Method of charging a lithium storage cell having a carbone anode

• US 5,604,418 A
• Filed: 02/23/1996
• Issued: 02/18/1997
• Est. Priority Date: 02/27/1995
• Status: Expired due to Fees

• Current Assignee: Alcatel Alsthom Compagnie Generale d'Electricite (Nokia Corporation)
• Original Assignee: Alcatel Alsthom Compagnie Generale d'Electricite (Nokia Corporation)
• Inventors: Andrieu, Xavier, Poignant, Philippe, Sonnet, Antoine
• Primary Examiner(s): Wong, Peter S.
• Assistant Examiner(s): Law, Patrick B.
• Application Number:
  US08/606,297
• Time in Patent Office: 361 Days
• Field of Search: 320/2, 320/20, 320/21, 320/27, 320/39, 320/48, 324/430
• US Class Current: 320/160
• CPC Class Codes: H02J 7/007182 in response to battery voltage

Abstract

The present invention provides a method of charging a carbon-anode lithium storage cell, which method comprises a first step in which a constant current is imposed and during which the voltage across said storage cell is allowed to increase until it reaches a reference value, and then a second step in which said reference voltage is imposed and said current decreases. The method of the invention is characterized in that, at each instant, said reference voltage is equal to the sum of the end-of-charge voltage of the cell plus the product of the current multiplied by the ohmic resistance of the cell.

Claims

1. A method of charging a carbon-anode lithium storage cell having as characteristics an end-of-charge voltage and an ohmic resistance, which method comprises a first step in which a constant current is imposed and during which the voltage across said storage cell is allowed to increase until it reaches a reference value, and then a second step in which said reference voltage is imposed and said current decreases, the method being characterized in that, at each instant, said reference voltage is equal to the sum of said end-of-charge voltage plus the product of said current multiplied by said ohmic resistance.

2. A charging method according to claim 1, in which said reference voltage is calculated and is readjusted on a continuing basis during said second step.

3. Apparatus for charging by implementing the method according to claim 1, the apparatus comprising:

a supply of voltage and current;

means for memorizing said end-of-charge voltage and said ohmic resistance;

means for measuring said current and said voltage of said storage cell;

calculation means for calculating said reference voltage by summing said end-of-charge voltage and said product of said current multiplied by said ohmic resistance;

comparator means for comparing said measured voltage with said reference voltage; and

voltage-imposing means for imposing said reference voltage on said storage cell.

4. Means for charging by the method of claim 3, in which said calculation means, said comparator means, and said voltage imposition means are suitable for calculating and readjusting said reference voltage on a continuing basis during said second step.