An uninterruptible power supply system comprising: an input configured to receive AC input power; power converter circuitry coupled to the input and configured to convert the AC input power to a first DC power, and to convert a second DC power to the first DC power; an output coupled to the power converter circuitry and configured to be coupled to a load; a battery pack including at least one battery, the battery pack being configured to provide the second DC power; a power relay mechanism coupled between the power converter circuitry and the battery pack, and arranged to selectively move between an open position and a closed position, the power relay mechanism coupling the battery pack to the power converter circuitry when in the closed position and isolating the battery pack from the power converter circuitry when in the open position; control circuitry communicatively coupled to the input and the power relay mechanism and configured to: provide a first control signal automatically to the power relay mechanism in response to determining that the AC input power at the input changes from being unacceptable for use in providing the first DC power to being acceptable for use in providing the first DC power; and monitor a safety condition associated with the UPS system and provide a second control signal automatically to the power relay mechanism in response to detecting an unsafe state of the safety condition; wherein the power relay mechanism includes a motor actuator coupled to the control circuitry the motor actuator being responsive to the first control signal to change the power relay mechanism from the open position to the closed position and being responsive to the second control signal to change the power relay mechanism from the closed position to the open position. an input configured to receive AC input power; power converter circuitry coupled to the input and configured to convert the AC input power to a first DC power, and to convert a second DC power to the first DC power; an output coupled to the power converter circuitry and configured to be coupled to a load; a battery pack including at least one battery, the battery pack being configured to provide the second DC power; a power relay mechanism coupled between the power converter circuitry and the battery pack, and arranged to selectively move between an open position and a closed position, the power relay mechanism coupling the battery pack to the power converter circuitry when in the closed position and isolating the battery pack from the power converter circuitry when in the open position; control circuitry communicatively coupled to the input and the power relay mechanism and configured to: provide a first control signal automatically to the power relay mechanism in response to determining that the AC input power at the input changes from being unacceptable for use in providing the first DC power to being acceptable for use in providing the first DC power; and monitor a safety condition associated with the UPS system and provide a second control signal automatically to the power relay mechanism in response to detecting an unsafe state of the safety condition; wherein the power relay mechanism includes a motor actuator coupled to the control circuitry the motor actuator being responsive to the first control signal to change the power relay mechanism from the open position to the closed position and being responsive to the second control signal to change the power relay mechanism from the closed position to the open position. provide a first control signal automatically to the power relay mechanism in response to determining that the AC input power at the input changes from being unacceptable for use in providing the first DC power to being acceptable for use in providing the first DC power; and monitor a safety condition associated with the UPS system and provide a second control signal automatically to the power relay mechanism in response to detecting an unsafe state of the safety condition; wherein the power relay mechanism includes a motor actuator coupled to the control circuitry the motor actuator being responsive to the first control signal to change the power relay mechanism from the open position to the closed position and being responsive to the second control signal to change the power relay mechanism from the closed position to the open position.