garmin GPSMAP 62st

Hey all First post here as well. I have just purchased a new garmin gpsmap62st and being a seasoned garmin user i have a question in regards to a usb connection. With my previous units 60 cs and 60 csx when i plug it into a power supply with the usb cable wether it be a computer or a universal usb adapter the backlight would come on full power and the unit would stay on and not use the batteries, this was great for when it was used in a vechile or on my quad. sadly with this new 62st which is the new version of the 60 series it goes straight to usb connected and i cannot do anything but transfer files back and forth. The unit will not power on when it is plugged in. In my mind this is a big fail for the new series and i cant believe they would not include this feature. Just wondering if anybody out there has any experience with this either with this unit or others.

Thanks Trail