The Gocycle with the battery installed is classed as UN3171, Battery Powered Vehicle.
This can be taken on passenger aircraft but it must be declared, have the correct paperwork and be cleared by the airline.
It is at the discretion of the airline so please check before you travel.
If checking in a Gocycle on a flight we strongly advise packing the Gocycle into the official Gocycle box designed for that Gocycle model. Any other packaging may not sufficiently protect the Gocycle during transit.