It's easy to forget that your handheld computer/PDA (mostly likely a Pocket PC or PalmOS device) can run out of powerpromptly losing all stored data and programs!especially when you're out of the office, and not popping it back into a charging cradle or synch cord regularly.
If your charging cradle feels a little too bulky for your road trip, consider one of the cord-only products, such as Belkin's USB Sync Charger for Jornada Pocket PC, which should charge and synchronize a Jornada PPC from a powered USB port or a car cigarette lighter socket, or try one of TeleAdapt's USB PDA sync/chargers.
Not packing a notebook? Something like Belkin's Compact AC Travel Charger for Dell Axim X5 Pocket PC may offer a smaller AC charger than you currently have.
Some PDAs let you change the batteries if you're packing a spare. Other away-from-power options for PDAs include the following:
For some Palm models, Palm's Power To Go (around $100) will recharge your Palm once, maybe even twice, when you're not even near an outletand you can recharge the Power To Go pack later.
Instant Power's zinc-air "power pouches" are another option. (For details, see the later section "For Cell Phones and PDAs.")
My advice: If you can use a spare battery, bring it on; if not, consider packing an Instant Power pouch along with a charging cable. (And remember to do frequent data backups!)