Method of regulating the charging of a set of electrical storage cells, and a facility implementing the method

• US 5,677,613 A
• Filed: 06/14/1996
• Issued: 10/14/1997
• Est. Priority Date: 10/18/1994
• Status: Expired due to Term

• Current Assignee: SAFT SA (Totalenergies Se)
• Original Assignee: SAFT SA (Totalenergies Se)
• Inventors: Perelle, Michel
• Primary Examiner(s): Tso, Edward
• Application Number:
  US08/656,302
• Time in Patent Office: 487 Days
• Field of Search: 320/6, 320/8, 320/9, 320/15, 320/17, 320/18, 324/434, 324/433, 429/149, 429/90
• US Class Current: 320/122
• CPC Class Codes: H02J 7/0016 using shunting, discharge or bypass circuits
• CPC Class Codes: H02J 7/00304 Overcurrent protection

Abstract

The method and the facility are intended for regulating the current supplied by a charger (3) to a set (1) made up of a plurality of units (2), each of which is provided with an individual interface (5) making it possible to measure voltage, to divert a portion of the charging current, when the voltage measured across the unit is greater than a threshold value, and to supply measurement signals to a controller (4) of the charger. The charging current is reduced as soon as one of the interfaces indicates that it is diverting current, and so long as the charging current supplied is greater than the sum of the currents that can be diverted by the interfaces. The charging current is then maintained at the same level until all of the interfaces indicate that they are diverting current.

Claims

1. A method of regulating the current supplied by a charger (3) to the end terminals of a set (1) of electrical storage cells, which set is made up of a plurality of units (2), each of which is identically made up of one or more identical electrochemical cells, the units being connected together in series via their respective power supply terminals, each unit being provided with an individual interface (5) including measurement means for measuring the voltage (V) across its power supply terminals, means (12, 13) for diverting a portion (Id) of the charging current (I) supplied to the unit, when the measured voltage is greater than a threshold value (VS), and means (15) for supplying measurement signals to a controller (4) of the charger, said method being characterized in that provision is made for the controller to reduce progressively the charging current supplied by the charger to the set, when a current measurement signal (i) is received from at least one of the interfaces, which current measurement signal expresses the existence of a current (Id) diverted at the interface, so long as the charging current (I) supplied to the set is greater than the sum of the currents (I) that can be diverted by the interfaces, after which the charging current (I) then being maintained at the same level until current measurement signals are received which indicate that the diversion means for all interfaces of the units of the set are operating.

2. A battery charger system associating, at least temporarily, a charger (3) with a set (1) of electrical storage cells, which set is made up of a plurality of identical electrochemical units (2) connected together in series via their respective power supply terminals (+, -), the charger being connected to the end terminals (A, B) of the set, each unit of the set being provided with an individual interface (5) which includes means (7 to 11) for measuring the voltage (V) across its power supply terminals, means (12, 13) for diverting a portion of the charging current supplied to the cell, when the measured voltage (V) is greater than a threshold value (VS), and means (15) for supplying measurement signals to a controller (4) of the charger, said system being characterized in that the means for supplying measurement signals from each interface transmit a current signal (i) representative of the charging current (Id) diverted at the corresponding interface.

3. A battery charger system according to claim 2, characterized in that it includes clock means (16) making it possible to activate successively and periodically the means (15) for supplying measurement signals from each of the interfaces, and in that these means supply their respective current measurement signals to a common transducer (14) serving as an interface relative to the controller (4) of the charger.

4. A method of charging a series of electrochemical storage cells in a battery connected to an adjustable charging current supply, each cell having a voltage sensor and a current diverter circuit monitored by a controller, said method comprising the steps of:

applying a charging current from the adjustable charging current supply to the battery;

diverting a portion of said current around each cell in proportion to the amount by which said corresponding cell voltage sensor detects a cell voltage that exceeds a predetermined threshold;

generating, for each cell, a current signal proportional to the amount of current being diverted (Id);

monitoring said current signals for each cell; and

signalling from said controller to said charging supply to reduce the charging current whenever at least one of said monitored current signals indicates a diverted current (Id).

5. The method of claim 4 wherein the sequence of monitoring the current signals and signalling the charging current supply is repeated as long as said charging current is greater than a predetermined current, and then said charging current is maintained at the same level until current signals from every said cell indicate a current being diverted.

6. The method of claim 4 wherein the step of monitoring said current signals further comprises the step of:

sequentially activating a switch associated with each cell, where said switch temporarily connects the diverter circuit to a transducer for measuring the current being diverted around said cell.

7. The method of claim 6 wherein said step of monitoring said current signals further comprises the steps of:

sending a pulse train from said controller through an activation circuit, where said activation circuit includes, for each cell, a serially connected activation means for activating a current-sampling switch in the corresponding cell, each activation means being activated only once during each said pulse train, and

measuring a signal pulse corresponding to each cell as its current-sampling switch is activated.