Drive efficiency question for owners

[GlennD]

You people in snow areas with a long commute might be better off with a different car. For me in Southern California it works fine. That white stuff is not allowed here. After 2 weeks I see nothing bad about the car. The bells and whistles impose a steep learning curve.

 

[sendler2112]

http://insideevs.com/real-world-test-shows-chevy-spark-ev-has-substainally-more-range-than-nissan-leaf-62-mph-wvideo/

Note the person who conducted the test

The test methodology needs to improve if real energy efficiency is to be determined. It's one thing to show the range. Which I will admit is the main concern among prospective buyers. But to extrapolate energy efficiency just from dividing the miles covered into the spec sheet value for the battery leaves quite a bit to fudging. I find it very hard to believe the Spark is 20% more efficient at 62 mph than the more aerodynamic and purpose built Leaf. 20%! No way. Rather than accepting the spec sheet value for the battery capacity, or the dash read out which could be skewed to anything, the only way to know how much energy the cars used on their test run would be to charge each car to full, make the run,and then charge them to full again at a known accurate charge station that is capable of measuring the power that is put back into the battery.
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The EPA test cycles show the Leaf at 114 MPGe and the Spark at 119.
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http://www.fueleconomy.gov/feg/Find.do?action=sbs&id=34918&id=35120
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[tomt]

That is exactly how the EPA calculates their efficiency numbers (Mpge)... And it does not surprise me at all that the Spark is more efficient than the Leaf... As Car and Driver discovered in their wind tunnel tests, the Leaf is actually not very aerodynamic... It was last in the field that they tested...

I find it very hard to believe the Spark is 20% more efficient at 62 mph than the more aerodynamic and purpose built Leaf. 20%! No way. Rather than accepting the spec sheet value for the battery capacity, or the dash read out which could be skewed to anything, the only way to know how much energy the cars used on their test run would be to charge each car to full, make the run,and then charge them to full again at a known accurate charge station that is capable of measuring the power that is put back into the battery.

 

[sendler2112]

That is exactly how the EPA calculates their efficiency numbers (Mpge)

EPA shows a difference of 8% highway. Not 20%.

 

[sendler2112]

Does anyone here know offhand how the EPA determines the energy efficiency numbers for EV's. Is it an extrapolation based soely on the capacity spec that the Manufacturer states? Or do they actually charge the car to ful, drive the test loop, and measure the power as they charge to full again?
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It seems unlikely to me that the Spark EV would beat the Leaf by 8% on the highway as the EPA specs show. Manufacturers are famous for figuring out how to cheat the test.

 

[tomt]

They measure power draw from the wall and drive until the car stops. It is basically miles divided by power.

Does anyone here know offhand how the EPA determines the energy efficiency numbers for EV's. Is it an extrapolation based soely on the capacity spec that the Manufacturer states? Or do they actually charge the car to ful, drive the test loop, and measure the power as they charge to full again?

 

[sendler2112]

They measure power draw from the wall and drive until the car stops.

I have read that they are quoting battery to wheels, not wall to wheels, which means they are using the onboard readout unless they have a logging amp clamp/ slash volt meter.

 

[esco]

FYI,

Mercedes
B-Class ED - 3.6*** miles per kWh (278 wattHours per mile) * 31.5kWh = 113 miles / EPA 104
*** Mercedes consumption meter is calibrated so that 3.6 miles per kWh will show 3.0 on the dash. The correction factor is 83.7%, or 1.2

seems accurate to me.

Last week I made a 96.5 mile trip on a single, standard charge, and had 18% charge remaining when complete. I wasn't sure I could make the projected 100 mile trip, so I did almost all my driving in the right lane:

5 AM departure at 45 degrees (F) for the 29 mile commute to work, in light traffic, losing a total of 700' elevation; stopped w/ 3.5 m/kwh displayed for the leg.
5 PM departure at 68F for a 45 mile trip, in heavy traffic, gaining a total of 1400' elevation; 2.9 m/kwh displayed when I stopped.
9 PM return home at 50F for 20 miles, very light traffic, losing 700'. On the initial, significant descent, I saw 11.1 m/kwh before I started climbing again, finishing at 4.1 m/kwh for that leg.

This is my first electric vehicle; I traded in an AMG E55 for this car... I'm a happy convert!

