mhvuWell, my mother's previous keyboard had a rechargeable battery and it died after 3 years. Her's has no access to the rechargeable battery, so replacement is not so simple, and the manufacturer no longer supports that model. With this one, you can use rechargeable AA batteries, so you won't have the same issue.
dvorcolA built in step up converter circuit solves the voltage part but the capacity would be an issue then. Still, I think two AA cells would be enough to power the device for a reasonable time if designed properly.