A self-contained backup power source such as a battery is provided for components within an electrically powered device such as a storage controller, photocopier or the like, to maintain diagnostic status data and to power a service indicator aid, or diagnostic indicator, such as an LED. A switch selects the backup power source when a primary power source of the electrically powered device is no longer available to the component, such as when the component is removed from the electrically powered device, the primary power source is disconnected as a safety precaution when servicing or replacing the component, or a higher-level assembly, in which the component is provided, is removed from the electrically powered device. The diagnostic indicator may be powered separately from the data storage device.