Patent ID: 6983212

Claim:
A battery management system for monitoring and recording a plurality of conditions in a battery having a string of units electrically connected in series, each of the units having positive and negative terminals, the system comprising: a voltage detector circuit for measuring the voltage across the terminals of a unit of the battery; a charge circuit for selectively supplying charge to the terminals of an individual unit of the battery; a selector for selectively coupling the terminals of unit to one of the voltage detector circuit and the charge circuit; and a microprocessor for controlling the selector to couple the terminals of each of the units to one of the voltage detector and the charge circuit and for recording the state of the selector and an output of the voltage detector, wherein the microprocessor includes means for detecting a discharge knee characteristic of the battery and wherein the means for detecting the discharge knee characteristic includes: means for periodically sampling a voltage of each unit in the battery; means for summing together the sampled voltages over a selected time interval; means for storing a sum of sampled voltages for a selected time interval; and means for comparing a current sum of sampled voltages to a stored sum of sampled voltages and indicating the knee discharge characteristic if the difference between the compared sums exceeds a threshold value.