This paper presents a method for estimating Remaining Dischargeable Time (RDT) with enhanced prognostic capabilities. The method introduces an innovative prognostic strategy to accurately predict RDT, utilizing the Differential Model Decomposition (DMD) method as the basis for its mathematical framework. The effectiveness of the proposed RDT prognostic method, equipped with built-in prognostic capabilities, is demonstrated through real battery degradation experiments. Finally, the performance of the RDT prognostic method is comprehensively assessed using various online prognostic evaluation metrics. The results indicate that the DMD approach improves the consistency of discharge patterns during long-term degradation.