Due to the increased brightness of the iFly 740, the battery pack last a little more than 2 hours vs the 720. With Shane's suggestion I added a second battery and taped the two back to back so the charging lamps still appear. I used the 12v OUT of the first battery to connect to the 12v IN of the second battery. From that battery's 12v OUT I connected the power cable to the GPS unit.
I connect the charger to the first battery and turn the power slide switch on. This will charge both batteries at the same time.