Musk says Leaf battery primitive.

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Well Tesla's needs to be complex...the batteries they use have been shown to catch fire if too hot.

But the Volt chemistry is similar to the LEAF I thought...and that chemistry and packing does not have the same fire risk...

So you could state, "I know why the Tesla needs advanced cooling, and I know why the LEAF doesn't need advanced cooling, but why does the Volt use Advanced cooling? It adds weight and complexity to the system."

Gavin
 
Gavin said:
... but why does the Volt use Advanced cooling? It adds weight and complexity to the system.
Click to expand...
Ah, but so does having an ICE system and all that goes with it. GM just can't help themselves in adding weight and complexity.

Sorry couldn't help myself. :)
 
Gavin said:
So you could state, "I know why the Tesla needs advanced cooling, and I know why the LEAF doesn't need advanced cooling, but why does the Volt use Advanced cooling? It adds weight and complexity to the system."
Click to expand...

While the chemistries are same, remember GM doesn't have much experience with Li batteries. They source theirs from LG - so I guess they weren't sure how it will behave and have heavily over engineered Volt. They not only liquid cool the battery, their DOD is only 50%. This has cost them complexity, weight, extra battery cost and the middle seat at the back (Volt seat is divided at the back and can only seat 2, not 3).

Infact at one time Lutz was saying they will factor a replacement battery in their price. But once it became known that it was not needed - the general perception was that Volt won't be priced at $40K. One of the reasons there is a general revolt about its price in gm-volt.
 
I think there are no fans inside the LEAF's battery pack. People have suggested that there could, might, or should be, but that is all.

EDIT: Oops (see posts below), one report stated that there will be a fan inside to better distribute the heat. That is quite possible, however I do not know if that is the "final word" on battery-box fans, ... and a fan would use extra energy.

With sufficient conduction inside the pack to the outside wall, fans are not necessary.

Every module in the pack has at least one side directly adjacent to the pack's outer box. The mechanism that holds the modules in place probably conducts heat to the box's bottom "skin". Apparently the box's top is removable, to allow modules to be removed and replaced.
 
garygid said:
I think there are no fans inside the LEAF's battery pack. People have suggested that there could, might, or should be, but that is all.
Click to expand...

From the article I linked earlier ...

Instead, Nissan has opted to use only an internal fan that circulates the air within the sealed pack to evenly distribute the heat, which escapes by passive radiation through the pack’s external case.
Click to expand...

http://www.wired.com/autopia/2010/01/nissan-leaf-2/#ixzz0vqrgIoxT
 
Nissans battery is probably the best solution for a small car with 100 mile range. But you can't use those modules for a battery that will power a large car for 300 miles, it would weigh at least 2000 pounds.

Teslas technology enables them to build such a battery with a weight of ~1200 pounds which is acceptable in a large car like the Model S.

I'd say around 40-45kWh of battery capacity is the point where Teslas battery starts to make more sense than Nissans.
 
Sorry guys - the Wired article is just wrong. There are no fans inside the box (there's no room and there's no benefit). There aren't any air ducts and there's no cabin air moving through the battery box.

We have some excellent high resolution battery box pictures now from various drive events. But the place to start is the October '09 Nissan 'slide show' http://www.absoluteefficiency.com/LEAF/NissanLeaf_Oct09.pdf

Page 24 shows how well the battery box is sealed. Not only is the battery box sealed well enough to withstand high pressure spray and dunking, but NISSAN also shows that the battery box is watertight when immersed in an ice water bath. The box is sealed well enough to resist water intake even when there's lower pressure inside the box.

The battery boxes on display have only four areas where items pass into the box. There's the disconnect plug on the top, and the three 'holes' in the front - two for the high-voltage connections and the third likely for the BMS communications to the car.

box_front.jpg


Andy
 
This fan, if it exists, would be inside the box and just move air around inside the box. There would be no in/out holes or ducting required.

But, I also suspect there will be no fan included in the production battery box, because the heat generated is already spread fairly evenly throughout the box, with each module generating essentially the same amount of heat. So, the benefits of using an internal fan might be too minimal.
 
jkirkebo said:
Teslas technology enables them to build such a battery with a weight of ~1200 pounds which is acceptable in a large car like the Model S.
Click to expand...

Prismatic batteries are better than cylindrical batteries (just simple math) in terms of volume.

Model S will apparently use new chemistry - that is why Tesla has been quoting 1200 pounds. Similar chemistry that is coming in gen 2 of Leaf will have about double the capacity for the same weight.

