View Full Version : Tesla's 18650s versus larger format automotive cells
Toyota sees Tesla EV battery cost at 1/3
http://www.reuters.com/article/idUSTRE70A4QY20110111
"Toyota Motor Corp's top engineer said the batteries that would power the electric RAV4 crossover being developed with Tesla Motors could cost as little as one-third of the electric car batteries being developed by conventional automakers."
The problem with that is commodity cells have been in development for years and further price reductions are probably going to be smaller than the new larger automotive cells that are just starting to be built in volume and might have greater cost reduction potential. With easier assembly and management the larger cells don't have to be as cheap as the smaller cells to make assembled pack costs competitive.
The problem with that is commodity cells have been in development for years and further price reductions are probably going to be smaller than the new larger automotive cells that are just starting to be built in volume and might have greater cost reduction potential. With easier assembly and management the larger cells don't have to be as cheap as the smaller cells to make assembled pack costs competitive.
It's true that commodity cells already benefit from economies of scale, and thus the price per cell is not likely to drop dramatically. However commodity cells also benefit from regular rolled-out improvements due the the rapid product cycles of consumer electronics. Will larger format automotive cells improve at a similar rate? (an honest question) It will be interesting to see how the $/kWh of assembled packs of both types track over time.
However commodity cells also benefit from regular rolled-out improvements due the the rapid product cycles of consumer electronics.
Not so sure about that, I think it's the other way around, unless I'm not understanding your point. Products benefit from improved cells, and cell improvements are limited by the technology used to make them. There is certainly demand for improved Automotive cells as well, and they are about to grow in usage from basically zero into millions of units.
Not so sure about that, I think it's the other way around, unless I'm not understanding your point. Products benefit from improved cells, and cell improvements are limited by the technology used to make them. There is certainly demand for improved Automotive cells as well, and they are about to grow in usage from basically zero into millions of units.
But if many different manufactures of different consumer products all demand the same battery in the billions for portable drills, laptops, and sports cars, won't that create/demand more improvement iterations on that form?
What it looks like (for now) individual car makers each have their own proprietary cellpack and their supplier only has one customer to answer to.
Not so sure about that, I think it's the other way around, unless I'm not understanding your point. Products benefit from improved cells, and cell improvements are limited by the technology used to make them. There is certainly demand for improved Automotive cells as well, and they are about to grow in usage from basically zero into millions of units.
What I mean is that new commodity cells are getting used in new products all the time, so the rate of iteration is high. Incremental improvements get implemented quickly. (Lotta polysyllabic "i" words there!)
Hmm... Although, given the nature of many consumer electronics, pressure is likely on higher energy capacity rather than longevity.
This_Video (http://www.youtube.com/watch?feature=player_detailpage&v=4kmP4STUnC0#t=205s) points out that the economy of scale benefits of mass manufacturing for 18650 cells keep costs down regardless of which chemicals you put inside. So when Panasonic started working with Tesla on new automotive specific chemistry for next generation cells, it seems they decided that 18650 was still the best way to package them.
I don't think we have heard Tesla mention of the Daimler "pouch cell" in a long time.
http://cleantech.com/news/4475/daimler-takes-10-percent-stake-tesla
...expected to give the electric car startup access to the newest lithium ion pouch-cell battery...
But if many different manufactures of different consumer products all demand the same battery in the billions for portable drills, laptops, and sports cars, won't that create/demand more improvement iterations on that form?My point is these cells have been in development for so long the easy improvements have already been done. Demand can't trump physics.
What it looks like (for now) individual car makers each have their own proprietary cellpack and their supplier only has one customer to answer to.
To some extent that's true but each supplier is also competing with the entire market. If one makes an improvement others must follow or be left behind.
EVNow
01-12-2011, 05:51 PM
My point is these cells have been in development for so long the easy improvements have already been done. Demand can't trump physics.
To some extent that's true but each supplier is also competing with the entire market. If one makes an improvement others must follow or be left behind.
