Challenges Loom on Tesla's Model S Project
The electric vehicle's 300-mile range and $49,900 price tag calls for smart engineering and innovation
Charles J. Murray, Senior Technical Editor -- Design News, June 24, 2009
Battery experts said last week Tesla Motors' proposed 300-mile, seven-seat electric vehicle (EV) will serve as a stiff test of EV technology, calling on engineers to employ the best batteries and lightest, strongest materials available.
Model S, which will roll out in 2011, is raising hopes in the electric car community because it offers a huge increase in driving range for a proposed cost of $49,900. Moreover, expectations for the vehicle soared even higher this week as Tesla received $465 million in low-interest loans from the U.S. Dept. of Energy, $365 million of which will be applied to the Model S production engineering and assembly.
Still, the challenge facing Model S engineers appears to be a formidable one. By comparison, Tesla's earlier vehicle, the Roadster, offered 244 miles of range for a $101,500 price tag. Similarly, Mitsubishi Motors' new i-MiEV small electric car will travel 100 miles between charges and cost about $47,000.
Those vast differences might sound imposing, but battery experts said they're not insurmountable.
"It's do-able," said David Swan, president of DHS Engineering, in reference to Tesla's technological goal. "But they're going to have to stretch everything to get there."
Indeed, battery experts said last week that Tesla will need more than the current state-of-the-art lithium-ion battery technology to make the goals work. They suggested that more advancements in battery technology might be needed, along with the application of stronger, lighter-weight body materials to keep the weight down.
"If they are willing to make an aluminum-intensive body or a fiberglass body, and maybe compromise on other high-mass components, they might be able to do it," said Donald Sadoway, the John F. Elliott Professor of Materials Chemistry at MIT. "But it's going to be tough to do that and keep the cost down."
Sadoway said current state-of-the-art lithium battery technology would be hard-pressed to supply enough energy for a big car to go 300 miles on a charge. According to Sadoway's rule of thumb for EVs, an electric sedan would need approximately 1 W-hr/kg of specific energy to go one mile, assuming that the battery comprises about 30 percent of the vehicle's mass. Using that rule, today's best batteries might supply enough energy for a four-door sedan to go 175 miles between charges. An EV-maker could, however, boost that range by packing more batteries on board, therefore losing some valuable volume elsewhere in the car, possibly in the trunk.
"If you're willing to put 40 percent of the mass of the car into the battery, it brings you closer," Sadoway said. "My hunch is that they have a very spiffy, advanced version of lithium-ion combined with an abnormally-high mass fraction of the vehicle in the battery."
Experts acknowledged, however, that a big battery would present a big cost challenge. Swan estimates that the 300-mile Tesla would need at least a 600-lb, 50-60 kW-hr battery, which could significantly raise costs. (An unofficial Design News survey of a group of five battery experts in 2008 indicated that state-of-the-art lithium-ion battery technology would cost between $500 and $1,000 per kW-hr. Making such cost assumptions, a 50 kW-hr battery could cost $25,000 or more.)
Such challenges come into sharper focus when comparing Tesla's proposed vehicle to Mitsubishi Motors' new i-MiEV. The i-MiEV, which rolls out in July, costs $47,000 and offers a 100-mile range. The small four-seater reportedly employs a 16 kW-hr battery, which according to the $500/kW cost estimate, would run only about $8,000.
Still, battery experts said they are optimistic about the Model S, especially if Tesla is ultimately willing to reduce the vehicle's stated range and possibly even subsidize its cost for consumers in the beginning. (However, Tesla's strategies are unknown at this point because the start-up car manufacturer is keeping a tight lid on its plans for the Model S. Responding to e-mail requests from Design News, the company said it is not yet ready for media interviews on the Model S.)
"Even with the 300-mile range, it's not impossible," said Swan, who owns three EVs and has designed batteries for the legendary 254-mph White Lightning electric vehicle during the 1990s. "But all they have to do is say it's a 200-mile vehicle and everything would get a lot easier."
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So much noise has been made about range. As mentioned by others the average daily drive is under 50 mi. You could charge your vehicle at work as well as at home and I would think that offering a small hydrogen fuelcell would keep the batteries topped off if you were to travel the 150 miles for a "short" overnite excursion. Four passenger EV's are the future.
There needs to be more positive and clearly stated information to the general public to get their heads around all of the advantages of EV's.
Smaller independant companies like Tesla will keep GM, Ford,Toyota, etc on their toes as they can move much quicker with the latest technology.
Rob Welch - 2009-31-7 11:54:50 EDT -
The problem with electric cars as a whole is for those of us in "fly-over" states. I don't make enough money to have a car to travel with and then one to commute with, so I can't drive to, say, Alabama from Indiana (actually faster than flying with layovers, smaller carbon footprint than flying) for business like I do without a series of 8-hour stops to recharge. Furthermore, we burn coal in Indiana for electric power, so until we do something other than that, electric usage comes with a heavy penalty in terms of carbon footprint.
Matt Sauers - 2009-30-7 09:59:42 EDT -
In this area people have been using non-ICE, non-electric vehicles for years for commuting.
P. Kellner - 2009-30-7 07:39:42 EDT -
Here, here to the comments thus far.
Range - exactly Dan. Why do the uninformed masses always try to talk smack about electric vehicles? "Oh, it ONLY goes 200 miles on a charge. Gee, I dunno know about...."
Wha?!? These folks make it sound like they drive to LA from SF everyday. Not. I came across a DoT figure that pegged the avg US commute at something like 29 miles/day. Throw in a few errands and let's say the daily tally is 60 miles. Even the 160 mile range option would be good for 2+ days of use before recharge.
And, what, you can achieve 80% in under an hour? What's all the whining about from the car-driving masses?
The ignorance out there about electric transportation is amazing.
People poo-poo electric cars, but once you start to question them they have not a clue about all the advantages:
1. No Oil changes
2. No Oil and air filters
3. No Coolant and radiators
4. No more spark plugs
5. No gas stations - smelly hands and wasted time. It would be interesting what all the gas station stops in one's life would total. 40 hours? 80 hours?
6. Being able to "fill-up" at home.
7. No noxious fumes from your garage into your home
8. Way more efficiency and lower cost per mile
9. QUIET, no more obnoxious ICE noise
10. 100% torque
11. No (direct) emissions
That last point is interesting too. Some smart-asses try to diss electric by saying, "Well the electricity you need just comes from polluting power plants, esp coal."
Bull straw argument. And really speaks to how, yes, we need to get rid of coal-fired asap not how electric vehicles "won't work". Coal is garbage!! "Clean coal" is a joke! There's a bit of truth to this argument IF you rely on a utility that is using dirty generation.
For now, in places like the Bay Area served by PGE, much of our electricity is pretty clean with more and more sustainables coming on line everyday. PGE will be exceeding 20% clean renewable generation pretty soon and currently use very little coal generation.
So, I keep saying over and over: GO.ELECTRIC.NOW.
Viva Tesla!
Christopher Gray - 2009-18-7 01:57:51 EDT -
Why does everyone want a car that can go so far anyway? The average commute isn't anywhere close to this, and most people drive at least half if not more of their miles commuting. I'd like to see a car with 100-150mile range with a nominal price tag that I can get to work in.
I could then use my minivan / truck to take the family on trips or haul stuff with (which the EVs aren't suited for anyway). I'll need that second utility grade vehicle anyway. Build me a reasonably priced 100mile car and I'd be interested. I don't need 300/trip.
Dan Holt - 2009-13-7 16:52:50 EDT
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