Batteries

Dry Cell Batteries
Any Alkaline, NiCad, Nickel Metal Hydride (NiMH), Silver Oxide and Carbon Zinc batteries similar to those used in flashlights or commonly used electronic devices are allowed onboard the aircraft.

These items must be securely installed in equipment or have exposed terminals protected in a manner to prevent short circuit. Electrical tape, individually bagging batteries in sealable plastic bags, or plastic covers designed to protect the terminals from short circuit would all meet this requirement.
Lithium Batteries

Updates from the Transportation Security Administration on Lithium Batteries in Checked and Carry On Baggage

Spillable Wet Cell
Wet cell batteries (like most car or motorcycle batteries) are not allowed in checked or carryon baggage.

The only exception is for a Customer’s wheelchair or assistive device. If your wheelchair/assistive device is powered by a spillable wet cell battery, the battery will be removed from the wheelchair and transported in a special battery box. To allow for proper handling, please arrive at the gate one hour prior to departure and notify the Customer Service Agent on duty that the battery is a wet cell spillable battery.
Nonspillable Wet Cell
Equipment containing nonspillable wet cell batteries (gel cell or absorbent glass mat) can be carried as cargo (Shippers must meet all applicable security requirements). The equipment with the battery installed must be protected from short circuit and securely packaged. The package must be marked "Nonspillable" or "Nonspillable Battery."

If you are traveling with a wheelchair or other assistive device that has a nonspillable battery, it is important to note that the battery will be disconnected at the quick disconnect, securely attached to the wheelchair/assistive device during transport, and reattached upon arrival at the destination.