But the important point (from Tesla POV) is that the improvements are "free". They don't have to pump in a lot of money like Nissan has to do, for eg. They also don't need to depend on a single source like Ford or GM.
But the downside is the complicated BMS.
But the downside is the complicated BMS.
And pack assembly time, complexity, more aggressive temperature management and higher energy use. Possibly shorter cycle life as well. Other than that.....
And pack assembly time, complexity, more aggressive temperature management and higher energy use. Possibly shorter cycle life as well. Other than that.....
pack assembly time
Probably doesn't take that long for a robot. Tesla seems to have simplified their packs into modules of 500 or so cells. I doubt pack assembly is a manufacturing bottle neck.
complexity
I'm not sure it's really that complicated. There is certainly high redundancy, but that's the sort of thing a computer is good at dealing with. There may be complicated cell balancing algorithms, but I suspect once figured out, it's not too hard to implement, again with a computer. Tesla should have a lot of experience by now with the Roadster.
temperature management, energy use, cycle life
these are more chemistry issues, somewhat independent of cell form factor (as TEG alluded to above). Your current argument seems to be one of packaging.
Again, it will be interesting to see how the pack $/kwh track for the two approaches. I'm sure Tesla will do/is doing whatever makes the most sense for them.
Tesla wins either way. They have the lowest cost NOW, and can switch to a better chemistry later if need be.
This is really a no brainer.
I'd say it takes about 68 times as long to assemble 6831 cells as a 100, even for a robot. As for chemistry constraints, the form factor means Tesla is stuck with what the manufacturers are building in volume for that form factor, which for now at least seems to be LiCo cells that need more baby sitting. Certainly this could change in the future.
stopcrazypp
01-12-2011, 08:40 PM
I'd say it takes about 68 times as long to assemble 6831 cells as a 100, even for a robot.
That's probably balanced by assembly time/cost for individual cells, assuming the overall assembly time is the same for smaller cells vs larger cells. There's probably extra time spend to assemble the module, but once a modules are made, the rest of the assembly should be very similar to large format cells.
a123 makes 18650s too, so that's at least one alternative.
I like to step in and say I really enjoy JR3P's take on all things electric. A good challenge makes me think.
Cobos
01-12-2011, 11:33 PM
I'd say it takes about 68 times as long to assemble 6831 cells as a 100, even for a robot. As for chemistry constraints, the form factor means Tesla is stuck with what the manufacturers are building in volume for that form factor, which for now at least seems to be LiCo cells that need more baby sitting. Certainly this could change in the future.
Well if the robot can make 40000 Model S battery packs a year it doesn't matter that it works more or longer.
Also keep in mind I did some back of the envelope calculations in another post where Tesla will be the around the 3rd largest user of 18650 cells. Ignoring Tesla will for the producers almost be as bad as ignoring Dell. Hence at that point Tesla got huge purchasing power.
Cobos
I like to step in and say I really enjoy JR3P's take on all things electric. A good challenge makes me think.
Thanks for the props. I feel the same way, challenge makes me did deeper into the issue and question what I know.
EVNow
01-13-2011, 09:19 PM
As for chemistry constraints, the form factor means Tesla is stuck with what the manufacturers are building in volume for that form factor, which for now at least seems to be LiCo cells that need more baby sitting. Certainly this could change in the future.
Whatever high density battery comes out in prismatic format is likely to find its way into consumer formats as well. Manufacturers are always looking for longer lasting Laptops. So, I expect NMC to come to laptops the same time (or earlier) it comes in Nissan Leaf.
I doubt, though, Tesla will ever become a mass market auto major. They will likely be bought out by someone and continue as a luxury EV niche.
But the price per wh has to be lower for the commodity cells to make sense in the laptop/Tesla model than it has to be for the large scale prismatic model. Now if the NMC allows easier management and temperature control that might help the efficiency of the Tesla system but unless it eliminates the need for active liquid cooling it probably won't lower pack costs.
theBike45
01-14-2011, 08:04 PM
There's simply no way any new battery technology will not end up in laptops and Teslas. Nor does the Tesla's cooling system
figure more than incidentally in its cost at this point or any likely point in the future. The Volt's cooling system is quite elaborate
as well, and it uses large format batteries. Mass production and competition is the key, and only LG is making Volt batteries. As to
the matter of 6800 cells, just look at the number of cells in the Volt's paltry 16 kWhr battery pack.
