Due to the intermittent characteristic of renewable sources, battery storage systems (BSS) play an important role in instantaneous power balance. In isolated microgrids, lead acid batteries are still widely used as storage and their useful life is directly related to the way they operate. The profile of renewable sources contributes to the loss of battery life. One way to mitigate this problem is to use a dual battery storage systems (DBSS), which enable better integration between renewable generation source and storage devices. However, this strategy strongly depends on the characteristic of the renewable source and in the case of tidal stream plants, its benefits have not been evaluated. In this paper, we use a DBSS formed by two storage subsystems with different functions and subjected to different charging/discharging conditions, according to the characteristics of the tidal currents source. A comparison is made between the source of tidal and photovoltaic currents evaluating the benefits of a DBSS microgrid. The Schiffer model to estimate the battery life as a way to evaluate the benefits of the applied strategy was used.