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First time eDrive and xDrive tech has been combined in one vehicle

BMW has unveiled the Concept X5 eDrive, which will be showcased at the New York International Auto Show. Although the vehicle is labeled as a concept, it’s a dead ringer for the production plug-in hybrid version of BMW’s popular crossover that it plans to bring to market sometime within the next year or two.
 
The hybrid drive system gets its primary motivation from a 245hp turbocharged 4-cylinder engine. That gas engine is combined with a 95hp/184 lb-ft electric motor developed by the BMW Group. Power for the electric motor comes from a lithium-ion battery pack (which is mounted under the cargo area) that can charge from any wall outlet.
 
The Concept X5 eDrive can drive on electricity alone for up to 20 miles at speeds up to 75 mph. BMW says that the car will have an average fuel consumption of over 74.3 mpg in the EU testing cycle (which means we’ll likely see less than half of that quoted figure under EPA guidelines). BMW says that the X5 concept can reach 62mph in under 7-seconds.

 
The Concept X5 eDrive is the first from BMW that uses its xDrive all-wheel-drive system paired with eDrive hybrid technology.
 
The concept also has a ConnectedDrive system that helps plan routes and lists the location of charging stations on the GPS map. This allows the driver to find a charging station when they are around town in electric mode.

Source: BMW



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RE: Tesla!
By EricMartello on 4/14/2014 10:42:27 AM , Rating: -1
Instant torque - irrelevant, since the engine produces no horsepower when it's not turning and it produces low horsepower when it is turning at low RPM. A gasoline engine also has "instant torque" as it is already idling at 800 RPM or so, and it has "instant horsepower" as well.

Ridiculous performance - it is quite ridiculous, since driving it in conditions that do not have california-like weather will result in severely compromised run times.

Long ev range - the energy density of batteries is nowhere near that of gasoline or diesel, and it is unlikely to be anytime soon.

If you bought an electric car with an onboard gas-powered generator, you would have to run the gas generator at full throttle for about 30 mins to fully charge the batteries. In that time you will have used 2-3 gallons of fuel.

You will then have a driving range of ~30 miles.

Congratulations. You burnt 3 gallons of fuel to charge your batteries so that you could drive 30 miles, or 10 miles per gallon.

But you don't think of it that way because you don't see electrical power being generated, even though most electricity in the US is generated by burning something.


RE: Tesla!
By amanojaku on 4/14/2014 11:25:06 AM , Rating: 3
quote:
Instant torque - irrelevant, since the engine produces no horsepower when it's not turning and it produces low horsepower when it is turning at low RPM. A gasoline engine also has "instant torque" as it is already idling at 800 RPM or so, and it has "instant horsepower" as well.
False. Torque accelerates a car; the heavier a car is, the more torque you need to reach a certain speed by a certain time. ICE engines do not produce "instant torque". When the OP says "instant torque", he/she means the tendency of electric engines to produce 100% of the torque at all RPMs. ICE engines don't do that; generally, ICE torque is 50% of the max at the lowest RPMs (generally 800-1,200) , peaks around 2,000-3,500, then drops to below 50% from 6,000 and beyond. The swing from 50%-100%-50% is what jerks the car during gear shifts up and pushes you back in the seat as you hold the gas.

Electric vehicles, producing 100% of the torque all of the time, generally lack the jerking and push back. Drivers have commented on how deceptive acceleration is in EVs since it's there, but you don't feel it. "Instant torque" makes acceleration smooth, something you can appreciate in a heavy vehicle.
quote:
Ridiculous performance - it is quite ridiculous, since driving it in conditions that do not have california-like weather will result in severely compromised run times.
The Model X isn't even in production yet. Wait until there are models on the road with recorded data before making these kinds of claims.

BTW, the OP meant the 4.4secs it's estimated to get to 60mph. That's better than many sports cars, and is comparable to some older supercars. Not bad for a car weighing more than 2,100kgs (that kind of performance is usually seen from a car weighing 1,400kgs with that amount of HP and a better aerodynamic drag coefficient).
quote:
Long ev range - the energy density of batteries is nowhere near that of gasoline or diesel, and it is unlikely to be anytime soon.
Which is why the OP said long EV range, as in "long for an EV." We have to see a real car in action, but the estimates are pretty good for a battery-only EV. Which invalidates the rest of your post, since Telsa doesn't create cars with gasoline generators...


