A hybrid electric vehicle having one or more controllers, voltage-current sensors, and batteries, which are configured to generate and respond to power signals that communicate vehicle operating and start-up conditions, among other parameters and data. The components also are enabled to detect vehicle and battery conditions that include an open circuit voltage (OCV), current, differentiated current (DFC), and near zero current (NZC). The controller(s) are further configured to generate a predicted battery state of charge (SoC) from a combination of the OCV, current, DFC, NZC, and other parameters, which are calibrated according to respective magnitudes and noise calibration factors, which enables the controller(s) to charge and discharge the battery according to the predicted SoC. The controller(s) also may compare the OCV to a predetermined battery performance array that correlates the OCV magnitude with one or more of a battery SoC, cell voltage and internal resistance, temperature, and cumulative charge-discharge cycles.