Editorial: Tesla's "coddled" and pricey energy storage system
The latest entry on the Tesla Motors corporate blog focuses on the heart of the new Roadster. The range and performance capabilities of the Roadster wouldn't be possible without a way to store a lot of energy on board and the Tesla energy have created what is arguably the most sophisticated automotive battery pack ever created. It is almost certainly the most complex and comprises roughly one third of the weight of the whole car. Weighing in at 900 lbs with a 53kWh capacity the Energy Storage System incorporates 6,831 individual cells, a cooling system to manage the temperature, sensors to monitor everything and electronics and software to help extract the most energy from the unit as well as put as much recovered or grid fed energy back in.
There's more - including some editorializing - after the jump.
[Source: Tesla Motors]
For a small start-up car-maker Tesla has done a remarkable amount of testing on both the car and battery system. Because of the nature of lithium ion batteries, there are a lot of international regulations governing the transportation of the components as well as the complete systems. Tesla announced earlier this week that they had received regulatory approval to proceed with deliveries of the pack and the latest post on their blog goes into more detail on the nature of the testing they had to conduct to verify the safety of their system.
We'll see before too much longer if the Tesla battery pack and Roadster are really up to the task of daily use in the real world, but even with all the work that's been done so far a more pressing issue still remains to be resolved with all the technology that Tesla has created: cost. This battery pack and the car that it "fuels" don't come cheap.
The number of people that will ever own let alone drive a Tesla Roadster (at least the first generation model) will probably remain in the low thousands at most. The car will surely satisfy the green urges of the privileged few who can manage to spend $100,000 on a two-seat sports car. However in the grand scheme of things it will mean nothing unless it can be made affordable enough that we can start to displace the hundreds of millions of cars that are on the road today.
In addition to caring about the environment, I love sports cars. I would love to own a Tesla Roadster. On the salary of an engineer and part time writer with a mortgage and two kids to put through college, it's just not going to happen. Lower cost solutions are imperative, and the upcoming WhiteStar is a step in the right direction albeit a baby step. Tesla (or Phoenix or Zap) is not likely to be a high-volume manufacturer any time in the foreseeable future but those companies that are producing cars by the millions need to work to bring this kind of performance to the masses quickly. GM has a massive effort to do it with E-Flex and others are similarly engaged and hopefully they will succeed. Companies like Tesla need to succeed as well even if they remain relatively small, because the big guys need a thorn in the saddle to spur them on.
Reader Comments (Page 1 of 1)
Mahmood1 2:24AM (8/12/2007)
The energy density with this pack is 129 Wh/kg (53 KWh /900 lbs).
They would have been much better off using lifepos (Lithium Iron Phosphate LiFePO4) that do not have heating or safety issues. Lifepo energy density is 125 Wh/kg, and can be recharged 8000 times at full DOD (-20% storage loss), and can operate at much colder temperatures than the older LiCoO2 that Tesla wasted so much time and money on. Nano-lifepo can also be charged in 10 minutes and can produce more acceleration than Tesla's battery. A 3.2 second acceleration will probably make it the fastest street car.
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ug 2:33AM (8/12/2007)
Long term Tesla would be stupid not to switch over to Lithium Iron Phosphate at the earliest opportunity. But there wasn't a steady supply of this new battery tech when they started working on the roadster and there probably still won't be for another year at least. Time will tell whether their approach was a good enough compromise or not. But I would be very worried about what is going to happen in a highspeed collision. The ESS won't prevent the cells from rupturing and exploding in an impact. The chemistry of the cells is just not roadworthy.
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Tony Belding 4:13PM (8/12/2007)
Mahmood, you need to get some perspective.
Tesla began designing the Tesla Roadster about four years ago. They were demonstrating engineering prototypes to the press a year ago, and they are getting ready to ship cars to paying customers before the end of this year. NONE of that would have been possible with the advanced battery chemistry you are calling for.
If Tesla held out for your "lifepos" batteries, they would be in the same boat with General Motors, hoping to ship something in 2010 if all goes well. Instead they chose to take what was available off-the-shelf, in quantity, at commodity prices, and they made it work. That's why Tesla has a product and GM only has a plan for a product.
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Tony Belding 4:20PM (8/12/2007)
Ug, you need to do some homework. Martin Eberhard recently gave a presentation where he covered this very subject of battery safety and durability.
Yes, the ESS will prevent cells from rupturing and exploding in an impact. It's designed to do exactly that, and so far it has passed all tests with flying colors. They had to subject the car to a crash test with a truck impacting the rear at 50 MPH, then turn the car upside-down and make sure nothing spilled out. The car was messed up pretty bad, but the passenger compartment was intact and the ESS was barely scratched. It also shut off all electric connections as it was designed to do.
Then they had to subject the ESS to tests without the car, to meet shipping regulations. It had to survive multiple forms of abuse, including a 30-foot drop onto a hard surface without rupturing, catching fire, etc. As a result, it's possibly the only large battery pack in the world now certified to be shipped internationally by air and sea.
The ESS is a very rugged, impressive piece of engineering work.
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why not the LS2/LS7? 2:50AM (8/13/2007)
Tony Belding:
What do you mean Tesla has a product and GM doesn't?
The Tesla Roadster isn't a product yet. On the other hand, GM already shipped a product similar to the Tesla Roadster almost 10 years ago now.
GM's vehicle was a market failure for a lot of reasons, most of which still apply to the Tesla Roadster.
The market for a $100K 2 seater like the Tesla Roadster is limited. It's non-zero, but it was too small a market for GM to chase, and it may be too small to even sustain Tesla, we'll just have to see.
Mahmood and Tony:
You cannot charge a Tesla in 10 minutes, regardless of battery technology.
To charge a 50KWh battery in 10 minutes would require a 330KW power input (assuming a 90% efficiency). Even at 480V (your house only has 220V), that's 690A. This is about 6x as much power as is available to the average household from the electric company.
Just another example of optimism overriding sense in the quest for the viable electric car. Even if you can get your house rigged for enough power to charge your car quickly, as soon as your neighbors want to join in the fun, you'll overload the local electric grid. Mass adoption of electric cars will require upgrades to our electrical infrastructure.
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Darryl 8:46AM (8/13/2007)
mahmood
Your comparison is not apples to apples. You are comparing the energy density of the overall ESS, including the case, battery management systems, cooling system, connectors and various other things, to the energy density of a LiFePO4 cell. The nature of a LiFePO4 cell is that it is high power and lower energy density, so if we used that cell (which we could if we chose) we would have a significantly shorter range, which is not useful. LiFePO4 may be better suited for PHEV or REEV (as in the Volt) use, where range is less of an issue and cycle life more of an issue.
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zaneofaten 8:56PM (8/13/2007)
Mahmood-we share your enthusiasm for the LifePo4 solutions! check out www.AtenEnergy.biz !
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Michael Hollander 1:24AM (8/14/2007)
Tony:
GM did NOT ship a product similar to the Tesla Roadster ten years ago. What they shipped was an ugly car that didn't appeal to car lovers at all, but rather to those who wanted to show off and say "look how green I am." Then they could kill the car and say there wasn't demand. My mother wouldn't drive anything as ugly as the EV1. Neither would anyone else who cares the least about cars. The roadster is designed for the person who LOVES cars. If you want to see how many of those people there are - who have pockets deep enough for the Roadster - please visit this Sunday's Pebble Beach Concours d'Elegance.
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