RAPID CHARGING OF BATTERIES

• US 3,700,997 A
• Filed: 02/24/1971
• Issued: 10/24/1972
• Est. Priority Date: 02/24/1971
• Status: Expired due to Term

• Current Assignee: Stephen Hagar Smith
• Original Assignee: Stephen Hagar Smith
• Inventors: Smith, Stephen Hagar
• Primary Examiner(s): Miller, J. D.
• Assistant Examiner(s): Hickey, Robert J.
• Application Number:
  US05/118,420
• Time in Patent Office: 608 Days
• Field of Search: 320/14,31,32,39,40,37,20,21
• US Class Current: 320/161
• CPC Class Codes: H02J 7/00711 with introduction of pulses during the charging process

Abstract

The high rate changing of a battery is terminated by monitoring the battery voltage during a fixed interval of time in which high rate charge current is removed. If the battery voltage decreases to a predetermined value in the fixed interval of time, then high rate charge current is again applied for a second fixed interval of time. The steps are repeated until the battery voltage with high rate charge current removed does not decrease to the predetermined value within the fixed interval of time.

Claims

1. A method of charging a battery comprising the steps of applying a high rate charge current for a first fixed interval of time;

interrupting high rate charging;

monitoring battery voltage with high rate charge current removed;

reapplying high rate charge if the battery voltage decreases at least to a predetermined voltage within a second fixed interval of time;

repeating the steps until the battery voltage with high rate charge current removed does not decrease to the predetermined voltage during the second fixed interval of time; and

thereafter inhibiting the further application of the high rate charge current.

2. A method of charging a battery comprising the steps of applying high rate charge current pulses with fixed repetition rate discharge pulses between each charge current pulse for a first fixed interval of time, reducing the charge current to a trickle charge rate at the end of each first fixed interval of time, monitoring the difference between the battery voltage during trickle charge and a reference voltage, reapplying high rate charge current each time said difference reduces to zero in less than a second fixed interval of time, and terminating high rate charge if said difference does not reach zero in said second fixed interval of time.

3. A method of charging a battery comprising the steps of applying a charging current in excess of the nominal 1 hour rate of the cells of the battery for a first fixed interval of time;

interrupting the charging at a rate in excess of the nominal 1 hour rate;

monitoring battery voltage with the charge current in excess of the nominal 1 hour rate removed;

reapplying charging current in excess of the nominal 1 hour rate if the battery voltage decreases at least to a predetermined voltage within a second fixed interval of time;

repeating the steps until the battery voltage with charge current in excess of thE nominal 1 hour rate removed does not decrease to the predetermined voltage during the second fixed interval of time; and

thereafter inhibiting the further application of charge current at a rate in excess of the nominal 1 hour rate.

4. An apparatus for charging a battery comprising a source of charging current pulses;

a first path between the source and the battery to be charged including a controllable switch having a high impedance state and a low impedance state for applying charge current at a rate in excess of the nominal 1 hour rate of the cells of the battery;

a trickle charge current path connected across said controllable switch; and

a control circuit including means for monitoring the rate of change of the battery voltage upon removal of the high rate charge current and means responsive to the monitoring means for controlling the operation of the controllable switch by holding said switch in its high impedance state after the rate of change of battery voltage is less than a preselected value.

5. An apparatus for charging a battery comprising a controllable switch having a high impedance state and a low impedance state connected between a source of charge current pulses and the battery to be charged and a control circuit for controlling the operation of the controllable switch;

the control circuit including circuit means for placing the controllable switch in its low impedance state to apply a high rate charging current to the battery for a first fixed interval of time, circuit means for interrupting the application of the high rate charge current by changing the controllable switch to its high impedance state, circuit means for comparing the battery terminal voltage to a reference voltage to generate a control signal to place the controllable switch in its low impedance state, and circuit means for rendering the control signal of the comparing circuit means ineffective if the control signal is generated after a second selected interval of time and for maintaining the controllable switch in its high impedance state.

6. An apparatus in accordance with claim 5 wherein the comparing circuit means includes a differential amplifier and bipolar detector.

7. An apparatus in accordance with claim 5 wherein the placing circuit means includes a first field effect transistor and a resistive-capacitive biasing circuit having a preselected time constant for biasing the first field effect transistor in a first state for the first selected interval of time and said rendering and maintaining circuit means includes a second field effect transistor and a resistive-capacitive biasing circuit for maintaining the second field effect transistor in a first state for the second selected interval of time.

8. An apparatus in accordance with claim 5 wherein the controllable switch comprises a silicon-controlled rectifier and a saturable transformer having a control winding, a series winding, and a gate winding, the gate winding being connected between the gate and cathode of said silicon-controlled rectifier, the series winding being connected between the anode and cathode of the silicon-controlled rectifier, and the control winding being connected to the control circuit for control of current flow therethrough.

9. An apparatus in accordance with claim 8 wherein the controllable switch further includes means for preventing surge current through the silicon-controlled rectifier.

10. An apparatus for rapidly charging a battery comprising a source of direct current, and inverter circuit for converting the direct current from the source to high frequency alternating-current;

a transformer connected to the output of the inverter;

a rectifying circuit connected to the secondary of the transformer for converting the alternating-current voltage from the inverter to direct current charging pulses;

said rectifying circuit including a pair of diodes connected to the opposite ends of the secondary of the transformer;

a controllable switch having a high impedance sTate and a low impedance state connected between the inverter and the source of direct current;

circuit means connecting the output of the rectifying circuit to the battery to be charged; and

control circuit means for controlling the operation of the controllable switch, the control circuit means including circuit means for placing the controllable switch in its low impedance state to apply a high rate charging current to the battery for a first fixed interval of time, circuit means for interrupting the application of the high rate charge current by changing the controllable switch to its high impedance state, circuit means for comparing the battery terminal voltage to a reference voltage to generate a control signal to place the controllable switch in its low impedance state, and circuit means for rendering the control signal of the comparing circuit means ineffective if the control signal is generated after a second selected interval of time and for maintaining the controllable switch in its high impedance state.

11. An apparatus in accordance with claim 10 wherein the comparing circuit means includes a differential amplifier and bipolar detector.

12. An apparatus in accordance with claim 10 wherein the placing circuit means includes a field effect transistor and a resistive-capacitive biasing circuit having a preselected time constant for biasing the field effect transistor in a first state for the first selected interval of time and said rendering and maintaining circuit means includes a field effect transistor and a resistive-capacitive biasing circuit for maintaining the field effect transistor in a first state for the second selected interval of time.

13. An apparatus in accordance with claim 10 wherein the controllable switch comprises a silicon-controlled rectifier and a saturable transformer having a control winding, a series winding, and a gate winding, the gate winding being connected between the gate and cathode of said silicon-controlled rectifier, the series winding being connected between the anode and cathode of the silicon-controlled rectifier, and the control winding being connected to the control circuit for control of current flow therethrough.

14. An apparatus in accordance with claim 13 wherein the controllable switch further includes means for preventing surge current through the silicon-controlled rectifier.

15. A method of charging a battery comprising the steps of applying a high rate charge current for a first fixed interval of time;

interrupting high rate charging;

monitoring the quiescent battery voltage;

reapplying high rate charge current if the quiescent voltage decreases at least to a predetermined voltage within a second fixed interval of time;

repeating the steps until the quiescent battery voltage does not decrease to the predetermined voltage during the second fixed interval of time; and

thereafter inhibiting the further application of the high rate charge current.