Electricity: battery or capacitor charging or discharging – Primary cell depolarization
Reexamination Certificate
1999-07-09
2001-02-06
Wong, Peter S. (Department: 2838)
Electricity: battery or capacitor charging or discharging
Primary cell depolarization
C363S025000
Reexamination Certificate
active
06184649
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention generally relates to power converters, and more particularly to power converters that are utilized to charge lead-acid batteries, still more particularly to a control module that selectively and/or adaptively changes the magnitude of the power converter's output voltage such that sulfation of a lead-acid battery is avoided and/or reduced.
Power converters for converting AC power to a regulated DC level are well-known and frequently utilized to charge lead-acid batteries. Low-cost power converters typically comprise a rectifier and DC voltage regulator. These power converters typically fix the power converter's output voltage at some pre-determined level based on an optimum or standard operating and/or storage condition. The output voltage of these power converters is typically subject to substantial variation and instability, which leads to overcharge and/or undercharge of attached lead-acid batteries. Undercharging and/or overcharging a lead-acid battery normally shortens its operating life and causes reduced performance.
Increasing a power converter's output voltage aids in preventing electrolyte stratification and can reduce sulfation, thus extending both the life and capacity of the battery. On the other hand, decreasing the power converter's output voltage can reduce water boil-off which typically reduces maintenance and extends the battery's operating life.
Typical lead-acid batteries include lead/lead dioxide plates submerged in sulfuric acid. These plates are formed into cells which normally produce around 2 volts. A typical 12 volt battery includes six 2 volt cells. As a battery discharges, a chemical reaction transforms lead dioxide to lead sulfate. Lead sulfate acts as an insulator and decreases current flow through the battery. Additionally, the build-up of lead sulfate on a battery's plates causes a drop in the battery's output voltage. When a lead-acid battery is not in use it slowly self-discharges. This self-discharge also leads to sulfate build-up on the battery's plates. When the lead-acid battery is recharged the lead sulfate is normally converted back to lead dioxide. However, when a battery is left in a discharged state for an extended period, the lead sulfate hardens and the battery becomes more difficult to charge. This, in turn, leads to increased lead sulfate build-up until the battery becomes useless.
SUMMARY OF THE PRESENT INVENTION
An embodiment of the present invention is directed to a control module for controlling a power converter output voltage. The power converter output voltage supplies a charging current to a rechargeable battery responsive to the control module. The control module includes a microcontroller, a memory coupled to the microcontroller and power converter code. The power converter code causes the microcontroller to determine a battery output voltage of the rechargeable battery. The power converter code also causes the microcontroller to provide a control signal to the power converter. The control signal adjusts the power converter output voltage responsive to the battery output voltage. An advantage of the present invention is that it provides for desulfation of a rechargeable battery when it is not being utilized, i.e, when the power converter is in a storage mode.
REFERENCES:
patent: 4061956 (1977-12-01), Brown et al.
patent: 5349668 (1994-09-01), Gladstein et al.
patent: 5396163 (1995-03-01), Nor et al.
Ample Power Company, Smart Charger Installation and Operating Manual, Dec. 8, 1992, pp. 1-16 (includes 3 sheets of drawings).
Luk Lawrence
Price Heneveld Cooper DeWitt & Litton
Progressive Dynamics, Inc.
Wong Peter S.
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