This work is focused on developing a model for a Battery management unit for a Solar PV based off grid standalone system and implementing the same using MATLAB tool. A secondary storage device in form a battery is essential to provide an energy backup in any autonomous system. In this work Lithium ion (Li Ion) battery has been considered for modeling as it offers good charge and discharge profile, high power density, occupies less space and less maintenance. It is essential to ensure secure function of such batteries by closely monitoring and control of their State of Charge (SOC). Determination of SOC ensures the remaining energy available in the battery which further helps in discharging the same based on system requirements. The major components of this work include representation of PV source, employing MPPT, regulating the DC output via boost converter, inverter and controlling the flow of energy between the source to battery, load and vice versa.