How do hybrid cars recharge the battery on highways

The electric part of the hybrid vehicle is only used in town for stop and go or low speed operation. Most hybrids use their gasoline engines for highway driving, and while the gasoline engine is running, it also recharges the batteries.

It depends the hybrid you're driving, but on good hybrids the battery is charged on the highway by the rolling motion of the wheels. It is not enough to power the car using the battery alone, but it is enough to provide enough power that most hybrids still get better highway mileage than their gas-only counterparts. A hybrid battery will virtually never die because there is always something charging it, whether you are braking or just simply moving. The most charge goes to the battery when you are rolling downhill and not pressing on the gas.