fromport said:
Smaller motors use less energy. Push the pedal to the floor, the larger motor uses more energy. It has to be, Newton's Second Law; F=MA. If you go faster from 0 to 60 you use more energy. More energy equals shorter range. Period!
Will the Chevy Bolt EV be a 'game changer'?
- Thread starter JimmYK
- Start date
Help Support Chevy Bolt EV Forum:
Smaller motors use less energy. Push the pedal to the floor, the larger motor uses more energy. It has to be, Newton's Second Law; F=MA. If you go faster from 0 to 60 you use more energy. More energy equals shorter range. Period!
Hi,Robaroni said:
Your energy accounting isn't correct. If you have a motor and drivetrain with a fixed efficiency over various acceleration rates, then for the same initial and final speeds, it doesn't matter how quickly you accelerate from the intial speed to the final speed. The change in kinetic energy of the vehicle between the initial and final speeds is the same, and we've posited the motor efficiency is the same, so the energy used is the same.
So the issue just comes down to the efficiency of a bigger versus a smaller motor, at various power levels.
Cheers, Wayne
SparkE
Well-known member
He's gotten so many things so wrong, and/or just changed the argument when is was so obvious even he figured it out, that it has become time to just ignore the senseless rants (which aren't about the Bolt).
wwhitney said:
The 100 HP motor with 80% efficiency wastes 20 percent or about 15,000 watts to propel the car to 60 mph in a specific time. The 10 HP motor with 80% efficiency wastes 1,500 watts in a specific time.
The 100 HP motor uses 100 HP to get to 60 faster, the most the 10 HP motor can utilize is 10 HP, while it takes longer to get to 60 the difference will not be 10 times longer. The efficiency of motors is at constant speed, due to its larger size the energy to reach constant speed is greater than the smaller motor with less mass. That adds up every time we accelerate, the more work we do the more energy we use. A larger motor is heavier thus the vehicle is heavier, this equals more energy used to reach the same speed. Add the difference in weight of the larger and smaller motor to the battery pack, now we go further with the smaller motor.
Batteries are rated in amp/hours. A 100 Ah battery can theoretically supply 100 amps for 1 hour. The problem is that the discharge curve is not linear. A 100 Ah battery discharging at a 10 Ah rate will last longer than 10 hours. Larger motors draw more current, more current means a shorter time the battery maintains its charge.
In fact, it will be 10 times longer, at least ignoring wind resistance. I'd have to think about it further to figure out if wind resistance and other losses means it will take more than 10 times longer or less than 10 times longer.Robaroni said:
Cheers, Wayne
Edit: definitely more than 10 times longer, as at any given speed, the power required to maintain that speed should be a fixed overhead, so the available power to accelerate with a 100HP motor will be more than 10 times the available power to accelerate with a 10HP motor.
SparkE said:
"so many things wrong"
Enlighten me, I'm always willing to learn.
As for the Bolt being a game changer, what will the Tesla Model 3 be when it come out? If anyone changed the game it was Musk, he came to market with a 200 plus range mass market car. I think the Bolt has real potential and I'm interested in it but I'm also interested in the Tesla.
Are you claiming that using 10 HP of a 100 HP motor has a 20% loss on the 100 HP figure? If you accelerate gently, the energy used is the same (or virtually so) no matter the maximum capacity of the motor. Once again, the driver dictates the efficiency - or there could be a software limit.Robaroni said:
The Fit EV has 3 modes:
ECON - 63HP with a very "slow" pedal response (and limits on Heat/AC draw)
Normal - 100 HP with "normal" throttle map
Sport - 123 HP with "aggressive" throttle map
I get a higher m/kWh figure using Sport mode than my wife does in ECON or Normal. But I also have the needed (or just wanted) acceleration on tap to pass/merge/dodge without having to hit a button to put it into the correct mode.
Even if you believe a 10 HP motor is more efficient at full throttle vs a 100 HP motor using 10 HP (unlikely), any difference would be very minor when it comes to the total range of an EV.