The reason why Tesla started using cylindrical was because
- cells can be sourced from a large number of vendors
- there was no prismatic battery vendor available

But the cons are
- Not as safe in LiMn that everyone else is using
- Needs complex BMS, liquid cooling etc
- Difficult to manufacture in volume because of 6000 cells that need to be soldiered

Here is a good reference : http://pubs.its.ucdavis.edu/download_pdf.php?id=1292

EVS24 : Stavanger, Norway, May 13 - 16, 2009
Performance Characteristics of Lithium-ion Batteries of Various Chemistries for Plug-in Hybrid Vehicles
Andrew Burke, Marshall Miller
University of California-Davis, Institute of Transportation Studies, California
Click to expand...

libatteries.png
 
AndyH said:
We have some excellent high resolution battery box pictures now from various drive events. But the place to start is the October '09 Nissan 'slide show' http://www.absoluteefficiency.com/LEAF/NissanLeaf_Oct09.pdfAndy
Click to expand...

AndyH, thanks for the link to that Oct 09 pdf document. I had not seen that before, and it answered a significant number of questions that I had.

Regarding the wired article referenced earlier, I think this is the sentence that tripped some of us up:

The key engineering trade-off Nissan has made is opting not to include active thermal management, where the temperature of the pack is controlled by an HVAC system similar to what cools the passenger cabin on a hot day. The bold emphasis is mine.

Read More http://www.wired.com/autopia/2010/01/nissan-leaf-2/#ixzz0vrMUYnG5

While they state "similar to", it is easy to see how it could be mis-read by some. But... they provide no source of their statement that temperature is controlled by an HVAC system. This just seems to be in error. It would appear, based on this entire discussion, that there truly is no active management system (which is what Mr. Perry has stated all along).
 
LEAFguy said:
While they state "similar to", it is easy to see how it could be mis-read by some.
Click to expand...

While that is possible - I "remember" reading / listening to someone from Nissan (probably Perry) saying "if you are comfortable in the cabin, the battery will be confortable too" or something to that effect. Ofcourse, we all know "memories" are anything but ...
 
evnow said:
jkirkebo said:
Teslas technology enables them to build such a battery with a weight of ~1200 pounds which is acceptable in a large car like the Model S.
Click to expand...

Prismatic batteries are better than cylindrical batteries (just simple math) in terms of volume.

Model S will apparently use new chemistry - that is why Tesla has been quoting 1200 pounds. Similar chemistry that is coming in gen 2 of Leaf will have about double the capacity for the same weight.
Click to expand...

As I understand Tesla will use Panasonic's 3.1Ah cells for their 300-mile battery. Those cells have been in mass production for around 8 months. Nissan's similar chemistry batteries are at least a couple of years off I understand, so they're not an option yet.
 
jkirkebo said:
As I understand Tesla will use Panasonic's 3.1Ah cells for their 300-mile battery. Those cells have been in mass production for around 8 months. Nissan's similar chemistry batteries are at least a couple of years off I understand, so they're not an option yet.
Click to expand...

It is somewhat confusing. I remember about the 3.1Ah Panasonic cells, but in the latest Tesla news they are talking about Cobalt Aluminum Oxide. BTW, the presser about 31.Ah cells don't mention S.

http://green.autoblog.com/2010/04/23/panasonic-delivers-first-3-1ah-lithium-ion-cells-to-tesla/

ps : Apparently the Pansonic ones use Nickel - but not yet Cobalt.

http://panasonic.co.jp/corp/news/official.data/data.dir/en091218-2/en091218-2.html

Capitalizing on this technology, Panasonic commercialized a high-capacity 2.9 Ah lithium-ion battery with a nickel positive electrode (energy density: 620 Wh/L) in 2006. Based on the cell construction with the nickel positive electrode and the HRL, the company added improvements to the battery and succeeded in developing the 3.1 Ah lithium-ion battery, the industry's highest capacity in the 18650-type*.
Click to expand...
 
LEAFguy said:
AndyH said:
We have some excellent high resolution battery box pictures now from various drive events. But the place to start is the October '09 Nissan 'slide show' http://www.absoluteefficiency.com/LEAF/NissanLeaf_Oct09.pdfAndy
Click to expand...

AndyH, thanks for the link to that Oct 09 pdf document. I had not seen that before, and it answered a significant number of questions that I had.

Regarding the wired article referenced earlier, I think this is the sentence that tripped some of us up:

The key engineering trade-off Nissan has made is opting not to include active thermal management, where the temperature of the pack is controlled by an HVAC system similar to what cools the passenger cabin on a hot day. The bold emphasis is mine.
Click to expand...

