Apparatus for delivering power from a battery node of a battery to an output node, the output node coupled to an analyte monitoring device, the apparatus comprising: a slow charging path between the battery node and the output node; a fast charging path parallel to the slow charging path, the fast charging path switchably coupled between the battery node and the output node; and control circuitry configured to: selectively couple the fast charging path between the battery node and the output node to allow faster transfer of charge between the battery node and the output node than the slow charging path.