Nissan Leaf

[redpoint5]

The EPA uses the amount of energy consumed at the wall, and does not rely on the on-board meter, which only displays how many kWh the battery accepted.

A Leaf thread showed a charging efficiency of 75% on 120v, and 85% on 240v when measured with a kill-a-watt meter and comparing to the on-board figure. Part of the extra loss associated with charging at 120v is that various cooling fans run while charging, and it takes much longer to charge at 120v. There is also more loss due to heat in the charging cable since lower voltages spend a greater proportion of their energy overcoming the resistance in the wire.

The 120v charging efficiency of 75% agrees with what I'm finding on my Prius plug-in. I'm seriously considering selling my beloved TSX and going with a Leaf, but I'll hold off and see what prices do when the upcoming Volt is released.

[gone-ot]

What's the basic co$t difference between 120VAC and 240VAC chargers (not including installation)?

[P-hack]

the leaf has a charger built in that can take either, so nada. 120 is ~%75 efficient (and slow) and 240v is ~%90 efficient and about 3 times faster. So %15 difference in costs I guess. The openevse kit is maybe $400 with a j1772 plug, + $30 @ lowes for 240v fixins. So that is another 240v cost if you charge @ home.


I've been poking about at charger design and 240 is a lot easier to design for at typical battery voltages/currents. You pretty much have to limit yourself to a 15 amp breaker for 120v capability to make any sense (~1.5kw) as an opportunity charge plus you have to boost it more.

[sendler]

Originally Posted by redpoint5

The EPA uses the amount of energy consumed at the wall, and does not rely on the on-board meter.

Do you have a link which outlines the measurement procedure? I'm still having a hard time accepting the results where the Spark is beating the Leaf.

[Astro]

Originally Posted by sendler

...The only way to measure the consumption is to fill up, drive, and top up again to take the reading from the fill station.

As long as the second fill up (charge) is done at the same efficiency as the original charge.
Easy enough done with an gas vehicle but with an EV getting all the conditions the same between the two charges might be difficult. A few percent difference in charge efficiency could skew the results.
But then, even with charging differences, it would probably still be much more accurate than the on board gauges.

[redpoint5]

Originally Posted by sendler

Do you have a link which outlines the measurement procedure? I'm still having a hard time accepting the results where the Spark is beating the Leaf.

While the Spark and Leaf have similar drag coefficients of about 0.32, the Spark has less frontal area. Not only that, but it weighs a whopping 1,000 pounds less than the Leaf.

I'm not surprised the Spark is more efficient with its electrons than the Leaf.

The Leaf is a fairly un-aerodynamic porker of a vehicle. In my opinion, the design fails both form and function because it is a very unattractive vehicle.

I do think Tesla will eventually pull ahead of the competition by selling affordable, well-engineered, attractive vehicles.

For battery electric vehicles, the U.S. Environmental Protection Agencys formula to calculate the battery-to wheel MPGe is based on energy standards established by the U.S. Department of Energy in 2000:[1][7][8]

MPGe = \frac { E_G} {E_M*E_E} = \frac{ 33,705 } {E_M}

where

MPGe is expressed as miles per gallon gasoline equivalent (as shown in the Monroney label)

E_G = energy content per gallon of gasoline = 115,000 BTUs/gallon, as set by U.S. DoE and reported by the Alternative Fuel Data Center.[8]

E_M = wall-to-wheel electrical energy consumed per mile (Wh/mi) as measured through EPA's five standard drive cycle tests for electric cars and SAE test procedures[7][30]

E_E = energy per KWatt-hour of electricity (BTU/Wh) = 3.412[8]

The formula employed by the EPA for calculating their rated MPGe does not account for any fuel or energy consumed upstream such as the generation and transmission of electrical power, or well-to-wheel life cycle, as EPA's comparison with internal combustion vehicles is made on a tank-to-wheel versus battery-to wheel basis.

Miles per gallon gasoline equivalent - Wikipedia, the free encyclopedia

[sendler]

Of course, your quote doesn't tell us how the EPA measures the energy consumption but it sounds like they are just quoting battery to wheels which means they are at the mercy of the onboard computer which can be skewed to any value to make the car look better than it is.

[redpoint5]

Originally Posted by sendler

Of course, your quote doesn't tell us how the EPA measures the energy consumption but it sounds like they are just quoting battery to wheels which means they are at the mercy of the onboard computer which can be skewed to any value to make the car look better than it is.

Perhaps so, but we all know MPGe is a stupid way to measure efficiency with an EV. It's like measuring my annual salary in BigMacs per year.

The EPA decided people are too stupid to understand kWh per 100 miles, or miles per 1 kWh despite the fact that their monthly utility bill is given in kWh, so they decided to measure efficiency in the way Americans can understand it; BigMacs MPG.

Regardless, the data exists from real users reporting real numbers, so reliable estimates exist for those motivated enough to research the topic. I know that I'm getting about 3 miles per billed kWh, and equates to a little less than 3 cents per mile. Compared to my average cost of 11 cents per mile in the Acura, and even 4 cents per mile in HV mode with the Prius with gas at $2/gallon.

EV is always the more economical fuel for me.

[redpoint5]

Originally Posted by Old Tele man

What's the basic co$t difference between 120VAC and 240VAC chargers (not including installation)?

I bought a used 120VAC Leaf charger for $200, and a used 120VAC Prius charger for $200. The new price of a Prius charger is something silly like $700.

As mentioned already, an OpenEVSE can be had for $350-$400, if you already have a 240VAC outlet.

It would take me ages to recoup the cost of a $400 240VAC charger in the energy savings it has over 120VAC.

Quick math:

1 charge per day @ 3 kWh measured at the wall on 120VAC @ $0.08/kWh = $0.24 per day to charge the Prius. Assuming 240VAC is 13% more efficient, my daily charge cost would be reduced to $0.21, saving $0.03 per day.

It would take me 36.5 years to recoup the cost of the 240VAC charger.

Granted, my vehicle only uses 3 kWh per charge and has a range of 15 EV miles. If I had a Nissan Leaf, I would for sure upgrade to 240VAC charging. Assuming I averaged 15 kWh per day on the Leaf, I would recoup the $400 in 6.5 years.

*My electric rate is among the lowest at $0.08/kWh. Most people will have a faster payback time to recoup the cost of a 240VAC charger since their rates are likely higher.

[NeilBlanchard]

I measure my charges, and I am sure that is what the EPA does, also.

They don't measure a Prius with the dash meter, do they?