I’ve assembled a compact mobile setup, comprising of an FT817 (plus CW filter), LDG qrp auto ATU and a Watson Multi-Ranger antenna.  Everything is powered from a small lead acid battery which is charged using a solar panel.  This, and the ATU etc lives in a plastic stacker box for easy removal from the car.

It seems to work ok as the photo below is W3LPL on 15m just after I worked him with 5w during the ARRL DX CW contest from the driveway.

W3LPL on 15m