Battery chargers

• US 3,890,556 A
• Filed: 09/24/1973
• Issued: 06/17/1975
• Est. Priority Date: 10/14/1972
• Status: Expired due to Term

• Current Assignee: Brian Turton Smith, John Barrington Knight, John Stevens, Peter George Mclellan, Richard Gascoine Massey, Robert Nigel Lang, William Gordon Melling
• Original Assignee: Brian Turton Smith, John Barrington Knight, John Stevens, Peter George Mclellan, Richard Gascoine Massey, Robert Nigel Lang, William Gordon Melling
• Inventors: Stevens, John, Smith, Brian Turton, Melling, William Gordon, McLellan, Peter George, Massey, Richard Gascoine, Knight, John Barrington, Lang, Robert Nigel
• Primary Examiner(s): Miller, J. D.
• Assistant Examiner(s): Hickey, Robert J.
• Application Number:
  US05/400,001
• Time in Patent Office: 631 Days
• Field of Search: 320/30,31,39,40,43,14,20,21
• US Class Current: 320/161
• CPC Class Codes: H02J 7/00718 in response to charge current gradient
• CPC Class Codes: H02J 7/007182 in response to battery voltage
• CPC Class Codes: H02J 7/007186 obtained with the battery disconnected from the charge or discharge circuit
• CPC Class Codes: Y10S 320/24 Inductor

Abstract

A battery charger control system is proposed in which the state of charge of a battery on a charger is assessed by an arrangement which intermittently interrupts the charge which is provided by the charger and during an interruption times a period at the end of which the battery voltage is sensed. Means is provided to then compare the sensed battery voltage which has been sensed earlier in an interruption of the charging current, with a logic circuit arrangement responsive to the result of the comparison for permitting, preventing or modifying the charging current after the interruption.

Claims

1. A battery charging control circuit in which the state of battery charge is assessed by measurement when the battery charging current is interrupted and including means operative during an interruption to time a period of time, means responsive to the end of said period to register the battery voltage, means to compare the registered battery voltage with the battery voltage registered earlier during an interruption of charging current and means responsive to the result of said comparison to control the charging current thereafter applied to the connected battery.

2. A control circuit as claimed in claim 1 including a sequence controller having a counter, a source of clock pulses and gates responsive to distinct states of the counter on counting the clock pulses to generate timing signals for the progress of the charge of the battery, including the duration and spacing of pulses of battery charging current.

3. A control circuit as claimed in claim 2 in which the source of clock pulses has different rates for different states of battery charge.

4. A control circuit as claimed in claim 2 in which the period of time is the time between a timing signal on the interruption of the charging current and a second, later, timing signal.

5. A control circuit as claimed in claim 1 in which the battery voltage is registered in analogue form as the charge stored on a capacitor supplied with battery voltage.

6. A control circuit as claimed in claim 5 in which the capacitor is charged during an interval beginning with the end of the period of time.

7. A control circuit as claimed in claim 6 in which the comparison between registered battery voltages is by a sensing means responsive to energy flow to or from the storage capacitor during said interval.

8. A control circuit as claimed in claim 4 in which the battery voltage is registered as a digital signal derived from the frequency of a voltage controlled oscillator controlled by the battery voltage.

9. A control circuit as claimed in claim 8 in which an interval is timed from the end of said period by a further timing signal and a change in battery voltage over the interval is recorded as a count in a counter counted in opposite directions for equal durations of time at the beginning and end of said interval by the output of the voltage controlled oscillator.

10. A control circuit as claimed in claim 9 in which the means to compare the registered battery voltage with the battery voltage registered earlier is responsive to the difference in the change of battery voltage during similar said intervals in similar said interruptions in the charging current.

11. A control circuit as claimed in claim 1 in which the means responsive to the result of the comparison is operative to modify the charging current when a change in registered battery voltage in successive measurements passes a threshold value and in which the modification is the supply of a timed pulse of battery charging current and thereafter interrupting the charging current until the battery voltage is measured as having fallen below a chosen value.

12. A control circuit as claimed in claim 11 in which the threshold represents the attainment by a battery being charged of the fully charged condition.

13. A battery charger including a battery charging control circuit as claimed in claim 1 and in which charger the charging current is controlled by means responsive to the magnitude of the battery voltage to generate a control signal representing a charging current in accordance with a predetermined relationship and in which the charger is adapted to a relationship appropriate to a battery to be charged by modifying an electrical circuit element of the means to generate a control signal.

14. A battery charger as claimed in claim 13 operative in an initial charging stage to supply a constant current of up to one-third of the ampere hour capacity of the battery unTil a sensor in the charger indicates that a gassing condition would have been achieved and in which the charging of the battery is thereafter controlled by the control circuit.

15. A battery charger as claimed in claim 13 for connection to an a.c. supply and including a rectifier and a choke and a semiconductor controlled rectifier in a charging current path and means to vary the firing angle of the semiconductor controlled rectifier to control the charging current in accordance with the state of charge of the battery assessed by the control circuit.

16. A battery charger as claimed in claim 15 in which the means to vary the firing angle is responsive to means responsive to the connection of a battery to the charger to delay the application of current to the battery for a period of time.

17. A battery charger as claimed in claim 15 in which the means to vary the firing angle is responsive to a sequence controler signal which indicates whether or not charging current is to be permitted.