Telsa Roadster uses 6800 li-ions

[Mark620]

The Tesla Roadster battery pack is comprised of about 6800 of these 18650 cells.

From:
http://www.teslamotors.com/display_data/TeslaRoadsterBatterySystem.pdf

 

[Chodes]

I would never have guessed that.
I would have guessed individual cells would be at least 10 times the size of an 18650.

 

[monkeyboy]

It seems unnecessary to use so many small cells. This makes it much harder to monitor the performance of each cell. I think these would be better:

http://www.gaia-akku-online.de/ENG/...kte&-Token.Link=Link1&-Response=produkte.html

 

[VanIsleDSM]

I've seen this car on the Discovery channel before.. pretty cool stuff.. very high performance.

It seems unnecessary to use so many small cells. This makes it much harder to monitor the performance of each cell. I think these would be better:

http://www.gaia-akku-online.de/ENG/...kte&-Token.Link=Link1&-Response=produkte.html

Did you read the datasheet provided and see all the advantages to using many small cells? No offense, but I'd trust what many engineers from silicon valley have to think first.

 

[monkeyboy]

Did you read the datasheet provided and see all the advantages to using many small cells? No offense, but I'd trust what many engineers from silicon valley have to think first.

Yes, I did read the article and the monitoring systems they use are extremely complicated. This could be greatly simplified by using larger cells. The only advantage of using smaller cells is cooling. Did you read the link I provided? Obviously these german engineers think differently.

 

[Fallingwater]

Must be the nightmare of all cell balancers...

What if one cell (or three...) goes dead in the middle of the pack's life?

Can't keep using it as it is, and can't replace just the dead cells with new ones or you get imbalance... you replace the whole multi-kilodollar pack for a bunch of cells?

 

[adamlau]

I wonder who the OEM for the cells is...

 

[VanIsleDSM]

I think cooling would be a main concern during periods of very large draw (acceleration) which the extra surface area of the 18650s will really help with. Also the fact that billions of them are made every year now probably makes for a much lower cost battery pack with the same reliability than low production large costly cells.

According to the datasheet there are 11 battery modules in the pack.. I'd imagine they are each individually replaceable.

 

[lctorana]

18650's?

:huh::huh2::shakehead

The "Laptop battery fire" video is still firmly in my mind.

Just imagine 6800 lions going , one at a time in rapid succession, and each hotter and more intense than the last.

And you are inside the car, which probably has both central locking and electric windows, so you can't get out or even breathe...

If we have to go with LiIon, I'd rather far fewer of these:
http://www.candlepowerforums.com/vb/showthread.php?p=2246264

Or these:
http://www.candlepowerforums.com/vb/showpost.php?p=2147663&postcount=14 (the ICR50360)

 

[TorchBoy]

Re: Telsa Roadster uses 6831 Li-ion cells

What if one cell (or three...) goes dead in the middle of the pack's life?

Can't keep using it as it is, and can't replace just the dead cells with new ones or you get imbalance... you replace the whole multi-kilodollar pack for a bunch of cells?

From their FAQ (http://www.teslamotors.com/learn_more/faqs.php):

What if one cell stops working? Does the whole battery pack stop working?
That particular cell stops working, but the driver would not notice any changes in performance, because it is just one battery among many. In fact, the Tesla Motors design can withstand multiple battery cell failures with no perceptible effect on performance.

According to the datasheet there are 11 battery modules in the pack.. I'd imagine they are each individually replaceable.

For some reason I find that incredibly interesting. That means each pack has 3 x 3 x 3 x 23 cells. What voltage are they? What dimensions?

Just imagine 6800 lions going , one at a time in rapid succession, and each hotter and more intense than the last.

I don't know that I have that much imagination after reading their web site (http://www.teslamotors.com/design/safety.php):

... we set out to simulate a worst-case scenario in which a cell develops a serious malfunction. In each test, we set a cell on fire in the middle of a Tesla Motors battery pack (by heating the heck out of it) and observed the results. Our design contained these failures to a single cell, demonstrating that malfunctions wouldn't spread.

 

[darkzero]

I wonder who the OEM for the cells is...

I hope it's not Sony....

 

[oregon]

I figured that plugin electric cars would develop around litiium-ion batteries. Interesting, 6800 small batteries in a luxury car, sounds like something to avoid doing (honey do you hear something rattling?).

This came to mind reading about plugins, sounds like a drunkard's dream/vapor but just maybe a supercapacitor could store plugin's electric energy...: http://en.wikipedia.org/wiki/EEstor

The CEO of ZENN, plans to produce a supercapacitor car before end of 2009, has a recent interview here: http://gm-volt.com/2008/06/01/exclu...ge-units-cityzenn-and-zennergy-drive-systems/

oregon

 

[IMSabbel]

Come on, supercapactors are bullshit vapourware as far as a replacement of batteries is concerned.

Talkabout 1/100th of the capacity for 10 times the price.
(and yeah, even the best they plan dont come even close to getting into the same ballpark than batteries. Except one or two minor startup that clearly want to scam some venture capital).

 

[oregon]

You and I are not the only skeptics regarding the viability of supercapacitors.

However Lockheed-Martin does not appear to be one of those. They have loaded in. They have an agreement with EEstor to complete joint product testing in 2008.

Some claims of EEstor:

"The claimed energy density is 1.0 MJ/kg (existing commercial supercapacitors typically have an energy density of around 0.01 MJ/kg, while lithium ion batteries have an energy density of around 0.54–0.72 MJ/kg).[2]
Based on these claims, a five-minute charge should give the capacitor sufficient energy to drive a small car 300 miles (480 km).
For a 52 kWh unit, an initial production price of $3,200, falling to $2,100 with mass production is projected."

