JP2016041000A - Storage battery device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a storage battery device in which each electric cell can be evenly charged even when an electric source the generated power of which changes with time is used.SOLUTION: A storage battery device 1 comprises a plurality of electric cells 2 and bypass circuits 3. The plurality of electric cells 2 are connected in series to each other. The bypass circuits 3 are connected in parallel to each of the plurality of electric cells 2 and have resistant elements 4 and FETs 5. The FETs 5 are connected in series to the resistant elements 4. The total values of resistant values of the resistant elements 4 and resistant values of the FETs in a conduction state are values obtained by dividing voltage values of the electric cells 2 connected in parallel to the bypass circuits 3 having the resistant elements 4 and the FETs 5 when the cells are fully charged, by the maximum values of charging currents charging the electric cells 2.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a storage battery device.

  Patent Document 1 describes a cell voltage balance device for a secondary battery. The cell voltage balance device includes a plurality of single cells, a current path, and current control means. The plurality of single cells are connected in series with each other. The current path is connected in parallel with each of the plurality of single cells. The current control means controls the current flowing through the current path. The current control means increases the current flowing through the current path as the difference between the voltage of the unit cell and the balance operation start voltage increases when the voltage of the unit cell rises above the balance operation start voltage. In this way, the cell voltage balance device equalizes the voltage of each single cell.

JP 2008-123868 A

  The above-described cell voltage balance device adjusts the current flowing through the current path connected in parallel with each unit cell, thereby equalizing the voltage variation of each unit cell due to the variation in the characteristics of each unit cell. Such a cell voltage balance device is designed on the assumption that each cell is charged by a constant current-constant voltage method. In the constant current-constant voltage method, each cell is supplied with a constant current to charge each cell to a predetermined voltage, and then each cell is supplied with a constant voltage to charge each cell to a target voltage. It is a method. Therefore, it can be said that the above-described cell voltage balance device is designed assuming that each unit cell is charged with power from a stable power source such as a system power source.

  However, some power supplies have a generated power that varies with time. For example, in a solar power generation system that generates power using solar cells, current and voltage change from moment to moment according to the amount of solar radiation, temperature, and temperature. It is difficult to charge each single cell by a constant current-constant voltage method using such a power source whose generated power fluctuates with time. Therefore, when each cell is charged with electric power from a solar power generation system or the like, the above-described cell voltage balance device takes a long time to equalize the voltage of each cell, and each cell. There is a problem that it is difficult to equalize the battery voltages sufficiently.

  Accordingly, an object of the present invention is to provide a storage battery device that can charge each unit cell evenly even when a power source whose generated power changes with time is used.

  A storage battery device according to the present invention includes a plurality of single cells connected in series to each other, a parallel connection to each of the plurality of single cells, a resistance element, and a switching element connected in series to the resistance element. A bypass circuit. The total value of the resistance value of the resistance element and the resistance value in the conductive state of the switching element is the voltage value at the time of full charge of the single cell connected in parallel to the bypass circuit having the resistance element. It is a value divided by the maximum value of the charging current to be charged.

  In this case, when the unit cell is fully charged, the voltage between both ends of the bypass circuit connected in parallel with the unit cell becomes the voltage when the unit cell is fully charged. Here, the total value of the resistance value of the resistance element included in the bypass circuit and the resistance value in the conductive state of the switching element is a value obtained by dividing the voltage value when the cell is fully charged by the maximum value of the charging current. Therefore, the current value flowing through the bypass circuit is the maximum value of the charging current for charging the unit cell. For this reason, the electric current which flows into a cell becomes zero, and charge to a cell is stopped. On the other hand, when the unit cell is not fully charged, the voltage value across the bypass circuit is smaller than that when the unit cell is fully charged. Therefore, the current flowing through the bypass circuit is smaller than the maximum value of the charging current for charging the cell. For this reason, the electric current which flows into a cell becomes a positive value which is not zero, and charge to a cell is continued. Therefore, according to this storage battery device, even when a power source whose generated power changes with time is used, each unit cell can be charged evenly until it reaches a fully charged state.

