JPH0646536A - Charger employing solar cell - Google Patents

Abstract

PURPOSE:To prolong service life of battery by interrupting charging operation of battery based on the difference between a battery temperature detected through a battery temperature detecting means and a charging environment temperature detected through an environmental temperature detecting means. CONSTITUTION:Upon irradiation with solar beam, a solar cell 1 generates power for charging a battery 2 through a power supply switch(SW) 7. Since charging environmental temperature detected through an environmental temperature detecting means 5 is identical to the battery temperature detected through a battery temperature detecting means 4 at that time, the SW7 is kept in ON state. When the battery 2 approaches fully charged state, battery temperature rises and when the difference between the battery temperature and the environmental temperature exceeds 10 deg.C, a charge control circuit 3 turns the SW7 OFF to interrupt charging of the battery 2. Charging operation is interrupted when the temperature difference exceeds 10 deg.C so long as the charging environmental temperature is lower than 20 deg.C but when the charging environmental temperature exceeds 20 deg.C, the temperature difference is decreased gradually such that the temperature difference is set at 5 deg.C for the charging environmental temperature of 40 deg.C.

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art Conventionally, a solar cell generates electric power according to the light intensity, such as when outdoor natural sunlight is used as a light source and when artificial light such as an indoor fluorescent light is used as a light source. ,
When performing this power generation, since the light intensity of sunlight is not constant, the values of constant current and constant voltage cannot be obtained, and the amount of power generation changes. For this reason, when investigating the state of charge of the storage battery for storing the generated power of the solar cell, -ΔV detection and voltage detection that are generally performed are not suitable.

On the other hand, in a charging device using a solar cell which cannot detect the charging state of the storage battery due to the constant voltage or the constant current, the charging state of the storage battery can be known by detecting the temperature of the storage battery itself, Attempts have been made to prevent overcharging and extend the life of storage batteries. As shown in FIG. 4, the charging device for detecting the temperature of the storage battery includes a solar cell 11, a storage battery 12, a charge control circuit 13 and a power source changeover switch 14, and the electric power generated from the solar cell 11 is stored in the storage battery 12. .

On the other hand, when the storage battery 12 approaches the fully charged state, the temperature of the storage battery 12 begins to rise, and when the temperature of the storage battery 12 exceeds a predetermined value, the charging state of the storage battery 12 is controlled by the charge control circuit 13. The power source changeover switch 14 is turned off and controlled by the signal from.

[0005]

However, in the above-described charging device, when the charging of the storage battery 12 is set to be stopped when the temperature of the storage battery 12 is 50 ° C. or higher, as shown in FIG. 5 (a), for example. Assuming that the charging environment temperature of the storage battery 12 is 40 ° C., the charging of the storage battery 12 proceeds, and when the battery 12 approaches a fully charged state, the battery temperature rises, and when the temperature reaches 50 ° C., the switch 14 is turned on. It is turned off and charging is stopped. At this time, the period T ₀ from the charging environment temperature of the storage battery 12 of 40 ° C. until the temperature of the storage battery 12 reaches 50 ° C. becomes the overcharge region.

On the other hand, as shown in FIG. 5B, when the charging environment temperature of the storage battery 12 is as low as 10 ° C., the period until the storage battery 12 reaches the charge stop temperature of 50 ° C., that is, the overcharge period T _As compared with the case of 40 ° C. shown in FIG. 5 (a), ₁ has a problem that it takes a longer time, the load on the storage battery 12 is increased, and the life of the storage battery 12 cannot be expected to be extended.

[0007]

The present invention has been made in order to solve such a problem, and a solar cell for generating power by receiving sunlight and a power generated by this solar cell are provided. Charge control consists of a storage battery that stores electric power, a charge control circuit that controls the state of charge from the solar battery to the storage battery, a battery temperature measuring unit that detects the temperature of the storage battery, and an environmental temperature measuring unit that detects the charging environmental temperature. The circuit knows the state of charge of the storage battery from the temperature of the storage battery measured by the battery temperature measuring means, and when the temperature difference between the temperature of the storage battery measured by the battery temperature measuring means and the charging environment temperature by the environmental temperature measuring means exceeds a predetermined value, the storage battery Charging is stopped.

[0008]

According to the present invention, the charging control circuit stops the charging to the electricity storage location due to the temperature difference between the temperature of the storage battery detected by the battery temperature measuring means and the charging environment temperature detected by the environmental temperature measuring means. You can

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail below with reference to the drawings. FIG. 1 is a circuit diagram of a charging device using a solar cell according to the present invention. 1 is a solar cell, for example, 8V, 1
It has a power output of 5A. 2 is a storage battery, for example,
A NiCd battery is used for 7.2V and 10Ah. A charging control circuit 3 stops charging of the storage battery 2 from the battery temperature measuring means 4 for detecting the temperature of the storage battery 2 and the environment temperature measuring means 5 for detecting the charging environment temperature. As the battery temperature measuring means 4 and the environment temperature measuring means 5, ordinary temperature measuring devices such as a thermistor are used. Reference numerals 6 and 6 are output terminals for supplying power to a load (not shown). Reference numeral 7 denotes a power source changeover switch which is turned off when the full charge range is reached by a signal from the charge control circuit 3.

