Bringing extended range to EV's..... by adding a trailer with a generator set?

  • March 7, 2016
  • Marcel Romijn

At BRACE there are several projects which involve Electric Vehicles or EV. Anyone working on these projects typically moves from a bit skeptical on the large scale roll-out to being close to an EV believer. An EV has many advantages. The big disadvantage remains the driving distance w/o charging. While already on the market we see very decent figures, and knowing that more is to come it will still remain a little bit different to drive an EV than it is for a conventional. Charging will be needed a bit more often which luckily can happen overnight at home as well. We recently stumbled upon some clever solutions involving generator sets to extend the range.

In Europe there are at least two start-up companies (EP Tender from France and Nomadic Power from Germany) that came up with similar ideas: add a small trailer to the EV which holds extra energy. The French approach "holds" the energy by means of a generator set. Both rely on a sort of rental system. EP Tender is rolling out a testfleet in France currently.

An obstacle that BRACE sees is first of all EV regulations such as the ECE100. Charging while driving is in principle prohibited and an EV must be designed such that it is made impossible. Typically this is designed by using the switches in the charge door and/or the charge plug. So it explains why it works to charge while driving; as long as you do not use the charge plug but make an extra high voltage connector.

This brings in an extra concern; both approaches use high voltage 400V DC charging which rules out the influence of the EV on-board charger. This is now an extra connection for which safety must be designed in. No problem in making the connection but without the cooperation of an OEM it can be hard to do it safely and to ensure the Safety Concept of the EV still works properly.

Especcially for the French solution; when adding a gasoline generator set we have exhaust gas pollution again. You could state it is still less than a conventional car however the emissions standards, control measures and lifetime requirements are very different between a gasoline car engine or a gasoline generator set engine. More investigation would be a strong advise to see if this approach really is cleaner. A comparison to Range Extender or PHEV's would be needed.

It can also be considered whether charging a battery while driving is the best solution. Some studies revealed that this approach is less efficient.

Find a paper from the two companies here:
Download PDF

A Dutch start-up came with an "emergency" jerry-can for EV's analogue to the conventional one. It holds 5 Liters gasoline which it converts to electric energy. This setup is designed to charge while standing still at a spot without charging infrastructure. For emergency purposes this type of use of a generator set places less focus on the specific exhaust gas emissions and since the charging occurs while standing still and via the normal charge port many other concerns are taken away as well.

We see a lot in the E-Jerry as, even when never needed brings a bit relaxation knowing that even when running out of a charging infrastructure there is at least a way to get some extra mileage. It's rare use will limit the extra emissions and in terms of safety it acts as a normal chargeing point.

The trailer approach has it's benefits however when a proper fast-charging infrastructure is present (as some countries in Europe already have) there's little point to it. It would be fair if the used generator set would be automotive emissions compliant to really be as clean as possible. If not it just becomes a dirty type of PHEV.


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