YOU: Fix the US Energy Crisis

[mheslep]

I entirely understand its design. FYI, parallel hybrids can operate without the ICE engine in the loop as well. They just can't drive as far with battery power alone due to a smaller battery pack, not due to limitations of concept.

If you knew this, and that the Volt can go 40 miles on batteries alone, then what was the point of your #1 "GM doesn't produce a single electric car (Volt is not an EV), what the hell is GE going to buy?"?

And what will you do after that, assuming you are no where near an electric power outlet or space heater?

Drive away?

I don't think you understand the workings of Li batteries.

Well I'm not an electrochemist, but I've been over the theory and market fairly thoroughly for work customers, but no need to believe me: I've cited references here before.
https://www.physicsforums.com/showpost.php?p=2526716&postcount=10

The majority of Li batteries that are suitable for EVs can not be charged or discharged below 0'C without some form of degradation.

https://www.physicsforums.com/showpost.php?p=2525412&postcount=9
Temporary degradation in capacity. A much more accurate statement than saying they "don't work".

The Volt has an ICE which can both power the car and heat the batteries in sub zero climates. This means that the car can still operate without the use of its Li batteries in cold temperatures. Your regular EV can't. Thats why the Nissan Leaf isn't being sold in the colder regions of the US.

If you knew this, and that GE is buying GM Volts, then what is the point of your statement #3 "Li powered EV's still don't work in cold weather. Are the GE employees that work in the sourthern part of the US only going to be allowed to drive EV's?"

My original comment stated "about 3 years" as in give or take 6 months or if you prefer, 3.5 years. Some of the newer batteries can probably last over 3 years but 4 is pushing it. [...]

Again, reference? The forum guidelines require you to support statements of fact with a reference. (That 2002 link is irrelevant). If you have questions instead, ask them.

 

[mheslep]

Here's a electric series hybrid w/ a little more go than the Volt. And a little more cost. Jag CX75. Four 190HP E-motors, one per wheel; dual diesel turbine 80,000 rpm generators charging the batteries. 0-60mph in 3.4s, top speed 200+ mph. http://www.dailytech.com/Jaguar+CX75+Concept+Features+Four+Electric+Motors+Two+Gas+Turbines/article19757.htm" .

Why turbines? A reminder that the turbine is remarkable invention:

“You see, the small gas turbines tip the scales at 55 pounds each. In addition, they don’t need oil lubrication or a catalytic converter, and they will run on almost anything from biofuel to LPG. Although they rev at up to 80,000 rpm, turbines are a very reliable known quantity. The fact that they may take up to 15 seconds to reach their optimum operating speed does not really matter here because they are only used to recharge the batteries.”

 

[mheslep]

Here's a electric series hybrid w/ a little more go than the Volt. And a little more cost. Jag CX75. Four 190HP E-motors, one per wheel; dual diesel turbine 80,000 rpm generators charging the batteries. ...

BTW, does anyone have more than a googling knowledge of the price per HP/KW of turbines? Now that hybrid's have come into their own, I'm curious if a turbine has a chance of supplanting piston reciprocating engines in the mass vehicle market.
Advantages: runs off all kinds of fuels, highest power density of any engine, highly efficient.
Disadvantage: limited RPM operating range, but that's no longer a problem w/ electric motors handling the traction.

I'm guessing the diesel-electric locomotive people evaluated turbine-electric designs and found diesels superior for some reason. But, given the continuing advances in turbines, and that the mass advantage is important for lightweight vehicles, perhaps the tradeoff results would be different now.

 

[mheslep]

2. ... Li batteries also have a life of only about 3 years before they are considered dead. What the hell are they going to do with all those batteries?

General Motors announces 8-year/100,000-mile warranty for Chevy Volt battery

http://green.autoblog.com/2010/07/1...nces-8-year-100-000-mile-warranty-for-volt-b/

 

[Topher925]

Drive away?

No you wouldn't, your lithium ion battery wouldn't generate any power.

Well I'm not an electrochemist, but I've been over the theory and market fairly thoroughly for work customers, but no need to believe me: I've cited references here before.
https://www.physicsforums.com/showpost.php?p=2526716&postcount=10

You didn't specify a source for cold temperature operation. Your other source doesn't say anything about degradation or performance at low temperatures, only the effects of high temperatures.

FYI, not all, and in-fact many, Li batteries used in electric vehicles don't use olivine Fe based cathodes. The batteries developed by LG (CPI) that are used in the Chevy Volt use a non-ferrous spinel structured cathode.
http://gm-volt.com/2009/01/12/its-official-gm-chooses-lg-chemcompact-power-inc-to-supply-chevy-volt-lithium-ion-battery-packs/
http://www1.eere.energy.gov/vehiclesandfuels/pdfs/merit_review_2010/electrochemical_storage/es00a_howell_2010_o.pdf (slide 11)

While you may get some power out of a very cold battery, you're not going to get much since the discharge reaction is limited by transport, specifically diffusion through the SEI, not migration through the electrolyte. The BMS (battery management system) will not allow the battery to operate when its at to low of a temperature, or in layman's terms, your battery won't work. This is the similar to the reason why you cannot charge a Li battery at cold temperatures as the low rate of diffusion will accelerate dendrite formation on the anode.
http://books.google.com/books?id=o-... cold temperature&pg=PA60#v=onepage&q&f=false

https://www.physicsforums.com/showpost.php?p=2525412&postcount=9
Temporary degradation in capacity. A much more accurate statement than saying they "don't work".

