Applying some math to the spec sheet on Nissan News

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lne937s

Well-known member
Joined
Apr 22, 2010
Messages
250
I was looking through the Nissan News site and ran across a spec sheet in attached files here:
http://www.nissannews.com/newsrelease.do?id=981&mid=
NISSAN LEAF Specs
Dimensions
Length: 4445 mm / 175.0 in.
Width: 1770 mm / 69.7 in.
Height : 1550 mm / 61.0 in.
Wheelbase: 2700 mm / 106.3 in.
Performance
Driving range over: 160km/100miles (US LA4 mode)
Max speed (km/h): over 140km/h (over 90mph)
Motor
Type: AC motor
Max power (kW): 80kW
Max torque (Nm): 280Nm
Battery
Type: laminated lithium-ion battery
Total capacity (kWh): 24
Power output (kW): over 90
Energy density (Wh/kg): 140
Power density (kW/kg): 2.5
Number of modules: 48
Charging times: quick charger DC 50kW (0 to 80%): less
than 30 min; home-use AC200V charger:
less than 8 hrs
Battery layout: Under seat & floor

Doing some quick math, the 24kWh divided by 140 Wh/kg works out to 171 kilograms for the battery or about 377 lbs (I assume that does not include the frame or casing for the pack). However, if you multiply 2.5 kW/kg for power density by 171 kg, it works out to 428kW-- quite a bit "over 90"...

It looks like Nissan's batteries are pretty impressive and are being used fairly conservatively in the LEAF application...
 
lne937s said:
I was looking through the Nissan News site and ran across a spec sheet in attached files here:
http://www.nissannews.com/newsrelease.do?id=981&mid=
NISSAN LEAF Specs
Dimensions
Length: 4445 mm / 175.0 in.
Width: 1770 mm / 69.7 in.
Height : 1550 mm / 61.0 in.
Wheelbase: 2700 mm / 106.3 in.
Performance
Driving range over: 160km/100miles (US LA4 mode)
Max speed (km/h): over 140km/h (over 90mph)
Motor
Type: AC motor
Max power (kW): 80kW
Max torque (Nm): 280Nm
Battery
Type: laminated lithium-ion battery
Total capacity (kWh): 24
Power output (kW): over 90
Energy density (Wh/kg): 140
Power density (kW/kg): 2.5
Number of modules: 48
Charging times: quick charger DC 50kW (0 to 80%): less
than 30 min; home-use AC200V charger:
less than 8 hrs
Battery layout: Under seat & floor

Doing some quick math, the 24kWh divided by 140 Wh/kg works out to 171 kilograms for the battery or about 377 lbs (I assume that does not include the frame or casing for the pack). However, if you multiply 2.5 kW/kg for power density by 171 kg, it works out to 428kW-- quite a bit "over 90"...

It looks like Nissan's batteries are pretty impressive and are being used fairly conservatively in the LEAF application...

I believe you may need to use 30Kwh to get the weight because we've all pretty much agreed that the actual (not usable) capacity is 30Kwh with the usable at 80% which would be 24Kwh.
 
EVDRIVER said:
Yes- closer to 30 kwh

In that case, 30kWh divided by 140kWh/kg= 214 kg (471 lbs). Multiply by 2.5 kW/kg and you end up with 535 kW max power output (717hp)... which means the battery is used very conservatively in its application. It also implies very high levels of thermal stability and that typical operation puts very little stress on the battery.
 
This could very well be why Chevy felt they needed to go with active cooling for their battery pack; being appreciably smaller in size, it might actually generate a bit of heat during freeway travel. Then again, could just be for the benefits of heating the battery, not vice versa. For the Leaf, sounds like we're not battery-limited on the performance side of things, but motor-controller and motor limited.

Think we'll ever reach a point of technical competence in this society where folks will be hacking into their EVs in their garages to eek out a few extra horsepower, or have these cars become so much proprietary black boxes that those days are gone?? I personally am looking forward to turning off the traction control on the Leaf to see if it can leave some rubber on the road... ;)
 
TLeaf said:
This could very well be why Chevy felt they needed to go with active cooling for their battery pack; being appreciably smaller in size, it might actually generate a bit of heat during freeway travel. Then again, could just be for the benefits of heating the battery, not vice versa. For the Leaf, sounds like we're not battery-limited on the performance side of things, but motor-controller and motor limited.

Think we'll ever reach a point of technical competence in this society where folks will be hacking into their EVs in their garages to eek out a few extra horsepower, or have these cars become so much proprietary black boxes that those days are gone?? I personally am looking forward to turning off the traction control on the Leaf to see if it can leave some rubber on the road... ;)

My Driver's Ed. teacher told us that every time you spin the tires, it shaves off 500 miles of tread. ;)
 
TLeaf said:
This could very well be why Chevy felt they needed to go with active cooling for their battery pack; being appreciably smaller in size, it might actually generate a bit of heat during freeway travel. Then again, could just be for the benefits of heating the battery, not vice versa. For the Leaf, sounds like we're not battery-limited on the performance side of things, but motor-controller and motor limited.

I think LG wants active cooling - thats why Ford is doing that as well. May be all Mn spinal batteries aren't created equal ...
 
