An apparatus for use in adapting to time-varying limitations of a power source in a vehicle, the power source comprising a combustion engine and a battery; the apparatus comprising: a first stage circuit including: a) an input terminal for operative coupling to a supply voltage provided by the power source; b) an analog electronics section (315, 320) configured to concurrently generate a first intermediate signal indicative of the supply voltage and a second intermediate signal indicative of the supply voltage, wherein the first intermediate signal responds at a first rate to variation in the supply voltage and the second intermediate signal responds at a second rate to variation in the supply voltage, the second rate different from the first rate; c) a comparator section configured to compare the first intermediate signal and the second intermediate signal and to output a change detect signal upon detecting at least a predetermined difference between the first intermediate signal and the second intermediate signal, said difference indicative of a change in limitations of the power source; d) an output configured to provide an output signal indicative of the change detect signal, the output signal usable for operating further circuitry in response to the change in limitations of the power source; and a second stage circuit configured to operate in an active mode and a standby mode, the second stage circuit configured, in response to the output signal, to: switch from the standby mode to the active mode; monitor the supply voltage while in the active mode; confirm or disconfirm the change in limitations of the power source while in the active mode; trigger further electronic operations upon confirming the change in limitations; and return to the lower-power standby mode upon disconfirming the change in limitations. a first stage circuit including: a) an input terminal for operative coupling to a supply voltage provided by the power source; b) an analog electronics section (315, 320) configured to concurrently generate a first intermediate signal indicative of the supply voltage and a second intermediate signal indicative of the supply voltage, wherein the first intermediate signal responds at a first rate to variation in the supply voltage and the second intermediate signal responds at a second rate to variation in the supply voltage, the second rate different from the first rate; c) a comparator section configured to compare the first intermediate signal and the second intermediate signal and to output a change detect signal upon detecting at least a predetermined difference between the first intermediate signal and the second intermediate signal, said difference indicative of a change in limitations of the power source; d) an output configured to provide an output signal indicative of the change detect signal, the output signal usable for operating further circuitry in response to the change in limitations of the power source; and a) an input terminal for operative coupling to a supply voltage provided by the power source; b) an analog electronics section (315, 320) configured to concurrently generate a first intermediate signal indicative of the supply voltage and a second intermediate signal indicative of the supply voltage, wherein the first intermediate signal responds at a first rate to variation in the supply voltage and the second intermediate signal responds at a second rate to variation in the supply voltage, the second rate different from the first rate; c) a comparator section configured to compare the first intermediate signal and the second intermediate signal and to output a change detect signal upon detecting at least a predetermined difference between the first intermediate signal and the second intermediate signal, said difference indicative of a change in limitations of the power source; d) an output configured to provide an output signal indicative of the change detect signal, the output signal usable for operating further circuitry in response to the change in limitations of the power source; and a second stage circuit configured to operate in an active mode and a standby mode, the second stage circuit configured, in response to the output signal, to: switch from the standby mode to the active mode; monitor the supply voltage while in the active mode; confirm or disconfirm the change in limitations of the power source while in the active mode; trigger further electronic operations upon confirming the change in limitations; and return to the lower-power standby mode upon disconfirming the change in limitations.