The EPA ratings for the Nissan Leaf

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The EPA ratings for the Nissan Leaf

Larry Gales
EPA rating for NIssan Leaf:
http://blog.caranddriver.com/2011-nissan-leaf-epa-ratings-released/

I am confused about some of the numbers coming out of the EPA ratings for
the
Nissan Leaf.  I was always under the assumption that most EV cars would use
about 80%
of the battery capacity.  The Leaf's battery is 24 KWH, so that would be
about 19.2 KWH
used.

The EPA rating is 34 KWH/100 miles, or 2.94 miles/KWH.  If we assume a 10%
charging loss,
then we get 3.27 miles/KWH.  Since the range is expected to be 73 miles that
works out
to 22.3 KWH used which is 93% of the available 24 KWH.  Even we assume a 12%
charging loss,
we get 3.34 mile/KWH or 21.86 KWH used which is 91% of the available 24 KWH.

So is Nissan actually using 90-93% of the available battery, or are the EPA
numbers
suspect?

-- Larry



--
Larry Gales
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Re: The EPA ratings for the Nissan Leaf

David Nelson-5
Is it possible that the 24kWh number is the usable amount rather than 100%?


--
David D. Nelson
http://evalbum.com/1328

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Re: The EPA ratings for the Nissan Leaf

Morgan LaMoore
In reply to this post by Larry Gales
On Fri, Nov 26, 2010 at 10:05 PM, Larry Gales <[hidden email]> wrote:
> ...
> So is Nissan actually using 90-93% of the available battery, or are the EPA
> numbers
> suspect?

It looks to me as though the 34kWh/100miles number is the energy drawn
from the wall.

The efficiency of the charger and battery charge cycle will reduce the
energy actually stored in the battery. Assuming the charger and
battery together are 90% efficient, the numbers work out quite well.

-Morgan LaMoore

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Re: The EPA ratings for the Nissan Leaf

Willie McKemie
In reply to this post by David Nelson-5
On Fri, Nov 26, 2010 at 08:57:52PM -0800, David Nelson wrote:
> Is it possible that the 24kWh number is the usable amount rather than 100%?

I THINK that that is the case.  Nissan has not been forthcoming with
information.  Still unknown (AFAIK) is whether the Leaf pack chemistry
is LiFePo or LiMn.

--
Willie, ONWARD!  Through the fog!
http://counter.li.org Linux registered user #228836 since 1995
Debian3.1/GNU/Linux system uptime  76 days  2 hours 40 minutes

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Re: The EPA ratings for the Nissan Leaf

NeilBlanchard
In reply to this post by Larry Gales
Hello,

> EPA rating for NIssan Leaf:
> http://blog.caranddriver.com/2011-nissan-leaf-epa-ratings-released/
>
> I am confused about some of the numbers coming out of the EPA ratings for
> the
> Nissan Leaf.  I was always under the assumption that most EV cars would use
> about 80%
> of the battery capacity.  The Leaf's battery is 24 KWH, so that would be
> about 19.2 KWH
> used.
>
> The EPA rating is 34 KWH/100 miles, or 2.94 miles/KWH.  If we assume a 10%
> charging loss,
> then we get 3.27 miles/KWH.  Since the range is expected to be 73 miles that
> works out
> to 22.3 KWH used which is 93% of the available 24 KWH.  Even we assume a 12%
> charging loss,
> we get 3.34 mile/KWH or 21.86 KWH used which is 91% of the available 24 KWH.
>
> So is Nissan actually using 90-93% of the available battery, or are the EPA
> numbers
> suspect?

They are using 95% of the 24kWh:

http://www.plugincars.com/nissan-leaf-116-mile-range.html

Sincerely, Neil
http://neilblanchard.blogspot.com/


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Re: The EPA ratings for the Nissan Leaf

Larry Gales
Thanks Neil, that was really helpful.  I winder if the EPA is being super
cautious about the range?

