In this paper, we propose a 2.45 GHz RF energy harvesting system to power a battery free Internet of Things (IoT) sensor node. The system operates from an RF signal with a power as low as -20 dBm and includes an RF to DC converter, a storage super capacitor and a voltage DC/DC up-conversion. The system components are sized to provide the required electric energy to operate the connected object. The tested connected object includes an ARM microcontroller, an ultra low-power sensor (temperature, pressure and humidity) and a Bluetooth Low Energy interface for a wireless transmission toward a terminal such as a smartphone or tablet. It requires 200 μJ per transmission cycle, which must be provided by the proposed harvesting system. This system is tested in an anechoic chamber and using a constant power RF signal to characterize the energy recovery time needed for measuring and transmitting the sensor data. Promising results show that the system is capable of sending data after 5 hours of RF energy harvesting from a source distant with one meter.