I'd be happy to respond to that.
From 100,000 feet, if you like, one of the most difficult technical things to do is to store energy. We're really quite good at transforming energy from one form to another, but storing energy is very difficult, as you identify.
I would say you're absolutely correct. Up until about 1992, not very much progress was made on battery storage after World War II. The batteries that people were putting in the very first generations of electric cars were not fundamentally different from the batteries in a World War II submarine. They were very heavy. They had very limited capacity; equally important, although less visible to the user, was that it took a long time to charge them, so this really limited their utility in mobile applications such as cars.
In that time frame in the 1990s and since then, lithium battery chemistry has evolved to the point where it really is quite remarkable. The progress has been quantum since then. When we started AUTO21 in 2001, battery vehicles were not really a big factor, and many people confidently predicted they would never get anywhere. Well, they're starting to come on the market now, and for certain applications, they actually are a pretty good choice for certain motorists for certain kinds of use.
The barrier is simply a scientific progress issue. New battery chemistries are being developed all the time that have higher energy capacity, can accept a charge more rapidly, and are lighter in weight. The big problem is cost and overall capacity. That's why, for instance, we have concentrated so strongly on lightweighting the car; lightweighting really is a fundamental technology.