 

[tcoombes]

I have had my car for over 6 months now and have put about 8,500 miles on it. I primarily use it for commuting in northern California and for mountain trips on the weekends (Sacramento and Placer counties). I drive in a variety of conditions every day. Commute round trip is 54 miles. Elevation change from home to work is 450 feet. Freeway driving 85% - relatively no stop and go in the morning early and in the HOV lane, but at least 9 miles of stop and go in the afternoon commute. I charge at the parking garage at work for free so I only use my home level 2 charger on weekends. ChargePoint keeps some nice stats so I have history of my commute efficiencies since the end of last July. Basically, I am currently getting 2.5 m/kwh on my daily commute at this time. In August, I got 2.9 m/kwh on average. The biggest variations I have observed are speed, temperature, and elevation. Over 65 mph the efficiency drops significantly and over 72 mph it is a real drain. Interestingly, stop and go on the freeway indicates 3.2 m/kwh according to dashboard readings. The .4 m/kwh difference between January/February commute driving and July/August commute driving I would attribute to temperature differences since most other significant variables are the same. In the mornings, temps are 35-55 degrees Fahrenheit in the winter and 55-75 in the summer. Afternoons are typically 45-65 in the winter and 85-105 in the summer. Uphill driving can be 1.5 m/kwh or less depending on speed. Downhill can be 3.5 m/kwh to 4.5 m/kwh or more, again depending on speed (and mode makes a slight difference). All in all, I really like the B Class Electric - it meets and exceeds my requirements for a commuter car. I will be moving further away from work into the Sierras later this year and daily roundtrip commute will be 90 miles. My charging strategy will need to change and I will probably charge at home and at work, but will find an optimum mix for charging (mostly at work) since there will be a nearly 2,000 foot elevation change and I will be able to "coast" much of the way from home to work.

 

[sendler2112]

So apparently the EPA doesn't do any of the certification testing for ev's right now. Instead they leave it up to each manufacturer.
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http://avt.inel.gov/pdf/uev/eva/etautp3r0.pdf
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"While EPA strives to periodically update the regulatory test procedures such that all technologies are appropriately addressed, there may be instances when some emerging technologies or fuels are not able to be tested using existing regulations. Because of this, EPA has special regulatory provisions that allow EPA to direct manufacturers to test such vehicles using methods specified by EPA. Similarly, EPA is able to determine the content and appearance of the fuel economy labels when existing regulations do not appropriately address the technology or the fuel being used. For example, the regulations do not currently address how to determine City and Highway fuel efficiency values for electric vehicles. During the period when regulations are being developed for electric vehicles, EPA has specified, for example, that manufacturers use an accepted procedure developed by the Society of Automotive Engineers: the procedure known as SAE J1634. Further, to better approximate expected real-world performance, EPA has directed that the manufacturers adjust the test results (including City and Highway fuel efficiency and driving range) for the fuel economy label using equations and methods specified in the regulations."

 

[TonyWilliams]

http://insideevs.com/real-world-test-shows-chevy-spark-ev-has-substainally-more-range-than-nissan-leaf-62-mph-wvideo/

Note the person who conducted the test

The test methodology needs to improve if real energy efficiency is to be determined. It's one thing to show the range. Which I will admit is the main concern among prospective buyers. But to extrapolate energy efficiency just from dividing the miles covered into the spec sheet value for the battery leaves quite a bit to fudging. I find it very hard to believe the Spark is 20% more efficient at 62 mph than the more aerodynamic and purpose built Leaf. 20%! No way. Rather than accepting the spec sheet value for the battery capacity

Really dude? Your "beliefs" are better than my testing? If you actually reviewed the multitude of tests I've conducted, you'd see that I don't just use the manufacturer's spec sheet, or EPA. That's why we test.

Let me just say that you're wrong in your "beliefs".

 

[sendler2112]

Yes dude. Apparently. You are not even measuring consumption in any way. Your just going off of the spec sheet for battery capacity. The Spark is not 20% more efficient than the Leaf. 5.0mpkWh for your stated spec for the Spark would be 170MPGe. Not happening.

 

[TonyWilliams]

Yes dude. Apparently. You are not even measuring consumption in any way. Your just going off of the spec sheet for battery capacity. The Spark is not 20% more efficient than the Leaf. 5.0mpkWh for your stated spec for the Spark would be 170MPGe. Not happening.

Sorry, but you're just flat wrong. While it's true that we do not measure consumption directly, we do know how big the useable capacity of many of the batteries are. And we know how many miles were traveled from external to the car measurements.

For instance, we were able to determine the the Mercedes B-Class ED does in fact report inaccurate consumption data at the dash (the only car to have a significant issue with this). We know that specifically because we know the exact battery configuration and cell spec sheets (not from Tesla or Daimler, but from Panasonic).

The same type of issue is true of the LEAF. Their advertised battery is 24kWh, but we know from government tests that the battery is 21.38kWh usable at room temperature when new. Our data reflects that (and all our tests are done at about room temperature). In addition, the LEAF has been hacked so that all the CAN bus info is readily available from the battery.

