Genset Trailer: I had no idea these existed:
A genset trailer is a range extending device for use with battery electric vehicles consisting of an internal combustion engine and an electrical generator(collectively called a genset). They run on traditional fuels such as gasoline or diesel and are sized to provide the continuous power requirements for the vehicle they are used with.
Related: a pusher trailer, which strikes me as being hella dangerous. The steering dynamics of that thing under power must be…remarkable.