Method of charging a battery, and a corresponding charger and battery

• US 8,212,531 B2
• Filed: 04/25/2007
• Issued: 07/03/2012
• Est. Priority Date: 04/26/2006
• Status: Active Grant

• Current Assignee: Safran Electronics & Defense
• Original Assignee: Sagem Defense Securite SA (Safran SA)
• Inventors: Nollet, Michel
• Primary Examiner(s): Berhanu, Samuel
• Application Number:
  US11/790,431
• Publication Number:
  US 20070252557A1
• Time in Patent Office: 1,896 Days
• Field of Search: 320/150, 320/152, 320/156
• US Class Current: 320/152
• CPC Class Codes: H02J 7/007182 in response to battery voltage
• CPC Class Codes: H02J 7/007194 of the battery

Abstract

The present invention relates to a method of charging a battery having internal resistance, the method including the step of feeding the battery with substantially constant charging current at a charging voltage that is regulated so as to compensate at least in part for the voltage drop generated by the internal resistance of the battery. The invention also provides a charger and a battery for implementing the method.

Claims

1. A method of charging a battery having internal resistance using a charger circuit connected to the battery, the method comprising:

feeding the battery with a substantially constant charging current at a charging voltage that is regulated to compensate at least in part for a voltage drop generated by the internal resistance of the battery during a constant current phase of a charging cycle;

acquiring a temperature of the battery; and

regulating the compensation in such a manner that the charging voltage is equal to the sum of a nominal charging voltage of the battery, plus the product of the corresponding charging current multiplied by twice the resistance of a reference resistor connected in series with the charger circuit and the internal resistance of the battery, which varies solely as a function of the temperature of the battery, and presenting resistance that is less than or equal to the internal resistance of the battery.

2. A method according to claim 1, in which the internal resistance presents a value made up of a fixed portion and of a variable portion, the method including the step of compensating the voltage drop that corresponds to the fixed portion of the internal resistance.

3. A charger for a battery having internal resistance, the charger comprising:

a charger circuit performing voltage regulation; and

a compensation circuit associated with the charger circuit and arranged to compensate at least in part for the voltage drop generated by the internal resistance of the battery during a constant current phase of a charging cycle;

the compensation circuit being arranged to compensate solely in relation to the battery temperature and including a reference resistor connected in series with the charger circuit and the internal resistance of the battery, which varies as a function of temperature, and presenting resistance that is less than or equal to the internal resistance of the battery, the compensation circuit being connected to a servo-control input for controlling the voltage of the charger circuit so that the charger circuit delivers a voltage equal to the sum of a nominal charging voltage of the battery plus the product of the corresponding charging current multiplied by twice the resistance of the reference resistor.

4. A charger according to claim 3, wherein the charger is arranged to receive at least temperature information from the battery and the compensation circuit is arranged to compensate at least in part the voltage drop depending on the temperature.

5. A charger according to claim 4, wherein the charger is arranged to receive temperature information from SMART-type batteries.

6. A battery having internal resistance and including a compensation circuit provided with means for connecting it to a charger and arranged to control the charger in such a manner that it delivers a voltage compensating the voltage drop caused by the internal resistance of the battery during a constant current phase of a charging cycle, the compensation circuit including a reference resistor connected in series to the charger circuit and to the internal resistance of the battery, which varies solely as a function of temperature of the battery, and presenting resistance that is less than or equal to the internal resistance of the battery, the compensation circuit being connected to a servo-control input for controlling the voltage of the charger circuit so that the charger circuit delivers a voltage equal to the sum of a nominal charging voltage of the battery plus the product of the corresponding charging current multiplied by twice the resistance of the reference resistor.