Please do check out the Reference Documents section of this forum: http://www.mynissanleaf.com/viewtopic.php?f=8&t=255

Pack thermal management definitions are a bit different than one might expect. An actively heated/cooled battery box has it's own heater and/or cooling system separate from the rest of the vehicle. Venting to ambient air, moving air from the cabin, or conduction thru a sealed battery box are all considered 'passive' thermal management.

The Leaf's 'pouch' cells make it very easy for heat to move in and out of the cell. Each 'sardine can' of four cells stacks with another. This means we have an aluminum sheet, four cells, two layers of aluminum, four cells, etc. all fastened to the steel battery box bottom.

The Wired author is incorrect in stating that Nissan made an 'engineering trade-off' by not using active management for the pack. The batteries in general use are in hybrids - and they're NiMh and they need thermal management. The Tesla's LiCo cells are also in the 'almost mandatory' management realm. The Leaf's lithium cells don't generate significant heat during use or charging - and we don't need a cooling system to remove heat that's not generated.
 
evnow said:
LEAFguy said:
While they state "similar to", it is easy to see how it could be mis-read by some.
Click to expand...

While that is possible - I "remember" reading / listening to someone from Nissan (probably Perry) saying "if you are comfortable in the cabin, the battery will be confortable too" or something to that effect. Ofcourse, we all know "memories" are anything but ...
Click to expand...

That's a reasonable statement because lithium cells are 'comfortable' in the human temperature zone. We get into problems when we assume in the wrong direction. ;)
 
I was involved with battery management systems for lithium-ion cobolt batteries in handheld computers in the 1990s. I was also the person who took the phone call from a panicking beta-test customer when the computer caught fire.

We had some great fun in the car park blowing up batteries under software control. With the right software settings you could fire one over the roof of the building. :lol:

The fact of the matter is, you can destroy pretty much any lithium-based battery chemistry with the wrong charging and discharging settings. But with the right settings, you can make the same batteries bullet-proof. What Tesla has done has been clever - take a low cost battery technology and make it perform to its absolute optimum in an entirely safe environment. As a consequence, their battery systems are the cheapest in the world and that is going to make them a force in the electric vehicle industry.

Nissan have some really clever battery design that allows them to build a larger capacity cell but with a much lower storage mass. In effect, they've taken away a lot of the temperature issues by keeping the cell mass as low as they possibly can. That is why they are not worried about heat.

My concern is with the cold, because that is where the low mass works against them. I'm going to be much more interested in seeing how the car manages -30°F in the winter than how it manages 100°F in the summer.
 
http://seekingalpha.com/article/181593-why-tesla-went-with-panasonic-as-its-battery-supplier

Why Tesla Went with Panasonic as Its Battery Supplier
 
MikeBoxwell said:
...Nissan have some really clever battery design that allows them to build a larger capacity cell but with a much lower storage mass. In effect, they've taken away a lot of the temperature issues by keeping the cell mass as low as they possibly can. That is why they are not worried about heat.

My concern is with the cold, because that is where the low mass works against them. I'm going to be much more interested in seeing how the car manages -30°F in the winter than how it manages 100°F in the summer.
Click to expand...

I agree until we get to cold performance. The relatively low mass with large surface area for the AESC cells is good for dumping heat as well as warming a cold pack. The real beauty of the Nissan pack is that all the cells are fastened to the bottom of the battery box. It would be easy to do - and very effective - to put a warming mat in the battery box before installing cells. (And we don't know that Nissan has or has not done this.)

http://store.kta-ev.com/FarnamBatteryHeaterPad.aspx
 
MikeBoxwell said:
I was involved with battery management systems for lithium-ion cobolt batteries in handheld computers in the 1990s. I was also the person who took the phone call from a panicking beta-test customer when the computer caught fire.

We had some great fun in the car park blowing up batteries under software control. With the right software settings you could fire one over the roof of the building. :lol:

The fact of the matter is, you can destroy pretty much any lithium-based battery chemistry with the wrong charging and discharging settings. But with the right settings, you can make the same batteries bullet-proof. What Tesla has done has been clever - take a low cost battery technology and make it perform to its absolute optimum in an entirely safe environment. As a consequence, their battery systems are the cheapest in the world and that is going to make them a force in the electric vehicle industry.

Nissan have some really clever battery design that allows them to build a larger capacity cell but with a much lower storage mass. In effect, they've taken away a lot of the temperature issues by keeping the cell mass as low as they possibly can. That is why they are not worried about heat.

My concern is with the cold, because that is where the low mass works against them. I'm going to be much more interested in seeing how the car manages -30°F in the winter than how it manages 100°F in the summer.
Click to expand...

Entirely safe environment for Tesla's batteries? ONLY IF the cooling system continues to function...if it doesn't for whatever reason, FIRE IN THE HOLE! :)
 

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