A system which enables battery powered devices such as notebook computers to efficiently charge smaller mobile devices such as music players, cell phones and PDAs using the power signals provided over their data connections is made more efficient by ensuring that the power to the small mobile device is not interrupted should the notebook computer otherwise go into a standby or low-power state. The presence of the small mobile device is known and any power-down capabilities of the notebook computer are limited, at least for the period where the small mobile device is being recharged. This detection can be done at any of the levels of software present in the notebook computer. This charging and not powering down can be further optimized by determining the particular device and its charging requirements or by having the device provide feedback as to its charge state.