  The plurality of single cells may be charged by a solar power generation system. In this case, the unit cell is charged by the photovoltaic power generation system in which the generated power changes with time. For this reason, even if it is a case where the power supply to which generated electric power changes with time is used, the effect of the present invention that each cell can be charged equally is exhibited suitably.

  ADVANTAGE OF THE INVENTION According to this invention, even when using the power supply from which power generation changes with time, the storage battery apparatus which can charge each cell equally can be provided.

It is the schematic which shows the structure of the storage battery apparatus which concerns on embodiment.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. In the description of the drawings, if possible, the same elements are denoted by the same reference numerals, and redundant description is omitted.

  FIG. 1 is a schematic diagram illustrating a configuration of a storage battery device 1 according to the embodiment. The storage battery device 1 includes a positive electrode terminal 11 and a negative electrode terminal 12. When charging the storage battery device 1, a charging power source is connected between the positive terminal 11 and the negative terminal 12. In this embodiment, the photovoltaic power generation system S is used as the charging power source. When discharging the storage battery device 1, a load (not shown) is connected between the positive electrode terminal 11 and the negative electrode terminal 12.

  The storage battery device 1 includes a plurality of single cells 2, a plurality of bypass circuits 3, a plurality of voltage sensors 6, and a plurality of control units 7. The plurality of unit cells 2 are connected in series with each other. One bypass circuit 3 and one voltage sensor 6 are connected in parallel to each of the plurality of single cells 2. One control unit 7 is provided in each of the plurality of single cells 2. In this embodiment, as shown in FIG. 1, as an example, three combinations of the unit cell 2, the bypass circuit 3, the voltage sensor 6, and the control unit 7 are connected in series. A diode for preventing a backflow of current from the unit cell 2 to the photovoltaic power generation system S may be inserted between the positive electrode terminal 11 and the unit cell 2 and the bypass circuit 3.

  The single battery 2 is a secondary battery that can be charged and discharged. Examples of the unit cell 2 include a lithium battery and a lithium ion battery. The positive electrode terminal 11 of the storage battery device 1 is connected to the positive electrode of the unit cell 2 connected to the highest potential side among the plurality of unit cells 2. The negative electrode terminal 12 of the storage battery device 1 is connected to the negative electrode of the single cell 2 connected to the lowest potential side among the plurality of single cells 2.

  The bypass circuit 3 is connected in parallel to each of the plurality of single cells 2. The bypass circuit 3 includes a resistance element 4 and an FET 5 (switching element). The resistance element 4 and the FET 5 are connected in series. The output terminal of the control unit 7 is connected to the gate terminal of the FET 5.

  Each of the plurality of control units 7 is connected to each of the plurality of voltage sensors 6 and each of the plurality of FETs 5. The voltage sensor 6 detects the voltage of the single cells 2 connected in parallel to the voltage sensor 6 and outputs information on the voltage to the control unit 7. Each control unit 7 individually controls the FET 5 of the bypass circuit 3 to be in a conductive state or a cut-off state based on the voltage information.

  As the switching element, a bipolar transistor or the like may be used instead of the FET 5. When the switching element is a bipolar transistor, the control unit 7 supplies a base current. Further, when the FET 5 is in a conductive state, the on-resistance value of the FET 5 (resistance value in the conductive state) is set to be sufficiently lower than the resistance value of the resistance element 4.

Here, the total value of the resistance value of the resistance element 4 and the resistance value in the conductive state of the FET 5 is the voltage when the unit cell 2 connected in parallel to the bypass circuit 3 having the resistance element 4 and the FET 5 is fully charged. The value is a value obtained by dividing the value by the maximum value of the charging current for charging the unit cell 2. For example, the voltage value when the unit cell 2 is fully charged is Vm, and the maximum output current value of the photovoltaic power generation system S is Ik. At this time, when the total value of the resistance value of the resistance element 4 and the resistance value of the FET 5 in the conductive state is Rv, the total value Rv is expressed by the following equation (1).
Rv = Vm / Ik (1)

Next, the current flowing through the unit cell 2 and the bypass circuit 3 during charging in the storage battery device 1 having the above-described configuration will be described. Now, it is assumed that the photovoltaic power generation system S generates power at the maximum output and outputs a current equal to the maximum output current value Ik. At this time, the current flowing through the unit cell 2 is I1, and the current flowing through the bypass circuit 3 connected in parallel to the unit cell 2 is I2. In this case, the maximum output current value Ik is expressed by the following equation (2).
Ik = I1 + I2 (2)

