EP0121325A2
Expired / Lapsed
EP
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Improvements in or relating to battery charging
Assignee: ELECTRONIC DESIGNS I W Ltd
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Filing: 1984-02-29
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Granted: —
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Expires: 2004-02-29
Abstract
Abstract A battery charger comprises a power supply 6 for supplying current pulses to a battery 71 to be charged. A microprocessor 3 receives from an analog-to-digital converter 20 codes representing the voltage between the battery terminals with the battery off-load between charging pulses and monitors the ratio of the voltage difference (V 3 -V 5 ) during a first period following a charging pulse to the voltage difference (V 10 -V 12 ) over a second period following the charging pulse, with the second period ending after the beginning of the first period. The value of this ratio reaches a peak value and then declines, and the microprocessor determines when the value of the ratio falls below a peak value thereof by a predetermined amount to terminate fast charging of the battery, after which the battery may be removed or may remain on a trickle charge. An accurate, reliable, and consistent determination of completion of charging of sealed nickel-cadmium batteries is thus provided.
Inventors
- 👤 Andrew John Taylor
- 👤 Philip James Mcgillivray
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-09 12:54
CPC Classifications
H; H02; H02J; H02J7/00; H02J7/90; H02J7/96
Claims Analysis
Total Claims: 22
Claim 1
Independent Claim
217 words
A method of charging a battery, comprising the steps of: a) supplying a plurality of current pulses of a first type to the battery (71); b) measuring the off-load voltage of the battery between current pulses of the first type; c) determining a first voltage drop ((V 3 -V 5 )) during a first period (t 3 to t 5 ) following a current pulse of the first type; d) determining a second voltage drop ( (V 10 -V 12 ) ) during a second period (t 10 to t 12 ) following the current pulse of the first type of step c) but before a next current pulse of the first type, where the end (t12) of the second period is later than the beginning (t 3 ) of the first period; e) determining the ratio of the first and second voltage drops ( (V 3 -V 5 ) / (V 10 -V 12 ) ); f) repeating steps c) to e) for subsequent current pulses of the first type to form a sequence of ratios; and g) stopping the supply of the current pulses of the first type after the sequence of ratios has reached a peak value and when a ratio is determined which is less than the peak value by a predetermined amount.
Claim 2
Independent Claim
217 words
A method of charging a battery, comprising the steps of: a) supplying a plurality of current pulses of a first type to the battery (71); b) measuring the off-load voltage of the battery between current pulses of the first type; c) determining a first voltage drop ((V 3 -V 5 )) during a first period (t 3 to t 5 ) following a current pulse of the first type; d) determining a second voltage drop ( (V 10 -V 12 ) ) during a second period (t 10 to t 12 ) following the current pulse of the first type of step c) but before a next current pulse of the first type, where the end (t12) of the second period is later than the beginning (t 3 ) of the first period; e) determining the ratio of the first and second voltage drops ( (V 3 -V 5 ) / (V 10 -V 12 ) ); f) repeating steps c) to e) for subsequent current pulses of the first type to form a sequence of ratios; and g) stopping the supply of the current pulses of the first type after the sequence of ratios has reached a peak value and when a ratio is determined which is less than the peak value by a predetermined amount.
Claim 3
Dependent Claim
35 words
A method according to claim 1, characterized in that the current pulses of the first type have an amplitude in amps equal to or greater than four times the capacity of the battery in amp-hours.
Claim 4
Dependent Claim
35 words
A method according to claim 1 or 2, characterized in that each of the current pulses of the first type has a duration of one second with a space of one second between consecutive pulses.
Claim 5
Independent Claim
33 words
A method according to any one of the preceding claims, characterized in that the end (t 5 ) of the first period is before the beginning (t 10 ) of the second period.
Claim 6
Independent Claim
75 words
A method according to any one of the preceding claims, characterised in that the off-load battery voltage (V 16 ) is determined at a predetermined time (t 16 ) after each current pulse of the first type to provide a sequence of battery voltage values and the supply of the current pulses of the first type is stopped when the battery voltage value falls below a peak value of the sequence of battery voltage values.
Claim 7
Independent Claim
33 words
A method according to any one of the preceding claims, characterized in that the supply of current pulses of the first type is stopped after the supply of a predetermined number of pulses.
Claim 8
Independent Claim
67 words
A method according to any one of the preceding claims, characterized in that, after the supply of current pulses of the first type has stopped, current pulses of a second type are supplied to the battery so as to perform trickle charging, the current pulses of the second type having the same amplitude as, but a smaller mark/space ratio than, the current pulses of the first type.
