BATTERY CHARGER FOR SINGLE CELLS

• US 3,626,270 A
• Filed: 03/20/1970
• Issued: 12/07/1971
• Est. Priority Date: 03/20/1970
• Status: Expired due to Term

• Current Assignee: John H. Bigbee III, Wilford B. Burkett
• Original Assignee: John H. Bigbee III, Wilford B. Burkett
• Inventors: Burkett, Wilford B., Bigbee, John H. III
• Primary Examiner(s): Miller, J. D.
• Assistant Examiner(s): Gunther, John M.
• Application Number:
  US05/021,438
• Time in Patent Office: 627 Days
• Field of Search: 320/4,5,20,21,22,35,36,37,38,39,40,51,53,14,DIG.2,DIG.1
• US Class Current: 320/129
• CPC Class Codes: H02J 7/00711 with introduction of pulses during the charging process

Abstract

A method and circuit for rapid charging batteries, and in particular single cells wherein a battery is charged by imparting a progressively increasing charge to the battery by subjecting the battery to alternating charging and discharging intervals after a first interval in which a net discharge takes place through a path including a thermal switch which opens the current path in response to current flow therethrough. During a charging interval charge current pulses are applied to the battery being charged through a current path including a unilateral impedance element, such as a silicon-controlled rectifier, and during each discharge interval, a charge-discharge path is applied in parallel with the unilateral impedance element to effect a net discharge of the battery. The rapid charging of the battery is terminated by monitoring a terminal characteristic of the battery such as the quiescent battery terminal voltage or the temperature of the battery being charged and converting to a trickle charge in response to the attainment of a predetermined value of the monitored terminal characteristic.

Claims

1. A rapid battery-charging circuit comprising a charge path having means for rectifying an alternating-current voltage, said charge path being connected between a source of alternatingcurrent voltage and a battery having one or more cells to be charged and, a charge-discharge path having a thermal-responsive element connected in the current path therethrough, said chargedischarge path being connected in parallel with the rectifying means of said charge path.

2. A rapid battery-charging circuit in accordance with claim 1 wherein said rectifying means is a silicon-controlled rectifier having its anode-cathode path connected between a source of alternating-current voltage and the battery to be charged, said circuit further including a Circuit for clamping the gate of the silicon-controlled rectifier at a predetermined voltage.

3. A rapid battery-charging circuit in accordance with claim 2 wherein the clamping circuit comprises a forward reference diode connected between the gate of the silicon-controlled rectifier and the negative terminal of the battery to be charged, with the cathode of the silicon-controlled rectifier being connected to the positive terminal of the battery to be charged.

4. A rapid battery-charging circuit in accordance with claim 1 further including a transformer having a center-tapped secondary with the primary of the transformer being connected to a source of alternating-current voltage, wherein said rectifying means comprises a silicon-controlled rectifier connected between the center tap of the secondary of said transformer and the positive terminal of the battery to be charged.

5. A rapid battery-charging circuit in accordance with claim 4 further including a current path connected between one end of the secondary of the transformer and the gate of the silicon-controlled rectifier.

6. A rapid charging battery circuit in accordance with claim 5 further including a forward reference diode connected between the gate of the silicon-controlled rectifier and the other side of the secondary of the transformer, and means for connecting the other side of the secondary of the transformer to the negative terminal of the battery to be charged.

7. A rapid charging battery circuit in accordance with claim 1 wherein said rectifying means comprises a silicon-controlled rectifier having its anode-cathode path connected between a source of alternating-current voltage and the positive terminal of the battery to be charged, the circuit further comprising a thermistor connected between the gate of the silicon controlled rectifier and the negative terminal of the battery to be charged with the thermistor being mounted in thermal proximity to the battery to be charged so that it is responsive to the temperature of the battery being charged.

8. A circuit for rapidly charging a battery having at least one cell from an alternating-current source comprising a silicon-controlled rectifier with the anode-cathode path being connected between the alternating-current source and the battery to be charged, a voltage clamping circuit connected between the gate of said silicon-controlled rectifier and the negative terminal of the battery to be charged, a gate trigger circuit connected between the anode and the gate of the silicon-controlled rectifier, and a thermal switch connected in parallel with said silicon-controlled rectifier.

9. A circuit for rapidly charging a battery from an alternating-current voltage source comprising a first current path between the source and the battery to be charged, a unilateral impedance element connected in said path, said unilateral impedance element having a control terminal for the application of a triggering current, said unilateral impedance element being responsive to smaller trigger currents as its temperature increases and larger trigger currents as it decreases, a thermal switch connected in parallel with said impedance element, means for clamping the control terminal at a selected voltage related to the normal output of the battery being charged, so that the increase in quiescent battery terminal voltage as charge progresses is compared to the selected voltage and causes the current through the element to decrease, with a consequent decrease in the temperature of the element for a regenerative termination of rapid charging.

10. A battery charger for imparting a progressively increasing charge to a battery having one or more cells from an alternating-current voltage source by subjecting the battery to alternating charging and discharging intervals after a first interval, the charger comprising a charge current path from the source to the battery, a unilateral impedance element connected in the first current path, and a charge-dischargE current path intermittently connected in parallel with the charge current path for intermittently discharging the battery.

11. A battery charger in accordance with claim 10 wherein the charge-discharge path comprises a thermal-responsive switch connected across the unilateral impedance element of the charge current path, the thermal switch having a thermal characteristic such that it is open substantially longer than it is closed.

12. A battery charger in accordance with claim 11 wherein the unilateral impedance element is a silicon-controlled rectifier having a resistor connected between its anode and gate and its cathode connected to the positive terminal of the battery to be charged.

13. A battery charging circuit for imparting progressively increasing charge to a battery having one or more cells from an alternating-current voltage source providing charging current in excess of the nominal 1-hour rate of the cells of the battery being charged by subjecting said battery to alternating charging and discharging intervals, said circuit comprising a first path for conducting direct current from the source to the battery and a second path in parallel with the first path for discharging the battery, the second path including circuit means responsive to current flow therethrough for intermittently opening the second path for an interval of time substantially longer than the interval of time during which the path is closed.