The charge control circuit 3 supplies power when the temperature difference between the charging environment temperature from the environment temperature measuring means 5 and the battery temperature from the battery temperature measuring means 4 reaches a certain value, for example, 10 ° C. or more. It is configured to output a control signal for turning off the changeover switch 7.

In such a structure, when the solar cell 1 is irradiated with sunlight, the solar cell 1 generates electric power, and the generated electric power is supplied to the storage battery 2 via the power source changeover switch 7 to be charged. To be done. At this time, since the charging environmental temperature obtained from the environmental temperature measuring means 5 and the battery temperature from the battery temperature measuring means 4 are equal, the power source changeover switch 7 maintains the ON state. The power supply to the storage battery 2 is continued and the storage battery 2
The battery temperature begins to rise when the battery temperature approaches the full charge state, and when the difference between the temperature and the environmental temperature exceeds 10 ° C., the temperature difference is detected by the charge control circuit 3 and the power source changeover switch 7 is turned on.
After FF, the charging of the storage battery 2 is stopped. Explaining with specific numerical values with reference to FIG. 2, when the charging environment temperature is 40 ° C., as shown in FIG. 2A, the period t until the temperature of the storage battery 2 reaches 50 ° C. is overcharged. Although it is the same as the case of FIG. 5A, the battery temperature is 10 ° C. + 10 even when the charging environment temperature is 10 ° C., for example.
The period t ′ until the temperature reaches 20 ° C. becomes the overcharge region, and this t ′ and the above t are almost equal, and the overcharge period at low temperature is shortened (see FIG. 2B).

By the way, generally, storage batteries such as NiCad batteries have an upper limit of operating temperature of 45 ° C. or 55 ° C., and if used at a temperature exceeding that temperature, the battery performance and life will be extremely reduced. . Therefore, for example, assuming that the upper limit temperature of use of the storage battery 2 used in the configuration of FIG. 1 is 45 ° C., at the high temperature (40 ° C.) shown in FIG. 2A, 40 ° C. + 10 ° C., that is, 50 ° C. Charging is continued until it reaches, and the upper limit temperature of the storage battery 2 is exceeded.

Therefore, in the present invention, as shown in FIG. 3, for example, when the charging environmental temperature is up to 20 ° C., as described above, when the temperature difference between the temperature of the storage battery 2 and the environmental temperature becomes 10 ° C. or more. Charging is stopped, but when the temperature exceeds 20 ° C., the temperature difference is gradually reduced, and is set to 5 ° C. when the charging environment temperature is 40 ° C. In this way, by changing the temperature difference between the temperature of the storage battery 2 whose charging is stopped and the environmental temperature in accordance with the change in the environmental temperature, the storage battery 2 will not be charged under an undesired temperature condition, and the battery will not be charged. There is no fear of deterioration of performance or life.

[0014]

According to the present invention, the charging state of the storage battery can be known from the temperature of the storage battery measured by the battery temperature measuring means of the charge control circuit, and the temperature of the storage battery measured by the battery temperature measuring means and the charging environmental temperature measured by the environment temperature measuring means. When the temperature difference exceeds the specified value, the charging of the storage battery is stopped, so it is possible to shorten the time of the overcharge region where the charging is stopped after the storage battery is fully charged, extending the life of the storage battery. be able to.

[Brief description of drawings]

FIG. 1 is a circuit diagram of a charging device using a solar cell of the present invention.

FIG. 2 is a relationship curve diagram between a charging time and a battery temperature of a charging device using the solar cell of the present invention.

FIG. 3 is a relationship diagram of a charging environment temperature and a temperature difference of a charging device using the solar cell of the present invention.

FIG. 4 is a circuit diagram of a conventional charging device.

FIG. 5 is a relationship curve diagram between a charging time and a battery temperature of a conventional charging device.

[Explanation of symbols]

 1 solar cell 2 storage battery 3 charge control circuit 4 battery temperature measuring means 5 environmental temperature measuring means

Claims (2)

[Claims] 1. A solar cell that generates power by receiving sunlight, a storage battery that stores the power generated by the solar cell, a charge control circuit that controls the state of charge from the solar cell to the storage battery, and It comprises a battery temperature measuring means for detecting the temperature of the storage battery and an environment temperature measuring means for detecting the charging environment temperature. The charge control circuit knows the charge state of the storage battery from the temperature of the storage battery by the battery temperature measuring means. Along with when the temperature difference between the temperature of the storage battery by the battery temperature measuring means and the charging environmental temperature by the environmental temperature measuring means exceeds a predetermined value,
A charging device using a solar cell, which is characterized in that charging of a storage battery is stopped. 2. The temperature difference between the temperature of the storage battery that stops charging the storage battery and the charging environmental temperature is set to be smaller as the environmental temperature increases.
A charging device using the described solar cell.