yes, you can trickle charge or jump from under the hood. don't trouble yourself climbing into the back.
2010 Manual says (p. 30): As the gasoline engine or regenerative brake charges the hybrid battery (traction battery), the battery does not need to be charged from an outside source. However, if the vehicle is left parked for a long time the hybrid battery will slowly discharge. For this reason, be sure to drive the vehicle at least once every several months for at least 30 minutes or 10 miles (16 km). If the hybrid battery becomes fully discharged and you are unable to jump-start the vehicle with the 12 volt battery, contact your Toyota dealer.
