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mwalsh
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Re: Musk says Leaf battery primitive.

Thu Aug 05, 2010 9:49 am

evnow wrote:The way Nissan explains this is - since the pack will be essentially maintained at the cabin temperature, if you are comfortable, so is the pack.


Ah, so the pack uses the cabin air to cool it and not outside air? How comes I missed that?
2011 Blue Ocean SL with 77,000 miles.
2015 pack under warranty 12/30/15.
Tinted windows.
Bridgestone Ecopia 422+ tires.
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garygid
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Re: Musk says Leaf battery primitive.

Thu Aug 05, 2010 10:09 am

For overheating issues, only "hot" days are really significant to discuss.

We are told that the Nissan battery pack (48 modules of 4 cells each) is completely sealed, so there is NO airflow through it.

They say that the heat (generated inside, or from the outside) flows by conduction through the battery pack shell, and mosty by conduction inside the LEAF's pack. Heat can be going in, or out, depending upon which is hotter.

So, what will the temperature of the air around the outside of the pack be during operarion, and during charging?

Charging:
The car is not moving and cabin A/C is typically OFF, so there is no airflow (that we know of), and the air is at "ambient", and the cabin might be 40 degrees over ambient if parked in the sun.

Driving:
Ambient airflow around the pack is certainly possible, and might be sufficient. Exhaust cabin air (if any) might be ducted around the outside of the pack, but one cannot count on there being very much "exit" air on hot days, because of the max-cooling "recirculate" A/C mode that would often be in use.

So, at this point, there is not any significant "cabin comfortable means battery pack comportable" mechanism ... that I know of.
See SOC/GID-Meter and CAN-Do Info
2011 LEAF, sold in 2015
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Zythryn
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Re: Musk says Leaf battery primitive.

Thu Aug 05, 2010 10:25 am

MikeBoxwell wrote:...
I can believe that Tesla has the more advanced battery management system, but I would suggest that Nissan has the more innovative battery design. Two different ways to get to the same result. Which is the best? Who can say to be sure, but I think both solutions have merit and it will be interesting to see which direction electric vehicle manufacturers go in the future.


Excellent way to sum up the issue.
And thanks to everyone for their insights. It is a very interesting topic as the batteries really are the foundation of an EV.

I would have more concerns with a more complicated management system design, by a little bit, than a more complicated battery design. But I also see how the latter could be much more expensive.

It probably comes down to design and quality control for both solutions.
Previous owner of Prius, Volt, Leaf & Model S
Current owner of Model 3
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mwalsh
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Re: Musk says Leaf battery primitive.

Thu Aug 05, 2010 10:26 am

garygid wrote:For overheating issues, only "hot" days are really significant to discuss.

We are told that the Nissan battery pack (48 modules of 4 cells each) is completely sealed, so there is NO airflow through it.

They say that the heat (generated inside, or from the outside) flows by conduction through the battery pack shell, and mosty by conduction inside the LEAF's pack.



I guess that is correct. Something else I must have missed:

viewtopic.php?p=2535#p2535

Are we getting to the point that we need a FAQ or Wiki just for ourselves? Seems to me that we are.
2011 Blue Ocean SL with 77,000 miles.
2015 pack under warranty 12/30/15.
Tinted windows.
Bridgestone Ecopia 422+ tires.
L1 EVSE upgrade.
FIAMM horns.
Superbright LED lighting.
2013 sun visors.
LED shifter.
Heated seats.
GT-R map lamp lenses.
AV L2 EVSE.

Gavin
Posts: 471
Joined: Fri Apr 23, 2010 2:51 pm
Delivery Date: 26 Jun 2015
Location: Albuquerque, NM

Re: Musk says Leaf battery primitive.

Thu Aug 05, 2010 10:31 am

Great post...

I liked the ending...

I will think of more questions and answers later. I spent 2 hours at the demo area. I was ready to write a check on the spot.


Gavin

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Re: Musk says Leaf battery primitive.

Thu Aug 05, 2010 11:02 am

Image

This photo clearly shows the battery back to be installed under the floor of the passenger compartment. Not really sure where the idea came from that the battery was installed inside.

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evnow
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Re: Musk says Leaf battery primitive.

Thu Aug 05, 2010 11:42 am

LEAFguy wrote:This photo clearly shows the battery back to be installed under the floor of the passenger compartment. Not really sure where the idea came from that the battery was installed inside.


It is not impossible to install the battery under the floor and yet have the cabin air flow over the batteries. As I said, Nissan has said the batteries will live in the same temperature environment as the cabin.
1st Leaf : 2/28/2011 to 5/6/2013
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garygid
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Re: Musk says Leaf battery primitive.

Thu Aug 05, 2010 11:52 am

Between the "modules" (4 cells each) that you see, and the floor of the car, is the top half of the sealed battery pack box.

Yes, exhaust cabin air COULD be directed around the pack box, at least between the floor and the top of the box.

But, in some (important) cases there might be very little airflow through the cabin.

I thought that the bottom of the battery pack box would be "exposed" on the underside, for easier removal, but maybe that is just in areas where the packs can be "swapped".
See SOC/GID-Meter and CAN-Do Info
2011 LEAF, sold in 2015
2010 Prius, 2014 silver Tesla S
Nissan EVSE, mod to 240/120v 16A
PU: SDG&E
Solar PV: 33 x 225W -> 7 kW max AC
To Sell: X-treme 5000Li EV motorcycle

LEAFfan
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Re: Musk says Leaf battery primitive.

Thu Aug 05, 2010 12:46 pm

garygid wrote:Between the "modules" (4 cells each) that you see, and the floor of the car, is the top half of the sealed battery pack box.

Yes, exhaust cabin air COULD be directed around the pack box, at least between the floor and the top of the box.

But, in some (important) cases there might be very little airflow through the cabin.

I thought that the bottom of the battery pack box would be "exposed" on the underside, for easier removal, but maybe that is just in areas where the packs can be "swapped".


I'm in Arizona, but I rarely (only when I have a passenger) use my A/C (just don't need it and there's a big reduction in mpg with civic cng cars) so I don't plan on using the A/C in the LEAF which will give no benefit to the battery pack underneath. :)
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AndyH
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Re: Musk says Leaf battery primitive.

Thu Aug 05, 2010 1:55 pm

Spin aside, the Tesla pack is made from lithium cobalt cells. The Leaf is using lithium manganese.

Lithium cobalt cells generate metallic lithium when overcharged. Lithium cobalt cells will go into thermal runaway and can catch fire (think overheated laptop batteries here) if temperature and voltage isn't tightly controlled. Metallic lithium is highly reactive with air and especially water. Burning lithium releases hydrogen gas for an added fire boost. ;)

Lithium manganese does not use or generate metallic lithium when overcharged. Lithium manganese does not go into thermal runaway when overcharged or abused. Lithium manganese and lithium iron phosphate are the two cells in the lithium family that are considered 'safe' for vehicle use.

While there are performance benefits to keeping the Tesla battery cooled and/or warmed, the cost is additional energy use. The cost of a failed climate control system can be a battery fire. Tesla isn't using extreme management because they're nice folks (while many likely are!), they're using the management devices because sales will likely drop a fair amount if Roadsters burst into a self-sustaining and high temperature fireball...

Nissan can make a more energy efficient, simpler, and lighter weight battery pack with fewer failure modes because they've selected a cell that doesn't require extraordinary thermal management for a long life.

Andy

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