Battery Design and Engineering Issues

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stupid

Member
Joined
Sep 6, 2009
Messages
13
Hi Nissan Leaf fans and skeptics!

Has anyone else noticed the surge of online buzz surrounding the Leaf and the battery pack engineering and possibility of issues?

http://green.autoblog.com/2010/01/25/is-the-nissan-leaf-battery-pack-under-engineered/
It all comes down to the Leaf's power pack lacking an active thermal management system, relying instead on a passive cooling set-up which, essentially, relies on a single fan to distribute heat evenly throughout the interior of the pack. If heat is not effectively dispersed, it may lead to early degradation of overall energy capacity and a premature shortening of the vehicle's range.

http://www.wired.com/autopia/2010/01/nissan-leaf-2/
It also appears Nissan has cut corners on the most critical aspect of electric vehicle technology — the battery pack. 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.

I love Nissan's answer to the accusations that they rushed to market and didn't properly engineer and plan properly when building the Leaf and most specifically the battery pack. Here's what Mark Perry, Nissan’s director of product planning for the United States says:
If it wasn’t our pack and it wasn’t our engineers and we weren’t working on it for 17 years … we wouldn’t make the statement if we weren’t confident in our ability to do so,
 
Um, the Nissan Leaf battery pack has a fan. How is that passive cooling? It has a fan, they put it their to actively try and keep the battery pack cool. Passive cooling would be putting the battery pack in the Leaf and saying 'I hope it doesn't overheat'.

It's funny how people are attacking the Leaf on all fronts. Don't hate the player, hate the game. If you don't have an all electric vehicle ready for production in 2011, you'll fall behind, and that's why there's so many Nissan Leaf haters.
 
Yeah, it's more accurately air cooling, not passive cooling.

I really don't think it will be a problem; rather, I'd be more inclined to argue that the Volt pack is overengineered.

Now, as for "100 miles range"...
 
I noticed a battery temp gauge, the same size as the battery charge status gauge, in the instrument cluster. It's a little disconcerting to see - I suppose if driving too fast on a very hot day, and the battery temp rises to near the red zone on the gauge, I should slow down?

Is there any info from Nissan on what the driver does with the battery temp indication?
 
Our Arizona "dry" heat will be a real test for the batteries and whether or not they will overheat. The heat radiating up from pavement on a 110 degree day can be 135 degrees. My car's thermometer has registered 135 degrees while driving slowly through a parking lot on a 112 degree day. Yikes.

I saw a video of Mark Perry done a few weeks ago in Oregon where he said they were testing some LEAFs in the Phoenix area and the hot temperatures. However, Tucson just reached out first 90 degree day today. Phoenix was probably 90 a couple weeks ago. I know that there is an auto test track near Phoenix owned by another car manufacturer. Maybe Nissan is using that closed track to test the LEAF. We'll be at a 100 degrees in a couple weeks, than all hell breaks loose with the heat in June!
 
electricfan said:
Um, the Nissan Leaf battery pack has a fan. How is that passive cooling? It has a fan, they put it their to actively try and keep the battery pack cool. Passive cooling would be putting the battery pack in the Leaf and saying 'I hope it doesn't overheat'.

The fan mentioned in the Wired article?

I seriously doubt there's a fan inside the battery box. Nissan shows in their documents that the battery box is completely sealed.

Leaf_Pack.jpg


Leaf_pack2.jpg


In the battery business 'passive' thermal management is anything less than 'active'. In active, the battery pack has it's own heating and/or AC system. Passive allows for air scoops, fans, using outside air, and using heated or cooled cabin air - or simply conduction from a sealed box.

The Leaf pack will not be stressed enough in use to generate significant heat so isn't likely to need cooling beyond the conduction provided by the aluminum cases and the metal box.

Having used lithium cells on the road for the past 14 months, I know the cells won't need cooling - I hope Nissan has a heater in the battery box for the winter.

Most of the press - even EV press - doesn't have a clue about batteries. Those that do tend to have heard something about lead acid and NiMH. Lithium is in a whole new league!

Andy
 
Azrich said:
Our Arizona "dry" heat will be a real test for the batteries and whether or not they will overheat. The heat radiating up from pavement on a 110 degree day can be 135 degrees. My car's thermometer has registered 135 degrees while driving slowly through a parking lot on a 112 degree day. Yikes.

I saw a video of Mark Perry done a few weeks ago in Oregon where he said they were testing some LEAFs in the Phoenix area and the hot temperatures. However, Tucson just reached out first 90 degree day today. Phoenix was probably 90 a couple weeks ago. I know that there is an auto test track near Phoenix owned by another car manufacturer. Maybe Nissan is using that closed track to test the LEAF. We'll be at a 100 degrees in a couple weeks, than all hell breaks loose with the heat in June!

I lived in Tucson for just over 2 years (stationed at DM) - and can confirm that a hot day is when the radio left in the back of the car has melted into the carpeting when one returns to the hatchback after work. :D

That being said, my lithium-powered motorcycle lives in a garage here in San Antonio and summer rides begin with a HOT garage and often a starting pack temperature of 120°F. Lithium loves heat - you'll have the best performance on hot days!

Andy
 
Andy, I read in a Hawaiian online newspaper today that Nissan announced the LEAF would be introduced in 3 places soon after the first of the year 2011. They were : Hawaii, Raleigh, N.C., and Houston. I know that is still about 150 miles away from you, but the LEAF is getting closer!
 
