There are four important factors for the improvement of the battery:<p>1. production cost
2. capacity
3. charge rate
4. life span<p>Double any two of these and all other fuel sources are done. Double any three of these and its a transportation revolution.<p>Certainly doubling two of these is possible within the next 10 years (assuming the fuel cartels to not succeed at sabotaging the R&D). So I fully agree with Elon, Hydrogen is a waste of time, money and ... wait for it ... energy.