Electricity: battery or capacitor charging or discharging – Battery or cell discharging – With charging
Reexamination Certificate
2001-01-03
2001-08-07
Wong, Peter S. (Department: 2838)
Electricity: battery or capacitor charging or discharging
Battery or cell discharging
With charging
C702S063000, C324S431000
Reexamination Certificate
active
06271647
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to battery technology, and more particularly to a method and apparatus for estimating the service life of a battery.
BACKGROUND OF THE INVENTION
For years single use and rechargeable nickel-cadmium (NiCd) batteries have been employed to power portable radios, shavers, laptop computers, non-volatile memory components, etc. NiCd batteries exhibit good capacity (i.e., the length of useable time between charges), reusability (i.e., the ability to be recharged) and service life (i.e., the length of time a battery may be used before a minimum useful battery capacity, such as 60% of the battery's maximum or “initial” capacity, is unachievable by re-charging). However, due to environmental concerns over the disposal of heavy metals such as cadmium, alternative battery technologies have been developed.
Nickel metal hydride (NiMH) batteries offer a more environmentally friendly alternative to NiCd batteries. NiMH batteries have better capacity than NiCd batteries, but suffer from poor battery service life in hot operating environments (e.g., above 36° C.). For example, for operating environments having a temperature of about 28° C. or less, the service life of a NiMH battery is about 36 months. However, for operating environments having a temperature of about 36° C. or higher, the service life of a NiMH battery is only about 19.5 months.
Because batteries typically are rated based on the worst case operating environment (e.g., about 40° C. for NIMH batteries) even though actual battery operating environments rarely approach the worst case operating environment, NiMH batteries often are changed prematurely. The high costs associated with service calls, service disruption and battery disposal that accompany battery replacement necessitate longer battery service life.
SUMMARY OF THE INVENTION
To address the need for longer battery service life, a method and an apparatus for estimating the service life of a battery are provided. Specifically, battery service life is estimated based on the actual temperature of the operating environment of a battery rather than on a worst case operating environment temperature. Preferably battery service life is estimated periodically or is otherwise “integrated” during battery operation to account for any changes in the operating environment temperature of the battery during its operation and to account for both the present and the past operating environment temperatures of the battery. By estimating the service life of a battery based on its actual operating environment temperature, a worst case service life need not be assumed for the battery, and the battery need not be replaced prematurely. Maximum service life is therefore extracted from every battery.
In a first aspect of the invention, an apparatus is provided for estimating the service life of a battery. The apparatus includes a temperature measurement circuit that measures a temperature of an operating environment of the battery and outputs a signal representative of the temperature of the operating environment. The apparatus further includes a controller coupled to the temperature measurement circuit that receives the temperature signal therefrom and estimates the service life of the battery based on the temperature signal. Preferably, the temperature measurement circuit outputs a signal representative of a temperature range in which the measured operating environment temperature resides and the controller estimates the service life of the battery based on the temperature range signal output by the temperature measurement circuit.
In a second aspect of the invention, a method is provided for estimating the service life of a battery by measuring a temperature of an operating environment of the battery and by estimating the service life of the battery based on the measured operating environment temperature. Preferably, measuring the temperature of the operating environment of the battery includes outputting a signal representative of a temperature range in which the measured operating environment temperature resides. The service life of the battery is estimated based on the temperature range signal.
In a third aspect of the invention, a computer program product is provided for estimating the service life of a battery as described above. The inventive computer program product is carried by a medium readable by a computer (e.g., a carrier wave signal, a floppy disc, a hard drive, a random access memory, etc.).
Other objects, features and advantages of the present invention will become more fully apparent from the following detailed description of the preferred embodiments, the appended claims and the accompanying drawings.
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Galbraith Robert Edward
Gisi Jessica Marie
Norgaard Steven Paul
Reetz Dennis David
Ziebarth Donald James
Dugan & Dugan LLP
International Business Machines - Corporation
Tibbits Pia
Wong Peter S.
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