Lithium sulfur rechargeable battery fuel gauge systems and methods

Abstract

Systems and methods for accurately determining the state of charge and the relative age of lithium sulfur batteries are provided. The cell resistance and taper input charge of a particular type of lithium sulfur battery are respectively measured to determine the state of charge and age of the battery.

Description

RELATED APPLICATIONS[0001]This application is a divisional of U.S. patent application Ser. No. 11 / 111,262, entitled, “Lithium Sulfur Rechargeable Battery Fuel Gauge Systems and Methods,” filed on Apr. 20, 2005, which is incorporated herein by reference.BACKGROUND OF THE INVENTION[0002]The present invention relates generally to the charging of lithium sulfur batteries, and more particularly to systems and methods for accurately determining the state of charge and the relative age of lithium sulfur batteries.[0003]The ability to discern how much energy is stored in a rechargeable battery of a portable consumer electronic device, such as a cellular telephone or laptop computer, is a feature that is highly valued by the user of the device. Therefore, common device systems, such as those using lithium-ion, nickel metal hydride, or nickel-cadmium rechargeable batteries, incorporate some technique to gauge the amount of energy or charge presently stored in the battery cell. One common appr...

AI Technical Summary

Benefits of technology

The patent text describes a method for accurately determining the state of charge and age of lithium sulfur battery cells. This is achieved by charging the battery until it reaches a maximum voltage, measuring the cell resistance at this state of charge, and recording this information. The battery is then discharged by a predetermined percentage of its capacity, and the cell resistance is measured at each state of charge until it reaches a lower cutoff voltage. This process creates a look-up table of cell resistance versus state of charge for the particular type of battery. The technical effect of this invention is to provide a reliable way to determine the state of charge and age of lithium sulfur battery cells, which can help to improve the performance and reliability of these batteries.

Problems solved by technology

However, the maximum capacity of a battery degrades with the “age” of the battery (i.e., the number of charge / discharge cycles to which the battery has been subjected, and not the actual amount of time that the battery has existed).

The above-described conventional open-circuit voltage-based algorithms do not use stored look-up tables that adequately represent the characteristics of the battery as it ages to determine its state of charge.

Images