Nice work using my post from another thread for your argument. Its completely taken out of of context though.

I of course was referring to batteries just experiencing cold temperatures as the OP stated, not being operated.

If you knew this, and that GE is buying GM Volts, then what is the point of your statement #3 "Li powered EV's still don't work in cold weather. Are the GE employees that work in the sourthern part of the US only going to be allowed to drive EV's?"

Please see the wiki article for vehicle naming conventions. You can call the Volt a PHEV, a SHEV, or a REEV, but it is most definitely not an EV.
http://en.wikipedia.org/wiki/Hybrid_vehicle_drivetrains

Again, reference? The forum guidelines require you to support statements of fact with a reference. (That 2002 link is irrelevant). If you have questions instead, ask them.

Cycle life for a battery is generally readily available from its manufacturer. LG/CPI for example, http://www.compactpower.com/lithium.shtml
More here: http://www1.eere.energy.gov/vehiclesandfuels/pdfs/program/2008_energy_storage.pdf

And the 2002 link is not irrelevant. Those targets haven't change and I doubt they ever will with exception of some small modifications.

 

[Topher925]

http://green.autoblog.com/2010/07/1...0-000-mile-[U][B]warranty[/B][/U]-for-volt-b/

No one is saying that the battery will actually last 8 years, only that GM will replace it when it dies.

 

[brainstorm]

What about tax deductions for businesses relative to the average commuting-distance for their employees? This would encourage them to relocate closer to where their employees live or hire more local employees to reduce their average commuting-distance.

Likewise, could government cover the closing costs and/or other fees associated with employees relocating closer to their work?

Could government somehow stimulate more mixed residential/commercial developments, such as incentives for apartment/condominium developers to make the ground level of their buildings commercial/retail or promoting mixed-zoning that increases job-density per unit population allowing more people to work close to home?

 

[mheslep]

No you wouldn't, your lithium ion battery wouldn't generate any power. [...]

From the NREL/Saft source Russ_Waters provided you previously. Lindzen's Battery Handbook also provides temperature data.

http://www.nrel.gov/vehiclesandfuels/energystorage/pdfs/evs17poster.pdf

We also have factual data on, e.g. the BMW E-Mini at cold temperatures. As we can see it manages to drive away, even when cold. Yes the range drops. No it is no prevented from starting by its 'BMS'.
http://si.wsj.net/public/resources/images/MK-BG780A_CarLi_G_20101017220417.jpg

Cycle life for a battery is generally readily available from its manufacturer. LG/CPI for example, http://www.compactpower.com/lithium.shtml
More here: http://www1.eere.energy.gov/vehiclesandfuels/pdfs/program/2008_energy_storage.pdf

Again, third time, I asked you to source your statement, not for general background reading on batteries.

Li batteries also have a life of only about 3 years before they are considered dead.

Which was probably some off the cuff comment based on experience with a laptop or the like. We are, of course, discussing batteries made for vehicle electric drive trains. Why not just retract or modify your statement?

 

[Topher925]

From the NREL/Saft source Russ_Waters provided you previously. Lindzen's Battery Handbook also provides temperature data.

The source that Russ provided only shows experimental data to 0'C and a theoretical model to -10'C. It also only addresses the effective capacity of the battery, not issues with degradation or specific power at those temperatures.

We also have factual data on, e.g. the BMW E-Mini at cold temperatures. As we can see it manages to drive away, even when cold. Yes the range drops. No it is no prevented from starting by its 'BMS'.

The graphic for the BMW E-mini only shows operation of the car to about 25'F of the ambient air temperature. Again, the question I originally stated was for a battery temperature of -20'F (~-30'C).

Again, third time, I asked you to source your statement, not for general background reading on batteries.

Ok, well for laboratory results for GenIII cells ("latest and greatest"), I again point you here:
http://www1.eere.energy.gov/vehicles...gy_storage.pdf
Page 29, Figure III-3
Page 30, Figure III-4

For blanket statements supporting my general point that Li batteries have poor cycle life you can look in just about any book or respectable resource. But since I have to provide a source:

Lithium batteries for EVs are far from commercialization
Lithium metal polymer suffers from poor cycle life. A stiffer solid polymer electrolyte with significantly improved ionic conductivity at room temperature is required.

www.ornl.gov/sci/sp/Pres/Duong.ppt[/URL]

If you need hard experimental data from battery manufacturers or OEMs, well I'm obviously not going to have it as that information is almost always proprietary. The majority of my practical knowledge of batteries and the vehicles that use them come from primary sources.

[QUOTE]
Which was probably some off the cuff comment based on experience with a laptop or the like. We are, of course, discussing batteries made for vehicle electric drive trains. Why not just retract or modify your statement?[/QUOTE]

My experience comes from classmates and colleagues that work at either A123 Systems or General Motors and work on the Chevy Volt. My experience also comes from classes I have taken about battery and hybrid systems as well as my general knowledge of electrochemical storage and conversion devices that I've obtained from my university research. I will not retract or modify my statement because there is nothing wrong with it and you have yet to prove otherwise.

