Electricity: battery or capacitor charging or discharging – Battery or cell charging – Multi-rate charging
Reexamination Certificate
2000-06-19
2001-04-10
Tso, Edward H. (Department: 2838)
Electricity: battery or capacitor charging or discharging
Battery or cell charging
Multi-rate charging
Reexamination Certificate
active
06215282
ABSTRACT:
BACKGROUND OF THE INVENTION
I. Field of the Invention
The present invention relates to techniques for applying charges to rechargeable batteries. More particularly, the invention concerns an especially low power, fast completion battery charge process that varies the charging voltage, current, and time according to the battery's state of charge.
II. Description of the Related Art
Along with increased computing power, portability has been an important hallmark of the electronic age. Some electronic products today are manufactured in handheld packages, where the same component in past years occupied an entire room. Such portability would be meaningless without the availability of similarly portable power supplies, so it is no surprise that batteries have also undergone significant development in storage capability, compactness, and other features.
Over the years, engineers have developed a number of different battery charging techniques. Although many of these techniques constitute significant advances, and some even enjoy widespread commercial use today, engineers at Qualcomm Inc. are nonetheless interested in improving the performance and efficiency of known battery charging processes. One area of possible focus concerns preventing premature battery decay and loss of battery capacity. For example, the inventors have recognized that certain discharge profiles, under some existing lead acid battery charging algorithms repeatedly undercharge their batteries, causing their batteries to suffer premature battery decay. Some other areas of possible focus include extending battery life, maximizing battery charge, and shortening charge time.
SUMMARY OF THE INVENTION
Broadly, the present invention concerns a battery charger that employs an especially low power, fast completion battery charge process that varies the voltage, current, and time of charging a battery according to the battery's state of charge. Initially, the charger applies a fast charge current to the battery. When the battery voltage increases to a target voltage, the battery charger applies a fast charge voltage to the battery. This continues until the current flowing through the battery decreases to a prescribed minimum current.
The battery charger then calculates the elapsed time between initially applying the fast charge current and the battery's later achieving minimum current. Using the elapsed time, the charger computes a proposed overcharge time comprising a multiplicative product of the elapsed time and a temperature-dependent adjustment factor. Next, the battery charger applies an overcharge voltage to the battery for the duration of the proposed overcharge time, not to exceed a prescribed maximum time. The charger may enter a float or trickle charge mode after completing the overcharge cycle.
The foregoing features may be implemented in a number of different forms. For example, the invention may be implemented to provide a method of charging a battery. In another embodiment, the invention may be implemented to provide an apparatus such as a battery charger. In still another embodiment, the invention may be implemented to provide a signal-bearing medium tangibly embodying a program of machine-readable instructions executable by a digital data processing apparatus to charge a battery as shown herein. Another embodiment concerns logic circuitry having multiple interconnected electrically conductive elements configured to perform battery charging as described herein.
The invention affords its users with a number of distinct advantages. Beneficially, the battery charging process of this invention utilizes a fast charge mode that achieves rapid charging of lead acid batteries. Also, by sensing battery source current, the invention provides a full charge over a wide temperature range, and avoids the premature loss of battery capacity that can result from repeatedly undercharging the battery. Also, the invention can help preserve the accuracy of battery source current measurements by temporarily decoupling the battery from its electrical load. The invention also provides a number of other advantages and benefits, which should be apparent from the following description of the invention.
REFERENCES:
patent: 5432429 (1995-07-01), Armstrong, II et al.
Balough, Laszlo, “Implementing Multi-State Charge Algorithm with the UC3909 Switchmode Lead-Acid Battery Charger Controller”, Unitrode Corporation, Texas Instruments Inc., 1999.
“Lead-Acid Fast-Charge IC”, bq2031, Benchmarq Products, Texas Instruments Inc., Jun., 1999.
Fleming, Frank A. et al., “Rapid Recharge Capability of Valve Regulated Lead Acid Batteries for EV & HEV Applications”, Hawker Energy Publication, 1999.
Jana, Kalyan, “Charging Pure Lead-Tin Batteries: A Guide for CYCLON and Genesis Products”, Hawker Energy Publication, First Edition, pp. 8-14, Mar. 1999.
“U-510 Using the bq2031 to Charge Lead-Acid Batteries”, Unitrode Corporation, Texas Instruments, Oct., 1997.
Hardgrove Charles E.
Richards Anthony M.
Ogrod Grgory D.
Qualcomm Incorporated
Thibault Thomas M.
Tso Edward H.
Wadsworth Phillip R.
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