evnow
Well-known member
Bicster said:
True. But I've read / heard about this air circulation to equivalize the temperature in multiple places. I'll update the thread when I find the right link.
Minnesota Leafs?
- Thread starter jgrode1
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Help Support My Nissan Leaf Forum:
True. But I've read / heard about this air circulation to equivalize the temperature in multiple places. I'll update the thread when I find the right link.
AndyH
Well-known member
The Wired author got it wrong. One of our members [<- That's a link!] in Phoenix has contact with the hot weather Leaf test folks, and he's reported that cooling is conductive. Nissan's PDFs in the media section show multiple photos of the sealed pack undergoing dunk and ice water bath testing.
The higher efficiency cells don't create as much heat as cylindrical cells so there's much less need for cooling, and the laminated LiMn cells in their stackable 'sardine cans' are excellent for transferring heat.
I build packs with cylindrical LiFePO4 cells and have bench tested a number of different cells and chemistries and the Nissan and forum data passes the 'gut' check while the Wired article does not.
Andy
The higher efficiency cells don't create as much heat as cylindrical cells so there's much less need for cooling, and the laminated LiMn cells in their stackable 'sardine cans' are excellent for transferring heat.
I build packs with cylindrical LiFePO4 cells and have bench tested a number of different cells and chemistries and the Nissan and forum data passes the 'gut' check while the Wired article does not.
Andy
evnow
Well-known member
AndyH said:
The pack can be sealed and has an internal fan that runs to equivalize the temperature - nothing wrong with that ;-)
Ofcourse the wired article was a hit piece against Nissan (on behalf of Tesla). Thats why it was picked up with alacrity by gm-volt.com.
Thanks for humoring me gang. I am hoping that by the time my market opens up to get my Leaf that they will have smoothed over anything they might have missed in the first production run. Plenty of time for me to get better educated about EV's too.
Pipemajor
Well-known member
I fly model airplanes - often with lithium-polymer batteries on board during some sub-freezing weather. True, they are sluggish when cold but the discharge process will heat them up a bit so that they return to near-normal performance. Some of my electric-powered models exhaust a full 11.3v battery pack in several minutes - our "draw" on packs is pretty high, thus the heat generated.
Lithium-polymer is a pretty volatile chemistry. Manufacturers warn against trying to fully charge a pack during sub-freezing weather, let alone sub-zero weather. Lithium-ion is a bit more "safe".
Lithium-polymer is a pretty volatile chemistry. Manufacturers warn against trying to fully charge a pack during sub-freezing weather, let alone sub-zero weather. Lithium-ion is a bit more "safe".
AndyH
Well-known member
Nothing at all wrong with that - except we've seen photos of the pack and there isn't any space in the lower portion of the battery tray for a fan, and the diagrams show that there's precious little room between the battery cans and the plastic lid for the pack. My vote is still 'no fan'.evnow said:
AndyH
Well-known member
Pipemajor said:
You're very right - lithium cobalt and LiPo are the most volatile, but today's cells are safer than LiCo/LiPo manufactured just 5 years ago.
It's important to remember when we read the EV press and try to compare battery performance that in the lithium ion family we have Li-Ion/lithium cobalt, lithium polymer, lithium manganese (LiMn2O4), lithium iron phosphate (LiFePO4), and others. Even in the same general chemistry family, manufacturers adjust the chemical soup a bit to favor one characteristic over another.
Lithium iron phosphate and lithium manganese are the 'safer' varieties, as they do not have free lithium when charged and thus don't catch fire when damaged or severely overcharged the way lithium cobalt will. Between LiFePO4 and LiMn, car companies are tending toward lithium manganese because of their relatively lower price.
Most of the on-line resources (wikipedia, battery university, and MpowerCoUK) have decent info, but the pace of research on lithium rechargeable cells has been so fast that most of the books and websites that include a look at lithium are out of date - some very out of date.
For example - lithium manganese cells have been used in electric power tools for a number of years and they're known to have a 500 cycle lifespan while lithium iron phosphate delivers 1000-2000 cycles. But that was the older LiMn. The LiMn cells made by LG Chem and used in at least the Volt hybrid have a much longer life than the old 500 cycles. And the >100,000 mile pack life shown by AESC for the Nissan/NEC LiMn cell suggests that they've significantly improved the cycle life as well.
It's hard to keep up with all the labs and companies working on Li-Ion cells, and we're doing better at it than the press. And the fast pace of development also means there's plenty of bad info available for a competitor to use in their FUD campaign.
LeafHopper
Active member
AndyH,
I talked to Paul Hawson, a Nissan product planner. He said that the Nissan had no active thermal management system. And he stated that all heat was dissipated by conduction through the metal battery case. He stated that the temperature rise was only 2 to 3 degrees above the ambient temperature.
I should have asked him if that was the Phoenix ambient temperature during the summer while driving on hot pavement. If so, we will be getting hot feet. :lol:
I talked to Paul Hawson, a Nissan product planner. He said that the Nissan had no active thermal management system. And he stated that all heat was dissipated by conduction through the metal battery case. He stated that the temperature rise was only 2 to 3 degrees above the ambient temperature.
I should have asked him if that was the Phoenix ambient temperature during the summer while driving on hot pavement.
If so, we will be getting hot feet. :lol:AndyH
Well-known member
LeafHopper said:AndyH,
I talked to Paul Hawson, a Nissan product planner. He said that the Nissan had no active thermal management system. And he stated that all heat was dissipated by conduction through the metal battery case. He stated that the temperature rise was only 2 to 3 degrees above the ambient temperature.
I should have asked him if that was the Phoenix ambient temperature during the summer while driving on hot pavement.
Rog - I linked to your post above. The AESC website says the temperature rise is very low in lab testing, but you've posted the first info I've seen that talks to temperature rise in a complete pack. Thank you again for your reports!
Pipemajor
Well-known member
Mullover said:
There are only 4 Nissan dealers in the Twin Cities metro area:
- Kline Nissan in Maplewood
- Morrie's Brooklyn Park Nissan in... Brooklyn Park
- Coon Rapids Nissan in... Coon Rapids
- Luther Nissan in Inver Grove Heights
I just got the bad news that Nissan won't even be taking firm orders for Leafs in Minnesota until "Fall or Winter 2011." So sit tight you Minnesota Leafers. We have a long wait ahead of us.
The thing that really ticks me off about this is that we will miss the $1000 tax rebate for the home charging station (set to expire at the end of this year). Major bummer! :x
The thing that really ticks me off about this is that we will miss the $1000 tax rebate for the home charging station (set to expire at the end of this year). Major bummer! :x
evnow
Well-known member
Mullover said:
That will be extended.
scottwilcox
Active member
- Joined
- May 11, 2010
- Messages
- 26
Anyone a little dissappointed that Nissan will be putting the LEAF in the rental fleets in January 2011 while some of us non rollout states will not be able to even order until the Fall/Winter of 2011.
