Solar cell battery charging control system

• US 4,240,021 A
• Filed: 05/12/1978
• Issued: 12/16/1980
• Est. Priority Date: 05/20/1977
• Status: Expired due to Term

• Current Assignee: Citizen Watch Co Limited (Citizen Electronics Company Limited)
• Original Assignee: Citizen Watch Co Limited (Citizen Electronics Company Limited)
• Inventors: Yoshida, Makoto, Kashima, Yoshinobu
• Primary Examiner(s): Hickey, Robert J.
• Application Number:
  US05/905,615
• Time in Patent Office: 949 Days
• Field of Search: 320/2, 320/35, 320/39, 320/40, 323/15, 350/331, 136/89 AC, 58/23 BA, 58/23 C
• US Class Current: 320/101
• CPC Class Codes: G04C 10/02 the power supply being a radioactive or photovoltaic source
• CPC Class Codes: G04C 10/04 with means for indicating the condition of the power supply in general G01R31/36
• CPC Class Codes: H02J 7/35 with light sensitive cells
• CPC Class Codes: H02S 40/38 Energy storage means, e.g. batteries, structurally associated with PV modules
• CPC Class Codes: Y02E 10/50 Photovoltaic [PV] energy
• CPC Class Codes: Y02E 70/30 Systems combining energy storage with energy generation of non-fossil origin
• CPC Class Codes: Y10S 136/291 Applications
• CPC Class Codes: Y10S 323/906 Solar cell systems

Abstract

A solar cell battery charging control system having a storage battery and a plurality of solar cells connected in series for charging the storage battery, which system comprises a heavy load means adapted to be driven by the storage battery to discharge the storage battery for thereby preventing overcharging of the storage battery when a battery charge level exceeds a predetermined value.

Claims

1. A solar battery charging control system having a storage battery and a plurality of solar cells connected in series with said storage battery to charge said storage battery, comprising:

detection means for detecting a battery charge level and generating an output signal when said battery charge level exceeds a predetermined value;

a driver circuit for generating a drive signal responsive to said output signal; and

heavy load means responsive to said drive signal to discharge said storage battery thereby preventing overcharging of said storage battery, said heavy load means discharging said battery for a predetermined interval of time, the duration of said predetermined interval of time being determined by said output signal from said detection means.

2. A solar cell battery charging control system according to claim 1, further comprising:

circuit means for generating sampling signals to operate said detection means; and

a memory circuit for memorizing the contents of the output signal from said detection means in response to said sampling signals, said heavy load means being controlled in response to an output signal from said memory circuit.

3. A solar cell battery charging control system according to claim 2, wherein said circuit means for generating sampling signals comprises means for generating a plurality of said sampling signals, and further comprising selection circuit means for selecting any one of said plurality of sampling signals responsive to at least one output signal of said detection means, said selected sampling signal being applied to said detection means.

4. A solar cell battery charging control system having a storage battery, and a plurality of solar cells connected in series for charging said storage battery, comprising:

detection means for detecting a battery charge level and generating an output signal when said battery charge level exceeds a predetermined value; and

a liquid crystal cell functioning as a light control valve to control a level of light incident upon at least one of said plurality of solar cells responsive to said output signal.

5. A solar cell battery charging control system according to claim 4, wherein said detection means comprises at least two resistors connected in series between terminals of said storage battery, a junction of said resistors being connected to one electrode of said liquid crystal cell and a terminal of said storage battery being connected to another electrode of said liquid crystal cell.

6. A solar cell battery charging control system according to claims 4 or 5, wherein said detection means comprises:

an MOS transistor connected in series with a variable resistor, a control terminal of said transistor being connected to said plurality of solar cells whereby the impedance of said transistor is controlled responsive to a photoelectric voltage generated by said plurality of solar cells;

oscillator means for generating switching signals;

switching means responsive to said switching signals for applying an alternating control voltage to electrodes of said liquid crystal cell, the amplitude of said alternating control voltage being proportional to the amplitude of a voltage developed across said variable resistor.

7. A solar cell battery charging control system according to claims 4 or 5, in which said liquid crystal cell controls a level of light incident on at least one of said plurality of solar cells for a predetermined period of time, responsive to said output signal.

8. A solar cell battery charging control system according to claim 7, further comprising:

circuit means for generating sampling signals for operating said detection means; and

a memory circuit for memorizing the contents of an output signal from said detection means in response to said sampling signals, said liquid crystal cell being controlled in response to an output signal from said memory circuit.