Highway Driving Consumption
To fully understand the range problem of modern electric vehicles, you have to comprehend the energy consumption circle. The advertised range that many manufacturers brag about is the average or city driving figure. However, the highway range is much smaller, sometimes up to 50 percent less (via Bloomberg).
The reason is that electric vehicles get a lot of energy from regenerative braking, which is the process of getting some power back from stopping or coasting. During city driving, you use your brakes a lot, which reduces your energy consumption. However, while driving on the highway, there is far less or even no braking, so the batteries drain quickly.