A “Versatile Power Stack Unit” (VPSU) for controlling electrical devices such as motors for electric vehicles is disclosed. The VPSU uses a DC/DC buck-boost converter that generates output voltage. By varying the voltage according to need, the system can maintain a Pulse-Width Modulation duty cycle of 50% without introducing any ripple current or voltage into the batteries or system, while minimizing losses due to internal resistance. Any number of VPSUs can be connected one to the other in order to provide the voltage and current needed to power the electrical device. Not only does the VPSU minimize ripple current and losses due to internal resistance, but it enables recharging at low voltage and according to the needs of small numbers of batteries with minimal temperature rise during the charging, thereby extending battery lifetime and improving battery performance.