Patent ID: 8269466

Claim:
A method for charging a battery, comprising: measuring the battery's voltage and comparing the battery voltage to a first threshold voltage; operating in a charging mode if the measured battery voltage is less than the first threshold voltage, wherein operating in the charging mode comprises applying a current charging signal to the battery, the current charging signal having an oscillating sawtooth current waveform superimposed on a DC bias; measuring the battery's current consumption and comparing the current consumption to a first threshold current; and operating in a maintenance mode if the battery's current consumption is less than the first threshold current, wherein operating in the maintenance mode comprises terminating application of the charging signal to the battery and monitoring a settling voltage of the battery in the absence of the charging signal; and wherein the oscillating sawtooth current waveform is characterized by a plurality of consecutive current pulses, each current pulse having a rise portion and a fall portion, wherein the fall portion of each current pulse comprises a first linear portion having a first slope followed by a second linear portion having a second slope different from the first slope, and wherein linearity for the second slope of the second linear portion is consistent from pulse to pulse in the sawtooth current waveform.