I ran across a very interesting video courtesy of viewer Brandon Hollinger http://ampREVOLT.com/. Brandon has done a lead acid conversion of a 1970 Saab 96 that looks quite well done for a Pb car. And he's started a LiFePo4 Miata project for someone else.
Jay Whitacre received his Phd in Materials Science in 1999 at University of Michigan Ann Arbor - so he's a lot smarter than I am. He worked for Jet Propulsion Laboratory 2000-2007 mostly on lithium battery projects. Today, he is an assistant professor in Materials Science at Carnegie Mellon university. He's also head of Whitacre Research Group which studies functional materials for electrochemical storage.
The group received a $5 million DOE grant for the development of a Sodium battery using a Sodium Metal Oxide cathode (Na4Nm9O18) with an aqueous electrolyte. These cells are 1.6 volts or thereabouts and a scant 45 Wh per kilogram. But they are totally benign, have a cycle life well over 5000 cycles, and cost about as much as lead acid cells to produce. Because of the low energy density, they are probably not suitable for electric vehicles. But for grid storaage, they are ideal. Inexpensive, rugged, very long lifetimes, environmentally totally benign, easily scalable, and did I mention inexpensive. Like buying lead acid cells that last 20 years and have no lead. The spinoff company is Aquion Energy.
They apparently do not have a web site up but HERE is a bit more about their product development.
In this video, Professor Whitacre addresses a group of EV guys to explain the chemical processes of Thundersky LiFePo4 cells.
The presentation is very interesting and answers a number of temperature questions quite well I thought. Amazingly, at about 1:05 into the presentation he's taking questions regarding Battery Management Systems. And he basically tells this group, who are all totally convinced you have to have a BMS, that essentially NO manufacturer, including Tesla, GM, and Toyota, use a cell level BMS and in fact are moving away from the module management they have now as just too expensive and apparently unnecessary. He stresses EXACTLY what I've been saying, closely matched capacities and string level management.
I found it fascinating. So I thought we'd store the video on our Amazon server and create a blog entry for reference.