Patent attributes
A vehicle incorporates a crank battery, a rechargeable auxiliary battery, and an onboard electrical power source separate from the crank battery and the auxiliary battery. A battery charge controller manages a supply of electrical energy to the auxiliary battery to charge the auxiliary battery. The battery charge controller includes a first comparator for monitoring a voltage level of the crank battery, and a second comparator for monitoring a voltage level of the onboard electrical power source. A first switching device electrically couples the crank battery and the auxiliary battery to charge the auxiliary battery when the voltage level of the crank battery exceeds a first voltage threshold, and electrically decouples the crank battery and the auxiliary battery when the voltage level of the crank battery is below the first voltage threshold. A second switching device electrically couples the onboard power source and the auxiliary battery to charge the auxiliary battery when: (i) the voltage level of the crank battery is below the first voltage threshold and (ii) the voltage level of the onboard power source exceeds a second voltage threshold; and electrically decouples the onboard power source and the auxiliary battery when the voltage level of the onboard power source is below the second voltage threshold.