Hybrid cars work using a battery-powered electric motor and a gas-fueled internal combustion engine. They automatically switch between the motor and the engine.

While they are somewhat similar, hybrid semi-trucks operate on a grander scale and need to maintain efficiency whenever possible for long haul trips.

A series hybrid only receives mechanical power from the electric motor, which gets its energy from a battery or a gasoline-powered generator. The electric motor and internal combustion engine can ...

But hybrid engines have to work hard, very hard, to maintain that unique balance of electrification and efficiency.

Added rear weight has made the cars a handful, say some who are slow to give the new package a ringing endorsement.