Disclosed herein is an embodiment of a charger having a power printed circuit board (PCB) that enables an alternating current (AC) power to flow into a self-contained automatic battery charging system. A first switchmode converter converts an AC input power into a direct current (DC) power thereby to provide an active power factor correction to obtain an improved power factor. The first switchmode converter comprising a high frequency isolation transformer which provides an electrical isolation between a primary circuitry and a secondary circuitry of the self-contained automatic battery charging system. A second switchmode converter connected to a DC output from the first switchmode converter regulates system output voltage and limits system output current to an electrical load. The DC output is connected to a battery and/or another electrical storage device to be charged and/or to a parallel-connected DC load to be powered. An optional accessory PCB is electrically connected to the power PCB, and they are housed in a same chassis or enclosure. The optional accessory PCB provides optional features including an LCD, alarm output relay(s), and/or a controller area network bus (CANbus) interface. Other embodiments are also disclosed.