I did the last update on mine with only ignition on and it works.
But I would really recommend to connect a intelligent charger with around 10A or higher as all electronics in the car use a bit when ignition is on.
Used a Ctek MXS 25 when I updated.
RS Edition , built 13/9-18 , and delivered 9/11-18
Mountune: R.M.M. / Roll restrictor, PTU Brace, Breather plate & Re-circulating valve.
Mishimoto: I/C + pipe kit, Catch can, Blue Aluminum expansion tank & Performance Air intake (with bigger AEM filter in place).
UPR Products: Baffled one-way valve cover crankcase breather kit & 0-100 psi Billet Check valve.
Ford Performance / Remus cat back Exhaust
HJS 200 cell Euro 6 downpipe & COBB Turbo Blanket
Turbosmart IWG75
FSWERKS short shift kit.
quantiTEC Smoked rear lights.