A portable electronic device, such as a fluid infusion device, obtains its operating power from a primary battery and a secondary battery. The primary battery may be a replaceable battery, and the secondary battery may be a rechargeable battery that can be charged with the primary battery under certain conditions. The device utilizes a power management scheme that transitions between the primary battery and/or the secondary battery to prolong the useful life of the primary battery. The device may also generate an intelligent battery life indicator that displays an accurate representation of the remaining life of the primary battery.