Charging circuit for battery-operated devices powered by solar cells

• US 3,921,049 A
• Filed: 09/25/1973
• Issued: 11/18/1975
• Est. Priority Date: 09/25/1973
• Status: Expired due to Term

• Current Assignee: Eveready Battery Company Incorporated (Energizer Holdings, Inc.)
• Original Assignee: Geoffrey W. Mellors, Glenn W. Sheffield, Robert A. Powers
• Inventors: Mellors, Geoffrey W., Powers, Robert A., Sheffield, Glenn W.
• Primary Examiner(s): Miller, J. D.
• Assistant Examiner(s): Hickey, Robert J.
• Application Number:
  US05/400,656
• Time in Patent Office: 784 Days
• Field of Search: 320/2,5,6,14,15,23,35,39,40,43,57,59 58/23BA,23C
• US Class Current: 320/101
• CPC Class Codes: G04C 10/02 the power supply being a radioactive or photovoltaic source
• CPC Class Codes: H01M 10/44 Methods for charging or discharging circuits for charging H02J7/00
• CPC Class Codes: H02J 7/35 with light sensitive cells
• CPC Class Codes: Y02E 10/56 Power conversion systems, e.g. maximum power point trackers
• CPC Class Codes: Y02E 60/10 Energy storage using batteries
• CPC Class Codes: Y10S 136/291 Applications
• CPC Class Codes: Y10S 320/22 Line impedance, e.g. resistor

Abstract

A charging circuit for battery-operated devices powered by photovoltaic cells comprising a first diode means connected in parallel to a series-connected resistor and at least one photovoltaic cell, and in parallel to a series-connected second diode means and at least one secondary battery. The terminals of the components of the circuit are connected such that the current from the photovoltaic cells is limited by the first diode means so as to prevent overcharge of the secondary battery while the second diode means is connected so as to prevent reverse current through the photovoltaic cells when the voltage of the secondary battery is higher than that of said photovoltaic cells.

Claims

1. A charging circuit for battery-operated devices powered by a photovoltaic battery comprising a photovoltaic battery having positive and negative terminals;

resistive means connected in series to said photovoltaic battery;

first diode means connected in parallel across said series-connected photovoltaic battery and resistive means so as to provide a first conductive circuit loop for said photovoltaic battery;

second diode means connected in series to a rechargeable battery having positive and negative terminals;

said rechargeable battery and second diode means connected in parallel across both the first diode means and the series-connected photovoltaic battery and resistive means;

said photovoltaic battery and resistive means connected in terminal relationship with the rechargeable battery and second diode means so as to provide a second conductive circuit loop in which the photovoltaic battery will charge said rechargeable battery while said second diode means will prevent reverse current flow through said photovoltaic battery when the voltage of said rechargeable battery exceeds the voltage of said photovoltaic battery;

said first diode means providing in said first conductive circuit loop a path so as to prevent excessively high current flow from said photovoltaic battery through said rechargeable battery; and

output terminals connected across said rechargeable battery and adapted for coupling to a battery-powered device.

2. The charging circuit of claim 1 wherein said photovoltaic battery is a solar battery.

3. The charging circuit of claim 1 wherein said rechargeable battery utilizes a solid ionically conducting electrolyte system.

4. The charging circuit of claim 1 wherein said first diode means are silicon.

5. The charging circuit of claim 1 wherein said second diode means are germanium.

6. The charging circuit of claim 1 for use in a battery-operated wristwatch wherein said photovoltaic battery is a solar battery and wherein said rechargeable battery utilizes solid ionically conducting electrolyte system.

7. The charging circuit of claim 6 wherein said first diode means are silicon diode means and wherein said second diode means are germanium diode means.

8. The charging circuit of claim 6 wherein said first diode means are three series-connected silicon diodes and wherein said second diode means is a germanium diode.

9. The charging circuit of claim 8 wherein said solar battery is a silicon solar battery.