 

[mheslep]

The source that Russ provided only shows experimental data to 0'C and a theoretical model to -10'C.

So? That they "dont work" cold is your claim. You have information showing the model suddenly fails at -30C (-20F)?

It also only addresses the effective capacity of the battery, not issues with degradation or specific power at those temperatures.

The model does. Spec power is ~linearly related to capacity per the model NREL shows on slide 3. That is, if capacity drops by 10%, spec power drops 10%.

Ok, well for laboratory results for GenIII cells ("latest and greatest"), I again point you here:
http://www1.eere.energy.gov/vehicles...gy_storage.pdf
Page 29, Figure III-3
Page 30, Figure III-4

Did you review the charts? They say what? That capacity degrades significantly per cycle with long term 55C / 131F usage, and very slowly at moderate temperatures. The GM Volt and Tesla batteries for example will be/are temperature controlled, hot and cold.

For blanket statements supporting my general point that Li batteries have poor cycle life you can look in just about any book or respectable resource.

No I don't think so, my https://www.amazon.com/dp/0071359788/?tag=pfamazon01-20 doesn't, and I've provided other sources showing the opposite previously in other threads.

But since I have to provide a source:

www.ornl.gov/sci/sp/Pres/Duong.ppt[/URL][/QUOTE]
You noted the source says [I]Lithium [B]metal polymer[/B] suffers from poor cycle life.[/I]? So? The forthcoming Volt, Leaf, iMiev, E-Mini, iMiev do not use metal poly.

Also from the EERE Duong,2007 ppt:
Slide 7: [QUOTE=Duong]Life: projections of 10-15 years are based on limited data[/QUOTE]
Slide 6:[QUOTE=Duong, ][small battery]CD: Energy scaled for range (10-40 miles), 5,000 deep discharge cycles
[large battery]CD only: Energy scaled for 100+ mile range, 1,000+ deep discharge cycles[/QUOTE]
CD = Charge depletion, ie discharge mode. The first gives 200,000 miles per battery, the second 100,000 miles.

Duong's statement that "Conventional" Li Ion HEV batteries are ripe for commercialization but the pure BEV batteries are not seems to be a statement about their cost, not their calendar or cycle life.
[quote]If you need hard experimental data from battery manufacturers or OEMs, [/quote]Nope, third party tests will do, such as the EERE figures above. I've provided national lab figures myself in another thread.
[quote]The majority of my practical knowledge of batteries and the vehicles that use them come from primary sources. [/quote]Which primary sources? If you can't provide them, can you name them?

[quote]I will not retract or modify my statement because there is nothing wrong with it and you have yet to prove otherwise.[/QUOTE]I'm only interested what you can clearly show through references. I don't have to prove your "about 3 years" claim false, though I can. The burden is on you to prove it true.

 

[Redbelly98]

From the NREL/Saft source Russ_Waters provided you previously. Lindzen's Battery Handbook also provides temperature data.

http://www.nrel.gov/vehiclesandfuels/energystorage/pdfs/evs17poster.pdf

Since the data go down to 0 C, I'm leery of using the model to extrapolate much below that. I would be curious to see actual data for -20 or even -30 C (-4, -22 F)

 

[mheslep]

Since the data go down to 0 C, I'm leery of using the model to extrapolate much below that. I would be curious to see actual data for -20 or even -30 C (-4, -22 F)

Yes I'd like to see the data too. Meanwhile, I'm much more leery of unqualified claims that a Li ion battery completely fails at those temperatures without any support what so ever (data or model).

 

[Topher925]

So? That they "dont work" cold is your claim. You have information showing the model suddenly fails at -30C (-20F)?

Do you have information that shows it doesn't? Its your source, not mine. You can't ask me to provide sources that completely prove my point and then just make yourself exempt of the same standard.

Did you review the charts? They say what? That capacity degrades significantly per cycle with long term 55C / 131F usage, and very slowly at moderate temperatures. The GM Volt and Tesla batteries for example will be/are temperature controlled, hot and cold.

What? The charts say absolutely nothing about capacity, they show the increase in ASI (Area Specific Impedance) over time. The purpose of those charts was to show that on average the Gen II and Gen III cells had an increase of ASI of about 25% within 45 weeks. The higher temperature tests are even much higher than that.

No I don't think so, my https://www.amazon.com/dp/0071359788/?tag=pfamazon01-20 doesn't, and I've provided other sources showing the opposite previously in other threads.

It appears that Linden is making the comparison between Li-ion to other batteries in general (like for commercial products) and not in the application of electrical vehicles. That book also appears to be very outdated and rather fuzzy when it comes to some of their statements. The fact that they don't really mention anything about Li battery safety and things like thermal runaway throws up a flag.
Linden, sections 35.42-43 Figures 35.45 and 35.46 clearly show severe (greater than 80% SOC) capacity reduction with less than 1,000 cycles. Keep in mind Figure 35.46 is data for a C/LiMn2O4 type battery which is the same anode and cathode materials used LG CPI batteries.