RE: Tesla!
By EricMartello on 4/14/14, Rating: -1
RE: Tesla!
By amanojaku on 4/14/2014 4:09:41 PM , Rating: 3
Considering your posts in this article, it's clear that you're not only woefully ignorant of this topic you're also fond of rambling and attacking people who don't agree with you.

If there is anyone who is reading this thread and would like to know why everyone else disagrees with Eric's comments (or finds them not worth reading) I would be more than happy to explain in greater detail. There's no point it explaining it to him since he's spouting nonsense that can be debunked by an introductory book on automotive concepts and physics.


RE: Tesla!
By EricMartello on 4/15/2014 4:13:58 PM , Rating: 2
quote:
Considering your posts in this article, it's clear that you're not only woefully ignorant of this topic you're also fond of rambling and attacking people who don't agree with you.


That's right, you're not able to refute anything I said because you know it's true so resort to making a sore loser comment like this.

quote:
If there is anyone who is reading this thread and would like to know why everyone else disagrees with Eric's comments (or finds them not worth reading) I would be more than happy to explain in greater detail. There's no point it explaining it to him since he's spouting nonsense that can be debunked by an introductory book on automotive concepts and physics.


The idiot thinks he's an authority on cars, or anything for that matter. Gotta say it adds a touch of humor to this whole bit.

Electric cars didn't work in the 1800s and nothing has changed now, 214 years later. The problems they had then are largely the same as the ones they have today.


RE: Tesla!
By Reclaimer77 on 4/14/2014 7:31:35 PM , Rating: 2
I'm one of the more aggressive drivers on the road, from my point of view.

But not even I go around launching my car for the best 0-60 times possible, and I don't see anyone else doing it either in normal driving.

It's great that electric motors give you "max torque" and all that, but I don't know why EV proponents go on and on about it so much. People simply don't drive like that in real life, even if they can.

Having said that, I find pretty much all of Eric's posts here embarrassing. And that's coming from ME lol.


RE: Tesla!
By flyingpants1 on 4/14/2014 7:44:25 PM , Rating: 2
And yet in other threads, you deride the Tesla as having a low top speed compared to other models.

News flash, people use quick acceleration a lot more often than they drive at 125mph+, mostly because one is legal and the other isn't.


RE: Tesla!
By Reclaimer77 on 4/14/2014 8:07:30 PM , Rating: 2
Yes because a car that costs that much is expected to have performance of a certain caliber, even if you never use it.

The Model S compared to cars in it's class has very poor interior amenities, and a pitiful top speed.

quote:
News flash, people use quick acceleration a lot more often than they drive at 125mph+


News flash, by any objective measure cars competing with the Model S have great acceleration as well.


RE: Tesla!
By Mint on 4/15/2014 10:52:38 AM , Rating: 2
Nobody cares about top speed in a full size sedan. If you go over 130mph on a public road outside Germany, you should have your license revoked.

This is more than "great" acceleration. MotorTrend has tested countless cars in it 45-65 passing test, and few are faster than the 1.7s that the Model S takes (even a Corvette Z51 is slower). None have as much interior room:
https://www.youtube.com/watch?v=PhTL13ai_mU

It's quicker than the S550, A7/A8, 650i Gran Coupe, Panamera GTS, etc. There's only one large car that can out-accelerate it under $120k, and it's barely any less. I'll leave it to you to figure that out.

Americans (and almost every buyer in this segment) have ALWAYS loved power, loved big cars, and loved good looks. Few cars match the Model S in acceleration, room, and appearance, and none under $100k.

That's why it's outselling its gas competitors, above all else (all other EV sales prove that the green factor barely helps at all). The sooner you realize that, the sooner you'll stop the nitpicking hate of Tesla.


RE: Tesla!
By Reclaimer77 on 4/15/2014 6:28:54 PM , Rating: 2
quote:
Nobody cares about top speed in a full size sedan.


Oh nice argument. Great supporting evidence too.

Well then I declare that "nobody" cares about acceleration in a full size sedan.

Ohhh, what now?

