A power system comprising: an electrical power bus; one or more loads (20) electrically coupled to the electrical power bus; a fuel cell (10); a DC-DC converter (14) electrically coupled between the fuel cell (10) and the electrical power bus; a battery (34); a switch (38) electrically coupled between the battery (34) and the electrical power bus; and a power system manager (22) configured to control operation of the switch (38); wherein the switch (38) is switchable between a first state and a second state; the first state of the switch (38) is such that the battery (34) is directly connected to the electrical power bus such that the battery (34) provides electrical power directly to the electrical power bus; and the second state of the switch (38) is such that the battery (34) is disconnected from the electrical power bus.