A powered air purifying respirator and method for directing a forced flow of air to a wearer. A battery operatively powers a fan fluidly coupled with the air flow path which exhibits, in some circumstances, a passivation. A voltage delay sensing circuit, operatively coupled to the battery, provides an indication related to the passivation. A signal may provide an indication to a user of the passivation of the power source. A correction circuit may correct such passivation.