Laptops, cellphones, cameras, two-way radios, PDAs, iPods, camcorders: Most of these consumer electronics are powered by lightweight, rechargeable lithium batteries. The batteries are the subject of new U.S. Department of Transportation rules that went into effect January 1.

Briefly, most lithium batteries are allowed on flights when installed in electronic devices. However, spare batteries are no longer allowed in checked baggage but can be placed in carry-on bags if packed properly.

However, it gets complicated, with lithium quantity limits on spare and installed batteries. The DOT Web site, http://safetravel.dot.gov, has a detailed chart explaining the new rules and information on how to safely pack spare batteries.