EVNow
01-14-2011, 10:13 PM
But the price per wh has to be lower for the commodity cells to make sense in the laptop/Tesla model than it has to be for the large scale prismatic model. Now if the NMC allows easier management and temperature control that might help the efficiency of the Tesla system but unless it eliminates the need for active liquid cooling it probably won't lower pack costs.
NMC doubles the density with little additional cost. So it will be cheaper when mass produced.
There's simply no way any new battery technology will not end up in laptops and Teslas.There are a lot of different battery chemistries out there that aren't used in laptops for various reasons.
Nor does the Tesla's cooling system
figure more than incidentally in its cost at this point or any likely point in the future.It's not just the production costs, it's the energy cost as well that reduces the charge efficiency.
The Volt's cooling system is quite elaborate
as well, and it uses large format batteries.I'm comparing to the LEAF system which is quite simple.
As to
the matter of 6800 cells, just look at the number of cells in the Volt's paltry 16 kWhr battery pack.288, if scaled to Tesla size it's less than 1000, 1/6 the number that Tesla uses, that is still significant.
NMC doubles the density with little additional cost. So it will be cheaper when mass produced.That's good to know. That means as theBike says it all comes down to volume, if the volume of large format cells increases enough they might become cost competitive with the laptop cells when considering the lower number of parts to assemble. Simple is usually better.
I'm comparing to the LEAF system which is quite simple.
Nissan is going to have to add a battery heater to the LEAF if they want happy customers in the states that have a winter. They are already working on that.
Every battery technology has drawbacks, there is no perfect choice.
Yes I expect some active heating would be necessary but that can be pretty simple. Most DIY builds intended for cold weather have insulated packs with resistance elements. Preheating from the wall is usually all that's necessary.
Yes I expect some active heating would be necessary but that can be pretty simple. Most DIY builds intended for cold weather have insulated packs with resistance elements. Preheating from the wall is usually all that's necessary.
Since incorporating some sort of battery temp control system is necessary for an all around car, why not just take Tesla's approach and add water cooling/heating?
I realize not all battery packs need cooling, but they all need some sort of heater for the winter. This to me seems like the easiest choice since the motor and electronics already require cooling via antifreeze, so you already have all of the components there.
Adding water passages is more complex and takes up more space than simple resistance elements. The systems would have to be separate since you'd want to be able to preheat the pack while plugged in but you don't want to preheat the motor.
Adding water passages is more complex and takes up more space than simple resistance elements. The systems would have to be separate since you'd want to be able to preheat the pack while plugged in but you don't want to preheat the motor.
The temp could be controlled within one system for everything.
It's going to be interesting to see how much range the Leaf gets in very cold climates in relation to the California, Florida, Arizona etc. cars. I'm sure there will still be a penalty.
Certainly there will be a penalty. However, if the reduced range is still within the range you need, there is no effective limitation. Charging and discharging the battery also generates some internal heat on it's own, and it's somewhat self regulating. Colder temps mean higher internal resistance, which causes more heating, as it heats up resistance drops again. Remember, unless the Tesla pack is plugged in it's range is also being affected by temperature, you can't take energy from the pack to heat the pack and not lose range.
Doug_G
01-15-2011, 11:12 AM
Remember, unless the Tesla pack is plugged in it's range is also being affected by temperature, you can't take energy from the pack to heat the pack and not lose range.
The Roadster doesn't heat the pack unless you're plugged in and not in Storage mode. Self-heating gets the pack up to the ideal temperature range in 10-15 minutes of normal operation, i.e driving, even if the car was stone cold when you started it. The only slight nuissance is that it disables the regen when the battery pack is below freezing.
I'd say it takes about 68 times as long to assemble 6831 cells as a 100, even for a robot.
