The roadster battery is built - I believe - with 2200 mAh cells. 2900 mAh cells are starting to be available. Panasonic has said that they will have 4000 mAh cells by 2013. I am actually excited about the prospect of replacing my battery in a few years with something that dramatically improves the car. If 2 new batteries were available for your roadster: 1) A smaller one with the same 53 kWh but weighed 500 pounds ( 400 pounds less ) 2) One the same size with 94 kWh and weighs the same 900 pounds. The 53 kWh battery, because of the reduced weight would increase the highway range by about 7-10% ( I'd call it 240 miles - up from 220 ), and the 0-60 should drop to about 3.5 seconds. The 1/4 mile would drop to about 12.2 seconds from 12.95 seconds. The 94 kWh battery would increase the range to about 400 miles, but performance would be the same. Of course the smaller battery should also cost less. Which would you choose?