I use a Scosche FM transmitter to send the music from laptop to shop. Transmitter uses two AAA batteries, which last for over 30 hours of play. Take them out and pop them into charger, and over nite they are ready to go. Use AA in WorkTunes in shop, also rechargable. A set of four of either size is about $7.00. So only after a couple recharges, I'm ahead of the game as compared to standard batteries. The NMH come in two different capacities (700 & 900 mah for the AAA, and 2000 & 2200 mah for the AA sizes.) I keep a couple sets charged and ready to go, so as to not lose music. Being NMH, they don't self discharge like Nicads do.