It depends on the robot. Depending on the physical design and program it might assemble many cells in parallel. Again, don't confuse redundancy for complexity. I'm sure they considered the cost/benefit in the assembly of the packs. And I'd bet they can finish making a pack before the rest of the car is done, so again, I don't see it as a manufacturing bottleneck at least.
Those cells provide for amazing packaging freedom and versatility. Tesla has managed to come up with a fantastically flat and dense pack for the Model S.
EVNow
01-16-2011, 09:39 AM
And as if on cue ...
http://www.reuters.com/article/idUSTRE70A4QY20110111
Toyota sees Tesla EV battery cost at 1/3
"It could be as low as one-third of the cost of batteries being developed by car makers, because (laptop) batteries are produced in massive volumes"
...
Toyota has said the RAV4 EV would target drivers traveling longer distances, while its own EV would be suitable for short distances.
...
Even if the RAV4 EV passes Toyota's rigorous durability tests and can be offered at relatively low prices, Uchiyamada said Toyota still believed hybrids and plug-in hybrid vehicles had the best chance of mass proliferation
Though we don't know what actual cost they are talking about here - the EV battery costs are quoted from anywhere near $1,500 to $500/kwh. Consumer Li batteries are about $200/kwh.
It depends on the robot. Depending on the physical design and program it might assemble many cells in parallel. Again, don't confuse redundancy for complexity. I'm sure they considered the cost/benefit in the assembly of the packs. And I'd bet they can finish making a pack before the rest of the car is done, so again, I don't see it as a manufacturing bottleneck at least.
I agree that the cars probably aren't sitting around waiting for the packs to be assembled. I see your point that once the robot is built and programmed it doesn't matter what it has to do as long as it's completed in time. Certainly their method can't be beat for cost vs. density at this point, but that may change as larger cells are built in volume.
And as if on cue ...
http://www.reuters.com/article/idUSTRE70A4QY20110111
Though we don't know what actual cost they are talking about here - the EV battery costs are quoted from anywhere near $1,500 to $500/kwh. Consumer Li batteries are about $200/kwh.
I think Nissan has quoted $375/kwh, real volume should bring that even lower. Without the cooling demands of Tesla's it's a more efficient pack.
Norbert
01-24-2011, 08:56 PM
I think Nissan has quoted $375/kwh, real volume should bring that even lower. Without the cooling demands of Tesla's it's a more efficient pack.
Although Tesla is getting a custom battery from Panasonic, it is also reported that using the 18650 format will give it the advantage of mass-production cost benefits. Why shouldn't Tesla be able to get quite close to the $200/kwh figure? Would you know how to compare the effects of cooling/heating demands on cost of either side?
Eberhard
01-24-2011, 11:01 PM
as i understand, only with the small form factor of the 18650 cells, the temperature controlled can be done more easily by liquid, compared the bigger cells, because of the heat which has to move from inside of the cells to the surface. Smaller cells means short ways and i do not think, that the cells material-composit has a high thermal conductivity.
second problem with big cells: if is there a little problem within the components of the big cell - the whole cells fail - big loss. if one of a hundred of smalls cells fail, 99 are still fine.
The higher number of small cells also means more possible failure points, the cells themselves and extra connections. The volatile nature of the LiCo chemistry forces the use of aggressive liquid cooling where other chemistry used in large format cells does not.
Eberhard
01-25-2011, 11:01 AM
why is water-glycol aggressive? there is no acid or similar inside. the liquid even prevents corrosion.
as i understand, only with the small form factor of the 18650 cells, the temperature controlled can be done more easily by liquid, compared the bigger cells, because of the heat which has to move from inside of the cells to the surface. Smaller cells means short ways and i do not think, that the cells material-composit has a high thermal conductivity.