-- Larry

On Sat, Nov 27, 2010 at 4:22 AM, Neil Blanchard
<[hidden email]>wrote:

> Hello,
>
> > EPA rating for NIssan Leaf:
> > http://blog.caranddriver.com/2011-nissan-leaf-epa-ratings-released/
> >
> > I am confused about some of the numbers coming out of the EPA ratings for
> > the
> > Nissan Leaf.  I was always under the assumption that most EV cars would
> use
> > about 80%
> > of the battery capacity.  The Leaf's battery is 24 KWH, so that would be
> > about 19.2 KWH
> > used.
> >
> > The EPA rating is 34 KWH/100 miles, or 2.94 miles/KWH.  If we assume a
> 10%
> > charging loss,
> > then we get 3.27 miles/KWH.  Since the range is expected to be 73 miles
> that
> > works out
> > to 22.3 KWH used which is 93% of the available 24 KWH.  Even we assume a
> 12%
> > charging loss,
> > we get 3.34 mile/KWH or 21.86 KWH used which is 91% of the available 24
> KWH.
> >
> > So is Nissan actually using 90-93% of the available battery, or are the
> EPA
> > numbers
> > suspect?
>
> They are using 95% of the 24kWh:
>
> http://www.plugincars.com/nissan-leaf-116-mile-range.html
>
> Sincerely, Neil
> http://neilblanchard.blogspot.com/
>
>
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Re: The EPA ratings for the Nissan Leaf

Morgan LaMoore
On Sat, Nov 27, 2010 at 2:40 PM, Larry Gales <[hidden email]> wrote:
> Thanks Neil, that was really helpful.  I winder if the EPA is being super
> cautious about the range?

When that journalist got 116 miles range, he was driving gently and
doing no more than 50 mph (45 mph when almost empty).

The EPA range is based on standardized driving cycles to represent the
'avarage' American driver. I don't know the details of the driving
cycle, but I know it was recently changed to be more aggressive and
realistic; it probably uses more stops and starts and plenty of time
spent at 65 mph.

I can definitely see the range changing from 73 miles to 116 miles
based on driving style.

-Morgan LaMoore

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Re: The EPA ratings for the Nissan Leaf

JoeS.
My first posting and apologies in advance if I'm confused, reinventing the wheel, and excessively wordy ... please bear with me -

The purpose of the EPA stickers is to give consumers some standardized idea of what it costs to drive a vehicle, considering only energy ("fuel"). To this end the EPA has spent a fortune designing models which attempt to simulate how a 'typical' consumer drives and how a vehicle behaves in those driving conditions.

Utilizing the same EPA standard drive cycle and since cost is the motivation, I contend that there are only three variables which should be considered when comparing "fuel" consumption performance amongst vehicles using disparate energy sources: ENERGY QUANTITY, ENERGY COST, and DISTANCE, measured by gallons or litres from the pump and kilowatt-hours out of an EVSE, $/gallon or $/litre and $/KWHr for that "fuel", and miles or kilometers for distance driven. Although I recognize the various conversions amongst energy units, since the purpose of the EPA sticker is to compare "fuel" consumption COSTS, I contend that $$ paid by the consumer is the reasonable common denominator yielding an apples-to-apples comparison.

Upstream or downstream energy costs (be it electricity generation or liquid fuel production) and recovery benefits and all the associated social, political, production, transportation, tax-related, health-related, etc., costs and benefits, although important and worthy of separate discussion, I believe to be irrelevant when discussing out-of-pocket expenses for the "fuel" to drive a vehicle.

For standardization, I accept whatever drive cycle the EPA wants to put out there, recognizing that a hypermiler can very easily beat the current gasoline ratings and that judicious use of regen could also have a significant effect on extending an EVs range.

The Leaf EPA sticker says 34KWHrs per hundred miles. They also say 99mpg equivalent combined city and highway (106mpg city and 92mpg highway).

I presume that is 34KWHr out of the EVSE (thus taking into account all the vehicle's subsystem's inefficiences), and that regeneration has been optimized. Although I personally think this number is high, for argument's sake, let's accept it.