DucRider said:
It depends on the load of the motor (electric motors are more efficient at higher loads). Will the 100 HP motor reach full load on acceleration? If both motors reach their full load then you and Wayne are right and there is no appreciable loss from using a larger motor aside from the non linearity of the greater load on battery life. If the 100 HP does not and the 10 HP does then I think the smaller motor has a slight edge but I do see that my initial premise of a smaller motor extending range substantially may be wrong.
oilerlord
Well-known member
SparkE said:
Incoherent, off-topic minutia. Perhaps the reason DVD's replaced the VCR accounts for why smaller electric motors are more efficient than larger ones. There must be a copy & paste about the virtues of renewable energy in Hawaii that helps it all make sense. :roll:
I'd rather trust engineers at Tesla, Nissan, and GM to work out all the metrics (power/weight, battery capacity, conversion losses, drag coefficients, etc) to size their motors for best overall efficiency.
Back to the original post...I think there's only so much game you can change with a $37,000 EV with a battery makes up 23% of the price of the car. Sure, the car is more affordable but because of that, GM lost the ability to put more amazing into the car.
SparkE
Well-known member
oilerlord said:
Personally, I'd rather have a less expensive car that meets my basic needs than pay for everybody else's bells and whistles. I don't need a calculator app in the dashboard, as I can generally do the math in my head - when I can't, I have a smartphone for that. (You are scratching your head about that, eh? Just keep reading.) I don't need navigation in my car - I almost always (over 98% of the time) KNOW where I am going before I get in the car. If I've never been there before, I look it up before I leave (including the closest DCFC stations if it's a new area). For the less than 2% of the time I don't know where I am going, I have a smart phone with mapping. And I don't want to pay extra because somebody ELSE wants navigation. (These days - whether it is CPU chips, game consoles, phones, or whatever - a LOT of 'options' are built into everything, but only 'enabled' if the user 'buys' it - it is still in the COGS, driving up the base price.)
But then I'm a pretty basic, no-frills guy. My first vehicle was a '66 VW van, followed by a '53 Chevy 3100 pickup. If you've ever driven either one, you'd know what I mean.
PS : COGS - Cost Of Goods Sold.
oilerlord said:
First, if you're going to repeat what I said get it right! I said, "Smaller motors use less energy. Push the pedal to the floor, the larger motor uses more energy. It has to be, Newton's Second Law; F=MA." Which is completely correct. Larger HP motors use more energy than smaller HP motors. A car using 100HP during acceleration uses more energy than a 10 HP motor accelerating. I also said," Power and efficiency are not mutually exclusive, you can have small motors with better efficiency than large ones. A 100 hp motor will use more energy than a 10 hp motor regardless whether it has 10% more efficiency or not. One HP = 746 watts. Period! A 100 HP motor with 80% efficiency uses about 89,000 watts. A 10 HP motor with 70% efficiency uses ~ 9,700 watts. You can't get something from nothing!" I never said "Perhaps the reason DVD's replaced the VCR accounts for why smaller electric motors are more efficient than larger ones." Those are your words.
And I stand by my choice. I'd rather have an EV with a smaller motor. One, it's lighter, two it's cheaper. Motors won't drop in price much, batteries will.
"I'd rather trust engineers at Tesla, Nissan, and GM to work out all the metrics (power/weight, battery capacity, conversion losses, drag coefficients, etc) to size their motors for best overall efficiency."
I did, the Leaf has a 107 HP motor that goes to 60 in about 10 seconds. I prefer it over the Tesla that does it in a much shorter time but with the added expense of the 250+ HP motor. The Tesla motor weight is claimed to be 70 lbs BUT this is not the whole story. As motor HP increases so does the inverter weight to accommodate the higher current. The Model S motor plus inverter weighs 350 lbs. Tesla was happy with a 200+ range. It's called design parameters. If the design parameter had favored range then we might have seen a 4 or 5k mile range from Musk over performance.