My Chemical Engineering background left me thinking that it had more to do with surface area. Heat Flux (transfer) is increased by more surface area. If you take two batteries with the same amount of heat energy, but one is broken up into 100 smaller parts. The one that is broken into parts has more surface area over which to transfer its heat. So the small form factor will be able to transfer heat more quickly and therefore remain at a constant temperature. (So it is not the distance that the heat has to travel, but rather the amount of surface area over which it has to transfer)
One of the down-sides to the small form factor that I see is something I like to call the "Hamburger bun phenomenon." Would you rather have a single quarter-pound burger in a single bun, or a hundred small sliders making up the same weight? The problem with small form factor is too much bun! Or in the case of batteries, you waste too many materials on packaging. It would be more efficient if someday the small form factor batteries did not come individually wrapped.
why is water-glycol aggressive? there is no acid or similar inside. the liquid even prevents corrosion.I didn't mean aggressive as in corrosive, I mean aggressive as in the LiCo cells tend to explode if they get too hot so you need more aggressive, or active, cooling, which usually means liquid cooling, to remove excess heat. LiFePO4 and LiMn cells aren't as heat sensitive so can get by with air cooling.
One of the down-sides to the small form factor that I see is something I like to call the "Hamburger bun phenomenon." Would you rather have a single quarter-pound burger in a single bun, or a hundred small sliders making up the same weight? The problem with small form factor is too much bun! Or in the case of batteries, you waste too many materials on packaging.
Right but even though there is wasted space and material with the small commodity cells the LiCo chemistry has higher density than LiFePO4 and LiMn so the Tesla pack still has better density. Theoretically I guess if you could make a LiCo cell in larger prismatic format you'd get even better density, but because of the aforementioned cooling issues with LiCo it may not be possible without some sort of chemistry breakthrough. Also C rates usually drop when going from cylindrical to prismatic construction so the LiCo prismatics might end up with lower C rates.
Eberhard
01-28-2011, 03:44 PM
i checked out the current price for chinese 18650 with 2200mAh. The price by 100.000 is only 20cent each? The whole battery of my roadster for less then 1.400€?
Probably not even close to the same quality and life cycle. I've heard some of the Chinese commodity cells are pretty bad.
Eberhard
01-29-2011, 01:00 AM
That not an issue with quality. Its an indication for how cheap the cells can be produced. Even if you assume double price for higher quality it is still well below 100€ per kWh. In the press, they still report prices per kWh from 500-1000€ per kWh and this is the reason why electric cars have to be expensive.
I realize the press is usually way off when quoting cell prices but talking to people who design and build cells there is a lot more involved in making a quality cell. The prices are a direct reflection of the quality. Also the press usually references low volume larger format prismatic cells used by most auto builders, actual production volume should lower those prices as well.
Bob Stempel on Tesla's commodity cell packs:
What about Tesla (http://www.autoblog.com/make/tesla)'s pack, which uses 6,000-plus laptop computer batteries wired together in series and in parallel? How can they make – and service – something like that cost effectively? "Their people came from the computer business, and they certainly had the capability to put together an algorithm to control that. But that's too many cells. I think over time, we'll see them shift to a more conventional kind of pack."
Yet Mercedes (http://www.autoblog.com/make/mercedes) is using Tesla batteries in its test fleet (http://green.autoblog.com/2009/05/19/live-blog-daimler-announces-new-strategic-partnership-for-evs/), and Toyota has partnered with Tesla (http://green.autoblog.com/2010/11/17/la-2010-toyota-rav4-ev-powered-by-tesla-hits-the-stage/). "The Toyota/Tesla partnership arose out of a series of other issues. It was really a convenient marriage for Toyota, because they needed to do something with the Fremont plant. When you unravel that story, there's a lot more to it than just batteries. And Mercedes has sold off part of their investment and is backing away from that. That multi-cell concept is very, very difficult, so I think you'll see Mercedes moving toward bigger cells and fewer of them. They wanted to get their feet wet on an experimental basis so were trying a little of everything.
http://green.autoblog.com/2011/02/16/gms-bob-stempel-talks-about-lithium-batteries-and-what-will-ma
Talking with a lithium battery researcher about the Tesla pack he commented that the Tesla temperature management system was overkill. If true this would lead me to hope that the design could be simplified and the amount of energy used to control cell temperature could be reduced in the future. I've never been comfortable with the 25% and more efficiency loss during charging that some have reported.
