Lead-Acid Batteries (LABs) remain a popular choice for energy storage due to their wide availability and reasonably low cost, but they exhibit a shorter cycle life and are non-eco-friendly. The objective of this study was to evaluate the discharge capacity of a flooded lead-acid battery using an electrolyte modifiedwith additives from natural plant extracts -Hibiscus Sabdariffa (H–S) and Bidens Pilosa (B–P) plants. The study utilized commercial LABs with electrolyte solutions of 100% sulfuric acid and varying volumes of plant extract solutions at concentration of 10% (w/v), 15.86% (w/v), 30% (w/v) and 44.14% (w/v). The effect of the additives was assessed by comparing the charge-discharge cycle times, coulombic efficiency and energy efficiency. The results show the longest measured discharge time of 4.63 h at 15.86% (w/v) of H–S additive-electrolyte solution, 0.13 h longer than for the standard electrolyte. The highest coulombic efficiency (CE) was 97.3% at 44.14% (w/v) of H–S additive electrolyte solution, 10% above the standard electrolyte. The highest value for energy efficiency (EF) was 83.8% achieved in the battery with 44.14% (w/v) H–S additive electrolyte solution. The best recorded performance with B–P additive electrolyte solution was, CE of 94.6% and EF of 81.3%, obtained at 15.86% (w/v) additive concentration. It is evident from the results that bio-active compounds present in the additive solution of plant extracts influenced the electrochemical performance of the battery. The novelty of this work lies in the choice of candidate plants named, H–S and B–P for green extracts and the methodology of extraction, which is low-cost, eco-friendly and sustainable. This study contributes to fundamental understanding and strategies towards economical and eco-friendly plant electrolyte batteries.