I drive it all the way down to the aircraft door. Put the charger, which is in a pack attached to the back of the seat, in the basket and then remove the basket and put it inside a cloth tote bag. (I have been asked a few times if I could walk down the jetway to the aircraft which would make it easier for them to get the
ECV to the plane. I was still preboarded.)
Normally I will walk up the jetway and tell the gate agent I am waiting for my ECV so when it is brought up they don't have to get it to the aircraft door.
And I do take my key with me.