The scooter will fly free. You can ride it right up to the door of the plane, where they gate check it. Then walk on or, if you need it, they have a wheelchair narrow enough to fit in the aisle to get you to your seat. At the end, your scooter will be brought to the plane door for you.
You can put the removable basket and charger in a tote bag and carry it on with you. As long as it contains only stuff for your
ECV, or other medicine/medical equipment, that bag is free and does not count against your carry-on baggage allowance.
All of this presumes that you are traveling to a destination in the US. Going outside on a foreign carrier may be different, but here you are protected by the provisions of the ADA.
Allow a little extra time to get through security. You will probably get routed through a special line. They will wipe down your scooter with those explosive-residue detecting wipes. If you can't walk through the metal detector, you will get patted down.
If you have a lay-over they will ask you if you need the scooter in the in-between airport. If you can walk some but not much, you can probably get a ride from one gate to the other in one of those golf-cart things and check the scooter straight through.