i3 v Tesla S - Elecric Efficiency Comparison

[psquare]

Higher, but not as high as claimed.

Would be interesting to see a comparison at lower average speeds. Sounds like as if it wasn't the most economical drive.

http://www.greencarreports.com/news/1095518_tesla-model-s-vs-bmw-i3-electric-car-efficiency-comparison-test

 

[Chrisn]

Intersting. Thanks for linking.

IMHO, efficiency comparisons are only helpful when comparing comparable cars-- roughly same size / cost / performance. From an economic perspective, obviously the amortized depreciation of a Tesla P85 is BY FAR the biggest cost-- something on the order of $1/mile. A 20% efficiency boost might save the i3 owner something like $0.02/mile on electricity. Rounding error in anyone's calculus.

If you live near a Supercharger, you could certainly claim that your Tesla is infinitely more efficient (given free charging), but you'll still have less money in your bank account (but perhaps more smiles).....

But, back to the energy efficiency (ignoring economics), I don't think that mass is necessarily your enemy for long range highway driving. If you spread the initial acceleration over a decently long steady-speed route, a larger mass (if mainly due to huge battery) can actually be your friend. During both discharge and (especially) charging, staying in the middle of the SOC with light amperage is where you want to be. A giant battery means that virtually all of your driving and, if you don't do a "long range charge," charging, is in this more efficient middle range. This might show up in a "grid to wheels" measurement where you started with both cars fully charged, then drive a 70 mile loop and recharge both at 50amps and measure the total kWh drawn from grid.

 

[psquare]

Chrisn,

Very good and valid points.

I have to say -and I might be on my own re this one- that I do like the almost educational part of the i3, where it teaches you to drive in a more efficient way. The Tesla -mainly due to the higher range- tempts to 'floor it' more often, I'd say.

I still think that the 16% difference in efficiency (if that can be compared in such a test anyway) could be increased with a more economical drive - and using EcoPro+. Let's not forget the comparison was all done in i3's Comfort!

 

[Jeffj]

From where I sit, this seems similar to deciding which car is better based on the number of cupholders. While having a cupholder where you want it certainly eliminates frustration with a car, it has little to do with the actual function of the car.

The "fuel" cost of a BEV (or a REx) is extremely small no matter what model you choose. Using $0.12/kWh (assuming you pay for all electricity), 4.0 miles/kWh and 12K miles/year, the fully loaded cost of electricity is $360. As the article states (I think this is called burying the lede), the efficiency difference "amounts to a piddling $8 a month in electricity costs".

Comparing efficiency as it pertains to the fuel cost is a waste of time.

Now, if we were talking ICE, and gas gets expensive again (I'm betting it will), then the real $ amounts matter. But its noise level in the EV's when compared to the cost of the vehicle

 

[I33t]

I still think that the 16% difference in efficiency (if that can be compared in such a test anyway) could be increased with a more economical drive - and using EcoPro+. Let's not forget the comparison was all done in i3's Comfort!

+1 Also, the test was between a Tesla and an i3REX. The numbers were fiddled to take out the REX efficiency loss, so it's a pretty vague and in no way accurate test between two EV's. The tester has already declared he doesn't like the look of the i3 in his Volt comparison.

He clearly loves his Tesla and is not an unbiased candidate to run a comparison test against it. The cars are not in the same price/size/performance/range market so any comparison is pretty much navel gazing.

 

[psquare]

My feeling is that he started out trying to make a fair comparison.

The important take away for me was that BMW's statement of a 39% higher efficiency and "i3 is the most energy efficient EV currently on the market" has to be taken with a pinch of salt, i.e. it's not as high as claimed.

Bottom line is: it's tricky to compare these cars. It's a bit like comparing a VW Golf and a Porsche just because they both have combustion engines.

I love the i3 and can't wait for mine to arrive.

 

[fdl1409]

This comparison is totally unfair and unscientific. Comparing board computer numbers???

AFAIK the Model S has an immense standby power loss as high as 4 kWh per day! Much as I love Tesla - considering to buy a Model III - this is something which would disqualify the car for me.

http://www.popsci.com/article/cars/life-tesla-model-s-even-after-update-vampire-draw-remains

With my i3 REx I could drive 6.000 miles per year with that amount of power loss if this is still true.

