An energy storage system determined to be at an operating point indicative of incipient threat to its condition is permitted to continue power flow for a duration that is a function of the state of charge before a diagnosis of a critical state of charge condition is rendered. If the state of charge returns to an acceptable region before the duration expires, no diagnosis of a critical state of charge condition is rendered. Generally, the duration increases as the state of charge trends toward the region of acceptable state of charge and decreases as the state of charge trends away from the region of acceptable state of charge.