High efficiency SBC NRG+ Low Power battery chargers with three stage IUoU battery charging. With inner mosfet charge separator and differentiated charging for open, sealed, GEL or AGM batteries. Ability of providing full output power with low supply voltage and possibility of using the battery charger as a power supply without batteries. Compatibility with any kind of generator and universal AC supply input with easy connectors. Protections against reverse polarity, overload, output short circuit, output overvoltage and overheating.