Not Driving Hybrid for Extended Periods

It might be a good idea to pull the orange plug on top of the High voltage battery during that time. The 12V battery will slowly drain also so I would put a trickle charge on it about 12 hours before a restart and putting the orange HV battery plug back in. Don't disconnect the 12V battery and leave the HV battery plugged-in because the PCM may not shutdown the 12V relay system and the HV battery will continue to drain through the DC/DC converter. Some posters have reported the HV battery draining with the 12V battery ground disconnected while working just a few hours on their radio. I read in the PCM/ED manual that the PCM needs to properly shutdown the relays and it needs the 12V battery connected to do that. An example of how long power is supplied is when you remove the key the radio and dome lights will work for ten minutes. The radio will stop working when you open a door but the relays have not shutdown yet. If you disconnect the 12V battery the PCM has no way to shutdown the relays. If the HV battery is still plugged-in, power will drain through the DC/DC converter till the 12V battery is reconnected and the relays are properly shutdown by the PCM. The '09 FEH may have a limit the HV will drain down because Ford removed the HV jump start button on that model. At any rate, no need to take a chance.