JPH06311669A - Storage-battery charging device using solar cell as power supply - Google Patents

Abstract

PURPOSE:To provide a storage-battery charging device wherein a storage battery which cannot obtain a sufficient charging amount even when it has been charged up to a charging last-stage voltage can be charged fully by using a solar cell as a power supply and the temperature rise of the storage battery can be suppressed. CONSTITUTION:A storage battery 3 is charged by the output of a solar cell 1. When a voltage detection circuit 10 detects that the battery voltage of the storage battery 3 has reached a set voltage corresponding to a charging last- stage voltage, a timer circuit 13 starts counting a time limit. Then, while the timer circuit 13 is counting the time limit, a transistor 12 is set to continuity, the storage battery 3 is discharged, and a DC fan motor 11 is driven. When the timer circuit 13 finishes counting the time limit, the transistor 12 is set to a noncontinuity state, and the discharge of the storage battery 3 is stopped. In this manner, while the charging operation and the discharge operation of the battery 3 are being repeated, the charging operation of the storage battery 3 is continued.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a storage battery charging device using a solar cell as a power source.

[0002]

2. Description of the Related Art As a storage battery charging device for charging a storage battery used as a power source for a street light or the like, a storage battery such as a sealed lead storage battery is charged with the output of a solar battery panel formed by connecting a plurality of solar battery cells in series. Storage battery charging devices are known. FIG. 4 shows a circuit configuration of an example of a conventional storage battery charging device. The conventional storage battery charging device has an overcharge prevention circuit to prevent overcharge of the storage battery.The overcharge prevention circuit detects the battery voltage of the storage battery, and when the battery voltage reaches the set voltage, the solar battery panel Short the output and cut off the charging current. In FIG. 4, reference numeral 1 denotes a solar cell including a cell row formed by connecting a plurality of solar cells in series. The output of the solar cell 1 is supplied to the storage battery 3 via the backflow prevention diode 2 whose anode is connected to the positive output terminal of the solar cell 1, and the storage battery 3 is charged with this output. The load 5 is connected in parallel to the output terminal of the storage battery 3 via the switch 4. Opening and closing of the switch 4 is controlled by the controller 9, and power is supplied to the load 5 in the ON state. Further, an anode / cathode circuit of a thyristor 6 which is forward biased by the output of the solar cell 1 is connected in parallel between the output terminals of the solar cell 1. The gate of the thyristor 6 has a constant voltage diode 8 whose cathode is directed to the cathode side of the backflow prevention diode 2, a resistor 7 having one end connected to the anode of the constant voltage diode 8 and the other end connected to the negative terminal of the solar cell 1. It is connected to the connection point of the series circuit with. In this circuit, the thyristor 6, the constant voltage diode 8 and the resistor 7 constitute an overcharge prevention circuit.

The constant voltage level of the constant voltage diode 8 is set so that a conduction signal is given to the gate of the thyristor 6 when the battery voltage of the storage battery 3 reaches the end-of-charge voltage. By the way, when a sealed lead storage battery is used as the storage battery 3, the end-of-charge voltage is about 2.5 V / cell.
When the battery voltage reaches the end-of-charge voltage and the thyristor 6 conducts, the output of the solar cell 1 is short-circuited, so that the charging of the storage battery 3 is stopped. When the output current of the solar cell 1 becomes smaller than the holding current of the thyristor 6 at night,
The thyristor 6 becomes non-conductive. The next day, when the solar cell starts power generation, charging of the storage battery 3 is restarted again, and the same operation as described above is repeated thereafter.

[0004]

As in the conventional charging device, when the battery voltage reaches the set voltage, the charging is stopped and the charging is not restarted on that day, so that the sufficient charging amount cannot be secured. There is a nature. For example, in a sealed lead-acid battery that uses a non-fluidized electrolyte, the set voltage can be increased compared to a storage battery that uses a liquid electrolyte because there is a limit to increasing the gas absorption capacity at the cathode. Therefore, there is a possibility that the charge amount will be insufficient. This example will be described in detail with reference to FIG. Figure 5 shows 2.5A
h, a characteristic line showing a change in discharge capacity of a battery when a 2 V sealed lead-acid battery is charged with a constant current at 0.05 C and charging is stopped when the battery voltage reaches 2.5 V It is a figure. In this example, the average charging rate was 98.7%, and it was not possible to secure a charging amount equal to or more than the discharging amount. Therefore, the discharging capacity of the storage battery was 41 times the initial capacity after repeating 20 charging / discharging cycles. It decreased to%.