People don't buy Tesla's because it's a performance car. Get a clue. If it drove like a dump truck, Elon Musk would still be a hero.


RE: Tesla!
By Mint on 4/15/2014 8:45:42 PM , Rating: 2
quote:
Oh nice argument. Great supporting evidence too.
Go find major reviews for the S-class, A8, 750i, etc where top speed is listed as a pro or con. Nobody cares.

quote:
Well then I declare that "nobody" cares about acceleration in a full size sedan.
Go find a review about such cars that doesn't talk about acceleration. It's a major review point.

quote:
People don't buy Tesla's because it's a performance car. Get a clue. If it drove like a dump truck, Elon Musk would still be a hero.
Then why are so many people buying the performance version? Tesla's ASP is over $100k (google it), so most sales would have to be the P85 model ($93k base).

All other EVs have tiny market share in their segment, except for BYD's Qin PHEV (5.9s 0-60, ~$32k), which is selling faster than they can make them in China.


RE: Tesla!
By Keeir on 4/14/2014 9:18:54 PM , Rating: 2
quote:
It's great that electric motors give you "max torque" and all that, but I don't know why EV proponents go on and on about it so much. People simply don't drive like that in real life, even if they can.


I think your missing the point.

The car buying public has general opinion that cars with low end torque are "premium".

Look no further than Chevy Cruze. The base 1.8 liter engine produces the same max horsepower as the 1.4 turbo engine. But the superior low end torque of the 1.4 liter engine gives the car better performance, more "premium" feel, and a higher price tag.

An electronic motor typically goes even further. In comparison to a gasoline engine of the same max horsepower, an electric engine will have better performance in most real world situations and will feel like the premium engine.

Having driven a NA gasoline, a turbo gasoline, and a electric motor all in the 150-175 max hp range in the last week, the electric is the car I'd prefer to drive daily (the Turbo still wins for pure fun).


RE: Tesla!
By Reclaimer77 on 4/15/2014 12:27:03 AM , Rating: 1
You just put "premium" and Chevy Cruze in the same sentence....

quote:
an electric engine will have better performance in most real world situations and will feel like the premium engine.


For nearly $100k it damn sure better feel like a premium engine.

Go drive a Leaf, I don't see people accrediting that with a "premium" feel in ANY area.


RE: Tesla!
By Keeir on 4/15/2014 9:46:33 PM , Rating: 2
quote:
Go drive a Leaf, I don't see people accrediting that with a "premium" feel in ANY area.


Premium in comparison to the comparable gasoline engine. Given that a Leaf is a B-segment Hatchback. So... a Nissan Versa Note with a 109 max hp/107 max torque. Hmmm... I bet a Nissan Leaf's electric engine does feel like a significant upgrade if you drive it right after a Versa Note.

quote:
For nearly $100k it damn sure better feel like a premium engine.


Constant fixation on a over estimate of an initial purchase price.

The Model S is pretty similiar to a BMW 5 series Gran Turismo. Once you consider TCO, they are nearly the same price, same size, and both are "4 door coupish hatches". Not sure the Model S is losing too many battles to the BMW 5 series Gran Turismo.


RE: Tesla!
By EricMartello on 4/15/2014 5:44:17 PM , Rating: 2
quote:
But not even I go around launching my car for the best 0-60 times possible, and I don't see anyone else doing it either in normal driving.


If you paid the premium for a fast car you should drive it fast. I'm at or near the redline quite routinely in my cars for no other reason than it's fun and I like the feeling I get.

quote:
It's great that electric motors give you "max torque" and all that, but I don't know why EV proponents go on and on about it so much. People simply don't drive like that in real life, even if they can.


High torque at low engine speeds, or with electric motors - zero engine speed, result in a car that "feels" fast because you feel that force pressing you back into the seat.

Despite this, the fastest Model S is only cutting high 12-sec quarter mile times...this is OK if you're in the $40K-$50K price range but it's on the slow side for something $80K plus.

The base Model S only does a low 14 sec pass...so all this hype about torque (which is heavily misunderstood by the average idiot) is for nothing.

quote:
Having said that, I find pretty much all of Eric's posts here embarrassing. And that's coming from ME lol.