You noted the source says Lithium metal polymer suffers from poor cycle life.? So? The forthcoming Volt, Leaf, iMiev, E-Mini, iMiev do not use metal poly.

I only added the Lithium Metal Poly part because a lot of people think that technology can lead to a significant cost reduction and think its the future of EV's. But you're right, no one uses them for vehicle apps as far as I know so I'll restate it;

Lithium batteries for EVs are far from commercialization

Also from the EERE Duong,2007 ppt:
Slide 7:
Slide 6:
CD = Charge depletion, ie discharge mode. The first gives 200,000 miles per battery, the second 100,000 miles.

Slide 6 clearly states "Energy scaled for 100+ mile range, 1,000+ deep discharge cycles" for EVs, the 5,000 cycles is for PHEVs. 1,000 cycles is just a little more than 2.5 years in estimated calendar life.

Duong's statement that "Conventional" Li Ion HEV batteries are ripe for commercialization but the pure BEV batteries are not seems to be a statement about their cost, not their calendar or cycle life.

No, I don't think it is.

Major R&D is focused on suppressing dendrite formation and stabilizing the lithium interphase
Additional barriers include cost, low specific energy and poor cycle and calendar life.

www.ornl.gov/sci/sp/Pres/Duong.ppt[/URL][QUOTE]Which primary sources? If you can't provide them, can you name them?[/QUOTE]

No, I'm not going to ask them for permission to serve as my primary source for someone I'm having a debate with on the internet.

So anyway, back to the temperature thing...

Linden 35.41, Figure 35.43 Approximate C-rate discharge of an 18650-type C/LiCoO2 battery at various temperatures...

The BMS and power electronics of an EV generally operate between a voltage of about 400 to 250V where 250V is the minimum operating voltage. This means that you will generally want your module OCV at around 350ish volts due to the voltage drop and hike when discharging and recharging the battery. So, using these ballpark numbers and a IR of 5mOhm ([url]http://www.a123systems.com/a123/products[/url] minus a little for err) and the data from the figure from Linden we can do a quick calculation.

At 25'C -> 350V/4.2 = 83 cells per module (~349V)

At -20'C -> 83*2.9V = 240.7V

10 Volts below that of the minimum operating voltage of the power electronics, which in other words will make the BMS turn off the battery making it "not work" as one of my previous sources stated. You could argue that I just pulled this 250V* number out of the air (which I didn't) but keep in mind I am just talking close OCV here. This doesn't include the temperature effects on current output due to increased impedance from the electrolyte and diffusion of Li ions through the SEI.
[URL]http://www.uqm.com/pdfs/HiTor%2010.13.08.pdf[/URL]

How do you think the Volt's batteries handles cold weather?
[QUOTE]The battery needs a minimum temperature of between 0 °C and 10 °C (32 °F and 50 °F) to be used and when the Volt is plugged in the battery will be kept warm enough so that it can be used immediately when the Volt is unplugged. If the Volt is kept unplugged and the temperature of the battery is below the minimum temperature, the gasoline engine will run until the battery warms up. This temperature regulation is done since electro-chemical batteries have degraded performance when they are very cold.[/QUOTE]
[url]http://en.wikipedia.org/wiki/Chevrolet_Volt#Specifications[/url]

[QUOTE]Another of the weaknesses of electro-chemical batteries is degraded performance when they are very cold. GM engineers have devised battery conditioning algorithms to help overcome this...if you're not plugged in and the battery is not conditioned and we've got to deal with the elements, right now we're thinking 0-10°C we won't use the battery.[/QUOTE]
[URL]http://greenfuelsforecast.com/ArticleDetails.php?articleID=686[/URL]

So, if the Volt can't use its batteries at 10'C and below, what is it that's going to allow a typical EV to do so?

 

[mheslep]

It appears that Linden is making the comparison between Li-ion to other batteries in general (like for commercial products) and not in the application of electrical vehicles.

Yes, just as the title indicates - a general battery handbook.

That book also appears to be very outdated

Yes it is a bit old, and not up with the latest improvements.
and rather fuzzy when it comes to some of their statements. The fact that they don't really mention anything about Li battery safety and things like thermal runaway throws up a flag.[/quote]Linden's text is a bible in the industry, cited as a basic reference in papers again and again. Thermal runaway is referenced throughout.

Linden, sections 35.42-43 Figures 35.45 and 35.46 clearly show severe (greater than 80% SOC) capacity reduction with less than 1,000 cycles. Keep in mind Figure 35.46 is data for a C/LiMn2O4 type battery which is the same anode and cathode materials used LG CPI batteries.

Good figures for discussion. Figure 45 is old Cobalt chemistry (laptops) and I agree it is important to note the difference w/ C/LiMn2O in Figure 46. Those figures however are for full discharge, 100% DoD cycles. The GM Volt, which uses LG batteries, does not swing through 100% DoD, more like 50-60%, as you no doubt know. See then Linden page 35.48 and figure 35.55 , which shows data for a 30% DoD case yielding "cycle lives between 55,000 and 137,000 cycles" [italics mine]. Then, the other pure BEVs like the the Leaf/Fluence which will do 100% DoD are using newer nano - particle anodes (not found in Linden) which brings the cycle life up considerably.

