup power-supply unit having a large-capacity battery pack using natural energy as a charging power supply. <P>SOLUTION: A small-capacity battery pack is connected in parallel to the large-capacity battery pack; and when battery temperature becomes lower than a predetermined value, the large-capacity battery pack is charged; and when the battery temperature becomes higher than the predetermined value, the small-capacity battery pack is charged, thus improving the charging efficiency of the back-up power-supply unit as a whole. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a backup power supply apparatus.

  In recent years, power generation systems using natural energy such as sunlight and wind power as a charging power source have been proposed. The output current from the power generation system is about 1 to 3 A because the natural energy output is not large.

  The backup power supply used in the power generation system can be discharged continuously for more than one day in consideration of the fact that charging by natural energy depends on the weather, and recently, a large capacity is desired. There is a demand for a nickel-metal hydride storage battery having a large capacity exceeding 30 Ah.

  The nickel-metal hydride storage battery is charged with a constant current. However, since the output current is as small as 1 to 3 A as described above, the charging current is a very small value of 0.1 It or less. In the case of nickel-metal hydride storage batteries, charging efficiency at high temperatures of 50 degrees or more generally tends to decrease especially at small charging currents. However, since power generation systems using natural energy are often installed outdoors, There is a concern that the charging efficiency is reduced in the summer and the required discharge capacity cannot be secured. Therefore, it is desirable that the power generation system be reliably charged even at high temperatures.

As means conventionally proposed for such a power generation system, means for diverting a charging current based on a charging efficiency difference between cells in an assembled battery connected in series (see, for example, Patent Document 1) A method has been proposed in which a small capacity battery is connected in parallel to ensure a necessary discharge capacity and a charging current of 0.1 It or more.
JP 2005-224024 A

  However, in the conventional method of diverting the charging current based on the difference in charging efficiency of the cells in the battery pack connected in series, the battery capacities connected in series must be almost the same. The current does not change greatly, and it is difficult to improve the charging efficiency by this means. In addition, in the method of connecting small capacity batteries in parallel, the control of battery charging and discharging becomes complicated, and the number of batteries to be used becomes very large, resulting in a high system failure rate. There are concerns such as

  An object of the present invention is to provide a backup power supply apparatus that can maintain the charging efficiency of the entire apparatus even at high temperatures by a simple method.

  In order to solve the above problems, a backup power supply apparatus according to the present invention measures a battery capacity of a large capacity battery pack, a small capacity battery pack connected in parallel to the large capacity battery pack, and the large capacity battery pack. A temperature sensor, and when the battery temperature detected by the temperature sensor is lower than a specified value, the large capacity battery pack is charged, and when the battery temperature is higher than a specified value, the small capacity battery pack is charged. It is composed.

Further, the backup power supply device has a configuration in which switching between charging to a large capacity battery pack and a small capacity battery pack is performed by a switching element that operates according to the output of a temperature sensor. Specifically, the battery temperature is 40 degrees. When the specified value is less than 50 degrees, the switching operation is performed. Thereby, even if the output current is 1 to 3 A, the charging current is high in the small-capacity battery pack, so that the charging efficiency of the entire device can be maintained even at high temperatures.

  According to the present invention, even when the battery temperature is high, the small capacity battery pack is reliably charged, so that the charge capacity is ensured even in a high temperature atmosphere such as in summer, so the necessary discharge capacity is ensured. As a result, a backup power supply device that contributes to improving the reliability of the entire system can be obtained.

  The best mode for carrying out the present invention will be described below with reference to the drawings.

  FIG. 1 is a configuration diagram of a backup power supply apparatus according to the present invention. In FIG. 1, a large-capacity battery pack 101 is composed of a nickel-metal hydride storage battery group of, for example, 30 Ah or more, and a small-capacity battery pack 102 is composed of a nickel-metal hydride storage battery group whose capacity is about 1/10 of that of a large-capacity battery pack. Both are connected in parallel with the temperature sensor 103 attached. The control circuit 104 is for instructing switching of charging based on the battery temperature measured by the temperature sensor 103, and the switching element 105 is an element that actually switches charging in response to a command from the control circuit 104. . The charging power source 106 is a device for supplying power to a load by using natural energy such as sunlight or wind power and charging a backup power source device. The DC / DC converter 107 is a device that converts the input voltage from the charging device 106 into an appropriate voltage. A diode 108 is connected to the large-capacity battery pack 101 and the small-capacity battery pack 102, and plays a role in preventing discharge current from flowing backward from each battery pack when discharging to the load 109.

  The backup power supply apparatus according to the present invention includes a DC / DC converter 107, a control circuit 104, a switching element 105, a large capacity battery pack 101, a small capacity battery pack 102, a temperature sensor 103, and a diode 108.