Claim 9
Dependent Claim
35 words
A method according to claim 7, characterized in that the average current in amps of the current pulses of the second type is equal to one tenth of the capacity of the battery in amp-hours.
Claim 10
Independent Claim
75 words
A method according to any one of the preceding claims, characterized in that an initial battery test is performed prior to performing steps a) to g), the initial test comprising performing step a) to e) for a predetermined number of current pulses of the first type and charging the battery if the ratio of the first and second voltage drops at the end of the initial test is between predetermined maximum and minimum limit values.
Claim 11
Independent Claim
46 words
A method according to any one of the preceding claims, characterized in that a battery conditioning step is performed prior to performing steps a) to g), the conditioning step comprising discharging the battery at a predetermined rate until a predetermined voltage per battery cell is reached.
Claim 12
Dependent Claim
25 words
ll. A method according to claim 10, characterized in that the predetermined discharge rate in amps is equal to half the battery capacity in amp-hours.
Claim 13
Dependent Claim
39 words
A method according to claim 10 or 11, characterized in that, following the conditioning step, the number of current pulses of the first type supplied to the battery is counted to provide a measure of charging of the battery.
Claim 14
Independent Claim
176 words
An apparatus for charging a battery, comprising: means (6) for supplying current pulses of a first type to the battery (71); means (20) for measuring the off-load voltage of the battery between current pulses; and means (3) for determining the first voltage drop ( (V 3 -V 5 ) ) during a first time period (t 3 to t 5 ) following each of at least some of the current pulses, for determining the second voltage drop ( (V 10 -V 12 ) ) during a second period (t 10 to t 12 ) following each of the at least some current pulses wherein the end of each second period follows the beginning of each first period, for determining the ratios of the first and second voltage drops ( (V 3 -V 5 ) / (V 10 -V 12 ) ) and for preventing the pulse supplying means from supplying current pulses of the first type when the value of the ratio falls below a peak value of the ratios by a predetermined amount or proportion.
Claim 15
Independent Claim
176 words
An apparatus for charging a battery, comprising: means (6) for supplying current pulses of a first type to the battery (71); means (20) for measuring the off-load voltage of the battery between current pulses; and means (3) for determining the first voltage drop ( (V 3 -V 5 ) ) during a first time period (t 3 to t 5 ) following each of at least some of the current pulses, for determining the second voltage drop ( (V 10 -V 12 ) ) during a second period (t 10 to t 12 ) following each of the at least some current pulses wherein the end of each second period follows the beginning of each first period, for determining the ratios of the first and second voltage drops ( (V 3 -V 5 ) / (V 10 -V 12 ) ) and for preventing the pulse supplying means from supplying current pulses of the first type when the value of the ratio falls below a peak value of the ratios by a predetermined amount or proportion.
Claim 16
Dependent Claim
28 words
An apparatus according to claim 13, characterized in that the pulse supplying means comprises a switched-mode power supply circuit (6) arranged to supply current pulses of constant amplitude.
Claim 17
Dependent Claim
34 words
An apparatus according to claim 14, characterized in that the power supply circuit (6) has a current-stabilizing negative feedback loop including a current transformer (11) in an output line (12) of the supply circuit.
Claim 18
Dependent Claim
40 words
An apparatus according to claim 14 or 15, characterized in that a direct current input line of the power supply circuit (6) includes a current transformer (14) for supplying a power supply shut-down signal when excessive input current is detected.
Claim 19
Independent Claim
46 words
An apparatus according to any one of claims 14 to 16, characterized in that the power supply circuit (6) includes an isolating transformer (112) having windings made of screened lead with the core and screen thereof constituting the primary and secondary windings, respectively, or vice versa.
Claim 20
Independent Claim
71 words
An apparatus according to any one of claims 13 to 17, characterized in that the determining means comprises a microprocessor (3), the measuring means comprises an analog-to-digital converter (20) connected to the microprocessor (3), and an electronically switchable attenuator (23) is connected to the input of the converter and comprises a potential divider having a plurality of tail resistors (37-40) selectively shortable to a common line (OV) by transistors (41, 42).
Claim 21
Independent Claim
29 words
An apparatus according to any one of claims 13 to 18, characterized in that it includes a battery discharging circuit (34) for selectively discharging the battery at constant current.
Claim 22
Dependent Claim
32 words
An apparatus according to claim 19, characterized in that the discharging circuit (34) comprises a voltage regulator (55) whose output is connected across a resistor (59, 59+60) for setting the constant current.
References Cited (Backward Citations)
No citation records indexed.
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