 

[mheslep]

So anyway, back to the temperature thing...

Linden 35.41, Figure 35.43 Approximate C-rate discharge of an 18650-type C/LiCoO2 battery at various temperatures...

The BMS and power electronics of an EV generally operate between a voltage of about 400 to 250V where 250V is the minimum operating voltage. This means that you will generally want your module OCV at around 350ish volts due to the voltage drop and hike when discharging and recharging the battery. So, using these ballpark numbers and a IR of 5mOhm (http://www.a123systems.com/a123/products minus a little for err) and the data from the figure from Linden we can do a quick calculation.

At 25'C -> 350V/4.2 = 83 cells per module (~349V)

At -20'C -> 83*2.9V = 240.7V

The packs can be put together in most any series / parallel combination that yields at least a couple hundred volts and can be efficiently converted to motor voltage from there, but that's beside the point. The ~2.9VDC figure Linden shows in Fig 43 is the -20degC full 1C discharge voltage. This is not the discharge rate required to roll out of a parking spot on a -20degC morning, rather ~0.1C will do that, with 10X less I*R voltage drop. So full acceleration power won't be available at startup, but then I don't put my foot to the floor right away w/ my gasoline vehicle either on -20degC days.

I'm sure you noted the capacity data in Figure 35.44 down to -20degC, maybe a 20% loss. So what we have is an EV that starts and drives a way even on the coldest mornings, but loses some range and top end power. Thus I think it was a dumb move for the Leaf/E-mini/Fluence not to include some kind thermal management on their battery.

 

[Topher925]

Thermal runaway is referenced throughout.

Show me where it gives more than two reasons for thermal runaway.

Good figures for discussion. Figure 45 is old Cobalt chemistry (laptops) and I agree it is important to note the difference w/ C/LiMn2O in Figure 46. Those figures however are for full discharge, 100% DoD cycles. The GM Volt, which uses LG batteries, does not swing through 100% DoD, more like 50-60%, as you no doubt know.

No, I don't know that because its not true. BTW, I don't think anyone uses Co, not even for laptops. Its been slated to be too dangerous for consumer products.

The Volt's 375 lb (170 kg), 220-cell lithium-ion battery (Li-ion) pack is anticipated to store 16 kW·h of energy,[1][67] but will be restricted (in software) to use only 10.4 kW·h of this capacity to maximize the life of the pack. It will only be allowed to charge to 90% of full capacity and to discharge only to approximately 25% SoC before the engine cuts in and maintains the charge near the lower level.

http://en.wikipedia.org/wiki/Chevrolet_Volt#Battery

See then Linden page 35.48 and figure 35.55 , which shows data for a 30% DoD case yielding "cycle lives between 55,000 and 137,000 cycles" [italics mine].

I don't have the book with me at the moment so I will have to look at the figures again later tonight. Regardless, BEVs will go beyond 30% DoD in order to meet their distance requirements.

Then, the other pure BEVs like the the Leaf/Fluence which will do 100% DoD are using newer nano - particle anodes (not found in Linden) which brings the cycle life up considerably.

No they are not.

Type: Laminated lithium-ion battery
Total capacity (kWh): 24
Power output (kW): Over 90
Number of modules: 48

Battery pack contents:
-Positive electrodes – Lithium manganate
-Negative electrodes – Carbon
-Cells
-Modules
-Assembly parts

http://green.autoblog.com/2010/05/2...eaf-battery-pack-including-how-recharging-sp/

The only material that can use nanoparticles on the negative electrode is lithium titanate oxide which used by manufacturers like Altair Nano. However, using Li2TiO3 drops the OCV considerably reducing the specific energy so much that those kinds of batteries are not suitable for EVs (~50Wh/kg).
http://www.targetdoc.com/viewer.asp?b=546&k=lchr4714LC&bhcp=1

I'm surprised you haven't mentioned this about the Leaf yet;

Battery life: After 10 years, the battery is expected to have 70-80 percent of its original storage capacity

http://green.autoblog.com/2010/05/2...eaf-battery-pack-including-how-recharging-sp/

 

[Topher925]

The packs can be put together in most any series / parallel combination that yields at least a couple hundred volts and can be efficiently converted to motor voltage from there, but that's beside the point.

So you think EV engineers should devise a system to rewire the modules depending on how cold the batteries are? Sounds expensive.

The ~2.9VDC figure Linden shows in Fig 43 is the -20degC full 1C discharge voltage. This is not the discharge rate required to roll out of a parking spot on a -20degC morning, rather ~0.1C will do that, with 10X less I*R voltage drop. So full acceleration power won't be available at startup, but then I don't put my foot to the floor right away w/ my gasoline vehicle either on -20degC days.

So the moment you pull out of your driveway you're going to keep going 1mph? How long and how much energy do you think it takes to heat up a 500kg battery? I would bet that in a practical case it would take a while even considering the battery to be at full power output just to heat itself up from -20'C in a reasonable amount of time. Its not like you're heating an internal combustion engine which has a smaller mass and where 75% of the energy you're using is being turned to heat.

