Current car batteries usually take several hours to fully charge, so Battery Electric Vehicle (BEV) usage is limited to commuting and other short trips by the battery range.
To extend the range, some BEV manufacturers add a highly efficient Internal Combustion Engine (ICE) powering a generator when the batteries are low. Such vehicles are called Extended-Range Electric Vehicles (EREVs), as well as Range-extended Electric Vehicles (ReEVs) or Series Plug-in Hybrid Electric Vehicles (SPHEVs). Several models are to be commercialised as of 2011 (including GM's Chevy Volt and Opel Ampera).
For short distances, which represent about 80% of cars mileage, EREVs can operate in full electric mode and are therefore as clean and energy-efficient as BEVs (unlike parallel hybrids).
For longer distances, which represent only about 20% of cars mileage, EREVs operate in generator mode, in which they consume noticeably less fuel than conventional Internal Combustion Vehicles (ICVs) because:
The engine of an EREV is significantly smaller than of a conventional ICV, because EREV engine must only cover average power needs (peak power being delivered by the batteries), while ICV engines also must cover peak power surges (accelerations).
The engine of an EREV operates at a constant, highly efficient rotation speed, while the engine of an ICV often operates at low or high rotation speeds at which its efficiency is low.
We do promote EREVs as long as their battery power is sufficient for most commuting and other short trips, for which they will run on batteries (because it is much cheaper).
We recommend that the minimum battery power should allow an effective electric range of 50 to 100 km (75 to 150 km nominal).
In a more distant future, two cleaner technologies should replace EREVs:
Ultrafast charging BEVs: Ultrafast charging stations, charging BEV batteries in less than 15 min, could spread on road networks. This would allow BEVs to charge nearly as conveniently as fuel cars and make them competitive against EREVs for long trips.
Fuel Cell Vehicles (FCVs): they are also very clean and can be refuelled quite fast. The could thererefore compete against EREVs in the future.
While FCVs are likely to become the winning technology in some transport applications, it is not yet clear which technology will win the passenger car market. It will largely depend on the cost of the vehicle and of the refuelling infrastructure (fast charging stations versus hydrogen refuelling stations). More...