Go ahead and show me were I'm wrong about anything I said, but don't embarrass yourself in trying to do so.


RE: Tesla!
By Mint on 4/14/2014 11:38:37 AM , Rating: 2
How much nonsense can you cram into one post?

"Instant" refers to zero lag when you press on the pedal. You may think there's none on a gas car, but that's because you don't know what zero lag feels like.

The peak power from a gas engine at cruising RPM (for any speed) will pale in comparison to Tesla's induction motor at the same speed. Gas can only compete when you downshift and rev the engine up.

A Model X will have ridiculous performance under all conditions. It faces no performance decline at altitude, like a gas SUV.

Your understanding of a PHEV is pathetic. You don't use the engine to fully charge the battery. You use it to power the car when the battery runs out. Your numbers are complete BS as well, as they imply 10% thermal efficiency for the engine.

61% of US electricity comes from nuclear, natural gas, and renewables, all of which are far cleaner than gasoline. More importantly, virtually all US electricity is generated away from populations centers, using domestic fuel, at a fraction of the cost per mile, for all ~15 years of a car's life.


RE: Tesla!
By EricMartello on 4/14/2014 3:48:44 PM , Rating: 2
quote:
How much nonsense can you cram into one post?


That record belongs to you, since everything you say is nonsense.

quote:
"Instant" refers to zero lag when you press on the pedal. You may think there's none on a gas car, but that's because you don't know what zero lag feels like.


Oh really? Was this "lag" a big concern for drivers across America? That's a frequent complaint - people saying how they wish their car didn't lag. Are you sure that this lag isn't the result of climate change?

quote:
The peak power from a gas engine at cruising RPM (for any speed) will pale in comparison to Tesla's induction motor at the same speed. Gas can only compete when you downshift and rev the engine up.


REALLY? So the fact that electric motors' torque declines sharply as RPM increases is better than a gas engine, whose torque curve remains relatively flat as RPM increases, only to decrease gradually near the redline.

quote:
A Model X will have ridiculous performance under all conditions. It faces no performance decline at altitude, like a gas SUV.


IS THAT A FACT? Well then you should get one so we have another reason to laugh at you.

quote:
Your understanding of a PHEV is pathetic. You don't use the engine to fully charge the battery. You use it to power the car when the battery runs out. Your numbers are complete BS as well, as they imply 10% thermal efficiency for the engine.


Oh, you got me here. I was a bit off with my numbers.

The tesla has a 85 kW/h battery and your typical gas powered generator at full load uses about 1 gallon of gas per hour, per 5 kW of output. So if you had a 20 kW generator you'd have to run it for 4 hours to fully charge the 85 kW/h battery, which means 16 gallons of gas.

Last I checked, 16 gallons to go 30 miles is a paltry 1 MPG.

What you and other morons don't seem to get is that charging batteries IS AMONG THE MOST INEFFICIENT USES OF ENERGY possible.

quote:
61% of US electricity comes from nuclear, natural gas, and renewables, all of which are far cleaner than gasoline. More importantly, virtually all US electricity is generated away from populations centers, using domestic fuel, at a fraction of the cost per mile, for all ~15 years of a car's life.


Nice misleading stats that you think are true but actually aren't because you're a moron.

None of this even matters, because you're already paying over ~$13 to drive 30 miles in an EV at TODAY'S electric rates. If the entire driving population shifted to EVs, electric rates would easily double or triple. Gasoline cars are far more efficient, lighter and more practical than EVs will ever be.

Most of America's electrical energy comes from burning coal or natural gas, and you'll be burning a lot more fuel to power a nation driving electric cars around as compared to how things are now, with most cars using gas.


RE: Tesla!
By snhoj on 4/14/2014 11:08:09 PM , Rating: 2
quote:
REALLY? So the fact that electric motors' torque declines sharply as RPM increases is better than a gas engine, whose torque curve remains relatively flat as RPM increases, only to decrease gradually near the redline.

Actually no. During the current limiting phase of the electric motor acceleration (zero RPM to peak power) the electric motor will produce pretty much constant torque due to constant current. When the motor reaches peak power it goes into the voltage limited phase where the back EMF of the motor limits the current and available torque goes into gradual decline. Current limits and battery voltage are not set in stone but are chosen by design for reasons like extending battery life.