Eberhard
03-19-2011, 07:32 AM
The whole system, that Tesla build around the 18650 cells including liquid-cooling with AC, BMS and lot of processors to supervise the system carry more cost then the cells itself plus the cost of assembly. Thats the reason for robot-assembling together with quality issues. This helps to increase the lifetime of standard cells from 300 full-cycles to more then 500 with the high-quality Panasonic cells (these cost properly a lot more then the cheaper chines cells)
William13
03-19-2011, 11:23 AM
I disagree with Bob Stemple. The Tesla battery system has built in redundancy but is actually cost effective. The form factor will also be allowing the Model S to have a lower center of gravity and stiffer body than the competition. I can only wonder at the cost of 90 kWh battery from system a123. Would it have the form factor ( flat )? Would it require heating and cooling?
Lloyd
03-19-2011, 12:24 PM
I don't believe that the temperature control is overkill if you are going to consistently charge this pac using a DC fastcharge system and keep all the parametes for the pacs under proper conditions. Watch what happens to the non-liquid cooled cars that try to charge an aging pac quickly. I predict a couple of fires!
ckessel
03-19-2011, 03:48 PM
I don't believe that the temperature control is overkill if you are going to consistently charge this pac using a DC fastcharge system and keep all the parametes for the pacs under proper conditions. Watch what happens to the non-liquid cooled cars that try to charge an aging pac quickly. I predict a couple of fires!
Yea, I'm not a lithium battery researcher, but I find it hard to believe Tesla would intentionally go way overboard in a non-profitable fashion. They've had years to gather numbers from actual field use, more than anyone else. I can respect the researcher, but I'd think it's more likely he's missing data about why Tesla found the solution useful.
The form factor will also be allowing the Model S to have a lower center of gravity and stiffer body than the competition.Other packs can be mounted in similar fashion. The LEAF pack is in the bottom of the vehicle.
I can only wonder at the cost of 90 kWh battery from system a123. Would it have the form factor ( flat )? Would it require heating and cooling?A123 would be much more expensive at the cell level since they don't have anywhere near the volume or years of working with the form factor. The cells are also not as energy dense as the LiCo cells, but they have much better power and lower internal resistance values so they heat up much less. They also don't have the thermal runaway issues that LiCo has, so they could probably get away without any active cooling, and some simple resistance heating should be enough in lower temps.
I don't believe that the temperature control is overkill if you are going to consistently charge this pac using a DC fastcharge system and keep all the parametes for the pacs under proper conditions. Watch what happens to the non-liquid cooled cars that try to charge an aging pac quickly. I predict a couple of fires!
I would not recommend fast charging any battery pack consistently other than an Altairnano pack, (which Proterra does on a daily basis in their buses). Fast charging should only be an occasional occurrence if you want your pack to last. Other chemistries, LiMn, LiFePO4, have less of an issue with thermal runaway than the LiCo that Tesla uses.
Yea, I'm not a lithium battery researcher, but I find it hard to believe Tesla would intentionally go way overboard in a non-profitable fashion. They've had years to gather numbers from actual field use, more than anyone else. I can respect the researcher, but I'd think it's more likely he's missing data about why Tesla found the solution useful.I can think of good reasons to go overboard, warranty issues and safety issues. I'm sure they did a cost benefit analysis and decided better safe than sorry. It's a good business practice. My hope is that with time, and possibly with better cells, they can at least reduce the energy used for cooling during a charge. A 25% charging loss does not help to make the case for EV's.
It has been noted that on rare occasions you can trigger an overheat condition (and temporarily reduced power output) if you manage to overheat the pack.
For instance, I saw this happen when "drag racing" with the Roadster on a hot day over and over in a row.
(Usually the air cooled PEM or Motor is the first to overheat, but it is possible to affect the pack too.)
Given that, it doesn't seem the cooling system is "over engineered". It has to handle the worse case and it seems to be just good enough to do that (up to a point).
