Graphene supercapacitors are 20x as powerful, can be made with a DVD burner 
I'll preface this by saying that I want my next vehicle to be electric.Here's my concern with regards to electric cars:  There's a huge difference between failure modes of electric vs. gasoline powered vehicles in crash scenarios.In a great deal of cases a crash with a gasoline-powered car  results in no spills or fires.  No problems.  In a few cases a spill might result.  Fires are only a factor when gasoline vapors are involved.If a pure electric vehicle has a range equivalent to that of a gasoline-powered vehicle, say, 200 to 300 miles, this means that it is storing a tremendous amount of energy.  Also, due to i-squared-c losses it is very likely that the system will be a high voltage system (hundreds of volts).In the case of a bad accident this energy could be released violently. There might come a day when we hear of an entire family electrocuted to death in their car after a crash.  I hope this never happens, but I have a feeling it could.As I see it this is the PR problem with the technology: Huge amounts of energy that could do serious damage if something goes wrong.  In contrast to that, a gas tank is a relatively harmless device.Yes, there are safety measures that can and are being utilized, like fusible links between batteries and intelligent management systems.  Still, it doesn't take much at, say, 500 volts, to cause a lot of damage quickly.  As someone who has worked with and designed very high power DC motor controls and have tested many designs to destruction I have to say that this is an area that really needs to receive a tremendous amount of attention.The last thing the industry needs is the media devoting weeks to cover how a family got fried in their electric car while the fire department was powerless to aid them until the batteries fully discharged (which could take a long time).  That would be a truly horrific sight to behold and a potential industry-killing event.  Close your eyes and imagine that for a moment.  Then imagine trying to convince someone who saw that on TV to buy an electric car.Super-capacitors could help in this regard in very meaningful ways.  If we could get battery packs to be small enough that leaves a lot of room for creating a crash and intrusion protection barrier around the battery.Today battery packs are very large and heavy.  And, while I am sure that a lot of work has gone into safety, they could be made far safer if the batteries had higher energy capacities.The other way super capacitors might be able to help could be as paradigm shift enablers.  Picture the case of not needing a range of 300 miles.  For most of us, 60 miles might be enough.  If that battery pack is small enough gas stations could morph into battery pack swap stations.  The fact that a super-capacitor has a useful life of tens of thousands of cycles means that there would be no concern of receiving someone's almost-dead battery.  The cost of re-fueling would include some amount of money to deal with packs near or at their end of life.  If you did need to go farther maybe cars could be designed with room for a second range-extension pack or some other means to connect a larger battery pack.From a safety standpoint, I want to see the kinds of tests companies like Volvo and Mercedes are known for:  Fling a car through the air and roll it multiple times.  In other words, extreme stuff that is unlikely to happen in most accidents.  After the tests the cars have to remain in a state that is safe enough for egress as well as for rescue personnel to approach, touch and render aid.In other words, electric cars have to be better in terms of safety than gasoline powered vehicles.