The transportation sector is responsible for approximately 25% of greenhouse gas emissions and for hundreds of thousands of deaths from pollution every year. The need for zero-emission vehicles (ZEVs) is obvious and urgent. The electric vehicle (EV) market continues to develop, but the range and refueling time of EVs make the widespread adoption of these ZEVs difficult. Most vehicle owners want to be able to take long trips, and the EV limitations are major hindrances to a faster uptake: The current new vehicle market share of EVs is under 1% in the U.S. There are plug-in hybrid electric vehicles (PHEVs) on the market with an internal combustion engine (ICE) range-extender integrated into the vehicle. However, the impact of the cost, complexity, and weight of the on-board range extender is excessive, and is often put into use only a small percentage of the overall driving.

The EP Tender (EPT) range-extending trailer (Patents: WO2013132468, EP2666704) is an off-board electricity source that uses gasoline to fuel an ICE and mated electric generator to supply the batteries and electric motor of the EV with electricity, thus controlling the depletion rate of the batteries. The EPT trailer is towed by the EV during a long-distance trip, and the combination provides the optimal solution between an EV, a PHEV, and a conventional vehicle. The range and refueling are the same as for a PHEV or conventional vehicle, and when longer range is not required, the advantages of an EV, namely home/work refueling, quiet driving, and ZEV operation, are not compromised by a rarely used, expensive, and heavy on-board range extender that needlessly adds to the complexity.

There are three requirements for the success of the range-extending trailer concept:
1. Ease of use: Able to be attached quickly by a non-expert without a large amount of required force; self-steering when backing up to avoid requiring expertise with trailer driving
2. Safety: Crash protection of the fuel tank; no compromising of the vehicle’s crash- or road-worthiness
3. Availability: Pick-up/drop-off at entries/exits of freeways; on-line booking, and 24/7 access

The EPT range-extending trailer has been designed with the first two conditions in mind and the prototype has been shown to succeed on all fronts. The business case to meet the third requirement is currently being developed that will be flexible enough to function in cities around the world.

The current version of the EPT system uses an ICE and gasoline tank. While not being a ZEV design, the ability for more prospective vehicle purchasers to select an EV based on the no-compromise of an EV paired with the EPT system would already reduce vehicular emissions by 90% or more. Generation II of the EPT system will substitute either a battery pack or a fuel cell and hydrogen tank so that the entire system will have zero emissions at the tailpipe.

The freedom of movement that the EPT range-extending trailer allows will enable dynamic growth in EV uptake and dramatically reduce the harmful emissions originating from the transportation sector.