The standalone Photovoltaic (PV)-based energy system for off-grid communities requires intermediate energy storage devices to supply/absorb the intermittently power from PV generation and balance the mismatch in generation and load consumption. Battery energy storage have been one of the major components that increase the operating cost of the standalone PV-battery energy system due to the accelerated failure caused by the unstable charge/discharge processes. This paper proposes a retrofittable supercapacitor module for existing standalone PV-battery energy system to mitigate the charge/discharge stresses in battery by removing the severely fluctuating current exchange. Based on local solar irradiance and estimated load data in Sarawak, Malaysia, Matlab/Simulink model was developed to study the effectiveness of the proposed system in mitigating battery stresses. The proposed SC module prototype was implemented and tested with actual PV-battery energy system. Both simulation and experimental results show significant reduction in battery current fluctuation which suggests improvement in battery cycle life.