> It seems to me that Tesla needs to incorporate some of the ideas from Space-X (in terms of redundancy) into its cars.

The need to continue on to orbit when an engine fails [http://motherboard.vice.com/blog/spacex-s-non-fatal-failure] > The inconvenience of having to get a tow. Cost/benefit tradeoff.

With that said, I see Tesla replacing the 12V battery with a Lithium pack at some point (vs a lead acid battery), not just for capacity but also for deep discharge durability.