In an embodiment of the present invention, a charge voltage is coupled between the positive and negative terminals of a rechargeable battery, to charge the battery. The charge voltage is disconnected for a predetermined relax time period. A rechargeable battery voltage is present between the positive and negative terminals of the battery during the relax time. The battery voltage is measured and compared to a predetermined target voltage that is associated with a sample time. The comparison is then used to determine if the battery is charged.