This phenomenon becomes remarkable when the capacity of the storage battery is made smaller than the capacity of the solar cell panel. This is because the capacity ratio of the charging current becomes large, so that the battery voltage of the storage battery reaches the set voltage earlier than when the capacity of the storage battery is large, and the charging rate becomes low.

In order to solve such a problem, it may be considered to use a voltage limiting circuit for limiting the charging voltage in the charging circuit. However, when the voltage limiting circuit is used, the heat generation becomes large, so that it becomes necessary to consider the heat radiation, and the number of parts increases and the cost of the charging device increases. Therefore, a storage battery charging device having a voltage limiting circuit is not used in a power supply system such as a relatively small street light.

An object of the present invention is to make it possible to sufficiently charge a storage battery that cannot obtain a sufficient amount of charge even if it is charged to the end-of-charge voltage without using a voltage limiting circuit for limiting the charging voltage in the charging circuit. It is to provide a storage battery charging device that uses a battery as a power source. Another object of the present invention is to provide a storage battery charging device using a solar battery as a power source, which can cool the storage battery in addition to the above objects.

[0008]

According to the present invention, a storage battery, which cannot obtain a sufficient amount of charge even if it is charged up to a terminal voltage of charge, has a set voltage at the output of a solar battery in which a plurality of solar cells are connected in series. A storage battery charging device that uses a solar cell as a power source for charging without exceeding the limit is targeted for improvement.

According to the first aspect of the invention, the battery voltage includes the voltage detection circuit for detecting whether or not the battery voltage of the storage battery has reached the set voltage, and the load in which a current larger than the maximum output current of the solar cell flows. And a discharge circuit that discharges the storage battery by supplying a current to the load for a predetermined period when the voltage detection circuit detects that

The load for passing the current may be a load of a system using a storage battery or another load. It should be noted that the predetermined period in which the current is supplied to the load is set to a period in which the overcharge state of the storage battery can be suppressed.

According to a second aspect of the present invention, a switch circuit in which a discharge circuit is connected in series to the load and a voltage detection circuit that detects that the battery voltage has reached a set voltage start timed counting and start the switch circuit. And a timer circuit which brings the switch circuit into a non-conducting state when the counting is completed in the conducting state.

According to the third aspect of the invention, the load is a DC fan motor arranged so as to cool the storage battery.

[0013]

According to the invention of claim 1, the battery voltage of a storage battery, such as a sealed lead-acid battery, which cannot obtain a sufficient charge amount even when charged to the end-of-charge voltage, reaches a set voltage (usually the end-of-charge voltage). Then, a load current larger than the maximum load current of the solar cell flows through the discharge circuit, and the storage battery is discharged for a predetermined time. This discharge causes the battery voltage to drop below the set voltage,
After the end of discharging, charging of the storage battery is restarted, and when the battery voltage reaches the set voltage again, discharging is performed again. Thereafter, this charging / discharging is repeated. As described above, according to the present invention, after the battery voltage reaches the set voltage, charging is continued while repeating charging and discharging, so that a sufficient amount of charge cannot be obtained even when the battery is charged to the end-of-charge voltage. Can be sufficiently charged without using a voltage limiting circuit for limiting the charging voltage in the charging circuit. When the sealed lead-acid battery is charged according to the present invention, the actual charging rate is as high as the constant voltage charging.

When the discharge time of the discharge circuit is controlled by using the timer circuit as in the second aspect of the invention, the storage battery can be surely discharged.

Although the load for discharging the storage battery is not particularly limited, when the DC fan motor for cooling the storage battery is used as the load of the discharging circuit as in the invention of claim 3, the battery temperature of the storage battery can be lowered. The storage battery charging device of the present invention is often arranged in a device installed outdoors, such as a street light power source. Particularly when the environmental temperature becomes high, such as in the summer, the battery temperature of the sealed lead-acid battery or the like may reach 60 ° C. or higher. When the battery temperature rises, a moisture permeation phenomenon occurs in which the water content in the electrolytic solution escapes through the battery case, the electrolytic solution decreases, the capacity of the battery decreases, and the service life is reached early.
As in the present invention, when the storage battery is cooled by driving the DC fan motor when discharging the storage battery, the battery temperature can be lowered and the moisture permeation of the electrolytic solution can be suppressed, and the decrease in the capacity of the battery can be suppressed. The battery life can be extended.

