US Patent 7386404 Method and apparatus for monitoring battery discharge state

One aspect of the invention involves: periodically sampling a voltage of a battery and an ambient temperature in order to obtain a sample that includes a temperature value and a voltage value; saving each sample in a sample group; selecting a subset of the samples in the group, wherein the temperature value of each sample in the subset is lower than the temperature value of substantially all of the samples of the group other than the subset; and determining as a function of the voltage of at least one the sample in the subset whether the battery is subject to a low voltage condition.