Bottom line, I'll take the smaller lighter motor in my EV and add the weight difference to batteries for range. If the Bolt came out with less HP and more range it would be more appealing to me.
Why anyone is calling this a "game changer" is beyond me, maybe if it went 400 miles on a charge. The Nissan Leaf has sold more EVs than anyone else and the Tesla broke new ground, the Bolt was just the first to market with a 200+ range relatively affordable EV and not by much. VW expects to bring out its 200+ EV for $30k.
GM? Aren't they're the ones who recalled and crushed all the EV1s?
Robaroni said:
If you DON'T push the pedal to the floor and use only 10 HP, the difference in energy use is negligible. When maintaining a steady speed, the 100 HP motor uses virtually the same amount of energy as the 10 HP motor. There are so many other factors using energy at say 55 mph, that motor efficiency differences are meaningless in comparison to wind resistance, etc. This is obviously not true if you treat the right pedal like an on/off switch, but if you use the same amount of energy to accelerate at the same rate, motor size is irrelevant. Much of your argument assumes all acceleration takes place at maximum motor HP, which is rarely the case. It;s compounded even more by the fact that the percentage of time an EV is accelerating is relatively low - more time is spent cruising at a set speed or decelerating.
Lighter - a little. Cheaper - not much. Cutting motor power in half and using the weight savings in battery will gain you a few miles, but nothing in the 50-100% range improvement you seem to claim.
And no GM did not recall the EV1 - they never sold it to begin with. It was a lease with no option to purchase and everyone leasing the car knew that going in (if they took the time to read). In fairness, the same amount of disdain should also be pointed at BMW for the Mini-E and Active E that were lease only. And Honda for the Fit EV that is the same deal. They were always planned and publicized as large scale Beta tests in real world conditions in order to learn more about how drivers and EV's worked on a daily basis.
oilerlord
Well-known member
SparkE said:
I agree. When car shopping, I start out that way but then bluetooth, heated seats, and little things like HID automatic headlights, and tap once / get three turn signals are things that I like to have. The Spark EV would meet our "basic" needs but the deal-breaker was that it was too small for us, or dog, and our stuff.
My point wasn't really about frivolous options, but about a manufacturer's ability to build a car that meets Joe Consumer's basic expectations like 300 miles on a tank, and filling up anywhere in minutes...things society has taken for granted for decades. EV's are expensive propositions with shortcomings that revolve around charging infrastructure. There are only so many environmentally motivated buyers that will shell out a lot more $$$ for Bolt vs similar ICE - just to make a planet-saving statement. Sure, there are real positives like near zero maintenance, reliability, and filling up at home, but even so, the case for money savings is at best dubious vs lower cost ICE alternatives.
I'd like to see GM give Joe Consumer a real game changer: A Bolt for the same price as a Sonic, that can go an minimum 300 miles without fail, and fill up anywhere in minutes, not hours. I wonder how many decades we are from that happening.
By the way, I saw a commercial about the Malibu. They took off all the decals, and wowed the "not actors" with the car. Then, the guy announced it was $23,500. One of the not actors then said "Wow, that's a game changer". We have so little regard for true innovation these days. Sadly a Malibu is now, officially, a game changer.
DucRider said:
Not true:
"Nissan justifies reducing the torque in its 2013 LEAF by stating that too much torque affects handling as well as range.
“ The natural response of an electric motor is to give its maximum torque from standstill, making it an excellent choice as a vehicle power unit, due to its rapid response to driver input,” Nissan said. “In an automotive application, it is desirable, particularly from standstill, to limit the torque from the motor to reduce the tendency to wheel-spin. Without this, customers would experience not only wheel-spin, but more front tire wear and unnecessary energy consumption.”