[0016]

Embodiments of the present invention will now be described in detail with reference to the drawings. FIG. 1 is a schematic circuit diagram of an embodiment of the present invention. In FIG. 1, the same members as those of the conventional configuration shown in FIG. 4 are designated by the same reference numerals as those in FIG. In this embodiment, a sealed lead storage battery is used as the storage battery 3. In order to measure the battery voltage of the storage battery 3, the voltage detection circuit 10 is connected in parallel to the storage battery 3.
A DC fan motor 11 is connected in parallel to the storage battery 3 via a cathode / emitter circuit of a transistor 12. The base of the transistor 12 is connected to the output terminal of the timer circuit 13, and the timer circuit 13 controls the conduction of the transistor 12. In this embodiment, the transistor 12 constitutes a switch circuit, and the DC fan motor 11
The transistor 12 and the timer circuit 13 form a discharge circuit.

The voltage detection circuit 10 detects whether or not the battery voltage of the storage battery 3 has reached a set voltage (usually the end-of-charging voltage), and when it detects that the battery voltage has reached the set voltage, it outputs a detection signal to a timer. Output to the circuit 13. The set voltage is set using a constant voltage diode or the like. When the voltage detection circuit 10 detects that the battery voltage has reached the set voltage, the timer circuit 13 starts timed counting and supplies a base current to the transistor 12 to make the transistor conductive and complete the timed counting. Then, the supply of the base current is stopped to make the transistor 12 non-conductive. The time limit set in the timer circuit 13 is
Even if charging and discharging are repeated, the storage battery should not be overcharged.

Since the DC fan motor 11 requires a drive current larger than the maximum output current of the solar cell 1 used, the storage battery 3 becomes the main power source when the transistor 12 is turned on. Is discharged. The DC fan motor 11 may be mounted in any state as long as it can cool the storage battery, and is not limited to a particular mounting state. If necessary, two or more DC fan motors may be driven. Charging / discharging of the storage battery 3 is repeated in the daytime, but when the solar cell 1 stops outputting at night, charging of the storage battery is stopped and driving of the DC fan motor 11 is also stopped.

In order to confirm the effect of the present invention, a rating of 12
Using a solar cell 1 of V, 20 W, a sealed lead acid battery of 12 V, 5.6 Ah, and a DC fan motor of 12 V, 20 W, a set voltage of the voltage detection circuit 10 is 15 V (2.5 V).
V / cell) and the time limit of the timer circuit 14 was 1 sec. The discharge amount of the sealed lead-acid battery is 2.8.
It was Ah. FIG. 2 shows the test results. The charging rate until the battery voltage first reaches the set voltage (15V) is 98.0%, and the conventional device stops charging in this state. In the present embodiment, even after the battery voltage first reaches the set voltage (15V), charging is continued while the DC fan motor is intermittently driven, and the storage battery is charged at the time when power generation by the solar cell is stopped. The rate was 134.5%.
The actual charging rate after subtracting the discharge amount to the DC fan motor was 104.1%, and a sufficient charging rate was obtained. And the number of discharges to the DC fan motor is 4448 times, about 2
A power amount of 5 Wh was available for cooling the storage battery. In FIG. 2, V indicates the charging voltage of the storage battery, I indicates the charging current, and the hatched area A is the area where the storage battery is repeatedly charged and discharged. In FIG. 2, it is shown that the charging voltage V does not reach 15V, but this is because a dot recording recorder having a measurement period of about 1 minute was used, and the charging voltage actually reaches 15V. .

