Could be. I can tell you from experience (and from the advice of other people) that if you choose a voltage under the "Ext-Power" setting, it will shut down the deck pretty quickly even if you select the lowest voltage (9v). When I run my R-44 off an external power source (DVD battery, Tekkeon, etc) I just choose the source in the menu as "Adaptor" and put AA batteries in the deck itself. That way, the R-44 will just see the external as an unlimited source and, should it run out of juice without me catching it, it will seamlessly switch to the internal batteries and not shut down.