I'm sure you noted the capacity data in Figure 35.44 down to -20degC, maybe a 20% loss. So what we have is an EV that starts and drives a way even on the coldest mornings, but loses some range and top end power. Thus I think it was a dumb move for the Leaf/E-mini/Fluence not to include some kind thermal management on their battery.

No I don't recall without the book in front of me, but what does capacity have to do power output in this case? And if this is true, why can't the Volt just drive away using only its battery when its 0'F outside? If the Leaf uses the same chemistry, why can it operate at those temperatures but the Volt cant?

The nixing of the TMS for the batteries wasn't necessarily a dumb move, it just wasn't a very smart one. Nissan is building the Leaf to a price point and in order to reach that point they have to have an air cooled battery. Will this shorten the life and reduce the performance of the battery? Most definitely. Will there be potential future lawsuits if the cells experience thermal runaway? Yeah, probably, but I bet Nissan is going to sell a lot of these cars.

 

[mheslep]

Show me where it gives more than two reasons for thermal runaway.

Search the Amazon reference for "thermal runaway" if you like.

The GM Volt, which uses LG batteries, does not swing through 100% DoD, more like 50-60%, as you no doubt know.

No, I don't know that because its not true.

http://en.wikipedia.org/wiki/Chevrolet_Volt#Battery

90-30 = a 60% DoD swing.

I'm surprised you haven't mentioned this about the Leaf yet;

Battery life: After 10 years, the battery is expected to have 70-80 percent of its original storage capacity

http://green.autoblog.com/2010/05/2...eaf-battery-pack-including-how-recharging-sp/

Yes and Nissan also warranties the battery for 8 years/100,000 miles. You knew this, and accepted it all along? Yet you still made the "about 3 years before they are considered dead" claim?

 

[mheslep]

No I don't recall without the book in front of me, but what does capacity have to do power output in this case?

The battery model is relatively simple for a first approximation as several of the references have shown: a simple idea voltage source at ~4.2V connected to the load via an internal (effective) battery resistance, with a dependency on state of charge, temperature, and life cycle as we have seen. Capacity then is the total energy delivered by the battery to a load which is not consumed by the I^2 * R losses, and power is simply the rate of delivery of that energy, also limited by voltage drop across the internal resistance.

And if this is true, why can't the Volt just drive away using only its battery when its 0'F outside? If the Leaf uses the same chemistry, why can it operate at those temperatures but the Volt cant?

The Volt's battery probably could, but as we've discussed driving around with a cold battery and thus high internal resistance wastes energy unnecessarily on internal losses and cuts the range significantly. GM wants to be able to say, I believe, that battery operation range is at least close to 40miles, always. So it makes perfect sense for the Volt's controller to use the combustion engine first to warm up the battery, given the Volt has that option. Same probably goes for hot temperatures in the Volt to avoid life time degradation - cool it off first.

 

[mheslep]

The ~2.9VDC figure Linden shows in Fig 43 is the -20degC full 1C discharge voltage. This is not the discharge rate required to roll out of a parking spot on a -20degC morning, rather ~0.1C will do that, with 10X less I*R voltage drop. So full acceleration power won't be available at startup, but then I don't put my foot to the floor right away w/ my gasoline vehicle either on -20degC days.

So the moment you pull out of your driveway you're going to keep going 1mph?

The tractive power required to travel 70mph vs 10mph in a sedan is about http://www.inference.phy.cam.ac.uk/withouthotair/cA/page_256.shtml"

How long and how much energy do you think it takes to heat up a 500kg battery?

http://nissan-leaf.net/2010/05/27/nissan-leaf-battery-specifications/", Fluence is 250kg, frame and all, only the electrolyte and separator matter, and as the curves show it need be warmed only only to ~ 0 degC or so.

I would bet that in a practical case it would take a while even considering the battery to be at full power output just to heat itself up from -20'C in a reasonable amount of time. Its not like you're heating an internal combustion engine which has a smaller mass and where 75% of the energy you're using is being turned to heat.

Well consider, for example, that the total battery pack is providing, say, 100A through an elevated internal resistance when cold of 10 milliohm. That's one KW of heating applied exactly where its needed. Yes the Leaf will be sluggish in extreme cold, and I imagine we'll hear people griping about it giving the car a bad rep. I suppose, as you say, Nissan's going for cheap, not good all weather performance. Of course some people are already used to taking additional measures in the extreme cold - Canadians and Scandinavians plugging in engine block heaters overnight.

 

[Topher925]

Search the Amazon reference for "thermal runaway" if you like.

I don't need to. I already searched the book itself. I couldn't even find where it states all of the root sources of thermal runaway.

Yes and Nissan also warranties the battery for 8 years/100,000 miles. You knew this, and accepted it all along? Yet you still made the "https://www.physicsforums.com/showpost.php?p=2980109&postcount=656"" claim?