For the Toyota Rav4 EV, we have hacked that too, and get real time BMS data from the CAN bus, not advertising or marketing data.

So, as to the GM Spark EV, I do not have the same level of external confirmation of the battery size, other than what GM produces and what the dash data shows (it actually shows kWh burned). For me to be wrong means that GM purposely put a larger battery in the car and is not advertising that, because that is the only way that is can go 97 or 89 miles at less than 5 miles per kWh. The same is true of the BMW i3... it showed exactly the 18.8kWh usable that BMW advertises.

Now, you tell me what is logical. Each manufacturer is HIDING a bigger battery (to make your assertion true that the consumption rate is too economical) or I'm right, and both the consumption and advertised kWh just happens to agree EXACTLY with the miles driven? What are the odds?

Yes, the Spark EV is that 25% (5 is 25% greater than 4, not 20%... Math 101) more efficient at 62mph than a LEAF, and we can FURTHER prove it with a recharge after the test with each car. It makes it a bit difficult to just discount all the "circumstantial" on your hunch, eh? I'll stick with facts, and you keep guessing.

 

[sendler2112]

It's great that you are trying to do some independent range testing but you have obviously made some mistakes in trying to report energy consumption. it's too bad that you seem to have an inflexible and belligerent attitude toward criticism because this will only serve to hold you back. Your protocol is obviously lacking since you do not attempt to measure consumption but you are making statements about consumption that someone with your experience and commitment should intuitively know is way wrong. The Spark is EPA rated at 109 highway and you are reporting it at 170 MPGe highway. This is obviously way wrong.
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http://www.fueleconomy.gov/feg/Find.do?action=sbs&id=34918&id=35120
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[TonyWilliams]

It's great that you are trying to do some independent range testing but you have obviously made some mistakes in trying to report energy consumption. it's too bad that you seem to have an inflexible and belligerent attitude toward criticism because this will only serve to hold you back. Your protocol is obviously lacking since you do not attempt to measure consumption but you are making statements about consumption that someone with your experience and commitment should intuitively know is way wrong. The Spark is EPA rated at 109 highway and you are reporting it at 170 MPGe highway. This is obviously way wrong.
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http://www.fueleconomy.gov/feg/Find.do?action=sbs&id=34918&id=35120
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Thank you keyboard commando for your input. Our testing is not "way wrong".

I've had this come up before (attempting to compare EPA to our 62mph steady speed range test), so you're not the first. The numbers don't add up for you because they are not the same test.

We do measure consumption... after the fact, as stated. Guess what? It supports the consumption data and battery usable kWh.

Again, for me to be wrong and you be right (without any testing whatsoever), either GM understates the battery size (and they have the world's most efficient onboard charger... maybe 105% efficient), or my data is correct. I'll let the reader be the judge. Your criticism is most definitely not holding me back. I welcome your assertions, I just haven't found any credibility in those assertions, and frankly the general concept that it has to match EPA to be valid is absurd.


EDIT: I'll add that one of the several reasons that we conduct these tests is because the EPA data really doesn't reflect what somebody would do when taking a long trip. It's not an EPA 5 cycle test. It's traveling down the road with the climate control off (if they want any EV to go the max possible distance) at a reasonable speed that isn't too slow to get rear-ended.

Another car that is WAY different between EPA 5 cycle and our 62mph test is the Rav4 EV. The EPA rates it at 103 miles, and we drove it 142. That doesn't mean either test is flawed... THEY ARE DIFFERENT TESTS.

 

[sendler2112]

Really dude?

Thank you keyboard commando

While it's true that we do not measure consumption directly, we do know how big the useable capacity of many of the batteries are.

Your condescending attitude does nothing to further your credibility. And your inflexibility to criticism is holding you back from improvement. At least you did finally relent the last time we got into a debate about battery charge/ discharge depth versus life cycle. People are not stupid and no one person knows everything. I would hope that you could relax and look at this as an opportunity to notice something that is not quite right with your reporting, and improve.
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You are not measuring consumption in any way as you already stated earlier. But maybe now you will find a way to start doing so if you want to persist in making statements about the energy efficiency of the cars that you range test. You are extrapolating consumption based on an assumption of the battery capacity that you have taken from the factory spec sheet. We have actually all heard gas car drivers make the same mistake when they figure their fuel economy based on the spec of their fuel tank capacity instead of reading what the pump says. "My tank holds 10 gallons and I always fill up when the gauge gets to 1/4 so I went XX miles on 7.5 gallons of gas". This might not even be close. That you have speced the Leaf to be 20% less efficient than the Spark should alert you that something is not quite right with these numbers. The most convenient way (and practical way since wall to wheels is the real question in paying for energy) would be to read what the charge station says the same as we do at the pump for gas cars. Charge the car. Drive the car. Charge the car again on a known logging station to read out the consumption. Or, invest in a logging power meter. Or, just refrain from making statements about efficiency since you have not actually measured it and your current method is obviously not giving good results.

