Battery charging circuit

• US 3,944,904 A
• Filed: 05/07/1975
• Issued: 03/16/1976
• Est. Priority Date: 09/24/1973
• Status: Expired due to Term

• Current Assignee: Alfred M. Hase
• Original Assignee: Alfred M. Hase
• Inventors: Hase, Alfred M.
• Primary Examiner(s): Miller, J. D.
• Assistant Examiner(s): Hickey, Robert J.
• Application Number:
  US05/575,125
• Time in Patent Office: 314 Days
• Field of Search: 320/21-24, 320/19, 320/39, 320/40
• US Class Current: 320/146
• CPC Class Codes: H02J 7/007182 in response to battery voltage
• CPC Class Codes: Y10S 320/24 Inductor
• CPC Class Codes: Y10S 320/28 Regulating transformer, e.g. high leakage, ferro-resonant

Abstract

A battery charging circuit is provided where a synchronous switch, such as a magnetic amplifier, saturable reactor, silicon controlled rectifier, triac or contactor, each of which is controllable, is inserted in a charging circuit and is controlled by a circuit such that when the terminal voltage of a battery which is being charged by a substantially constant, ripple-free DC current reaches a predetermined level, an intermittent DC charge is initiated. The periods of operation are of a predetermined, fixed length and at a predetermined current level. Means may be provided to reduce the finish charge to an intermittent trickle charge when the terminal voltage of the battery reaches its rated level. Counting means can be provided for determining the number of periods of operation of intermittent charging current delivered to the battery, for surveillance of battery condition and so as to determine ampere-hour back charge. The control circuit is arranged so as to be fail safe, by insertion of a current level bias control element in series in the control circuit for the synchronous switch, with the knowledge that such bias control elements fail "open". Thus, no override protection devices are required. The method of charging the battery includes supplying a constant, substantially ripple-free DC charging current until the battery terminal voltage reaches a predetermined level, and then initiating an intermittent DC charging current while continuously sensing the battery terminal voltage.

Claims

1. A battery charging circuit for charging storage batteries, including;

Dc circuit means for supplying an initial constant DC charging current to a battery from an alternating current source;

first and second adjustable battery terminal voltage sensing means;

control circuit means connected with said first battery terminal voltage sensing means and said DC circuit means for initiating an intermittent DC charging current supply to said battery, the first operating period of which is initiated at the instant when said battery terminal voltage reaches a first predetermined level;

synchronous switch means connected in the alternating current source side of said DC circuit means;

gate means connected to said first and second battery terminal voltage sensing means and to said synchronous switch means, said gate means being adapted to control said synchronous switch means so as to initiate and stop the supply of alternating current to the DC circuit means and thereby to control each operating period of time of said intermittent DC charging current supply; and

a timing circuit which is connected to said gate means so as to control the length of each operating period of time including the first operating period of time, of said DC circuit means after said intermittent DC charging current supply has been initiated;

said second battery terminal voltage sensing means being connected to said gate means and adapted to operate after the first operating period of time of said DC circuit means;

said second voltage sensing means being set to initiate an operating period of said intermittent DC charging current supply each time the battery terminal voltage reaches a second predetermined battery terminal voltage level which is below said first predetermined voltage level.

2. The battery charging circuit of claim 1 where said first predetermined battery terminal voltage level is set so as to be below the battery terminal voltage above which the continued supply of said DC charging current over a long period of time may result in over-charging of the battery, and at a non-critical level which the battery terminal voltage will always reach.

3. The battery charging circuit of claim 1 where current level control means are provided in said control circuit that if said level control means fails, said gate means turns off to stop the supply of alternating current to said DC circuit means and thereby to stop supply of DC charging current to said battery.

4. The battery charging circuit of claim 1, further including means to reduce the amplitude of said intermittent DC charging current when the terminal voltage of said battery reaches a third predetermined level higher than said first predetermined level.

5. The battery charging circuit of claim 1, further including means for altering said second predetermined level of said second battery terminal voltage sensing means after a predetermined number of periods of operation of said intermittent DC charging current.

6. The method of charging a storage battery including the steps of:

supplying an initial constant DC charging current to the battery until the terminal voltage thereof reaches a first predetermined level;

then immediately initiating the first operating period of an intermittent supply of DC charging current to the battery, where each operating period of said intermittent supply of DC charging current supplied to said battery is predetermined; and

at the same time as said intermittent supply of DC charging current is initiated, simultaneously beginning operation of voltage sensing gate means which senses the terminal voltage of said battery and starts each subsequent operating period of said intermittent DC charging current whenever the terminal voltage of said battery reaches a second predetermined level which is below said first predetermined level.

7. The method of claim 6, further including the step of initiating a trickle charge of DC charging current when the terminal voltage of said battery reaches a third predetermined level higher than said first predetermined level.