Scooters use one of three types of batteries:
- Sealed Lead Acid (SLA)
- Deep Charge Marine (DCM)
- Lithium Ion
For purposes of this discussion, the first two kinds of batteries are identical in terms of how airlines treat them. These first two types of batteries are certified for travel on commercial airlines and other vessels of travel. For aircraft, they fall beneath Title 49 CFR173.159. This attachment contains the text of the FAA regulations for traveling on aircraft with Sealed Lead Acid batteries.
Lithium Ion Batteries
A small number of scooter models, usually the folding type use Lithium Ion (LiOn) batteries. Because unlike the first two types of batteries, they do not come in standard sizes and because there have been issues of heat and fire with lithium ion batteries (mostly relating to smartphones), airlines are much more cautious about allowing lithium ion battery packs on their aircraft.
First of all most, if not all airlines will require that lithium ion battery packs be removed from the scooter and carried on-board the aircraft in carry-on luggage; they may not be carried in the plane's baggage compartment. Secondly, it is entirely the airline's prerogative as to whether they allow such batteries at all.
In the case of any of the above three types of batteries, you'll want to contact the airline in advance of travel, explain what you'll be travelling with and confirm that you have all of the proper documentation with you when you arrive at the airport.
By the way, if you haven't purchased a scooter yet and are considering buying one for travel via air, please do think twice. Folding scooters are notoriously delicate and subject to damage by baggage handlers. Transportable scooters that disassemble are a much better choice. Airlines are accustomed to them and they're very resistant to rough handling. You would ride to the gate and check it there as you would a wheelchair, baby stroller, etc.