ICE's have zero torque available at zero RPM and therefore must idle. To get a car moving some slippage has to occur either by clutch or torque converter. An ICE's torque curve is far from flat anywhere in the RPM range.

From a design perspective constant torque is a nice thing to have. A constant torque at the driven wheels divided by the (constant) rolling radius of the wheels will produce a constant driving force pushing the car forward.


RE: Tesla!
By EricMartello on 4/15/2014 5:35:04 PM , Rating: 2
quote:
Actually no. During the current limiting phase of the electric motor acceleration (zero RPM to peak power) the electric motor will produce pretty much constant torque due to constant current. When the motor reaches peak power it goes into the voltage limited phase where the back EMF of the motor limits the current and available torque goes into gradual decline.


You say no, and then basically say what I just said followed by something you paraphrased from wikipedia in an attempt to seem smart but likely don't understand.

Back EMF does not limit current, it represents an increase in voltage that will rise until it matches the input voltage.

Voltage determines the speed of the engine; the current drawn will rise if a load is placed on the motor (which causes a drop in voltage). Current itself is limited by system wiring and the motor's windings, and exceeding this current would cause the motor and/or wiring to overheat.

Will be funny to see what happens if a tesla motor stalls while stuck at "full throttle". It will basically weld itself into a clump of molten metal in seconds.

quote:
Current limits and battery voltage are not set in stone but are chosen by design for reasons like extending battery life.


Current limits are more-less set in stone, as there is a limit to how much current can flow over a given gauge of wire before the wire heats up like a light bulb filament.

This limit also applies to the motor windings, and thus there is a practical limit as to how thick of a wire you can use for windings while still making the motor small enough and light enough for a certain application.

Increasing voltage may increase speed but the power of the motor will never exceed the maximum watts available from the batteries.

So it doesn't matter if you do 250 volts and 40 amps or 500 volts and 20 amps - in both instances the motor will never be able to produce more than 10 kW of power.

The Model S top version is rated at 416 HP (310 kW) and has 85 kW batteries that operate at 400V. To produce its peak rated power with 400 V, the batteries need to supply at least 775 amps to the inverter.

Since the motor is a 3-phase AC, they type often used in industrial applications like saws, pumps and large fans, it requires an inverter to change the direct current supplied by the batteries into 3-phase alternating current.

At full power, the batteries would last roughly 15 minutes before being fully depleted. There is a reason that peak numbers are played up, but the range of the vehicle is listed at (55 MPH), meaning that there will be substantial deviations from advertised miles based on driving conditions and style...and if you buy a car for its power, you'll want to use that power. With the Tesla, you could easily find yourself out of batteries after doing a few 0-60 sprints "for fun" at full throttle.

quote:
ICE's have zero torque available at zero RPM and therefore must idle. To get a car moving some slippage has to occur either by clutch or torque converter. An ICE's torque curve is far from flat anywhere in the RPM range.


Torque converter are viscous couplings and do not "slip". They do have a stall speed, which is the engine speed required before the torque converter spins the driveshaft. There is a lot of flexibility in what the manufacturer can select as the stall speed to optimize it for the particular engine.

Torque converters also have a property called "torque multiplication", which boosts the input torque by a certain amount when the converter is at its stall speed. If you have a fairly common 2:1 torque multiplication factor, an engine producing 200 ft-lbs of torque at the converter's stall speed (with the car not moving) will transmit 400 ft-lbs of force down the drive shaft. This phenomena lasts several seconds after the car starts moving.

ICE engines' produce a torque curve that rises with engine RPM does so fairly linearly.


