Patent ID: 8508183

Claim:
A charging unit for charging a rechargeable battery on an external mobile device, the charging unit configured to be electrically coupled to the mobile device for electrical communication thereof, the charging unit comprising: a charging circuit comprising a charger, the charger configured to: operate in a first mode to provide a constant pre-defined charge current to the external battery based on an output voltage of the charger; operate in a second mode to provide a constant pre-defined charge voltage to the external battery; switch from the first mode to the second mode when the output voltage of the charger reaches a predefined threshold voltage; an offset compensator configured to apply an offset voltage to the charger to maintain the charger in the first mode to compensate for impedance loss between the charger and the external battery; and a charging processor configured to: receive pre-defined battery parameters associated with the rechargeable battery from the mobile device; determine an occurrence of a current decrease for the battery being prior to a measured battery voltage being at least at the pre-defined threshold voltage based on the pre-defined battery parameters; and provide a trigger to the offset compensator in response to the occurrence; wherein the offset compensator is configured to apply the offset voltage in response to the trigger to adjust the output voltage of the charger such as to maintain the charger in the first mode.