Subtitle: That’s Kokum, Not Hokum, Lutz Baiters
As previously noted, Maxwell Technologies and Argonne National Laboratory have been investigating combinations of batteries and ultra capacitors. Green Car Congress now reports that General Motors is “actively exploring” the concept, which is especially suited for the EREVs (Extended Range Electric Vehicles) “because of the combined requirement for high energy and high power.”
General Motors had indicated previously that their concept vehicle, the Volt, would an EREV. During a recent presentation at an AABC (Advanced Automotive Battery Conference) in Tampa, Florida, Dr. Mark Verbrugge, Director, Material and Process Labs at GM’s Tech Center, said that GM is testing a proof of concept system consisting of 6 100F Nesscap supercapacitors and two Kokum high-energy lithium-ion batteries.
Initial results from General Motors tests show improved power delivery from a combination of 6 100F Nesscap super capacitors and two Kokum high-energy lithium-ion batteries compared to two conventional Li-ion battery systems (Supercap-Li-ion combo is the green line). (Note: Although contraindicated, no DC/DC converter was used in order to keep complexity down.) The tests were conducted at lower battery surface temperatures and testers noted a slight sacrifice in energy density.
AG readers may recall that researchers at the Electric Vehicle Institute at Bowling Green State University developed and patented a supplemental, electric drive that uses ultra capacitors to complement an existing propulsion system. Nesscap super capacitors were in the proof of concept transit bus developed for NASA. More recently, implemented there have begun pilot projects with Maxwell ultra capacitors helping to power transit buses. However, this has been with super capacitors alone rather than a combination. Super capacitors alone have also been proved on the race car track.
On the other hand, AG readers may recall that PML Flightlink has tested a combined system in a passenger car. And, more recently, AFS Trinity Power Systems of Bellvue, Washington, has tested a converted Saturn Vue. Not only was the AFS test vehicle a flex-fuel, plug-in, the energy storage system was a combination of ultra capacitors and standard, deep-cycle batteries.