It depends on what sort of usage you have with the bookport, and the type of batteries you're using. Reading text gets you the most battery usage. MP3 and other audio files take more power. Also, you get longer usage from regular alkalines than from rechargeables. But I use rechargeables anyway that charge with a quick charge IC3 charger. So there are variables. Lois -- No virus found in this outgoing message. Checked by AVG Free Edition. Version: 7.1.371 / Virus Database: 267.13.13/200 - Release Date: 12/14/2005