Now, in Northern California the PG&E E-9 EV rate is around $0.06/KWHr (http://www.pge.com/includes/docs/pdfs/about/rates/rateinfo/rateoptions/res/e-9.pdf). Today's typical gas-pump cost here is $3.20/gallon.

Using these simple numbers, here's what I get:

34KWHr/100miles x $0.06/KWHr = $2.04 per hundred miles "fuel" cost for Leaf

Fuel cost equivalency conversion: $2.04/100mi x 1Gallon/$3.20 = 0.6375Gal/100mi

Inverting this, 100mi/0.6375gal = 157 miles/gallon.

Tables could easily be produced for other values of liquid fuel and KWHr cost.

How did the EPA arrive at their 99mpg "equivalent" for the Leaf?

JoeS.




Joe Siudzinski
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Re: The EPA ratings for the Nissan Leaf

tomw
Hi Joe,

Nice first post.  I think the main root of the discrepancy likely is what is assumed for the cost per kWh of electric.  I expect the EPA used some national average, and likely not strictly night time rates, assuming not all charging would be done then.  I also wonder how they accounted for differences between winter and summer, like stiffer drive train and cabin heating in winter.  If you give a different weight to each of the variables you get quite different numbers.  I think that is what makes it so difficult for them.
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Re: The EPA ratings for the Nissan Leaf

EVDL Administrator
My understanding of the way EPA calculates MPGE is that they consider the
energy content of gasoline vs a kWh of electricity.  The relative cost
doesn't enter the picture.  

I suppose they could add a second figure for MPGE based on national energy
cost averages.  Thing is, energy costs vary from month to month and from
place to place, so I'm not sure it would be accurate enough to provide
really valid comparisons for any time or area.

David Roden - Akron, Ohio, USA
EVDL Administrator

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Re: The EPA ratings for the Nissan Leaf

Dennis Miles
David,
     That way the numbers do not change as prices vary for electrical power
or gasoline but it does little to help my PRO EV arguments, unless I do the
Dollar equivalency calculations each time I make a presentation. Of course
with the price of gasoline and diesel rising so rapidly it makes my results
better each month than the previous. Also doing the calculations as part of
the presentation, adds extra credibility to my statements.
 Regards,                                                 (I can rant about
fuel prices.)
Dennis Miles
------------------------------------------------------------------------
On Sun, Nov 28, 2010 at 2:57 AM, EVDL Administrator <[hidden email]> wrote:

> My understanding of the way EPA calculates MPGE is that they consider the
> energy content of gasoline vs a kWh of electricity.  The relative cost
> doesn't enter the picture.
>
> I suppose they could add a second figure for MPGE based on national energy
> cost averages.  Thing is, energy costs vary from month to month and from
> place to place, so I'm not sure it would be accurate enough to provide
> really valid comparisons for any time or area.
>
> David Roden - Akron, Ohio, USA
> EVDL Administrator
>
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Re: The EPA ratings for the Nissan Leaf

NeilBlanchard
In reply to this post by Larry Gales
Hi Larry,

I think the EPA is using heat and cooling at various parts of their test?  If you drive a Leaf, it would make sense to do those things while charging; right before you leave on a drive, so that it doesn't affect the pack as much.  And good ecodriving takes practice; and keeping good energy logs is good incentive, as well.

> Thanks Neil, that was really helpful.  I winder if the EPA is being super
> cautious about the range?

>> They are using 95% of the 24kWh:
>>
>> http://www.plugincars.com/nissan-leaf-116-mile-range.html

Sincerely, Neil
http://neilblanchard.blogspot.com/


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Re: The EPA ratings for the Nissan Leaf

NeilBlanchard
In reply to this post by JoeS.
Hi Joe,

> I presume that is 34KWHr out of the EVSE (thus taking into account all the
> vehicle's subsystem's inefficiences), and that regeneration has been
> optimized. Although I personally think this number is high, for argument's
> sake, let's accept it.

