If you are traveling with batteries, especially on a plane, make certain that they are installed in your device and that you carefully package spare batteries.
Of course it is permissible and safe to take battery operated devices on a plane as long as they are safely packaged. These items include cell phones, cameras, notebook computers, camcorders, various devices for entertainment, equipement needed for medical reasons, battery operated shavers and other personal hygeine devices, and so forth.
Lithium Ion Power Tools
As per Federal regulations, "airline passengers who carry batteries or electrical devices in carry-on or checked baggage are responsible for ensuring appropriate steps are taken to protect against dangerous levels of heat that can be generated by inadvertent activation or short-circuiting of these devices while in transportation".
It is recommended by the Department of Transportation that you pack spare batteries in carry-on baggage. Potential fires are easier to detect in the passenger compartment of an airplane and flight crews have fire extinguishers in the event of a fire involving batteries.
Batteries are designed to generate an electrical current and transmit power through terminals made of a conductive metal. You should effectively isolate spare batteries from contact with each other and other objects.
Also you should note that there have been fires of notebook computers caused by defective lithium ion batteries. Major notebook computer manufacturers have recalled lithium ion batteries because of fires and overheating due to production defects.
Finally, always engage the trigger lock when traveling with batteries installed in cordless power tools. Of course, you should lock any device that has a locking mechanism and you should travel with tools and devices in their case.