Rob, et al, Since my alkaline batteries died, I have been using Ni-MH (nickel-metal hydride) batteries purchased from Radio Shack (~$10.50 for a two-pack). The first set I used had been previously used in a radio, and they were indicating 64% when first inserted into Book Port. they seem to be holding up reasonably well with Beta21 and Beta22 for reading text files. I tried playing an MP3 music file when the battery level was indicating about 39%, and the song did not quite finish before it was interrupted with a low battery message. I forced it to resume playing for the final seconds, and when I checked battery level it was about 6%. Surprisingly, the battery level began to recover with the Book Port not playing any file, and as I checked, it continued to rise until it reached about 39%. I then played a microphone recording of a music file (WAV), and the result was very similar to the MP3 file. The song did not quite complete before the low battery message was announced. This time the level was about 9% when I stopped, but again, it recovered to about 39% with only a few minutes of "rest". Next I tried playing a text file for about 5 minutes straight, and the battery level did not drop any lower than 33%. After I stopped and let the unit "rest", the battery level recovered to about 36%, where it seems now to be remaining with no active use of files. Mike Justice. www.mpnhome.net