Good areas I guess...Hawaii is perfect for EVs...no range aniety at all :)

Raleigh has lots of colleges and tech business...and Houston is...well big.

Still, give the little guys a chance...Albuquerque/Santa Fe is hella green...lots of old hippies wanting to trade in their VW campers for EVs :) Plus we have the perfect weather for EVs...rarely too cold, rarely too hot. Kinda like San Diego but without the water in the spring and summer and fall...but we do get usually mild winter weather.

Gavin
 
The downside to hawaii is that most of their electricity comes from burning oil ;) Of course, with a good PV system...
 
Azrich said:
Andy, I read in a Hawaiian online newspaper today that Nissan announced the LEAF would be introduced in 3 places soon after the first of the year 2011. They were : Hawaii, Raleigh, N.C., and Houston. I know that is still about 150 miles away from you, but the LEAF is getting closer!

Yes - I guess if it is sold within your state, it is easier to get it. You can always strike a deal with the dealership ... and don't have to worry about registration issues etc.
 
"Our Arizona "dry" heat will be a real test for the batteries and whether or not they will overheat. The heat radiating up from pavement on a 110 degree day can be 135 degrees. My car's thermometer has registered 135 degrees while driving slowly through a parking lot on a 112 degree day. Yikes."

I got a chance to drive the Leaf test vehicle in Phoenix. I spoke to two members of the design team and 3 members of the test team from Arizona. They have been testing the vehicle all over Arizona and their test track is on the west side of Phoenix near Sun City. They said that all of the cooling is conductive with no active cooling. When I asked about temperatures inside the battery, they replied that the temperature only rose 1 or 2 degrees above the ambient temperature. They did admit that the high temperatures reduced the mileage by 10 to 20%. They also said that they were doing tests in Japan's northern island of Hokkaido this last winter. So they have done an excellent job of testing performance under extreme environmental conditions.
 
I got a chance to drive the Leaf test vehicle in Phoenix.


LeafHopper, can you tell us somethings about your test drive. Acceleration ? Noise? Were you on a road or track where you could drive fast? Was the test vehicle one of the black and white versions with the old style headlights? What can you tell us?
 
Acceleration ? Noise? Were you on a road or track where you could drive fast? Was the test vehicle one of the black and white versions with the old style headlights? What can you tell us?

Acceleration was very smooth and constant through the highest speed that I drove it, which was 40 mph. The test area was laid out in a parking lot so the track was not that big. The acceleration will not set you back in the seat, but it is perfectly adequate for entering a freeway with a short ramp.

The road feel is the best that I personally have ever felt. The low center of gravity makes the vehicle very stable. Turning was effortless and precise. Braking was smooth, but I did not do any hard stops.

The test vehicle was not a black and white version. It was the one that traveled with the tour. It is shown in the following video:

http://www.youtube.com/watch?v=cby8cHHScow&feature=player_embedded

This video is an excellent way of experiencing the noise. I do not remember hearing any noise except for the tire noise. No motor or wind noise during my test. And I also rode in the back seat on 2 other test drives. So I was in the vehicle a total of 4 trips around the track. I hate noise so much. It was a joy to be in a nearly silent car. Since this was a test car, it is impossible to judge how much noise insulation will be used in the production car.
 
In Hawaii, other than rooftops, are there large area of unproductive, relatively barren land?

Perhaps cover the southern slopes of the volcanoes and some mountains with PV panels?
 
garygid said:
In Hawaii, other than rooftops, are there large area of unproductive, relatively barren land?

Perhaps cover the southern slopes of the volcanoes and some mountains with PV panels?

There was a graphic I saw sometime back which listed the year by which they expect PV to be grid competetive. Hawaii is one place where without any subsidy PV is grid competetive !

And my place, western WA, where it will not be competetive in a looong time :(
 
KarenRei said:
The downside to hawaii is that most of their electricity comes from burning oil ;) Of course, with a good PV system...

Well, that is my plan! My PV system is producing about a 150 kWh a month than I currently use and we have net metering here in Hawaii, not reverse metering, so the electric company is essentially getting that 150 kWhs for free. I don't really need a car (I bicycle pretty much everywhere) but I figured what WTH I got to do something with those 150 kWhs ... figure that gets me about 600 miles a month. That should be more than I actually drive.
 
Azrich said:
Andy, I read in a Hawaiian online newspaper today that Nissan announced the LEAF would be introduced in 3 places soon after the first of the year 2011. They were : Hawaii, Raleigh, N.C., and Houston. I know that is still about 150 miles away from you, but the LEAF is getting closer!

:( So I could drive 6 hours West to pick up my LEAF in Tennessee or drive 6 hours South and pick up my LEAF in Raleigh! Bugger, can't we just set up a sales location in Washington, D.C. so I can drive my LEAF by the Capitol building and remind Congress that we need more EV subsidies?

Murphy's law dictates New York and New Jersey, who already have the Mini-E, will get it next, so my choice gets to be 6 Hours West, 6 Hours South or 6 Hours North. Then, what? Barbados?
 
all this makes me wonder?? when is heat an issue the most?

when charging or discharging?

i thought it was when discharging. when the car is moving, air will be moving as well. if the pack is passive heat control, that would mean, heat exchangers, cooling fins, etc. seems to me that ventilation would be ample at all but parking lot speeds.
 
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