RE: Tesla!
By Mint on 4/15/2014 7:29:53 PM , Rating: 2
quote:
Back EMF does not limit current, it represents an increase in voltage that will rise until it matches the input voltage.
I don't know if it was true that he was just quoting wikipedia, but back EMF does indirectly limit current. You are correct about the current limit due to wire heating, but that's at low RPM. At higher RPM, there's a power limit due to battery/electronics/cooling, so V*I*pf is roughly constant, and voltage goes up while current (and torque) goes down with RPM. At even higher RPM, you hit a voltage limit from wire insulation and/or IGBT limits. So now you can't keep V*I constant, and ever increasing back-EMF with RPM limits current even faster.

quote:
With the Tesla, you could easily find yourself out of batteries after doing a few 0-60 sprints "for fun" at full throttle.
If by "a few" you mean "hundreds", then sure.
https://www.youtube.com/watch?v=d82NP89O_ZQ

0-114mph sprint, and cruising back to zero. 1 mile travelled, 0.5kWh used. So even with a leadfoot, you can cover 150+ miles on a charge.

quote:
Torque converter are viscous couplings and do not "slip".
"Slip" is defined as the difference in rotation speed between input and output. Yes, viscous couplings have non-zero slip.


RE: Tesla!
By EricMartello on 4/15/2014 10:03:05 PM , Rating: 2
quote:
I don't know if it was true that he was just quoting wikipedia, but back EMF does indirectly limit current. You are correct about the current limit due to wire heating, but that's at low RPM. At higher RPM, there's a power limit due to battery/electronics/cooling, so V*I*pf is roughly constant, and voltage goes up while current (and torque) goes down with RPM. At even higher RPM, you hit a voltage limit from wire insulation and/or IGBT limits. So now you can't keep V*I constant, and ever increasing back-EMF with RPM limits current even faster.


Back EMF happens because all electric motors are also generators. If you turn an electric motor by hand and connect a voltmeter to the power terminals, you will see that you are generating a voltage.

When power is applied to turn the motor, it is applied at a certain voltage. The motor will accelerate and spin to the RPM at which the voltage generated from back EMF matches the input voltage. If you are driving the motor with 400V, then the maximum no-load RPM will be achieved when the motor is producing 400V of back EMF.

This has nothing to do with wire insulation; it's a property of all electric motors.

quote:
If by "a few" you mean "hundreds", then sure.

0-114mph sprint, and cruising back to zero. 1 mile travelled, 0.5kWh used. So even with a leadfoot, you can cover 150+ miles on a charge.


You find one youtube video that doesn't even show the car being driven and believe it. That's nice.

The fact of the matter is, that each time the batteries are discharged at such a high rate their effective capacity diminishes - yes, they hold less of a charge. Even with regenerative braking you'll be losing range and perhaps permanently damaging the batteries themselves.

BTW good luck recharging your batteries if you happen to drive beyond the range and do not have enough charge to get back home. Even with the "supercharger" stations (fastest) take 20-30 minutes for a partial charge. Meanwhile it takes like 2 minutes to fill a tank with gas, and then drive 400-500 miles.

quote:
"Slip" is defined as the difference in rotation speed between input and output. Yes, viscous couplings have non-zero slip.


Modern torque converters do not slip; they have a lock-up feature which causes the connection between the driveshaft and transmission to act as if it were mechanically coupled, similar to the clutch plates in a manual transmission. Sorry, but electric drivetrains have no advantage here.


RE: Tesla!
By snhoj on 4/15/2014 9:47:22 PM , Rating: 2
quote:
You say no, and then basically say what I just said followed by something you paraphrased from wikipedia in an attempt to seem smart but likely don't understand.


I'm not paraphrasing anybody!! Because your statement implieded that torque drops off (sharply) from zero RPM I stand by my disagreement with that.

quote:
Voltage determines the speed of the engine; the current drawn will rise if a load is placed on the motor (which causes a drop in voltage). Current itself is limited by system wiring and the motor's windings, and exceeding this current would cause the motor and/or wiring to overheat.
Will be funny to see what happens if a Tesla motor stalls while stuck at "full throttle". It will basically weld itself into a clump of molten metal in seconds.


You might know the electrical theory but you don’t know how EV’s work. The motor controller will limit the current available to the motor. At low motor RPM it will chop the voltage to ensure that the current doesn’t exceed its preset limit. This is what I call the current limited phase. As the current available is the preset limit it is constant as is available torque. It’s the motor controller that limits the current not the load. Of course that is semantics as the load will increase to match the current i.e. the car will accelerate there by loading up the motor. As the motor crosses peak power (maximum voltage, maximum current) the back EMF generated by the motor is sufficient to prevent the current from exceeding the preset limit of the controller.

