The Tesla Motors paper at AABC, “Development of Advanced Li-ion Battery Pack for EV and PHEV Applications,” from JB Straubel, Tesla CTO, had several gems in it.

Here are the basic numbers for the pack and motor:

--Well-to-wheel efficiency >135 mpg

--56 kWh

--Total pack energy density: 125 Wh/kg, fully tested, including vents, cooling, etc.

--50 Wh/kg is the overall energy density for the car itself as it rolls off the line.

Straubel made the point that lithium ion cell pricing has improved by a factor of ten over the past ten years when you factor in the improvement in energy density and the drop in cell price. Compare $/cell vs. $/gallong of gas, and you have a very attractive lithium ion pricing figure for the near future. (I wasn’t at the tutorial on Monday, but I heard that the conference organizer, Dr. Menahem Anderman, was predicting the adoption of lithium ion batteries in autos by 2010.)

As you would expect, Straubel made a strong case for the use of standard, existing-technology lithium ion cells as the building block for EV (electric vehicle) batteries: “It’s easy to jump to the panacea of the new technology, and forget the lessons that have been learned in the past.” And we do have ten years of a learning curve on Li-ion. Thermal runaway is one of the scary aspects of Li-ion, and a catastrophic failure is easier to handle with small individual cells than with a single large prismatic battery.

Here are the steps Tesla takes to approach battery safety:
1) Use good cell manufacturer – Don’t just believe a vendor’s claims that it meets the 1642 safety standard. What is the vendor's record? How long has it been in business?

2) Prevent thermal runaway. 

4) Monitoring and protection. (With an emphasis on fuse design).

5) Extensive testing. (Specifically of the fuse design.)

6) 3^rd party reviews: Consultants, professors – get some outside eyeballs involved.

Sadly, the paper didn’t go into any specifics of just what Tesla’s battery pack secret sauce is. And attendees I spoke with who had signed a non-disclosure with Tesla hadn’t gotten any additional information about its battery pack design secrets. Maybe that’s where Tesla Energy comes in.