A conversion circuit device for connecting lithium based batteries to a standard inverter/charger for lead-acid batteries and an Uninterruptible Power Supply (UPS) system for homes and facilities comprising a standard inverter/charger for lead-acid batteries, at least one lithium based battery, and a conversion circuit device connecting the at least one lithium based battery to the standard inverter/charger; the conversion circuit device translating the state of the at least one lithium based battery into signals that correspond to the state of a lead-acid battery.