Essentially, Nissan is sacrificing initial torque in order to improve energy consumption and reduce tire wear during the frequent stopping and starting of city traffic. Although we’ve heard from several drivers that this makes the 0-30 time feel slower in the 2013 LEAF. "
Smaller motors run more time at higher load, the higher the load the more efficient the motor (see illustration).
Smaller motors are lighter and require lighter inverters. Not "a little", the Tesla weighs 350 lbs, motor + inverter. The Leaf motor + inverter weighs 210 lbs. Tesla uses the 18650B battery, an 18650B battery weighs ~45 grams. A Panasonic 18650B battery produces about 3 Wh.
(63.5K/.045) x 3 = 4.2 KWh.
The Leaf goes 107 miles on a 30KWh battery; 107/30 = 3.56; 3.56 x 4.2 = about 14.7 miles more range using a smaller motor and adding the weight in batteries.
By the way, the Tesla goes 265 miles on 85Kwh battery = 3.11 mile per KWh, the Leaf does better at 3.56 miles per KWh.
You don't get something for nothing, bigger motor = shorter range. I'll take the mileage.
And GM leased the EV1, refused to sell the vehicles at the end of the lease and crushed them ALL! BMW is not selling the Bolt, GM is.
oilerlord
Well-known member
Robaroni said:
Rob, you need to consider the overall weight of the car, and sizing the motor to efficiently move it's mass based on the target audience. At 3342 pounds, the Leaf 30kWh weighs ~1600 pounds less than a Model S 85. While it's true that electric motors are more efficient at higher loads, the Tesla's larger motor that is lugging around nearly 5000 pounds, designed with a 0-60 in 4.2 seconds - is being subjected to a higher load. I trust Tesla engineers sized the motor and it's efficiency to how their customers drive their cars*, the same way Nissan engineers did for Leaf drivers**. I'll take the range - 265 fun-to-drive miles vs 107 grandpa miles regardless of MPGe.
* Model S drivers typically murder electrons, your mileage may vary.
** Leaf drivers typically conserve electrons, your mileage may vary.
And let's not forget the Bolt is more efficient than the LEAF (119 MPGe vs 112), even with a 150 kW motor vs 80 kW. And that's with the weight of twice the batteries.oilerlord said:
The efficiency of an electric motor is much more complex than Roboroni is making it out to be. The graph above in his earlier post is for an unknown motor type, but is used to illustrate the correct motor size in a pumping application - steady load and steady RPM - vastly different than what is desired in an EV. It does show the varied efficiency under different loads, but at an unknown steady state RPM. Those motors are most likely to be speed controlled, and of a lower cost design that is indeed much more efficient at their 50-60% load "sweet spot".
The AC motors in EVs are both torque and speed controlled, and need to handle a wide variety of loads and speeds. Yes a smaller motor will be somewhat more efficient, but not on the order that he has suggested.
A better representation can be found on Nissans site, and they did make changes in the 2013 model year to gain some greater efficiency by trading torque (I think the goal was actually to reduce the amount of rare earth elements in the motor)
SparkE
Well-known member
So ... is the Bolt a 'game changer' ??
DucRider said:And let's not forget the Bolt is more efficient than the LEAF (119 MPGe vs 112), even with a 150 kW motor vs 80 kW. And that's with the weight of twice the batteries.oilerlord said:
The efficiency of an electric motor is much more complex than Roboroni is making it out to be. The graph above in his earlier post is for an unknown motor type, but is used to illustrate the correct motor size in a pumping application - steady load and steady RPM - vastly different than what is desired in an EV. It does show the varied efficiency under different loads, but at an unknown steady state RPM. Those motors are most likely to be speed controlled, and of a lower cost design that is indeed much more efficient at their 50-60% load "sweet spot".
The AC motors in EVs are both torque and speed controlled, and need to handle a wide variety of loads and speeds. Yes a smaller motor will be somewhat more efficient, but not on the order that he has suggested.