If the Tesla was floored while resting against an immovable object the motor controller would limit the current flow and protect the motor just as it would even if the car wasn’t stalled.


RE: Tesla!
By EricMartello on 4/16/2014 4:34:10 PM , Rating: 2
quote:
I'm not paraphrasing anybody!! Because your statement implieded that torque drops off (sharply) from zero RPM I stand by my disagreement with that.


It does, and it must, as power is a derived value that's calculated from torque x RPM.

The point is that electric motors' having full torque from 0 RPM is not an advantage over the gas engine. Sure, it makes the car "feel" fast but the performance figures tell the full story, and they're not exactly shattering any records.

quote:
You might know the electrical theory but you don’t know how EV’s work. The motor controller will limit the current available to the motor. At low motor RPM it will chop the voltage to ensure that the current doesn’t exceed its preset limit. This is what I call the current limited phase. As the current available is the preset limit it is constant as is available torque. It’s the motor controller that limits the current not the load. Of course that is semantics as the load will increase to match the current i.e. the car will accelerate there by loading up the motor. As the motor crosses peak power (maximum voltage, maximum current) the back EMF generated by the motor is sufficient to prevent the current from exceeding the preset limit of the controller.


Current itself is not what drives the motor, it is VOLTAGE that makes things move. Voltage must be high enough to overcome the resistance of the system, and when a load is placed on the motor, resistance increases and voltage drops. To maintain a speed at a given voltage, more current is drawn by the motor.

The tesla uses an inverter to drive the motor. The inverter not only increases the battery voltage, but it generates 3 sine waves to provide 3-phase power to the motor. It controls the speed of the motor by varying the voltage and maintaining the flow of current required to sustain a given voltage level.

I do not know the specific operation current of tesla's drive unit, but I would estimate that it can sustain somewhere in the ballpark of 1,000 amps across its operating voltage range.


RE: Tesla!
By snhoj on 4/16/2014 9:09:14 PM , Rating: 2
quote:
The point is that electric motors' having full torque from 0 RPM is not an advantage over the gas engine. Sure, it makes the car "feel" fast but the performance figures tell the full story, and they're not exactly shattering any records.

The advantage is not having to have a clutch or some other device to engage the drive. It’s a mechanical simplification. In the case of Tesla the range of the motor is so broad that it also doesn’t need a gearbox and can make do with a single reduction ratio. A further mechanical simplification. This is of course a design compromise as motor redline limits top speed. A second ratio would allow a much higher top speed. I personally think 125 MPH is more than enough for a road car.
quote:
Current itself is not what drives the motor, it is VOLTAGE that makes things move. Voltage must be high enough to overcome the resistance of the system, and when a load is placed on the motor, resistance increases and voltage drops. To maintain a speed at a given voltage, more current is drawn by the motor.

In an EV we don't want to control the speed of the motor but the torque it puts out. If the accelerator position controlled speed the vehicle would be very difficult to drive. Hence the motor controller manipulates the current by manipulating the voltage but the voltage doesn't bear any direct relationship to the accelerator position. None of this is in disagreement with what you have said I’m just trying to add a different perspective. As for load when you encounter a hill the driver must adjust the accelerator pedal to maintain speed (as you currently do in your ICE powered car) increasing the current to maintain the voltage.


RE: Tesla!
By Mint on 4/15/2014 7:04:41 AM , Rating: 2
quote:
So the fact that electric motors' torque declines sharply as RPM increases is better than a gas engine
Of course it is. For engines with the same peak power, constant power with declining torque is far more useful than flattish torque and rising power. The whole reason we have transmissions is to convert the latter into the former at the wheels.

quote:
The tesla has a 85 kW/h battery and your typical gas powered generator at full load uses about 1 gallon of gas per hour, per 5 kW of output.
WTF is "typical"? Some POS from Home Depot? That's not where automakers get their engines, genius. Once again, you're using a 15% efficient engine for no reason. Hell, even off-the-shelf generators are way better than that:
http://www.irproducts.biz/Documents/Manuals/950-01... (pg. 21)
11.04oz of gasoline per kWh, so using 1 gallon will give you 11kWh, not 5 like you claim.
quote:
So if you had a 20 kW generator you'd have to run it for 4 hours to fully charge the 85 kW/h battery, which means 16 gallons of gas.
What on earth makes you think a car needs 85kWh to travel 30 miles? The Tesla does well over 200 with that much energy, even under bad conditions.

