In general, techniques are disclosed for efficiently transferring power from a portable power bank to an electronic device. More particularly, a disclosed power bank incorporates a switching mechanism capable of routing battery voltage (novel) or a stepped-up voltage (e.g., from a boost regulator) directly to a common portion of an output connector. In addition, electronic devices as described herein also incorporate a switching mechanism to allow them to accept direct battery output (novel) or a stepped-up voltage at a common portion of the device's connector (e.g., a USB connector). When used in combination, the disclosed portable power bank can transfer power to the electronic device with no more than half the loss attributable to voltage conversion operations of the prior art.