Similar to politics isn't it. Claims and bluster until rubber meets the road, literally.

oregon

 

[Fallingwater]

Just imagine 6800 lions going poof, one at a time in rapid succession, and each poof hotter and more intense than the last.

And you are inside the car, which probably has both central locking and electric windows, so you can't get out or even breathe

A car that can't be opened with the electric system offline is broken by design. There's always a manual release.
It's fun how people imagine great disasters caused by the flammability of LiIon cells, and then go and peacefully drive around cars full of dozens of litres of highly volatile liquid (susceptible to boiling vapour explosions, I might add).

 

[2xTrinity]

You and I are not the only skeptics regarding the viability of supercapacitors.

However Lockheed-Martin does not appear to be one of those. They have loaded in. They have an agreement with EEstor to complete joint product testing in 2008.

Some claims of EEstor:

"The claimed energy density is 1.0 MJ/kg (existing commercial supercapacitors typically have an energy density of around 0.01 MJ/kg, while lithium ion batteries have an energy density of around 0.54–0.72 MJ/kg).[2]
Based on these claims, a five-minute charge should give the capacitor sufficient energy to drive a small car 300 miles (480 km).

Let's see... the Tesla is just under 200 miles assuming EPA driving cycle, using about 60 kWh of energy. 300 miles would require nearly 100kWh. Charging that in five minutes would require 2 megawatts of electrical input -- extremely dangerous voltages and/or copper conductor the size of larger hoses would be needed to accomplish something like that. Not to mention even the slightest inefficiency in the charging process (eg at contact points for charging) will produce massive amounts of waste heat.

Also, one of the big advantages of overnight charging is the fact that if it were adopted on a large scale, the additional energy consumption would take place at night when the power plants are not under heavy demand. Thousands of people charging vehicles simultaneously on the order of Megwatts during midday is not something any part of the electric grid can handle.

In fact, even in the case of the Tesla, the battery isn't what limits the charging rate as much as the power output of the outlets from which it is charged.

 

[bob_ninja]

The choice of such a small size is simply driven by commercial considerations.

Getting someone to build a bigger size custom cell for you requires a lot of money. You have to commit to a certain volume/duration, etc. Very expensive.

GM is doing this with their Volt. Then again they have the money. These people don't have the money, so they have no choice but to go with an existing popular format. It is simple bussines issue. Nothing to do with technical considerations.

Yes, clearly it will be easier to recycle good cells from an old pack using larger format, compared to this one.

 

[oregon]

The quickcharge models electric "gas stations" in that you arrive needing a charge and depart with your charge after a quick fill up. Out back of the filling station, in Arizona perhaps, is a solar farm (bypass the grid) with supercapacitors.

oregon

 

[VanIsleDSM]

Once electric cars are the norm the grid will be much more equipped to charge up super capacitors in the middle of the day... as so many people will have their cars plugged into the grid at home.. creating a massive energy storage system that will really help with the intermittent energy we'll be harvesting from the wind, sun and waves... But first we have to kill off all the oil mongers that keep us stuck in this perpetual waste of money and material.

I imagine if there is a 5min fill for a huge super capacitor.. it will probably involve superconductors. Massive roadside hydrogen fuel cells could supply the power.. and the hydrogen stored in liquid form can cool things down enough to be superconductive.

 

[IMSabbel]

You and I are not the only skeptics regarding the viability of supercapacitors.

However Lockheed-Martin does not appear to be one of those. They have loaded in. They have an agreement with EEstor to complete joint product testing in 2008.

Some claims of EEstor:

"The claimed energy density is 1.0 MJ/kg (existing commercial supercapacitors typically have an energy density of around 0.01 MJ/kg, while lithium ion batteries have an energy density of around 0.54–0.72 MJ/kg).[2]
Based on these claims, a five-minute charge should give the capacitor sufficient energy to drive a small car 300 miles (480 km).
For a 52 kWh unit, an initial production price of $3,200, falling to $2,100 with mass production is projected."

Similar to politics isn't it. Claims and bluster until rubber meets the road, literally.

oregon

_Those_ caps are a whole differnt ballpark from whats usually known as supercapacitor, thought.
Normaly: Supercap= low voltage, extreme surface capacitor (nanostructored anode and cathode).
Those things (if they are the same i ready about last year) get high energy densities.
But there _IS_ a downside:

Power stored is only linear in capacity, but square in voltage. So they have extremely high voltage cells, with (IIRC) glass insulators.
Handling this stuff is infinitly more tricky than lithium ion batteries.
They can literally discharge all their energy in a few us in a singly flash of lighning. With more than a few MJ storage, this will detonate you car (and not a fake "a bit of flame" LiIon detonation, but a _real_ one).
Not to mention the problems with charging and discharging (you have to handle multi-kV voltages. Tricky in a metal car chasis).

But for stationary applications, they are really good.


To reinforce another point: Low voltage caps will NEVER reach the energy density of batteries. Chemical storge goes directly to the molecular bonds, whereas with the low power ones you have to be content with with magnetic field energy (which increases with sinking structure size, but you never reach the eV/molecule level).

_High_ voltage "supercaps", otoh, more or less have the sky as their limit. You can get dielectric materials with enormous breakthrough voltages.
If your cap has 200 uF, and you can put 50kV on it, thats still better than a "normal" 5V supercap with 20 000 Farad...