At least I would expect several trips with varying speed, charging every day and then compare meter figures.

Frank

 

[I33t]

The important take away for me was that BMW's statement of a 39% higher efficiency and "i3 is the most energy efficient EV currently on the market" has to be taken with a pinch of salt, i.e. it's not as high as claimed.

The i3 IS the most efficient EV currently on the market. Fueleconomy.gov rates it at 124MPGe combined 137MPGe city, and here is the rest:

The 85kW Tesla gets 89MPGe combined, +39% = 124MPGe so the 39% claim is in range, I haven't seen the 39% claim but I bet they have a little asterisk and an explanation how they arrived at the numbers.

 

[elptex]

AFAIK the Model S has an immense standby power loss as high as 4 kWh per day! Much as I love Tesla - considering to buy a Model III - this is something which would disqualify the car for me.

That significant problem was fixed more than a year ago (if not 2 years) as part of software updates. They now experience less than 1% loss per 4-5 days, which is more than acceptable.

 

[ultraturtle]

I'm of the minority opinion that efficiency matters. On an individual basis, it does not seem like much, but in the aggregate, it does. An ocean can't exist without many drops of water, and 31% more drops is a lot of ocean.

While the folks that initially got the EV movement off the ground largely because of its long term potential to reduce our impact on the environment are becoming a much smaller percentage of the growing base of EV owners, they occasionally deserve to be heard.

We currently have government mandates forcing ICE automobile manufacturers to increase the efficiency of their offerings, and for good reason. Unfortunately, no such efficiency mandates exist for electric vehicles, even though the well to wheel emissions are generally on par with highly efficient ICE vehicles. As a matter of fact, the Tesla Model S, charging from the grid, is responsible for more greenhouse gas emissions per mile than a Toyota Plug-In Prius (PiP) in every state of the Union except for the 13 with the cleanest electrical grids (Vermont, Washington, Idaho, Oregon, South Dakota, Connecticut, New Jersey, New Hampshire, New York, South Carolina, California, Illinois, and Virginia). See http://www.climatecentral.org/news/a-roadmap-to-climate-friendly-cars-2013-16318

31% energy consumption difference between two vehicles that accomplish basically the same mission is a big deal, because that energy comes from somewhere. If it is the electrical grid, it emits (well to wall, on a USA national average basis) 1.52 lbs per kWh. Comparing the most efficient PHEV operating on gasoline (25.9 lb CO2e per gallon) to the most efficient PHEV operating on electricity, and overlaying the Tesla Model S for comparison:

we see that that, as expected, the BMW i3 REx emits the least of the three up to its EPA range limit of 72 miles. Because of its cleanliness advantage over the Plug-In Prius (PiP), it remains cleaner after its gasoline engine kicks in all the way to 109 miles, where it emits the same greenhouse gasses as the PiP, and above which point the PiP remains the cleanest means of getting around. Note that the Tesla Model S is responsible for more emissions per mile than the PiP at any distance (except in the 13 states mentioned above), but it does equal the emissions of the BMW i3 REx at 184 miles. This is significant, because (on a national average) every single trip you take in a fully charged REx that is less than 184 miles will result in fewer emissions than the same trip in a Tesla Model S 85 kWh. These breakeven points, of course vary - lower for cleaner grids, higher for dirtier ones.

The in-car numbers observed in the OP referenced article are not comparable, as they reflect only a battery to wheel estimate, and are not measured by the same instruments. The only meaningful measurement comparison is wall to wheel, in a carefully controlled test with calibrated instruments and repeated runs, as the EPA carefully oversees measurement of. Those numbers are accurate - 31% advantage for the REx and 39% advantage for the BEV. While I have no doubt that a 90 mph continuous run would lower these numbers somewhat given the Tesla Model S's aerodynamic advantage, the EPA measurements reflect a more reasonable mix of driving speeds.