  The charging operation of the backup power supply device in the present embodiment will be described in detail with reference to FIG. The electric power output from the charging power source 106 is supplied to the battery packs 101 and 102 through the DC / DC converter 107 with a charging current of 1 to 3A. A temperature sensor 103 is attached to the center of each battery pack, and these temperature sensors are connected to the control circuit 104. Based on the battery temperature measured by the temperature sensor 103, the control circuit 104 charges the large-capacity battery pack 101 when the battery temperature is lower than the specified value, and supplies the small-capacity battery pack 102 when the battery temperature is higher than the specified value. The switching element 105 is controlled to be charged. As a result, there is a specific effect that the charging capacity of the entire backup power supply device is ensured even when the battery temperature increases. In addition, the specified value of the battery temperature when switching charging is preferably in the range of 40 degrees to less than 50 degrees, particularly around 45 degrees.

  The battery pack to be charged is switched according to the above-mentioned specified value, but in order to prevent chattering due to the temperature changing around the specified value, the small-capacity battery pack 102 is charged when the specified value exceeds a specified time. It is preferable to make it. At this time, depending on the system configuration, the specified time may be set to a preferable time of about 5 seconds to 1 hour.

The reason why the temperature for switching the charge is in the range of 40 degrees or more and less than 50 degrees is that when the nickel hydride storage battery is generally taken as an example, the charging efficiency is lower than 25 degrees when the charging current is 0.1 It. This is because the temperature range to start is in the range of 40 degrees to 50 degrees. From the above, since the charging operation can be performed without reducing the charging efficiency of the entire battery pack by performing the switching operation of charging according to the battery temperature, the reliability of the entire system is improved. It becomes possible.

  Further, since the diode 106 is connected to each of the large-capacity battery pack 101 and the small-capacity battery pack 102, current does not flow backward from one system to the other system when discharging, and the load 107 Can be reliably discharged.

  In the present invention, a large-capacity battery pack refers to a battery pack having a capacity of 30 Ah or more, and a small-capacity battery pack refers to a battery pack having a capacity of less than 30 Ah and 1/3 or less of the large-capacity battery pack. The difference in capacity between the large capacity battery pack and the small capacity battery pack is in the range of 3: 1 to 20: 1. The effect of maintaining the charging efficiency is obtained, but about 10: 1 is most preferable in terms of charging efficiency.

  In the present invention, the temperature sensor 103 measures the battery temperature of both the large-capacity battery pack 101 and the small-capacity battery pack 102, but only the battery temperature measurement of the large-capacity battery pack 101 is essential for the implementation of the present invention. . However, it goes without saying that measuring both temperatures is useful for detecting abnormalities and diagnosing faults.

  The present invention is particularly effective when the charging current is low, and the effect is remarkable when the charging current to the large-capacity battery pack 101 is 0.3 It or less. In the case of a lead storage battery, it becomes particularly significant in the case of 0.25 It or less, and in the case of a nickel metal hydride storage battery, it is 0.1 It or less.

  Further, when the small capacity battery pack is charged and becomes fully charged, the large capacity battery pack may be charged even if the charging efficiency is lowered. In that case, when the capacity of the small-capacity battery pack decreases to a specified value (eg, 90%) or less due to natural discharge or the like, the small-capacity battery pack may be charged again. At that time, the control circuit 104 can also have this charge control function.

  In the present embodiment, only one small-capacity battery pack is provided. However, a plurality of small-capacity battery packs are provided, and the battery temperature is regulated even when the first small-capacity battery pack is fully charged. When the value is greater than or equal to the value, the second small capacity battery pack may be charged.

  The backup power supply device of the present invention is useful for a device that uses natural energy as a charging power supply and needs to be backed up for a long time of one day or longer.

Block diagram of power generation system using backup power supply device of the present invention

Explanation of symbols

DESCRIPTION OF SYMBOLS 101 Large capacity battery pack 102 Small capacity battery pack 103 Temperature sensor 104 Control circuit 105 Switching element 106 Charging power supply 107 DC / DC converter 108 Diode 109 Load

Claims (4)

A large-capacity battery pack, a small-capacity battery pack connected in parallel to the large-capacity battery pack, and a temperature sensor for measuring a battery temperature of the large-capacity battery pack,
The large-capacity battery pack is charged when the battery temperature detected by the temperature sensor is lower than a specified value, and the small-capacity battery pack is charged when the battery temperature is higher than a specified value. Backup power supply.   2. The backup power supply apparatus according to claim 1, wherein the switching of charging to the large-capacity battery pack and the small-capacity battery pack is performed by a switching element that operates according to an output of a temperature sensor that detects the battery temperature.   2. The backup power supply device according to claim 1, wherein the specified value for switching charging to the large-capacity battery pack and the small-capacity battery pack is set in a range of 40 degrees to less than 50 degrees.   2. The backup power supply device according to claim 1, wherein a diode for preventing a reverse flow during discharging is connected to each of the large capacity battery pack and the small capacity battery pack.

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