They do not say that you can consume 34kWh in one charge, and at that rate of consumption (340Wh/mile) it would take about 1 1/2 charges to go the 100 miles -- which is fair lousy driving, really.  The 116 mile drive was doing just 196Wh/mile, and Nissan has said that you can go 138 miles at ~35mph on level ground without any heat or A/C (if my memory serves me!).  That abstemious kind of driving would be under 166Wh/mile (24kWh x 95% = 22.8kWh net).

So, a huge range of consumption is possible, with the heat being the worst way to use up power.  I'll most folks will do around 200-250Wh/mile?  Which is ~91-114 miles range.

Sincerely, Neil
http://neilblanchard.blogspot.com/


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Re: The EPA ratings for the Nissan Leaf

JoeS.
Thank you all for your responses. I'm tending to think the EPA rating of the Leaf is a pretty pessimistic scenario rather than what an astute EV driver will achieve. We'll soon find out and hopefully the early adopters are not lead-footers :-)

tomw wrote:
> ...I expect the EPA used some national average...

Agree, as they've also assigned a figure of $561 for what they call Annual Electric Cost. I just read the fine print on that sticker and as best I can make out it says 12 cents/kWh and 15,000miles. Hmmm, that would give 34kWh/100mi x 15000mi x $0.12/kWh = $612  :-(

David, you're right about the EPA using energy content of gasoline vs. kWh electricity, as the fine print on that sticker says (I think) "MPGequivalent 33.7kWhrs = 1 gallon gasoline energy".  My premise is that MPG-equivalency is a cost discussion, which is why I consciously restricted myself to simple units that the consumer relates to and can measure: energy consumed, cost of that energy, and distance traveled. My common denominator is $$, not BTUs. :-)

Recognizing the variability of electric rates and liquid fuel costs, my mpg-equivalency approach would require a small table on the ratings sticker with perhaps four or five entries each of $/kWh vs. $/gallon (yielding MPG equivalent) which should cover most USA situations. Now we're over-cluttering the sticker and TomW, you're right, the EPA has a difficult task and can't possibly please everyone.

Dennis, doing a simple dollar mpg-equivalency calculation as part of any EV presentation should certainly be transparent and understandable. You can have fun with that one!

Neil, we'll need to understand EPA's testing methodology in order to be able to assess their numbers. We don't know how much heating and aircon were used and how much these contribute to the rating deterioration, although subjectively we cringe; furthermore, we don't know if their methodology includes optimizing Regen use. The Leaf certainly provides plenty of feedback to the driver which can't help but eventually improve the driver's range-extending performance.

Neil, I recognize that 34kWh was not a single-charge number. I was hopefully reinforcing the concept that whenever Wh/mile or kWh/100mile or miles/kWh or whatever metric is used to define "fuel" consumption COST is that it does refer to the energy provided from the wall socket and not some intermediate figure (such as, e.g., energy from the battery as measured by an onboard e-Meter). The cost figure includes the battery and charger inefficiency. Morgan LaMoore touched upon this nicely.

Again, thank you all for your informed comments and thank you Larry for starting this thread.

JoeS.
Joe Siudzinski
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Re: The EPA ratings for the Nissan Leaf

Lee Hart
On 11/29/2010 12:42 AM, JoeS. wrote:
>
> Thank you all for your responses. I'm tending to think the EPA rating of the
> Leaf is a pretty pessimistic scenario rather than what an astute EV driver
> will achieve.

In the past, the auto industry has lobbied heavily to influence the test
methods the EPA uses. They of course want their cars to look as good as
possible (and anyone else's to look as *bad* as possible). They have
even been caught "cheating" on the test, by having the car's computer
look for the EPA test sequence, and then operating in a special mode to
make the MPG number artificially high.

They did all this with hybrids, and I have no doubt they will do it
again with EVs.