That only means a sensor got hot and triggered a power reduction, it doesn't mean that temperature was actually dangerous for the cells. Powering down seems a reasonable response to hot passes on a hot track since its not what most passenger vehicles expect to see. I will agree that being a sports car the Roadster has to be designed for a more aggressive driving profile than most vehicles and the cooling system may indeed be appropriate.
I can think of good reasons to go overboard, warranty issues and safety issues. I'm sure they did a cost benefit analysis and decided better safe than sorry. It's a good business practice. My hope is that with time, and possibly with better cells, they can at least reduce the energy used for cooling during a charge. A 25% charging loss does not help to make the case for EV's.
I don't know where you get your info from, but the Roadster gets comparable mi/kwh (wall to wheel) with the Leaf when both are driven conservatively. In cold weather, I bet the Leaf gets substantially worse numbers.
From all of the reading and research I have done about both vehicles, Elon may turn out to be right in his "primitive battery pack" statement.
There were many "overdesigned" features on the first Roadster. The charger originally came with a fire detector and had several shutoff features that have been eliminated.
Other packs can be mounted in similar [i.e. low] fashion. The LEAF pack is in the bottom of the vehicle.
True, but no one has such a thin yet energy dense pack. That Model S pack is truly amazing, ideal packaging.
http://gigaom2.files.wordpress.com/2011/03/teslaalphatourbattery1.jpg
I can think of good reasons to go overboard, warranty issues and safety issues. I'm sure they did a cost benefit analysis and decided better safe than sorry. It's a good business practice...
There were many "overdesigned" features on the first Roadster. The charger originally came with a fire detector and had several shutoff features that have been eliminated.
It is good practice and Tesla was certainly very careful in the beginning. Martin (or someone) said that they worried if they ended up having a fire, it would set EVs back again by years.
I don't know where you get your info from, but the Roadster gets comparable mi/kwh (wall to wheel) with the Leaf when both are driven conservatively. In cold weather, I bet the Leaf gets substantially worse numbers. I get my numbers from people on this board. Miles/kwh takes into account vehicle efficiency, I'm talking strictly charging efficiency. 25% loss is terrible.
From all of the reading and research I have done about both vehicles, Elon may turn out to be right in his "primitive battery pack" statement.How so? Have any LEAF packs been damaged from overheating?
True, but no one has such a thin yet energy dense pack. That Model S pack is truly amazing, ideal packaging.Yes the density of LiCo is superior.
It is good practice and Tesla was certainly very careful in the beginning. Martin (or someone) said that they worried if they ended up having a fire, it would set EVs back again by years.
Totally agree.
I get my numbers from people on this board. Miles/kwh takes into account vehicle efficiency, I'm talking strictly charging efficiency. 25% loss is terrible.
How so? Have any LEAF packs been damaged from overheating?
So do I. There are numerous owners who get around 3 miles per kwh wall to wheel consistently with the roadster. The leaf is able to match that energy usage, but no one has reported getting any better(leaf forums).
It's hard to compare because of different drivers/roads, but it's not like the Leaf is more efficient to operate.
I didn't insinuate overheating of the Leaf pack. The very few instances of a Leaf in cold climate has the battery losing massive range due to cold temps and heater use. As of right now the Leaf is much less efficient than a roadster, in cold weather. I'm sure Nissan could work on this and improve, but I'm comparing existing vehicles.
The Roadster is likely more efficient when driving than the LEAF, which is taller and heavier. That still does not change the poor charging efficiency of the Roadster and the high energy consumption of the pack. An EV should be able to sit for weeks unplugged and not end up with a dead pack.
... The LEAF pack is in the bottom of the vehicle....
As are Coda's.
Doug_G
03-20-2011, 09:43 AM
An EV should be able to sit for weeks unplugged and not end up with a dead pack.
If it doesn't need active cooling, my Roadster loses a mere .5% SOC per day when in storage mode. Contrary to some reports it doesn't heat the pack when parked, unless it is plugged in and not in storage mode (and below freezing).