They're re-powered by the gas engine and by generators activated by braking. The gasoline engine is the main power. The electric motor kicks in when passing or accelerating hard, and gets the vehicle rolling from a dead stop when the gas engine is off. The two power plants are pysically merged into the single IMA system, and they drive the front wheels. Batteries for the electric motor are recharged by the gas engine and when braking.
Main power is the electric motor.
The gasoline engine comes on when more power is needed, and to recharge the batteries when low. The batteries also are recharged when braking. The gas engine provides the main power, and drives the rear wheels. The electric motor drives the front wheels. It kicks in when more power is needed, and when traction is poor, giving the vehicle four-wheel drive.