Power supply apparatuses

A method of operating a battery apparatus, the apparatus comprising a power input, a power converter having an input side and an output side, a battery assembly, a switching arrangement, a controller, and a power output connected to the output side of the power converter, wherein the switch arrangement is configured to be operable to connect the battery assembly to the input side of the power converter for or to the output side of the power converter for battery charging;

• wherein the method comprises the controller operating the switch arrangement to operate in one of a plurality of connection states, the plurality of connection states comprising:
• a connection state which is a first connection state in which the battery assembly is connected to the input side of the power converter and in which the switch arrangement is configured such that the battery assembly, the power converter and the power output are electrically connected so that the battery assembly is to output stored power through the power converter and the power output;
• and
• another connection state which is a second connection state in which the battery assembly is connected to the output side of the power converter and the power input, the power converter and the power output are electrically connected such that the battery assembly is to be charged by power of an external power source connected to the power input.