AUTOMATIC BATTERY CHARGER WITH MULTIPLE RATE CHARGING

• US 3,678,363 A
• Filed: 04/06/1970
• Issued: 07/18/1972
• Est. Priority Date: 04/06/1970
• Status: Expired due to Term

• Current Assignee: Richard Bertrem Ringle
• Original Assignee: Richard Bertrem Ringle
• Inventors: Ringle, Richard Bertrem
• Primary Examiner(s): Miller, J. D.
• Assistant Examiner(s): Hickey, Robert J.
• Application Number:
  US05/025,916
• Time in Patent Office: 834 Days
• Field of Search: 320/33,DIG.2,39,40,48,22-24
• US Class Current: 320/160
• CPC Class Codes: H02J 7/007182 in response to battery voltage
• CPC Class Codes: Y10S 320/12 Precharging analysis, e.g. determining presence of battery
• CPC Class Codes: Y10S 320/18 Indicator or display

Abstract

A battery charging circuit is disclosed having a multiple mode program of operation for fully automatic battery charging. In a first mode a rectified power supply provides a constant charging current flow to the terminals of a substantially discharged battery. In a second mode, initiated when a prescribed minimum charge is reached, the flow of charging current and the resultant rate of charge are reduced as the battery terminal voltage approaches a certain percentage of full charge. In a third mode, initiated at a prescribed intermediate voltage, charging continues through an unregulated rectified power supply until a maximum terminal voltage is reached. The unregulated current supply is cut off when the maximum voltage is reached, and the limited current supply comes back on in a fourth standby mode which impresses a float voltage upon the battery. This mode continues until the battery is discharged below the prescribed minimum voltage or another battery is connected to the charging circuit, at which time the program is automatically repeated.

Claims

1. In a battery charging circuit having input and output terminals and coupled between a source of charging current and a battery to be charged to a prescribed terminal voltage, the combination which comprises:

controllable means associated with the charging current source for limiting the flow of charging current to said battery, measuring means connected across said output terminals for developing a signal proportional to the terminal voltage of said battery, voltage responsive means disposed between said measuring means and said current limiting means and responsive to said voltage proportional signal for initiating the flow of charging current to the battery in response to a signal indicating a prescribed minimum terminal voltage existing across said output terminals, and cutting off the flow of charging current in response to a signal indicating a prescribed intermediate terminal voltage, so that said battery charger is capable of continuous fully automatic operation, means for supplying an unregulated charging current to said battery, and means for cutting off said unregulated charging current supply means when said prescribed maximum terminal voltage exists across said output terminals.

2. A battery charging circuit as claimed in claim 1 wherein said voltage responsive means includes zener diode means having an effective breakdown voltage at said prescribed minimum terminal voltage for generating a control signal proportional to the terminal voltage of said battery.

3. A battery charging circuit as claimed in claim 2 wherein said control means includes interposed means between said measuring means and said controllable means and responsive to said control signal to vary the degree of current limitation by said controlable means and thereby modulate the flow of charging current to a battery whose terminal voltage is between said prescribed minimum voltage and said prescribed intermediate terminal voltage.

4. A battery charging circuit as claimed in claim 3 wherein said controllable means includes a first transistor having a base terminal and an emitter-collector resistance circuit coupled serially between said source and said battery, and said interposed means includes a second transistor coupled between the base of said first transistor and said sensing means, said second transistor controlling the resistance of said emitter-collector circuit so that said controllable means passes charging current having a magnitude related to battery terminal voltage for all terminal voltages between said prescribed minimum and said prescribed intermediate voltage.

5. A battery charging circuit as claimed in claim 1 including means for indicating that current is flowing through the controllable means.

6. A battery charging circuit as claimed in claim 1 said unregulated current supply means including a diode having its anode coupled to said current source and its cathode coupled to said battery output terminal, and said unregulated current cut off means including a switching transistor responsive to said measuring means to reverse bias said diode when said prescribed maximum voltage level is detected, cutting off said unregulated current supply means.

7. A battery charging circuit as claimed in claim 6, said measuring means including a voltage dividing means for generating a signal indicating that said battery has reached said prescribed maximum voltage level, and means associated with said unregulated current cut off means for indicating that said battery is at said prescribed maximum voltage.

8. A battery charging circuit as claimed in claim 1 including means coupled between said current source and said battery and cooperating with said current limiting means and responsive to the cut off of said unregulated current supply means to impress a float level voltage across said output terminals.

9. A battery charging circuit as claimed in claim 8 including means including a voltage divider in parallel with said first measuring means for generating a second signal proportional to said battery terminal voltage, and a bistable multivibrator having first and second transistors having first opposite conductivity states disposed between said second signal generating means and said unregulated current cut off means, said multivibrator transistors being responsive to said second signal reaching a level proportional to the prescribed maximum terminal voltage to reverse their conductivity states and thereby energize said unregulated current cut off means to cut off said unregulated current supply means.

10. A battery charging circuit as claimed in claim 9 including means for restoring the flow of unregulated current, said restoring means being coupled between said measuring means And said bistable multivibrator and responsive to the detection of said prescribed minimum voltage to return the transistors of the multivibrator to their first state.

11. A battery charger for charging a battery to a prescribed maximum voltage comprising:

controllable means for limiting the flow of charging current from a current source to the battery;

control means coupled between said battery and said controllable means for sensing the terminal voltage of said battery and responsive to a prescribed minimum terminal voltage of said battery to initiate the operation of said current controllable means to limit the flow of charging current, and responsive to a prescribed intermediate battery terminal voltage to deactivate said controllable means;

said control means including measuring means coupled across the terminals of said battery and including a zener diode having an effective breakdown voltage at said prescribed minimum terminal voltage for generating a control signal proportional to the terminal voltage of said battery, and means interposed between said measuring means and said controllable means and responsive to said control signal to vary the degree of current limitation imposed by said controllable means on the flow of charging current to a battery whose terminal voltage is between said prescribed minimum voltage and said prescribed intermediate terminal voltage, and said controllable means including a first transistor having a base terminal and an emitter-collector resistance circuit coupled serially between said current supply source and said battery;

said means for varying the degree of current limiting including a second transistor coupled between the base of said first transistor and said signal generating means, said second transistor controlling the resistance of said emitter-collector circuit so that said controllable means allows charging current to flow at a maximum rate when said terminal voltage is below said prescribed minimum level, allows a diminished current flow when said terminal voltage is between said prescribed minimum and intermediate levels, and cuts off current through said controllable means at a terminal voltage equal to said prescribed intermediate level;

means for supplying unregulated current to said battery;

second measuring means cooperating with said first measuring means for generating a second control signal proportional to the battery terminal voltage; and

unregulated current control means responsive to said second control signal for cutting off said unregulated current supply means when the battery reaches the prescribed maximum terminal voltage.

12. A battery charger as claimed in claim 11 further including means responsive to said unregulated current control means for impressing a float voltage on said battery terminals.

13. A battery charger as claimed in claim 12 further including means for indicating that said battery terminal voltage is below said prescribed intermediate voltage, and means for indicating that said battery terminal voltage is equal to said prescribed maximum terminal voltage.