At this time, if the voltage of the unit cell 2 is V, V satisfies the inequality (3).
0 ≦ V ≦ Vm (3)

Further, the following equation (4) is established from Ohm's law in the resistance element 4 and the FET 5 of the bypass circuit 3.
I2 = V / Rv = (Ik / Vm) · V (4)

  Therefore, when the unit cell 2 is in a fully charged state, V = Vm, so that I2 = Ik from the equation (4). Therefore, from equation (2), the current value I1 of the current flowing through the unit cell 2, that is, the current charging the unit cell 2, becomes zero. That is, charging to the unit cell 2 is stopped.

  On the other hand, when the unit cell 2 is not fully charged, V <Vm. Therefore, from the equation (4), I2 = (Ik / Vm) · V <(Ik / Vm) · Vm = Ik Become. For this reason, from the formula (4), I1 = Ik−I2> Ik−Ik = 0, and the current value I1 of the current flowing through the unit cell 2 is a positive value that is not zero. That is, charging to the unit cell 2 is continued.

  Therefore, according to the storage battery device 1, even when a power source whose generated power changes with time is used, each of the plurality of single cells 2 can be charged evenly until it reaches a fully charged state.

  Thus, according to the storage battery device 1, when the unit cell 2 is fully charged, the voltage across the bypass circuit 3 connected in parallel with the unit cell 2 is the voltage value when the unit cell 2 is fully charged. Vm. Here, the total value Rv of the resistance value of the resistance element 4 included in the bypass circuit 3 and the resistance value in the conductive state of the FET 5 is the maximum value that is the maximum value of the charging current. It is a value divided by the output current value Ik. Therefore, the current value I2 flowing through the bypass circuit 3 becomes the maximum output current value Ik for charging the single cell 2. For this reason, the electric current which flows into the cell 2 becomes zero, and the charge to the cell 2 is stopped. On the other hand, when the unit cell 2 is not fully charged, the voltage value V across the bypass circuit 3 is smaller than that when the unit cell 2 is fully charged. Therefore, the current value I2 of the current flowing through the bypass circuit is smaller than the maximum output current value Ik that is the maximum value of the charging current for charging the unit cell 2. For this reason, the current value I1 of the current flowing through the single battery 2 becomes a positive value that is not zero, and charging of the single battery 2 is continued. Therefore, according to this storage battery device 1, even when a power source whose generated power changes with time is used, each of the single cells 2 can be charged evenly until it reaches a fully charged state.

  In particular, in this embodiment, the unit cell 2 is charged by the solar power generation system S. For this reason, even if it is a case where the power supply from which generated electric power changes with time is used, the effect of this embodiment that each of the cell 2 can be charged equally is exhibited suitably.

  As mentioned above, although preferred embodiment of this invention has been described, this invention is not limited to the said embodiment. For example, instead of the photovoltaic power generation system S, various DC power sources may be used as a power source for charging the storage battery device 1. For example, the technology according to the present embodiment can also be used for power generation systems other than solar cells, such as wind power generation.

  DESCRIPTION OF SYMBOLS 1 ... Storage battery apparatus, 2 ... Single cell, 3 ... Bypass circuit, 4 ... Resistance element, 5 ... FET (switching element), Ik ... Maximum output current value (maximum value of charging current which charges a single cell), Rv ... Resistance The total value of the resistance value of the element 4 and the resistance value of the FET 5 in the conductive state, Vm: the voltage value when the unit cell 2 is fully charged.

Claims (2)

A plurality of single cells connected in series with each other;
A bypass circuit connected in parallel to each of the plurality of unit cells, and having a resistance element and a switching element connected in series to the resistance element;
With
The total value of the resistance value of the resistance element and the resistance value in the conductive state of the switching element is the voltage value at the time of full charge of the single cell connected in parallel to the bypass circuit having the resistance element. A storage battery device that is a value divided by the maximum value of the charging current to be charged.   The storage battery device according to claim 1, wherein the plurality of single cells are charged by a solar power generation system.

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