Importance

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Abstract

Methods and apparatus are described for providing a time-based warning indicating that the energy capacity of a primary energy source of a battery-powered computer has discharged to a low level, and using residual energy of the primary energy source to perform at least one pre-cutoff function. The time-based warning ensures that the warning is provided in a timely manner by overcoming problems caused by analog to digital converter voltage measurement accuracy limitations and flat battery operating voltage versus discharge curves. The primary energy source can be a rechargeable battery, which can also be the sole energy source for the computer. The battery provides power to operate the computer until the battery voltage discharges to the cutoff voltage. The methods and apparatus provide advantages because they reserve the residual energy in the battery to perform at least one pre-cutoff function within a first duration before the battery discharges to the cutoff voltage. For example, the residual energy can be used to retain data stored in the computer between opportunities to charge the battery. Some embodiments of the invention include hardware resources coupled with the processor to lock out power and application activation when the rechargeable battery has discharged to a predetermined hardware lockout voltage. The value of the hardware lockout voltage can be based on the battery retaining a residual energy sufficient for performing the corresponding pre-cutoff function within an amount of time that is expected to enable the user to perform the function.

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First Claim