Recently, maximum power point trackers (MPPTs) that based on single variable (IPV or VPV) have a great attention. That is due to their simplicity and easiness in implementation, when compared to the other tracking techniques. In this paper, two methods have been proposed to design a variable step size MPPT using only a single current sensor for stand-alone battery storage PV systems. These methods utilize only the relationship between the PV array measured current and the converter duty cycle (D) in order to adapt automatically the step change in the duty cycle to reach the maximum power point (MPP) of the PV array. A comparison has been held between the proposed methods to investigate their performance in transient and steady state as well using PSIM software. Furthermore, a hardware implementation for one of the proposed methods has presented using field programmable gate arrays (FPGAs) to verify the performance of the suggested schemes.