BATTERY CHARGER

• US 3,855,516 A
• Filed: 08/06/1973
• Issued: 12/17/1974
• Est. Priority Date: 08/06/1973
• Status: Expired due to Term

• Current Assignee: Toro Company (Toro)
• Original Assignee: Harold W. Fairchild
• Inventors: Fairchild, Harold W.
• Primary Examiner(s): Miller, J. D.
• Assistant Examiner(s): Hickey, Robert J.
• Application Number:
  US05/385,986
• Time in Patent Office: 498 Days
• Field of Search: 320/22-25,37,38,39,40
• US Class Current: 320/160
• CPC Class Codes: H02J 7/007182 in response to battery voltage

Abstract

Disclosed herein is a battery charging circuit including rectifying means for converting a source of alternating current to direct current, means connected to the rectifying means for applying the direct current to the battery at a level providing a high charge rate, means connected to the rectifying means for diminishing the current level applied to the battery to a reduced level after charging of the battery to a predetermined voltage level, and time controlled means for further reducing the current level applied to the battery to a trickle level after the expiration of a given time.

Claims

1. A circuit for charging a battery from an alternating current source comprising rectifying means for converting a source of alternating current to direct current, positive and negative battery charging terminals adapted to be respectively connected to like terminals of a battery to be charged, and means connected to said rectifying means and to said battery charging terminals for charging the battery and including a main transistor having an emitter-collector path connected between said rectifying means and one of said battery terminals and also having a base, said battery charging means also including a timer including normally open switch means, means for manually closing said switch means, and means for opening said switch means after expiration of a given time period unrelated to the battery voltage level, said battery charging means also including means subject to said switch means being closed and connected to said transistor base for applying the direct current to said battery charging terminals at a high current level to provide a high charging rate, said battery charging means also including means subject to said switch means being closed and connected to said transistor base for applying the direct current to said battery charging terminals at a reduced current level below said high current level after charging of the battery to a predetermined voltage level, and said battery charging means also including means connected to said transistor base for applying the direct current to said battery charging terminals at a trickle current level lower than said reduced current level when said switch means is open.

2. A battery charging circuit in accordance with claim 1 wherein said means for applying the direct current at said reduced level comprises a first shunt circuit path connected to said rectifying means in parallel with the application of current to the battery and including a transistor including an emitter and a collector in said shunt path and a base, said means for applying the direct current at said reduced level further comprising a second circuit path connected to said rectifying means in parallel with said shunt path and including an SCR having an anode and a cathode in said shunt path and a gate, said second circuit path being electrically connected to said transistor base to turn on said transistor in response to conduction by said SCR, and said means for applying the direct current at said reduced level further including a voltage breakdown device connected to said rectifying means and to said gate and operable to breakdown in response to charging of the battery to a given voltage level and accordingly to cause said SCR to conduct.

3. A battery charging circuit in accordance with claim 2 wherein said means for applying the direct current at said reduced level further includes a variable resistor means associated with said voltage breakdown device for varying the battery voltage level which causes breakdown of said device.

4. A battery charging circuit in accordance with claim 2 wherein said means for applying the direct current at said reduced level further inclUdes, in said second circuit path, a variable resistor means for varying the level of conduction of said transistor.

5. A battery charging circuit in accordance with claim 1 wherein said main transistor includes a base and said means for applying direct current to said battery terminals at a high current level includes means for applying current to said main transistor base including a first circuit branch having a second transistor with a base, an emitter connected to said rectifying means, and a collector connected to said main transistor base, said base current applying means also including a second circuit branch connected to said rectifying means in parallel with said first circuit branch and including resistance means and a connection between said second transistor base and said second circuit branch to turn on said second transistor at a first conduction level to cause said main transistor to be turned on at another conduction level.

6. A battery charging circuit in accordance with claim 5 wherein said means for applying direct current to said battery terminals at a high current level includes a variable resistor means connected between said first and second circuit branches to vary the current applied to said main transistor base and thereby to vary the conduction level of said main transistor.

7. A battery charging circuit in accordance with claim 2 wherein said main transistor includes a base and said means for applying direct current to said battery terminals at a high current level includes means for applying current to said main transistor base including a first circuit branch having a second transistor including a base, an emitter connected to said rectifying means and a collector connected to said main transistor base, said base current applying means also including a second circuit branch connected to said rectifier means in parallel with said first circuit branch and including resistance means and a connection between said second transistor base and said second circuit branch whereby to turn on said second transistor at a first conduction level so as to cause said main transistor to be turned on at a second conduction level.

8. A battery charging circuit in accordance with claim 7 wherein said first and second circuit branches have a common portion.

9. A battery charging circuit in accordance with claim 1 wherein said means for applying direct current to said battery charging terminals at a trickle current level includes a shunt current path including a resistance connected to said main transistor collector, to said main transistor emitter, and to said main transistor base to apply current to said base in accordance with the value of said resistance in said shunt path.

10. A battery charging circuit in accordance with claim 1 and further including means for preventing damage to said circuit in the event of reverse battery connections, said damage preventing means including a diode having an annode connected to said negative battery charging terminal and a cathode connected to said positive battery charging terminal, and a fuse electrically connected between said diode and said battery.

11. A circuit for charging a battery from an alternating current source comprising rectifying means for converting a source of alternating current to direct current, positive and negative battery charging terminals adapted to be respectively connected to like terminals of a battery to be charged, and means connected to said rectifying means and to said battery charging terminals for charging the battery and including a current level control means having a control input connected between said rectifying means and one of said battery terminals, said battery charging means also including a timer including normally open timer switch means, means for manually closing said timer switch means, and means for opening said timer switch means after expiration of a given time period unrelated to the battery voltage level, said battery charging means also including means subject to said timer switch means being closed and connected to said control input of said current level control means for applying the direct current to said battery charging terminals at a high current level to provide a high charging rate, said battery charging means also including means subject to said timer switch means being closed and connected to said control input of said current level control means for applying the direct current to said battery charging terminals at a reduced current level below said high current level after charging of the battery to a predetermined voltage level, and said battery charging means also including means connected to said control input of said current level control means for applying the direct current to said battery charging terminals at a trickle current level lower than said reduced current level when said timer switch means is open.