 

[wtzouris]

I think the tone of this conversation needs to be mediated! Guys, it shouldn't be emotional , and it certainly shouldn't be personal! There seems to be a basic disagreement about the methodology of the tests. And maybe certain assumptions about the specs of the battery size/useable battery capacity should be double-checked. It's math, it's science. It's not personal. I see that someone might feel that it is unlikely that the GM Spark EV is more efficient than the Leaf. (I don't know why -- brand loyalty or pride? GM vs. Nissan? That's silly. Let's use logic, and other ways to prove the original results. There is more than one way to solve the equation, and if the data seems off, it is a good idea to try a different approach to prove/disprove the original result.

Can't we all get along?

Questions:

Does efficiency matter? I guess everybody is thinking about the energy used/carbon footprint. I personally think ANY BEV is a huge step in the right direction and there can be heavy ones and lightweight ones for just 2 passengers and large ones and small ones -- all serving a different purpose. So 85 MPGe or 200 MPGe doesn;t really impress me. Unless I am charging with solar and trying to be off the grid. Most of us want the maximum number of miles travelled per charge. And fast charging.

Are we defining efficiency in the same way, do we all agree on the definition? It is defined by MPGe or something else?

Are we measuring the overall battery size and useable battery (in kW) in the same way? Can we prove it 2 different ways?

Are we sure about the weight of each vehicle (with one passenger)?

What other factors (data) do you need other than overall battery capacity, useable battery capacity, energy used to charge the battery (On board charger efficiency, usually 80-85%, right? -- ), vehicle weight, and miles traveled? Is there anything I am missing? Is vehicle weight irrelevant?

Let's use math and good data to get to the accurate result here.

 

[TonyWilliams]

Are we defining efficiency in the same way, do we all agree on the definition? It is defined by MPGe or something else?

Folks are welcome to generate any data they wish, and determine how important or appropriate that data may be. I'm not defining efficiency; I'm reporting miles traveled in prescribed conditions. The stored useable kWh is divided into those miles to determine the consumption rate. Whatever somebody does with that is solely up to them, including denying that the information is accurate.

Are we measuring the overall battery size and useable battery (in kW) in the same way? Can we prove it 2 different ways?

As explained above, there are multiple ways to determine usable battery kWh. We've been doing it for several years at the highest level of scrutiny (I blast this stuff out to the big, bad internet). I don't work with beliefs over data. You guys are welcome to.

Are we sure about the weight of each vehicle (with one passenger)?

If you read any of my tests, you'd know how we determine weight.

What other factors (data) do you need other than overall battery capacity, useable battery capacity, energy used to charge the battery (On board charger efficiency, usually 80-85%, right? -- ), vehicle weight, and miles traveled? Is there anything I am missing? Is vehicle weight irrelevant?

Why not read the multitude of documented range tests that I've done? Yes, there are other factors that we identify and document.

Let's use math and good data to get to the accurate result here.

The odd part (for me) is that I've done that math, and your assumptions are that nobody has. If you start with "there's no way that this test is valid because EPA is different" or the test is "way wrong", well, good luck!

I'll let you guys develop your own data, and I'll keep doing our tests covering all the issues that affect range, document that, and making valid comparisons to other EV's.

Yes, the Spark EV has 19 and 18 kWh of stored useable energy. Sorry if that offends some folks. Complaining about it doesn't change the data.

Here's a concept... why not do your OWN TEST, and I'll critique it?

 

[JupiterRed]

Tony, I appreciate your information on this and on other forums.

 

[sendler2112]

I don't work with beliefs over data. You guys are welcome to.

You ARE working with a belief without your own measurement. You believe that whatever the factory publishes for the battery capacity is correct. Spec sheets are notoriously inaccurate. And, there is always some variation between design and production. The SparkEV spec sheet doesn't even know how much the car weighs. "Base curb weight -TBD-".

http://www.chevrolet.com/spark-ev-electric-vehicle/specs/dimensions.html

Right now, the only thing you are measuring is range. You are not measuring capacity or consumption in any way. Which would be very easy to do. If more than a little time consuming. It's too bad that you have to take positive criticism as an attack. All you have to do is add a measured recharge after the range test to get a valid comparison. Any ChargePoint or similar charging station will show you the power that you used so you don't have to just BELIEVE what the automaker puts out in PR.