A better representation can be found on Nissans site, and they did make changes in the 2013 model year to gain some greater efficiency by trading torque (I think the goal was actually to reduce the amount of rare earth elements in the motor)
Nissan cut dysprosium in their motors. Dysprosium is used to keep NdFeB magnets from losing their magnetic properties when hot. It's a hard to get and expensive element, they claim to have cut it by about 40%. They may have also reduced the neo magnets to save dysprosium but limiting torque is an easy task for modern electronics which would save them re-configuring their motors.
Regardless of efficiency bigger motors still weigh more and require bigger heavier inverters. That is what I used in my formulas, efficiency benefits of smaller motors was not taken into account but it is still a factor. My simple graph just illustrated the fact that it is also a factor. A vehicle moving down the road at a constant velocity uses a small amount of its power. Also the graph you posted highlights that the motor is optimized for "urban areas" which are not the case.
The Tesla weighing more and still getting a high efficiency attests to their motor management, they could have done better with the smaller motor, grandpa would not have minded!
"There is more to life than speed"
MK Gandhi
SparkE said:
Why would it be? It's claim to fame is being the first affordable EV with an over 200 mile range. If no other car companies had cars in the works than maybe it would. Had it come out at the same time as the Leaf or the Tesla than yes it would have been but the thing that made it capable of its range was battery technology that is now available to everyone. That's why the flood gates are now opening. Tesla uses the 18650B battery which you can buy on eBay, there are people building battery packs with it. In fact I'm working on an electric tractor with the 18650 myself. Inverters are pretty straight forward today thanks to the latest semiconductors. Tesla uses the same semiconductors available to every engineer. The new MOSFETs and IGBTs used in 'H' bridge motor controllers for DC and sine wave controllers for AC motors are what make inverter efficiency possible. Certainly Tesla's engineers were very creative in the application but we all get to use the same components.
The credit really has to go to Musk, he proved EVs are viable. Because he's a small company he needed to take steps to produce an affordable car for the masses. First he proved the technology is his luxury sedans. The sales and knowledge gained gave him the capital and expertise to make an affordable EV. Had he had GM's resources and experience than his car would have come to market first, as it stands he has over 400 deposits on the Model 3. Musk was the pioneer, Nissan certainly deserves credit for where we are today. GM had the chance with the EV1 but people like Lutz didn't have the foresight Musk and Ghosn did.
I'm thrilled about the Bolt, GM did a wonderful job with the Volt which blew the doors off the Prius and they may turn out to be the innovative EV car company of the future but not with this move, it's just the first step. Let's see where they take it.
oilerlord wrote:
"I'll take the range - 265 fun-to-drive miles vs 107 grandpa miles regardless of MPGe."
It's apples and oranges. You're paying for those 265 miles with Tesla's acceleration (fun).
Germany is working to ban all ICE vehicles by 2030, that a little over 13 years. How many gas stations do you think will exist in 30 or 50 years?
"Last week, Germany’s Bundesrat approved a resolution that calls for a ban on new internal combustion engine cars by 2030."
http://cleantechnica.com/2016/10/09/germany-steps-calls-ban-gasdiesel-cars-2030/?utm_source=feedburner&utm_medium=feed&utm_campaign=Feed%3A+IM-cleantechnica+%28CleanTechnica%29
"I'll take the range - 265 fun-to-drive miles vs 107 grandpa miles regardless of MPGe."
It's apples and oranges. You're paying for those 265 miles with Tesla's acceleration (fun).
Germany is working to ban all ICE vehicles by 2030, that a little over 13 years. How many gas stations do you think will exist in 30 or 50 years?
"Last week, Germany’s Bundesrat approved a resolution that calls for a ban on new internal combustion engine cars by 2030."
http://cleantechnica.com/2016/10/09/germany-steps-calls-ban-gasdiesel-cars-2030/?utm_source=feedburner&utm_medium=feed&utm_campaign=Feed%3A+IM-cleantechnica+%28CleanTechnica%29
Similar threads