Next, in order to confirm the effect of cooling by the DC fan motor, a storage battery is arranged on the back side of the solar cell panel in which the solar cell 10 is housed, and the conventional charging device and the charging device of this embodiment are connected. The change in battery temperature during charging was measured. The conditions of the used solar cell, storage battery, etc. are the same as the test results shown in FIG. Even in the conventional charging device, the set voltage was set to 15V. In the test, the charging was started after the storage battery was fully charged. Therefore, when the conventional charging device was used, the battery voltage reached 15 V at the same time when the charging was started and the charging was terminated. The test results are shown in Figure 5.
5, T1 shows the change in battery temperature when charged by the conventional charging device, and T2 shows the change in battery temperature when charged by the charging device of this embodiment. , T3 indicate changes in the outside air temperature. As can be seen from this figure, the maximum battery temperature was 30 ° C, which was 7 ° C higher than the outside air temperature. The reason why the battery temperature rises despite the fact that charging is stopped is that the battery is placed immediately behind the solar cell panel and is affected by the temperature rise of the solar cell panel. On the other hand, when the battery is charged by the charging device of the present embodiment, the maximum temperature of the battery is 26 ° C. even if the battery is cooled by the DC fan motor, which is higher than the ambient temperature. Was only 3 ° C higher. As can be seen from this result, when the charging device of this embodiment is used, the charging rate can be increased without raising the battery temperature.

[0021]

According to the invention of claim 1, after the battery voltage reaches the set voltage, charging is continued while repeating charging and discharging, so that a sufficient charge amount can be obtained even if the battery is charged to the end-of-charge voltage. There is an advantage that a storage battery that cannot be obtained can be sufficiently charged without using a voltage limiting circuit that limits the charging voltage in the charging circuit.

According to the invention of claim 2, there is an advantage that the storage battery can be surely discharged by controlling the discharge time of the discharge circuit by using the timer circuit.

According to the third aspect of the invention, when the storage battery is discharged, the DC fan motor is driven to cool the storage battery, so that the temperature of the battery is lowered and moisture permeation of the electrolytic solution can be suppressed, and the capacity of the battery is reduced. There is an advantage that the decrease can be suppressed and the life of the battery can be extended.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a configuration of a storage battery charging device according to an embodiment of the present invention.

FIG. 2 is a diagram showing a charging characteristic when a sealed lead-acid battery is charged by the storage battery charging device of the embodiment of FIG.

FIG. 3 is a characteristic diagram showing a change in battery temperature when a storage battery is charged using the charging device of the embodiment of the present invention and a conventional charging device.

FIG. 4 is a schematic circuit diagram of a storage battery charging device using a conventional solar battery as a power source.

FIG. 5 is a characteristic diagram showing a capacity transition of a sealed lead-acid battery when charging and discharging are repeated in a charging cycle in which charging is stopped at 2.5 V / cell.

[Explanation of symbols]

 1 Solar Cell 2 Backflow Prevention Diode 3 Storage Battery 4 Switch 5 Load 6 Thyristor 7 Resistor 8 Constant Voltage Diode 9 Controller 10 Voltage Detection Circuit 11 DC Fan Motor 12 Transistor 13 Timer Circuit

Claims (4)

[Claims] 1. A solar battery for charging a storage battery, which cannot obtain a sufficient amount of charge even when it is charged to the end-of-charge voltage, so that the output of the solar battery does not exceed the set voltage. A storage battery charging device using a battery as a power source, including a voltage detection circuit for detecting whether or not the battery voltage of the storage battery has reached the set voltage, and a load in which a current larger than the maximum output current of the solar cell flows. A power source for the solar cell, comprising: a discharge circuit that discharges the storage battery by causing a current to flow through the load for a predetermined period when the voltage detection circuit detects that the battery voltage has reached the set voltage. Storage battery charging device. 2. The switch circuit, wherein the discharge circuit starts a timed count when the voltage detection circuit detects that the switch circuit is connected in series to the load and the battery voltage reaches the set voltage. 2. The storage battery charging device using a solar cell as a power source according to claim 1, further comprising: a timer circuit that brings the switch circuit into a non-conducting state when the counter circuit is brought into a conducting state and the counting of the time period is completed. 3. The load comprises a DC fan motor arranged to cool the storage battery.
A storage battery charging device using the solar cell according to item 1 as a power source. 4. The storage battery charging device using a solar cell as a power source according to claim 1, 2 or 3, wherein the storage battery is a sealed lead storage battery.