Once again, no PHEV charges up the battery with the generator. The electricity drives the wheels, and only a trickle goes in to balance the occasional battery draw.
quote:
Last I checked, 16 gallons to go 30 miles is a paltry 1 MPG.
LOL
quote:
What you and other morons don't seem to get is that charging batteries IS AMONG THE MOST INEFFICIENT USES OF ENERGY possible.
WTF are you talking about? Round trip efficiency for lithium ion is 90% efficient.

Seriously, where on earth are you getting all this nonsense from? Is there some website polluting your mind?


RE: Tesla!
By EricMartello on 4/15/2014 9:04:00 PM , Rating: 2
quote:
Of course it is. For engines with the same peak power, constant power with declining torque is far more useful than flattish torque and rising power.


You can only have constant power with declining torque, since power is calculated from engine speed times torque. This is true for all engines.

quote:
WTF is "typical"? Some POS from Home Depot? That's not where automakers get their engines, genius. Once again, you're using a 15% efficient engine for no reason.


Yes, I listed a typical generator. The one you linked to in desperation to prove me wrong only highlights the fact that you brain is the size of a grain of rice.

The minimum fuel consumption does not equate to actual 'full load' fuel consumption. Fuel consumption for a given load increases as the generator capacity increases. You linked to a generator whose peak sustainable output is 7 kW, and running it at its peak output for the 11 hours you'd need to charge an 85 kW/h battery will require.

Even if we use your unrealistic 11 oz / kWh consumption at full 7 kW load figure, that's 77 oz per hour or 6.6 gallons.

Congratulations, instead of 1 MPG you are not talking 4.5 MPG (unless you drive < 55 MPH and never have to stop-n-go). This doesn't even factor in weather, where extreme hot or cold can have a drastic effect on range.

quote:
What on earth makes you think a car needs 85kWh to travel 30 miles? The Tesla does well over 200 with that much energy, even under bad conditions.


What on earth makes you keep citing the 200 mile range that even tesla's own website indicates is below 55 MPH. Any car driven conservatively on a highway at a constant speed can achieve longer ranges. Mixed use is not going to be anywhere near 200 miles...but hey, you probably believe in global warming and income inequality so why not believe that your electric car can go 200 miles on a charge in real-world driving conditions.

quote:
Once again, no PHEV charges up the battery with the generator. The electricity drives the wheels, and only a trickle goes in to balance the occasional battery draw.


Just shut up; seriously, you have no idea about how these things work and you have terrible reading comprehension. Maybe wipe the jizz off of your douchey thick-framed glasses.

quote:
WTF are you talking about? Round trip efficiency for lithium ion is 90% efficient.


Why are you asking me what I'm talking about when it's quite obvious to anyone who graduated high school?

Efficiency is the difference between input energy vs how much of it is converted to usable work.

Let's just say that that 90% of the electricity a charger draws is stored in the battery...that means charging your 85 kW/h batteries would require (85 * 1.1) 94 kW of electricity.

Now, when you drive, your batteries' effective capacity fluctuates based on how much current is being drawn from them. Drawing a high current, i.e. hard acceleration, will cause your batteries to lose more of their stored charge than applying moderate current draws.

This means that if you ran the engine at its full power to utilize that power you paid for, the engine will use up to 310 kW of power, drawing nearly 800 amps from the batteries. The higher discharge rate lowers the available capacity, even if you fully charged them, meaning that you would expect fully charged 85 kW/h batteries to last about 15 minutes under full load, but in reality, they would probably be spent in about 6-7 minutes - meaning you lose about half of your rated capacity.

Not really going to spend more time to explain how discharge rates affect battery life...suffice it to say that if you're dumb enough to buy into the hype then you deserve to suffer the limitations that come along with driving an electric car.

quote:
Seriously, where on earth are you getting all this nonsense from? Is there some website polluting your mind?


If you were smart enough to understand what I'm saying you probably would have realized that electric cars, as they are today, are at best a toy for some rich kid.


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