Musk says Leaf battery primitive.

[mwalsh]

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?

 

[garygid]

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.

 

[Zythryn]

...
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.

 

[mwalsh]

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:

http://www.mynissanleaf.com/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.

 

[Gavin]

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

 

[LEAFguy]

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.

 

[evnow]

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.

 

[garygid]

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".

 

[LEAFfan]

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.

 

[AndyH]

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

 

[planet4ever]

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.

Why would it have to be exhaust cabin air? If I were designing the battery temperature control system, and wanted to minimize costs, I think I would split the flow of air coming into the cabin from the heater or air conditioner so that part of it went to the battery pack instead. I would use a computer to balance the split between what the driver is calling for and what the battery conditioner is calling for, and drive the heater or AC based on the sum of those requests.

 

[Azrich]

As I said, Nissan has said the batteries will live in the same temperature environment as the cabin.

Where did you hear this? I've never seen this anywhere. The battery chamber is not open to the passenger cabin in any way. I don't want it connected in any way - too much heat coming into the cabin from hot batteries.

 

[lne937s]

From all the images I've seen, I can see no way that the battery shares the same airspace as the interior- it is below the floorpan....

However, If you look at the underside of the car, you can easily see that there are air outlets to cool the battery pack (even if the pack itself is sealed). But, if you look at the front of the battery, there is a fairly wide diameter pipe going to the front of the pack, which appears to be below where the elctrical cables would be exiting to go to the inverter. Perhaps this is connected to the HVAC system.

http://www.nissanusa.com/leaf-electric-car/tags/show/news#/leaf-electric-car/gallery/view/car/12

 

[EVDRIVER]

Using directed AC to cool the pack would be very, very inefficient.

 

[mitch672]

I thought the pack was just "air cooled" via a circulation fan within the pack, and then conduction cooled to the pack case... which is air cooled via the movement of the car itself of the battery pack housing. The pack generates very little heat, from whats been said/rumored from AESC.

 

[EVDRIVER]

I thought the pack was just "air cooled" via a circulation fan within the pack, and then conduction cooled to the pack case... which is air cooled via the movement of the car itself of the battery pack housing. The pack generates very little heat, from whats been said/rumored from AESC.

This is my understanding as well, I heard the circulation fan was for even aging of the pack so it would be the same temp which makes sense.

 

[evnow]

This is not the first time Tesla has tried to spread FUD about Nissan's battery.

http://www.wired.com/autopia/2010/01/nissan-leaf-2/#ixzz0qraatkFw

 

[evnow]

Where did you hear this? I've never seen this anywhere. The battery chamber is not open to the passenger cabin in any way. I don't want it connected in any way - too much heat coming into the cabin from hot batteries.

I've to search to get the quote - it might have been some video of Perry answering questions.

 

[LEAFer]

This is not the first time Tesla has tried to spread FED about Nissan's battery.

http://www.wired.com/autopia/2010/01/nissan-leaf-2/#ixzz0qraatkFw

Ok ... I know you meant "FUD" ... but to be fair, that was *NOT* Tesla that was doing the "spread FED[sic]". It was Darryl Siry's article, who used to work at Tesla, but by late January 2010 has not had any association with Tesla for a LONG time.

Edit: Reference: http://www.darrylsiry.com/2008/12/switching-off.html

 

[evnow]

Ok ... I know you meant "FUD" ... but to be fair, that was *NOT* Tesla that was doing the "spread FED[sic]". It was Darryl Siry's article, who used to work at Tesla, but by late January 2010 has not had any association with Tesla for a LONG time.

Essentially all these (ex & present) Tesla guys - and Volt people too - have been trying to defend their complex & expensive liquid cooling systems - by saying Nissan's won't work.

It is natural. The question would be why is your battery so complex - if Nissan's can be that simple & work well.