Then the battery gets too heavy. Twice the battery would not equal twice the range as the added weight would consume much of the added power. Connecting in series would add voltage or speed but not neccesarily range.
Battery technology is still mundane and the limiting factor. This compromizes to acheive a vehicle that would work in many lifetstyles.
40 miles on a charge gets most of us to work and back. There is also the capability to charge at work if employers provide the access. So the average car buyer would have to make very limited changes to their driving routines of today.

Until automakers can pack more potential in less weight and space, there is going to be a limit on range. It is what put gas over electric in the past as electric cars were always fast.

There is , of course, the other issue. Cost. Twice the battery is more than twice the cost. To get range without on board charging requires a deep cycle battery system.
A good deep cycle forklift battery is $3,600 or more and weighs 1,100 lbs. With a service life of 1,100 cycles thats 3 years of driving every day. Where as a smaller shallow cycle battery pack would be about $1,200 and have 2,300 or more cycles lasting 6 to 8 years.
In pratice the Chrysler concept should have lower initial cost, lower vehicle weight, and a longer service life. And it is a far, far simpler system than a hybrid.


roadster with a stick