Poll: Guess 70 mph Steady State Range of Model 3 Vs Bolt

[Rashomon]

I hope you are right, but I came up with 13.5 kW for air plus road resistance.

I may be a little low: the 0.21 Cd may not be quite achieved and my 0.46m2 CdA estimate may be too low, at least until the DOT lets Tesla drop sideview mirrors. (I can't imagine EU and Japanese M3s will ever have such antiques.) I'm also assuming that the M3 base tires will be very free-rolling, at least as good as the Michelins on the Bolt. But I think your 13.5 kW at 70 estimate and my 12 kW pretty much bracket what will be achieved. The highway range at real freeway speeds will be outstanding.

 

[Cloxxki]

270 kWh per 100 miles​

Doesn't it say 28kWh?

At 60kWh available capacity that would be 60/28 * 100 = 214 miles. Makes no sense to me. More battery than they're letting on to, still, perhaps to disguize not so great economy at realistic speeds?​

 

[SageBrush]

I may be a little low: the 0.21 Cd may not be quite achieved and my 0.46m2 C

Strange, we both used .21 cd and 2.22 area. I think one one of us has an arithmetic error.

 

[omgwtfbyobbq]

So far, Tesla has balanced aero drag and weight/rolling resistance such that their EPA city and highway numbers have been pretty close compared to other manufacturers. That may change with the 3, but I don't think it will. At the same time, if Tesla just gets close to .21, even with a 20% smaller battery "capacity", they may still manage 15% better range at highway speeds.

At the same time, their EPA highway range would be closer to the Bolt because the average speed of the year is lower than 70mph.

 

[Jeff N]

Doesn't it say 28kWh?

At 60kWh available capacity that would be 60/28 * 100 = 214 miles. Makes no sense to me. More battery than they're letting on to, still, perhaps to disguize not so great economy at realistic speeds?​

The EPA 28 kWh per 100 miles estimate for the Bolt EV includes charging overhead and implies that it takes roughly 67 kWh to fully recharge a completely empty Bolt battery.

67/28 * 100 = 239 miles.

 

[Jeff N]

The M3 should take about 12kW of delivered mechanical power to maintain 70 mph. I suspect its base pack will have somewhere around 52 kWh of usable energy, so at 85 percent efficiency, it should go somewhere around 250 miles at 70.

That seems like an implausibly good result. The 2014 Model S85 draws 21 kW DC from the battery at a steady 70 mph, according to the Idaho National Labs.

The INL report for the 2015 Spark EV shows it using 19.6 kW at 70 mph in the same test scenario. However, a closely related calculation shows the "DC consumption per mile" as 280 Wh in the S85 vs. 301 Wh in the Spark EV. I'm not sure why the S85 is ~7% worse on average DC consumption at 70 mph but the Spark EV is ~7% worse at DC Wh per mile. Seems odd. It might have to do with the relative battery sizes in that taking energy out of the battery at lower states of charge could be less efficient at ~20 kW on the Spark EV's 18.4 kWh battery (greater than 1C rate). This would not be an issue when comparing a 60 kWh Bolt vs a ~55 kWh Tesla M3.

There are lots of complex interactions between powertrain and tire efficiency and aerodynamics as speed increases.

Unfortunately, the INL reports on the Spark EV and Tesla S are missing differing large sections of results which makes them hard to compare directly at any speed other than 70 mph although you can interpolate the missing data. Generally speaking, the increasing rate of energy use between steady state 45 mph, 60 mph, and 70 mph tests do not seem to show a significant relative advantage at higher speed during that 45-70 speed range between the Spark EV and the S85. This is surprising. The two cars show roughly a 27% increased DC energy use between 45 and 60 mph and a 20-22% increase between 60 and 70 mph (the Spark EV had the slower increase).

The Spark EV seems to have a similar or just slightly worse Cd than the Bolt EV but should have a somewhat smaller CdA total drag area. The Spark EV has essentially identical EPA ratings as the Bolt EV for city and highway.

Without side-by-side comparison's using the same test scenarios it's hard to make precise comparisons right now. However, I think the bottom line is that the Tesla M3 will almost certainly be somewhat better at DC Wh per mile at ~70 mph than the Bolt EV and the Bolt EV will have perfectly reasonable and usable highway range at ~70 mph for use during occasional long-range travel.

Here are the INL reports:

https://avt.inl.gov/sites/default/files/pdf/fsev/fact2015chevroletspark.pdf

https://avt.inl.gov/sites/default/files/pdf/fsev/fact2014teslamodels.pdf

The LEAF does not seem to do well at higher speeds perhaps because of powertrain inefficiencies.

https://avt.inl.gov/sites/default/files/pdf/fsev/fact2013nissanleaf.pdf

 

[Rashomon]

That seems like an implausibly good result. The 2014 Model S85 draws 21 kW DC from the battery at a steady 70 mph, according to the Idaho National Labs.

