Aim: The aim of this research is to improve the voltage conversion ratio in electric vehicle battery systems using novel coupled inductor bidirectional DC-DC converter compared with unidirectional converter by optimizing duty cycle. Materials and Methods: The voltage conversion ratio of a bidirectional DC-DC converter is compared with a unidirectional DC-DC converter using seven samples per group and duty cycles ranging from 0.3 to 0.9. G power is taken as 0.8. Results: Based on the findings, it is inferred that the coupled inductor based bidirectional DC-DC converter has improved the average overall voltage ratio of 0.5182F while the unidirectional DC-DC converter has a voltage conversion ratio of 0.4006. The significance value is determined as 0.32 (p>0.05, statistically insignificant) based on SPSS analysis. Conclusion: Compared to a unidirectional DC-DC converter, a novel coupled inductor based bidirectional DC-DC converter provides a better voltage conversion ratio for the selected data.