Just to pre-address the inevitable flood of responses justifying excess consumption because of personally owned photovoltaic systems, keep in mind that we are talking about the marginal case here - that is where your next electron comes from, not the ones you already use. Unless all of your electrical needs are completely covered by your PV system on an annual basis, and you have excess electricity to spare, that 31% excess consumption is coming from the grid, not your rooftop.

As with any discussion of measures to help our planet, none is more effective than conservation.

 

[WoodlandHills]

This comparison is totally unfair and unscientific. Comparing board computer numbers???

AFAIK the Model S has an immense standby power loss as high as 4 kWh per day! Much as I love Tesla - considering to buy a Model III - this is something which would disqualify the car for me.

http://www.popsci.com/article/cars/life-tesla-model-s-even-after-update-vampire-draw-remains

With my i3 REx I could drive 6.000 miles per year with that amount of power loss if this is still true.

At least I would expect several trips with varying speed, charging every day and then compare meter figures.

Frank

I agree, they should have also switched drivers between cars as well as who led and who followed. Any pilot knows that formation flying uses a lot more fuel than simply setting the throttle and flying alone, they should have just driven separately.
The writer had a bias and his "test" confirms that bias. One see this sort of thing in print magazines all the time, so why not online too?

 

[fdl1409]

That significant problem was fixed more than a year ago (if not 2 years) as part of software updates. They now experience less than 1% loss per 4-5 days, which is more than acceptable.

Sure about that? Read in the above link, which was posted after the Version 5.8 update which was supposed to solve the problem of vampire drain one year ago.

So far I've run three overnight tests with the kWh meter. For each test, I charged the car up in the evening to its usual selected level (In my case, about 80 percent). Then I removed the charge plug. I allowed the car to sit unplugged overnight and on into the next day, until I needed to drive it. (Typically a span of 12 to 24 hours.)

Before driving it, I plugged it back in to top off the vampire-depleted battery back to its original level. Then I checked the kWh-meter.

The three tests showed vampire losses of 2.3 kWh in 17 hours, 1.9 kWh in 23 hours, and 4.2 kWh in 18 hours. Total vampire power lost was 8.4 kWh in 58 hours.

That's an average of 3.5 kWh per day--roughly 25 percent lower than the losses I measured previously.


I`ve had my i3 Rex for 188 days now. A loss of 3.5 kWh per day would have summed up to 658 kWh. I have driven 7.453km ( 4.658 miles ) so far with 875 kWh measured including all losses from kWh meter. An extra 658 kWh would be 75% on top of my power consumption.

This is not meant to be Tesla bashing. I am a big fan of Elon musk and think that Tesla is the most important company in the world. Model 3 is a serious candidate for my next car after the i3. But they have to get a few things right, and standby loss is on top of the list here.

Frank

 

[wraithnot]

That significant problem was fixed more than a year ago (if not 2 years) as part of software updates. They now experience less than 1% loss per 4-5 days, which is more than acceptable.

Sure about that? Read in the above link, which was posted after the Version 5.8 update which was supposed to solve the problem of vampire drain one year ago.

Frank

If you look at the very bottom of the page you linked to, you'll see:

"Update: Power drain problem solved, at last."

And this points to the following article : http://www.greencarreports.com/news/1088929_life-with-tesla-model-s-electric-draw-vampire-slain-at-last

And the ultimate conclusion is: "And so it looks like my vampire was indeed my car's defective 12-Volt battery"

 

[fdl1409]

OK, thank you. That sounds a lot better.

But the losses have not been totally eliminated. In that link you posted the driver checked again after the 12V battery was exchanged:

3.6 kWh of vampire power consumed in 81 hours. That was 1.1 kWh per day--only a quarter of my previous long-term vampire draw, and three times better than my initial tests with 5.8.

Yesterday I posted a reply to that report by David Nolan, which is the subject we are talking about here.
David replied to that as follows:

I typically lose about 1 kWh per day on the Tesla. That amounts to about 90 miles per month, or about 7 percent of my total driving.

So there still is some significant standby loss, approximately 400 kWh per year which is enough for a driving distance of ~1.200 miles. Much better, but still a lot of room for improvement. And a factor which has to be considered in any comparison between the two cars.