Did I know that all along, yes. Did I "accept" it, a very strong No. There's a lot of controversy and suspicion over Nissan and the battery they put in the Leaf. 1,2,3 Stating that their battery can last essentially 10 years and even do it without a TMS is quite the statement, especially from a company that can't even build a much simpler competitive hybrid. Nissan has to buy their hybrid powertrains from their competitor, Toyota.4

1. http://www.dailytech.com/Tesla+CEO+...imitive+Boasts+About+Model+S/article19286.htm
2. http://gm-volt.com/2010/01/28/nissan-taking-shortcut-on-leaf-battery-no-thermal-management-system/
3. http://www.technologyreview.com/energy/26832/?p1=A1
4. http://en.wikipedia.org/wiki/Hybrid_Synergy_Drive

 

[Topher925]

Capacity then is the total energy delivered by the battery to a load which is not consumed by the I^2 * R losses, and power is simply the rate of delivery of that energy, also limited by voltage drop across the internal resistance.

Ok? Still not seeing the connection here. You can have a relatively small or large I and not have a big change in capacity, but it doesn't really work the other way around. Also, when Li ion batteries get really cold, their power output and perceived capacity is time dependent as the reaction is limited by diffusion of Li⁺ through the SEI.

The Volt's battery probably could, but as we've discussed driving around with a cold battery and thus high internal resistance wastes energy unnecessarily on internal losses and cuts the range significantly. GM wants to be able to say, I believe, that battery operation range is at least close to 40miles, always.

Do you have any way to support this claim? The sources I pointed out very clearly state it to be a performance issue suggesting that its an issue with power and not one of capacity.

 

[Topher925]

The tractive power required to travel 70mph vs 10mph in a sedan is about http://www.inference.phy.cam.ac.uk/withouthotair/cA/page_256.shtml"

Alright. But what's your point other than traction power increases with speed?

http://nissan-leaf.net/2010/05/27/nissan-leaf-battery-specifications/", Fluence is 250kg, frame and all, only the electrolyte and separator matter, and as the curves show it need be warmed only only to ~ 0 degC or so.

OK, either way 300kg is a large mass to heat, especially when the battery is air cooled and designed to have efficient convective heat transfer. Even if you assume the battery is made entirely of something like aluminum, that's about 1.5kWh to raise the battery from -20'C to 0'C. Or in other words, about 12% of your usable battery capacity.

And no, its not just the separater and electrolyte that matter, the electrodes, especially the negative electrode, matter as well. Its not like you can just heat one without the other anyway.

Well consider, for example, that the total battery pack is providing, say, 100A through an elevated internal resistance when cold of 10 milliohm. That's one KW of heating applied exactly where its needed. Yes the Leaf will be sluggish in extreme cold, and I imagine we'll hear people griping about it giving the car a bad rep. I suppose, as you say, Nissan's going for cheap, not good all weather performance. Of course some people are already used to taking additional measures in the extreme cold - Canadians and Scandinavians plugging in engine block heaters overnight.

See comment above. At 1kW of heat, its going to take well over an hour to heat up that battery. Although 10mOhm for resistance of an entire battery pack sounds pretty small to me. Were you referring to just a single cell or module?

 

[mheslep]

Alright. But what's your point other than traction power increases with speed?

Right, required traction power increases with speed. The point is that the vehicle won't need anywhere near the sustained full power for which the EV battery was designed until it hits the highway, and then only at high speed.

OK, either way 300kg is a large mass to heat, especially when the battery is air cooled and designed to have efficient convective heat transfer. Even if you assume the battery is made entirely of something like aluminum, that's about 1.5kWh to raise the battery from -20'C to 0'C. Or in other words, about 12% of your usable battery capacity.

And no, its not just the separater and electrolyte that matter, the electrodes, especially the negative electrode, matter as well. Its not like you can just heat one without the other anyway.

See comment above. At 1kW of heat, its going to take well over an hour to heat up that battery.

The heat comes only from the active part of the battery, and there will be a heat flux down a temperature gradient between the active battery area and the remainder. Let's look at the details.

As we discussed, the power limitation is due to ion diffusion temperature sensitivity, in this case Li ions. Thus we need look at only that which contains Lithium and is actively transferring ions, namely most of the electrolyte and the surface of the cathode. The electrolyte is about http://www.transportation.anl.gov/pdfs/TA/149.pdf" for one cell. Sixty such 100Ah cells at ~3.5kg/cell make up a 24KWh - 100 mile EV pack, for ~210kg, the rest is infrastructure (wiring,housing,etc), leaving maybe only 40kg of active material. The electrolyte is a salt, say LiPF6; I don't know its specific heat capacity but assuming it is similar to other salts at ~0.9 kj/kg-K, we have 0.9 *~20kg * 20degK / 1kW = 720s, i.e. a 20deg C rise in 12 minutes. Yes some of the heat is dissipating away to the rest of the battery, but via a salt and non-metal electrodes I'd guess that's a down ~20degC temperature gradient to the outside housing at max power.

 

[Topher925]

Right, required traction power increases with speed. The point is that the vehicle won't need anywhere near the sustained full power for which the EV battery was designed until it hits the highway, and then only at high speed.

And what about acceleration and driving up hills? What if I live in San Fransisco? Not everyone is driving Ms. Daisy.

The heat comes only from the active part of the battery, and there will be a heat flux down a temperature gradient between the active battery area and the remainder. Lets look at the details...some of the heat is dissipating away to the rest of the battery, but via a salt and non-metal electrodes I'd guess that's a down ~20degC temperature gradient to the outside housing at max power.