I did say this was mechanical power delivered to the wheels, so the power losses of the drive train have to be factored in to get battery power requirement. The calculation is based on 20 percent reduced aerodynamic drag relative to an S (lower Cd and slightly less A), and about 25 percent reduced rolling losses, from lower weight and better tires. (Michelin is on record saying that Tesla has been aggressive on their rolling friction target.) If you assume 15 percent powertrain losses, you end up with 21kw*0.8*0.75*0.85, or about 11kW. The same spreadsheet formulas I used for the M3 calculate about 17kW of total road load for a Model S at 70 mph. Again, if you, multiply the measured 21 kW of battery power at 70 mph by an 0.85 efficiency, you get about 17.9 kW of mechanical power delivered. I'm least sure of the efficiency, so these calculations seem to be in the ballpark.

 

[Rashomon]

Strange, we both used .21 cd and 2.22 area. I think one one of us has an arithmetic error.

Perhaps. More likely I'm using a much lower rolling coefficient: 0.007

 

[Red Sage]

Doesn't it say 28kWh?

At 60kWh available capacity that would be 60/28 * 100 = 214 miles. Makes no sense to me. More battery than they're letting on to, still, perhaps to disguize not so great economy at realistic speeds?​

That entire post was a typographical error. I owned up to it on subsequent posts. At least, I remember doing so... I had not realized I had some saved 'Personalize' settings on the EPA's website within my web browser. So, all the numbers were off.

 

[Red Sage]

So far, Tesla has balanced aero drag and weight/rolling resistance such that their EPA city and highway numbers have been pretty close compared to other manufacturers.

I have a strong feeling that traditional automobile manufacturers do their wind tunnel testing without exterior mirrors attached.

 

[MichFin]

You got a point here, but you misses a bit...
I need thous 200 miles range - when not going at a road trip. So yes, I can live with 215 miles range, and have 15 miles of buffers. But as the range goes up from 200 miles, I get more buffers = less strain on the battery = longer battery life.

As a Model S owner I've never one come close to using up my 90% 240 mile range in my daily driving. So if the range is 215 or 250 miles it's NOT going to make any difference unless you have some crazy driving habits. Which in that case I suggest an electric car is not right for you. I'm not saying it's not important but it should be 5 or 6th on the list.

Size, performance, comfort, styling and reliability are all way more important.

 

[SageBrush]

Perhaps. More likely I'm using a much lower rolling coefficient: 0.007

Ah, yes. 0.009

 

[Booga]

As a Model S owner I've never one come close to using up my 90% 240 mile range in my daily driving. So if the range is 215 or 250 miles it's NOT going to make any difference unless you have some crazy driving habits. Which in that case I suggest an electric car is not right for you. I'm not saying it's not important but it should be 5 or 6th on the list.

Size, performance, comfort, styling and reliability are all way more important.

It might depend on what that person is planning - it sounds like you have a place to charge every night. If they don't, then I can see it being a bigger constraint. (I will not and so I'm planning around that)

 

[omgwtfbyobbq]

I have a strong feeling that traditional automobile manufacturers do their wind tunnel testing without exterior mirrors attached.

They probably (and unfortunately ) do a lot more than that...

Emissions test loopholes breed culture of fudging
http://www.beuc.eu/documents/files/FC/FuelConsumption/T&E_Real_World_Fuel_Consumption.pdf

When the road load test procedures were drafted 30 years ago, no-one expected carmakers to adjust the brakes, pump up the tyres, and tape up all the cracks around the doors and windows to reduce the air and rolling resistance. These practices are now commonplace, with testing facilities being paid to optimise the results of the tests. There is no evidence that carmakers are breaking any formal rules - but they don’t need to - the current test procedures are so lax there is ample opportunity to massage the test results. Testing undertaken by an independent laboratory has found that for older vehicles, road load results in realistic tests – e.g. using regular production vehicles - were on average 19% higher than the results obtained in official tests. For more modern vehicles the average difference was 37%, supporting other evidence that the manipulation of the road load part of the test is increasing. These differences would result in around a 12% reduction in measured fuel economy.

 

[Model 3]

As a Model S owner I've never one come close to using up my 90% 240 mile range in my daily driving. So if the range is 215 or 250 miles it's NOT going to make any difference unless you have some crazy driving habits. Which in that case I suggest an electric car is not right for you.

Maybe I have some crazy driving habits, but that is not the point of my post. But I have some trouble reading the rest of what I quoted here. Ether you have misunderstood me, or I misunderstand what you are trying to say. I do not think I would not have any problem with making my mentioned driving using your mentioned 240 miles range. Especially when this is only a 90% charge. So why would an electric car be worse for me then it is to you?

And yes, a total 100% range of 215 or 250 is a difference. Not that I did not suggest that I would get any range anxiety with a 215 miles range, but that I rather have 50 "unused" theoretical miles left when I put the charging cable in when I get home then only 15 miles - or more precisely have 25 miles left and let 25 miles at the top be unused by only charging to 90% - or 80% if that still let me have range left back at home.

Size, performance, comfort, styling and reliability are all way more important.

