Battery technology besides its importance and exceptional characteristics is not still a mature technology and there is a real need for research and innovation in their lifetime, charging rate, second use, etc. The dependency of our daily lives on batteries is irrefutable and they are becoming growingly ubiquitous in our daily lives. Battery performance is degrades with battery aging and therefore a battery diagnostics and prognostics tool to enhance the effective use of the battery system is necessary. This paper deals with some challenges that remain unsolved in battery diagnostic and prognostic techniques. A review of recent battery diagnostic approaches for battery state estimation is performed and their relative advantages and disadvantages are emphasized while comparing the available methods to predict the battery end of life (EOL) or remaining useful life (RUL) as a key tool in battery prognostics