Thursday, August 17, 2006

Teslamotors car

The premise:
Electric cars are potentially sustainable, can use any source of fuel to make the energy, and are economically viable per mile. has created a sports car that uses lithium-ion batteries to power their EV. Original Article
Stated facts:
0-60mph in 4 seconds
250 mile range
2.53km/MJ electric performance
over 100,000 mile or over 5 years before replacing batteries
$7 per 4.6Wh li-ion battery (wholesale, 100 unit, small size)

This all looks incredible, the holy grail of electric vehicles with high range, great power, etc. $90k for a sports car puts the EV out of most consumers reach. The next model is part of their overall plan and will cost about half as much. The third model will have even lower costs. So far so good. But... you need to replace the battery. Time to do some math.

Calculated facts:
45KWh battery storage
$67,000 wholesale small unit per battery pack (This is just a comparison, because isn't announcing how much battery replacements cost and they haven't mentioned it anywhere.)

Stipulated figures:
$15,000 estimated replacement cost for the 45KWh battery pack on the CEO's corporate blog as a comment. $15k seems reasonable considering the economies of scale (1/4 for large consumer with a big battery).

Every 5 years you need to pay $15k? For 100,000 miles that is 15 cents per mile. If gas is $3 per gallon, and you get 30 miles to the gallon, you are spending $4.50 in battery costs to go the same distance. The power may only be 5 cents per mile but the battery costs 15 cents per mile. Total cost would be $6 of electric-battery compared to $3 per gallon of gas, 30 mpg.

According to battery experts you have to pay for those batteries whether you drive or not. Keeping them cool will help, but they still degrade. The same blog comment quoted earlier claims that the batteries are in a sealed temperature controlled environment. Increasing the efficiency 10 fold using nanotechnology would help quite a bit, but there may be extra cost for those batteries. If we estimate double the cost, 5x the lifetime (they may have estimated against typical use, and not controlled environment use), that puts the cost of the battery at 6 cents per mile, lasting 25 years or 500,000 miles using the above numbers. (11 cents per mile total, same as paying $3.30 per gallon 30mpg at the pump.)

Maybe in 5 years we'll have a nice middle ground between cost, durability and range. Perhaps that middle ground is 20 year batteries, 500,000 miles, $5000 cost, 150 mile range, with 30 minute recharge. If the electricity costs are 2 cents per mile, that brings the cost per mile to 3 cents. Compared to the $3 @ 30mpg tank of gas, that would $0.90. Drive for 2 hours, stretch your legs or eat for 30min, back in the car for another 2 hours.

My estimate based on the numbers provided, is that electric vehicles cost too much in batteries. Hydrogen costs too much electricity and storage (price is coming down, storage is a challenge being handled), and ethanol is rarely a net positive producer (especially when the fact petroleum based fertilizers are used is included).

What transportation do I recommend for daily commuters? Same as Bush Birth Control: Don't. Live where you work, walk or bicycle, build smaller more compact cities, and ship cargo by electric train. If we take trips, use fast electric trains (150-200 miles per hour, no time spent circling). I'll post details about other transit soon.

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