Electric vehicles drive further thanks to supercapacitors

October 04, 2013 // By Dr Peter Harrop
Supercapacitors are increasing the range of electric vehicles in several ways and by doing so they are hugely increasing the addressable market for those vehicles, lasting for the life of the vehicle regardless of how many cycles are endured.

Conventional vehicles that switch off when they stop, however briefly, are called stop-start or, misleadingly, micro hybrid (because they do not usually provide electric traction and they are not therefore a form of electric vehicle). The fuel saving, or increase in range, is 5-8% and the response in the marketplace is dramatic because this is both an easy way of meeting ever tougher pollution regulations and providing a valued sales proposition.

Even manufacturers of mining, material handling, agricultural and earth moving vehicles are now incorporating the technology which is mainly based on advanced lead-acid batteries, increasingly with a supercapacitor added so they do not fail to work in cold weather or when many stops occur.

Maxwell Technologies has sold over 600,000 supercapacitors for this use, mainly in cars, and followed on with a complete conventional vehicle battery replacement consisting of supercapacitors across a smaller lead acid battery with both a cost and a performance advantage claimed. Use of a lithium-ion battery is another option for stop-start but that has cost issues.

 

Increasing range by battery deep discharge

What if we could gain another 5% in range for the vehicles of the future? These vehicles use lithium-ion traction batteries in pure electric or hybrid powertrains. Years ago, one demonstration of a supercapacitor in action used to be running a battery-driven toy until it stopped; then putting the supercapacitor over the rechargeable battery makes it run again. The supercapacitor enables more of the battery charge to be used by maintaining the necessary voltage. However, since then it has been commonly taught that this is a curiosity and insignificant with passenger vehicles. At other times it is taught that vehicle range can be increased in this way but such deep discharge intolerably shortens the life of the lithium-ion battery. Nonetheless, the supercapacitor and automotive industries are revisiting this "impossibility". For example the publicity for the Bollore Bluecar in France claims that the