A. Most mobile devices use lithium ion batteries, which don't suffer any ill effects from constant charging. However, in general, it's best to keep the battery charged whenever possible. If you own a Compaq iPAQ series Pocket PC device, the battery will eventually die after a few years and you'll have to send the device to Compaq for repair. If you're still in the market for a PDA, consider the new Hewlett-Packard (HP) Jornada Pocket PC device, which lets you purchase spare batteries.