The world is actively concerned about renewable energy to solve the global warming issue, especially in Indonesia. Indonesia had set a target of 23% renewable energy in 2025 but still reached 11,20% in 2020. Indonesia has relatively high renewable energy sources but has not utilized them optimally. Indonesia's renewable energy was dominated by hydro, geothermal, biomass, and solar, while the use of wind energy has a challenge, considering that Indonesia is located in equatorial region, with unstable wind power. Combining two or more renewable energy sources with a battery-connected dc-dc converter with multiple inputs could be an alternative solution to overcome the weakness of a single renewable energy source. This research aims to implement fuzzy logic control on the output voltage of the multi-input buck converter. The results of the output control system on the multi-input buck converter shows that the average error value is 0,54% and the highest error value is 3,68% at 13,87 V.