This old article gives lots of specs on the AESC battery, and it seems to match what we know:

http://www.greencarcongress.com/2008/05/aesc-lithium-io.html

energy density of 89Wh/kg and power density of 2060W/kg

If we assume the capacity is really 24kW, and the weight of the cells is around 270kg then the power density is 89Wh/kg as stated in the above link.. so I think Nissan is really using a 24kWh pack.

The high power density (745hp!!) is a side effect of designing the cells to have low resistance, so that they wont generate much heat in use and thus do without active cooling.
 
EVDRIVER said:
Yes- closer to 30 kwh
I would like to know where this ~30 kWh number came from.

Because all my digging is coming up with 130-140 Wh/kg for each module which would put the capacity at 24-25 kWh.

See Herm's post, too.
 
It was estiamted that Nissan's BMS doesn't allow the Leaf to discharge to below %10 SOC, and also fully charge to no more than %90, leaving %80 SOC as the "usable" KWH. This is wherre the extra %20 seems to have come from (24 * .20 = 4.8 additonal KW), so the thought was the 24KW pack was 24+4.8, or nearly 29KW. That may not be the actual case, it seems.
 
mitch672 said:
It was estiamted that Nissan's BMS doesn't allow the Leaf to discharge to below %10 SOC, and also fully charge to no more than %90, leaving %80 SOC as the "usable" KWH.
In other words - it's not based on factual information at all and purely a guess...

I certainly am hoping that the pack actually can hold more than 30 kWh, but so far the facts don't show it.

If you google for "Automotive Energy Supply Corporation" and Wh/kg you can find a bunch of articles referencing 130-140 Wh/kg per module.

Each module appears to weigh about 3.8 kg and there are 48 of them in the Leaf's battery pack.

130 * 3.8 * 48 = 23.7 kWh...
140 * 3.8 * 48 = 25.5 kWh...

http://www.eco-aesc-lb.com/en/bmodule.html

I will be pleasantly surprised if Nissan is actually using modules that are 150+ Wh/kg and the data on the AESC website is outdated...
 
drees said:
In other words - it's not based on factual information at all and purely a guess...

What facts? Nissan has released very little ACTUAL data on the battery pack or it's warranty.
 
Carlos Ghosn stated in the Charlie Rose interview than the cells weighed about 260kg, can someone double check it?.. I cant see videos with my PC.

http://www.charlierose.com/view/interview/10718
 
Herm said:
Carlos Ghosn stated in the Charlie Rose interview than the cells weighed about 260kg, can someone double check it?.. I cant see videos with my PC.
I couldn't see/hear the interview, either, but the transcript said 200 kg.

I suspect he's talking about the entire pack and not the weight of each module so the energy/weight ratio will be lower than what you normally hear quoted.

Anyway, if you assume 24 kWh and 200 kg, you get 120 Wh/kg which sounds about right if you're using 130-140 Wh/kg modules.
 
Don't forget that Nick Chambers of plugincars drove a LEAF 116 miles, and the dash readout said he got 5.1 miles/kWh. Simple division tells you he must have used 22.5 to 23kWh, and the car still hadn't gone into "turtle mode". Now if you want to believe that the total capacity is 24kWh and that Nissan is letting you use more than 95% of that, fine. I prefer to believe that the usable capacity is 24kWh and there is something like a 10% margin on each end.

http://www.plugincars.com/nissan-leaf-116-mile-range.html
 
I thought someone just posted yesterday that Nissan (Perry?) confirmed the actual total battery size is 24kW - not something bigger with a usable amount of 24kW.

ETA - Here is where the claim of 24kW total size is. Perhaps still debatable?
http://nissan-leaf.net/2010/10/29/nissan-europe-releases-spec-sheet-on-leaf-weighs-3362lbs/
 
The customer usable size is 24 KWh.

Until someone takes a battery pack out of a Leaf and actually does a charge/discharge test, bypassing any BMS that is set up, we will have no idea of the actual pack size. Nissan only lets us use a maximum of 24 KWh, so that will be the only number advertised...

If I had to guess, it will probably be mid-January when someone announces how big the actual battery is... I just wonder if they will be leasing or buying! :D
 
If someone can get a fresh spare/replacement/removed cell, that would be enough to tell the full story.

I have the equipment to cycle a battery under calibrated load and graph the results, so if anyone knows how to get a cell (someday), I'm game.
 
Looking at the way the batteries are composed the smallest you would get is a " module"

one of the 48 , not a cell, my guess is cells are not replacable at dealer level , but modules will be certainly.

still you could test a module.
 
I'm still hoping and thinking the pack is closer to 30kwh based on the range of the car and the cycle limits for life. 19.2 KW usable seems low to me. In addition I asked a factory rep what the pack size was and I was told "closer to 30 kwh" and that the "reserve" would not be used to extend range later in life and 24 kw was usable. So the rep was either wrong or making it up and the range for suggests otherwise. I really hope it is 24kw usable as that makes me feel more comfortable about the pack life. If it's not then I see why there are not making claims on capacity life and it gives me another reason to rethink a leaf based on the battery warranty.
 
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