--
Lee A. Hart | Ring the bells that still can ring
814 8th Ave N | Forget the perfect offering
Sartell MN 56377 | There is a crack in everything
leeahart earthlink.net | That's how the light gets in -- Leonard Cohen

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Re: The EPA ratings for the Nissan Leaf

Dave Hymers
I don't really like the way the EPA sticker works. You *can't* extract
33.7kwh of power from a gallon of gas and use it all in an EV or ICE car,
there are fundamental differences between how an EV receives its energy and
vice versa. (preaching to the choir I know ...)

(think of using a generator to charge your EV, you'll see between 45-60mpg,
but if you use MPGe math, it will be different,
and if that 33.7kwh is generated at a power station, its going to be
different, worse, again)

I am currently attempting to nail down an analysis of both, primarily to see
the differences in emissions lbs/co2 per mile (gasoline vs coal fired plant)
its pretty hard, has anyone seen a definitive attempt ?

This one is fairly good:
http://theeestory.com/topics/5607

But I still think it falls short.
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Re: The EPA ratings for the Nissan Leaf

k7rni

The bottom line for the Leaf is actual range.  If the Leaf only gets 50
miles with normal driving, it will be a dud.  If the Leaf gets close to
100 miles range, it will be a winner.

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Re: The EPA ratings for the Nissan Leaf

EVDL Administrator
In reply to this post by Dennis Miles
On 28 Nov 2010 at 5:01, Dennis Miles wrote:

> That way the numbers do not change as prices vary for electrical power or
> gasoline but it does little to help my PRO EV arguments ...

As we've discussed many times here, I'm not so sure that we're well served
to sell EVs on operating cost.  The customer is apt to be disappointed (or
angry) when he finds out that the total out-of-pocket cost usually isn't
lower, and may even be higher.

I think it's easier to sell the EV grin, the conveninence (refuel at home),
the quiet, the high-tech-ness.  IMO, cost is less likely to be a winner for
us.

David Roden - Akron, Ohio, USA
EVDL Administrator

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Re: The EPA ratings for the Nissan Leaf

Roger Heuckeroth
In reply to this post by Dave Hymers

On Nov 29, 2010, at 12:32 PM, Dave Hymers wrote:

> (think of using a generator to charge your EV, you'll see between  
> 45-60mpg,
> but if you use MPGe math, it will be different,
> and if that 33.7kwh is generated at a power station, its going to be
> different, worse, again)

Dave, where did you figure that if you use a generator you will get  
45-60 MPG?

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Re: The EPA ratings for the Nissan Leaf

NeilBlanchard
In reply to this post by Dave Hymers
Hello,

> I don't really like the way the EPA sticker works. You *can't* extract
> 33.7kwh of power from a gallon of gas and use it all in an EV or ICE car,
> there are fundamental differences between how an EV receives its energy and
> vice versa.

Yes, but there is a mathematical equivalency -- a gallon of (typical) gasoline has the same number of BTU's as the 33.7kWh of electricity.  That's it -- you do not need to *actually* convert the gasoline to electricity, or vis versa -- it is an equivalency!  Gasoline doesn't just materialize out of thin air, either.

> I am currently attempting to nail down an analysis of both, primarily to see
> the differences in emissions lbs/co2 per mile (gasoline vs coal fired plant)
> its pretty hard, has anyone seen a definitive attempt ?
>
> This one is fairly good:
> http://theeestory.com/topics/5607
>
> But I still think it falls short.

If you find it, please do tell us!  There are several large omissions in that analysis; on both sides of the equation:

Oil has to be found first, and drilled and transported and stored and refined and stored and transported, etc.  Materials and energy used *all* through this process should be counted; not just refinement.  Extraction is not trivial, and things like drilling mud take a lot of energy to produce.

If you measure the power used to charge the car, then why do you need to measure anything "inside" the car system?  Charge the car, drive it, and then measure what it takes to charge it again; just like measuring fuel economy on an ICE vehicle.

Sincerely, Neil
http://neilblanchard.blogspot.com/


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