What is most important to me should be up to me to decide? No, I'm not blind to all the rest of the cars, but I will not even consider buying a new car if it is not an BEV. Mind that I do not say "Ah... It's a BEV? I buy it no mater what!". Yes both cars seems to check most (but none check them all!) of the check-boxes that are important to me. And no, my checklist is not equal your's.

 

[Rashomon]

The M3 should take about 12kW of delivered mechanical power to maintain 70 mph. I suspect its base pack will have somewhere around 52 kWh of usable energy, so at 85 percent efficiency, it should go somewhere around 250 miles at 70. The Bolt requires about 17 kW at 70, so with 58 kWh of usable energy, it should go about 200 miles at the same efficiency. The difference gets considerably worse as you go faster. At 80, the Bolt requires about 25kW, while the M3 requires only what the Bolt required at 70: 17kW. The M3 goes about 210 miles at 80 mph, while the Bolt can range only 160 miles.

It does make you think what the 70 mph highway range of the M3 with the largest optional pack will be, assuming it's 30 percent bigger than the standard pack. I'd bet around 325 miles. And the 60 mph range could be over 400 miles!

The M3 should take about 12kW of delivered mechanical power to maintain 70 mph. I suspect its base pack will have somewhere around 52 kWh of usable energy, so at 85 percent efficiency, it should go somewhere around 250 miles at 70. The Bolt requires about 17 kW at 70, so with 58 kWh of usable energy, it should go about 200 miles at the same efficiency. The difference gets considerably worse as you go faster. At 80, the Bolt requires about 25kW, while the M3 requires only what the Bolt required at 70: 17kW. The M3 goes about 210 miles at 80 mph, while the Bolt can range only 160 miles.

It does make you think what the 70 mph highway range of the M3 with the largest optional pack will be, assuming it's 30 percent bigger than the standard pack. I'd bet around 325 miles. And the 60 mph range could be over 400 miles!

Car and Driver just obtained 190 miles at 75 mph on a production or pilot-production Bolt -- an excellent performance by GM. I don't have a calculation for 75 mph above, but using the same equations, I get around 182 miles predicted range for the Bolt -- so my assumptions are a little pessimistic. I suspect the drivetrain efficiency is a little higher than I assumed, though the available battery capacity may be a little higher as well, or rolling resistance a little lower. The overall conclusion remains the same: the base M3 will have significantly more range on the highway than the Bolt, though the difference will likely be a little less than predicted above, on the order of an extra 40 miles range at 80 mph, rather than 50.

 

[jonnyg]

Interesting article of real world range, charging etc for a Bolt and a Model S: The Chevrolet Bolt and Tesla Model S 60: Range, Charging - and Travel - Motor Trend

The next morning, the Bolt had absorbed 68 kW-hrs of energy, the Tesla, 64.7. Is the Bolt’s charging that much less efficient? (For those of you without electrical engineering degrees, absorbing more energy is a bad thing, an indicator of inefficiency, similar to spilling gasoline at the pump, but instead it’s wasted electrons.) However, this was not the case. The Bolt’s battery is evidently larger than claimed, its usable size likely larger than its stated, 60 kW-hrs capacity (which I had run extraordinarily low; GM says a typical charge is 66.6).

Sounds like the Bolt battery is somewhere in the 70-75 kWh range, right?

Also, here's a related article: 2017 Chevrolet Bolt EV vs. 2016 Tesla Model S 60 Comparison

 

[Rashomon]

Interesting article of real world range, charging etc for a Bolt and a Model S: The Chevrolet Bolt and Tesla Model S 60: Range, Charging - and Travel - Motor Trend



Sounds like the Bolt battery is somewhere in the 70-75 kWh range, right?

Also, here's a related article: 2017 Chevrolet Bolt EV vs. 2016 Tesla Model S 60 Comparison

No, I wouldn't say that the pack is that big. More likely the 58kWh usable with 60 (or just slightly more) kWh nominal estimate is close, but maybe it's 60 kWh usable and 62 kWh nominal. Also, my powertrain efficiency numbers might be off by a few percentage points. A very good PMAC motor and latest technology inverter might be 88 percent efficient overall rather than 85 percent. But something has to be better about the Bolt!

 

[jonnyg]

No, I wouldn't say that the pack is that big. More likely the 58kWh usable with 60 (or just slightly more) kWh nominal estimate is close, but maybe it's 60 kWh usable and 62 kWh nominal. Also, my powertrain efficiency numbers might be off by a few percentage points. A very good PMAC motor and latest technology inverter might be 88 percent efficient overall rather than 85 percent. But something has to be better about the Bolt!

Oh. So the EVSE said it used 68 kWh to charge the battery, but that doesn't include charging efficiency (or whatever the correct term is here)? That makes sense.

 

[bro1999]

Oh. So the EVSE said it used 68 kWh to charge the battery, but that doesn't include charging efficiency (or whatever the correct term is here)? That makes sense.

The 68 kWh used would include charging losses. If we assume a 10-15% loss, that puts usable capacity right around 60 kWh. So the actual battery size is likely a little bigger.