Changed my mind and decided to try the Map Update in Ignition Mode II. But when I plugged my battery charger I could hear a constant wine under the hood. Not sure if its the fuel pressure pump or something and I don't know if it runs while the engine is running or only for start up...I got the update done in Ignition Mode II. Obviously I won't try this with the map update.
So I switch to Mode I instead. Went allot faster than expected as I only had to re-open the driver door and close it 4-5 times to get the Sensus to re-start. It detects the usb key and continues without any intervention. Has a nice progress wheel on the screen with a percentage completed in the middle. After it 100% completed it says I have to leave the car to finish the installation. Strange way of putting it. Basically it needs a reboot. So I put the ignition in Mode 0 and back to I and Nav is updated.