On the R-44, don't make "Ext-Power" set to a particular voltage, just set it to "Adaptor". Put a set of fresh/fully charged AA's into the R-44 and plug in your external battery. Now if your external battery should run out of juice, the R-44 will seamlessly switch over to the internal batts and your deck, and recording, won't stop. This is the way I've been using mine for years and it works great.