Frank

 

[alohart]

So there still is some significant standby loss, approximately 400 kWh per year which is enough for a driving distance of ~1.200 miles. Much better, but still a lot of room for improvement.

I have read that because of the Tesla's battery chemistry, the battery cells must be monitored continuously to prevent problems. This monitoring requires power, so it's likely that Tesla will never be able to reduce its cars' standby power consumption to a level that I would accept. But then Tesla doesn't promote efficiency when selling its cars as much as it promotes high performance. Many of us don't want to drive a big 2+ ton car and don't need a car that can accelerate to 60 mph in less than 4 seconds.

 

[ultraturtle]

Many of us don't want to drive a big 2+ ton car and don't need a car that can accelerate to 60 mph in less than 4 seconds.

+1

 

[mindmachine]

Many of us don't want to drive a big 2+ ton car and don't need a car that can accelerate to 60 mph in less than 4 seconds.

+1

+2

 

[wraithnot]

OK, thank you. That sounds a lot better.

But the losses have not been totally eliminated. In that link you posted the driver checked again after the 12V battery was exchanged:

3.6 kWh of vampire power consumed in 81 hours. That was 1.1 kWh per day--only a quarter of my previous long-term vampire draw, and three times better than my initial tests with 5.8.

Yesterday I posted a reply to that report by David Nolan, which is the subject we are talking about here.
David replied to that as follows:

I typically lose about 1 kWh per day on the Tesla. That amounts to about 90 miles per month, or about 7 percent of my total driving.

So there still is some significant standby loss, approximately 400 kWh per year which is enough for a driving distance of ~1.200 miles. Much better, but still a lot of room for improvement. And a factor which has to be considered in any comparison between the two cars.

Frank

I completely agree that my wife's i3 has a significantly lower "vampire drain" than my Model S since the i3 doesn't seem to lose any range at all over the course of a day or so. But putting an exact figure on the Model S vampire drain is tricky as there are a total of six different combinations of energy saving modes. With the version 6.0 software, you can turn the energy savings to "on", "off", or "nightly" and there is an independent option of "always connected" that keeps the car extremely responsive to the smartphone app by keeping at least some of the processors online. Perhaps different energy savings settings accounts for this test that gives better results than David Nolan's: http://insideevs.com/video-tesla-model-s-vampire-drain-after-27-cold-days-of-being-unplugged/ (the loss of 3.7 NEDC km per day should work out to about 2.1 EPA miles of range per day)

 

[fdl1409]

Very interesting. Tesla still has to work on this. I really get p...ed off by such standby waste. In my private home I have managed to cut nightly standby loss to 0.4W if the heating isn`t working or a fridge.

My i3 doesn`t lose any noticable energy in standby and still I can start it and drive away in a second or maybe three. Same with my previous car which was a Mitsubishi i-MiEV. Read the same about all other electric cars except Tesla.

Model 3 is the top contender for my next car. But I simply can`t buy that unless they have reduced standby to an acceptable level which for my is under 0.1 kWh in 24 hours.

By the way those standby losses also mean that while driving there is an unnecessary drain to the battery by secondary users. If you drive with an average speed of 45 mph and 32 kWh/100 miles a reduction of secondary power drain by 500W would improve range by as much as 3.5%!
Look what a smartphone can do with a few watts and then use the same technology on a car. A huge battery should not seduce to use power wastefully.

Frank

 

[Gonville]

I see Tesla are thinking maybe they can make use of carbon fibre and perhaps change the 'vampire' technology......wonder who might help them do that.....

Tesla is in talks with BMW over a possible partnership in battery technology, charging stations and light-weight components, Elon Musk told German weekly Der Spiegel. In an interview published on Sunday, Musk called BMW's (OTCPK:BAMXY) carbon fiber reinforced car body parts "interesting" and "relatively cost efficient," and expects Tesla (NASDAQ:TSLA) to have a battery production plant in Germany in five to six years.
Both companies first met in June over a possible alliance. TSLA +1% premarket

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http://www.reuters.com/article/2014...NC20141124?feedType=RSS&feedName=businessNews