One of the details you didn't include is the heat transferred to the electrodes and current collectors. The geometry of the electrolyte and seperater obviously provide a large area of contact to the electrodes providing a lot of surface area per volume for heat transfer. The electrodes are constructed from graphite and spinel, both materials which have very good thermal conductivity. The current collectors are constructed from aluminum and possibly copper, again very good thermal conductivity. Its not realistic to make the assumption that only the electrolyte and seperater are generating heat and mostly only heating themselves, especially with a 20'C temperature gradient. To be realistic, you should at least consider the entire mass of the battery itself, 210kg, to account for convective heat transfer to the surroundings.

 

[mheslep]

I don't need to. I already searched the book itself. I couldn't even find where it states all of the root sources of thermal runaway.



Did I know that all along, yes. Did I "accept" it, a very strong No. There's a lot of controversy and suspicion over Nissan and the battery they put in the Leaf. 1,2,3 Stating that their battery can last essentially 10 years and even do it without a TMS is quite the statement, especially from a company that can't even build a much simpler competitive hybrid. Nissan has to buy their hybrid powertrains from their competitor, Toyota.

Oh I agree, a lack of a thermal system is going to be big problem, and the Leaf is going be all over the place in performance as a consequence. Some owner in San Jose, Ca w/ 80F 365 days a year will get 10 years, but some other guy in Vegas who drives hard in 110F summers may get half. That's completely different from the blanket statement "Li batteries also have a life of only about 3 years before they are considered dead", especially in the context of the recent GE buy of GM Volts which do have TMSs.

1. http://www.dailytech.com/Tesla+CEO+...imitive+Boasts+About+Model+S/article19286.htm
2. http://gm-volt.com/2010/01/28/nissan-taking-shortcut-on-leaf-battery-no-thermal-management-system/
3. http://www.technologyreview.com/energy/26832/?p1=A1

Thanks for these references. The bit from today's TR story I didn't know and is especially interesting:

Nissan recommends a cold weather package that includes a battery heater, but this doesn't come as standard. And the option is not available for the first Leafs to come off of the assembly line, and it cannot be added to a car later. If the Leaf pack gets too cold, or too hot, it enters a limited power mode, which restricts acceleration and top speed.

 

[mheslep]

And what about acceleration and driving up hills? What if I live in San Fransisco? Not everyone is driving Ms. Daisy.

If the location is SF then an EV will never see -20C, nor anywhere else in Ca outside the mountains. Let's not turn this around as if I have claimed all EV/PHEV's will work perfectly without downsides, all the time, everywhere. As I've said, an EV/PHEV without TMS in extreme cold weather is going to be sluggish until it warms itself up. I objected up front only to absolute claims that "EV's still don't work in cold weather", and then digging in deeper with claims that an EV won't "start" in the cold, and then won't drive away from the parking lot if started.

One of the details you didn't include is the heat transferred to the electrodes and current collectors. The geometry of the electrolyte and seperater obviously provide a large area of contact to the electrodes providing a lot of surface area per volume for heat transfer. The electrodes are constructed from graphite and spinel, both materials which have very good thermal conductivity. The current collectors are constructed from aluminum and possibly copper, again very good thermal conductivity.

I did consider the electrodes for heat flow and discounted them. What's important is not that the electrodes are good thermal conductors, but that salts (solid) are relatively very poor thermal conductors - probably 20-30x worse than metals, and thus won't quickly give up their heat. Imagine a hot brick (poor thermal conductor). Embedding several metal rods in it won't cause it to cool markedly faster.

 

[mheslep]

I came across these sticker prices for the Nissan Leaf EV vs a comparably sized gasoline vehicle, the Chevy Cruze, and wanted to extend them to ten year cost of ownership. Both are 5 door, 5 seat smallish vehicles.

The Leaf EV price of $26,380 is after the $7500 tax credit.

Here's ten year total cost of vehicle plus fuel/electricity, with the Cruze at $1457/yr and the Leaf at $396/yr:
Leaf: $30,340
Chevy Cruze: $31,565
Prius: $30,960

Maintenance:
For other maintenance, both vehicles will both need tires, but the Leaf needs no: oil changes, transmission work, radiator flushes, fuel/water pumps, little or no brake work, etc, etc. On experience, I'd guess that's $400/yr (not including tires) for a small vehicle like the Cruze, or $4000/ten years. The Leaf is going to need a new battery at ten years; replacement cost is complicated ten years out. Currently the battery is ~$10,000-12,000; by 2020 probably $5000. But then it may not make sense to buy a brand new ten year (non-swappable) battery for a ten year old car, so perhaps a half-life battery would do, if such a thing could be bought on the market at that time.

 

[brainstorm]

The solution to energy crisis has been discovered and I have already invested: the Snuggie (blanket with sleeves).

As for the problem with heating electric cars, how much propane would it take to keep an electric car at 70F for a 1-hour commute?

 

[mheslep]

The solution to energy crisis has been discovered and I have already invested: the Snuggie (blanket with sleeves).

As for the problem with heating electric cars, how much propane would it take to keep an electric car at 70F for a 1-hour commute?

Which day of the week?