An apparatus comprising: a case having an internal surface and an external surface; a battery charger circuit inside the case, wherein the battery charger circuit is configured to charge a battery with a current, the battery charger circuit comprising a current limit circuit configured to set a maximum current limit in the battery charger circuit; and a thermal sensor circuit arranged on the internal surface of the case; wherein the apparatus is a mobile device, wherein the mobile device is configured to be handheld; wherein the thermal sensor circuit is configured to sense a temperature on the internal surface, to decrease the maximum current limit in the battery charger circuit when the temperature on the internal surface of the case is greater than a first temperature (Tc), to further decrease the maximum current limit in the battery charger circuit if the temperature on the internal surface of the case continues to increase towards a pre-defined maximum temperature (Tmax) after decreasing the maximum current limit, and to increase the maximum current limit in the battery charger circuit when the temperature on the internal surface of the case is less than a programmable minimum temperature (Tmin); wherein the first temperature (Tc) is higher than the minimum temperature (Tmin); and wherein the first temperature (Tc) is a programmable threshold temperature within a temperature window defined by the pre-defined maximum temperature (Tmax) and the minimum temperature (Tmin). a case having an internal surface and an external surface; a battery charger circuit inside the case, wherein the battery charger circuit is configured to charge a battery with a current, the battery charger circuit comprising a current limit circuit configured to set a maximum current limit in the battery charger circuit; and a thermal sensor circuit arranged on the internal surface of the case; wherein the apparatus is a mobile device, wherein the mobile device is configured to be handheld; wherein the thermal sensor circuit is configured to sense a temperature on the internal surface, to decrease the maximum current limit in the battery charger circuit when the temperature on the internal surface of the case is greater than a first temperature (Tc), to further decrease the maximum current limit in the battery charger circuit if the temperature on the internal surface of the case continues to increase towards a pre-defined maximum temperature (Tmax) after decreasing the maximum current limit, and to increase the maximum current limit in the battery charger circuit when the temperature on the internal surface of the case is less than a programmable minimum temperature (Tmin); to sense a temperature on the internal surface, to decrease the maximum current limit in the battery charger circuit when the temperature on the internal surface of the case is greater than a first temperature (Tc), to further decrease the maximum current limit in the battery charger circuit if the temperature on the internal surface of the case continues to increase towards a pre-defined maximum temperature (Tmax) after decreasing the maximum current limit, and to increase the maximum current limit in the battery charger circuit when the temperature on the internal surface of the case is less than a programmable minimum temperature (Tmin); wherein the first temperature (Tc) is higher than the minimum temperature (Tmin); and wherein the first temperature (Tc) is a programmable threshold temperature within a temperature window defined by the pre-defined maximum temperature (Tmax) and the minimum temperature (Tmin).