[ANGLÈS] By technological evolution and development of societies there is more and more interest in alternative forms of power supply. Solar power is a renewable source of energy, which has become increasingly popular in modern times. To get the most advantage of this source, rechargeable battery are needed to store its energy, so devices powered by sun can work even in absence of light. These rechargeable batteries need observation and maintenance to work properly for long time. The purpose of this project is to make Power monitoring system for a photovoltaic autonomous system .This goal is reached using multi cell battery gas gauge; the device measures accumulated battery charge and discharge as well as battery voltage, current, and its own temperature. This information is accessible via a microcontroller and can be indicated through user interface. Also user will be informed if any critical limit assigned for quantities being measured is exceeded. The system prototype was made and has been tested in laboratory; the results shows that overall error of the system is less than 1%. This system later has been used to observe photovoltaic system power.