EVNow
Well-Known Member
Musk has been terrible at managing expectations. Looks like unless Tesla breaks laws of physics people will think he has failed
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Musk has been terrible at managing expectations. Looks like unless Tesla breaks laws of physics people will think he has failed
It is well within the realm of physics (and current technology) to achieve 240 EPA miles on a 55kWh pack, if they manage to get the Cd down to 0.2, and keep the curb weight under 3,600 lbs (base). Their new generation drivetrain will be tweaked for range, more than performance, on the model 3.
I have full faith they will acheive those specs without much problem. Their main challenge is keeping costs down. And, MY only concern is if Tesla is going to unveil a physical prototype on March 31st, or just release pictures. I'm praying it isn't the latter. That would suck.
stopcrazypp
Well-Known Member
The most efficient EV on the market today is the BMW i3, which gets 81 miles from 18.7kWh usable (22 kWh pack). So 240 miles requires 55.4 kWh, and assuming 2-3% brick protection, that is 57kWh.
i3 has Cd=0.29 and CdA=0.690 m^2. This is not good, but the car is also extremely light at 2634 lbs and with extremely narrow 155mm tires (for low rolling resistance).
http://bmwi3.blogspot.com/2014/03/an-aerospace-engineer-from-uk-compares.html
GM EV1 Lead-acid 3086 lb gets 55 miles from 18.7 kWh (81.6 kWh for 240 miles)
GM EV1 Nimh 2908 lb gets 105 miles from 26.4 kWh (60.3 kWh for 240 miles)
GM EV1 has Cd=0.19 and CdA=0.37 m^2 (3.95 sq ft)
https://www.fueleconomy.gov/feg/Find.do?action=sbs&id=30968&id=30969
The likelihood of getting 240 EPA miles from a 55kWh pack is quite low even with a 0.2 Cd and 3600 lb curb weight (both specs which I suspect won't be achieved on Model 3).
i3 has Cd=0.29 and CdA=0.690 m^2. This is not good, but the car is also extremely light at 2634 lbs and with extremely narrow 155mm tires (for low rolling resistance).
http://bmwi3.blogspot.com/2014/03/an-aerospace-engineer-from-uk-compares.html
GM EV1 Lead-acid 3086 lb gets 55 miles from 18.7 kWh (81.6 kWh for 240 miles)
GM EV1 Nimh 2908 lb gets 105 miles from 26.4 kWh (60.3 kWh for 240 miles)
GM EV1 has Cd=0.19 and CdA=0.37 m^2 (3.95 sq ft)
https://www.fueleconomy.gov/feg/Find.do?action=sbs&id=30968&id=30969
The likelihood of getting 240 EPA miles from a 55kWh pack is quite low even with a 0.2 Cd and 3600 lb curb weight (both specs which I suspect won't be achieved on Model 3).
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Battery pack efficiency has so many factors, that you can't realistically compare i3 specs to M3 specs. The drivetrain efficiencies are different, the inverter tuning/calibration is different, and Cd has a lot more impact on real world range than rolling resistance. That's just a few. The best way to make a "rough estimate" for Model 3 range for any given pack, is to base your calculation on known information for existing Tesla drivetrains. Also, BMW uses lower-grade (in efficiency) Samsung cells, while Tesla is going to use a totally new cell chemistry & size (higher power density) for the Model 3 platform, on top of the new pack architecture (cheaper manufacturing) and their new generation motors (higher efficiencies). If I can calculate a 200 to 220 EPA mile range for 55kWh pack for a Model 3, using current Tesla technology, then the assumption of 240 EPA mile rating is not unrealistic knowing that Tesla is working on an improved Gen III platform for this car.
It all comes down to how Tesla can achieve the 4.36miles/kWh sweet spot.
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stopcrazypp
Well-Known Member
We are talking about EPA range however, not "real world range". The i3 has bad range in the real world at higher highway speeds because of the poor aerodynamics, but the EPA cycle is has a lower average speed, so it still gets the best rating there despite this (the rolling resistance savings makes up for it).
240 EPA from a 55kWh pack might be possible if Tesla went to the extreme (using light weighting, narrow tires, a small frontal area with a shape like EV1), however Gen 3 is focused on cost, not extreme efficiency. I believe Straubel's recent comments alluded to this. I don't think the Gen 3 drivetrain platform will have significantly higher efficiency (when talking purely about the percentage losses from battery/inverter/motor etc, not talking about gains from having a smaller car).
EVNow
Well-Known Member
Yes, as I said, people expect Musk to produce a very sexy looking car (i.e. classical looks, not avant-garde) with a lot of interior & cargo space, high power, low price and extraordinarily high efficiency. All this "without much problem".
Now, this is how I see musk prioritizing
- Competitive with 3 series
- Good looks
- Range
- Price
..
..
..
..
- Efficiency
They would rather throw in $500 worth of battery than compromise on looks, interior space and produce a "weird looking" car with low utility just to get better cd just to save a few bucks. Their main competition is with BMW 3 series - not i3, nor EV1.
BMW went to extraordinary lengths to produce a light weight car (i3) - but they didn't save much money compared to Leaf '15 (3kWh less for 2 miles less EPA).
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Here's something I just learned. 90kWh battery has 16 modules, so each module is 5.625kWh
70kWh battery has 14 modules, with each module being 5kWh (14 X 5 = 70kWh)--older battery
85kWh battery has 16 modules, also each being 5kWh (16 x 5 = 80kWh)--older battery
So the newer batteries have a different config/energy storage than the older systems.
So 16 modules * 0.8 = 12.8 modules, let's say 12 modules.
This would give us 67.5 kWh battery for the Model 3 (12 modules for 70kWh?), with possible base of 56.3 kWh (10 modules for 60kWh).
Speculation I know, but gives more credence to the idea that the base will be at least a 60 kWh.
70kWh battery has 14 modules, with each module being 5kWh (14 X 5 = 70kWh)--older battery
85kWh battery has 16 modules, also each being 5kWh (16 x 5 = 80kWh)--older battery
So the newer batteries have a different config/energy storage than the older systems.
So 16 modules * 0.8 = 12.8 modules, let's say 12 modules.
This would give us 67.5 kWh battery for the Model 3 (12 modules for 70kWh?), with possible base of 56.3 kWh (10 modules for 60kWh).
Speculation I know, but gives more credence to the idea that the base will be at least a 60 kWh.
Candleflame
Active Member
An improved batter chemistry sure, but a totally new cell chemistry is unlikely. What do you mean by totally new?
The new Panasonic 26650 cells are larger, and also have different cathode chemistry (read it in some German article over a year ago). They expect over 40% higher energy density compared to the current gen 18650 cells. This basically means lower weight for packs, faster & cheaper manufacturing, and best of all - faster charge times (cut in half, is what Jerome Guillen claimed in that article). I'll try to find that article and link it here.
ModelNforNerd
Active Member
This article? Tesla stellt in Gigafactory nicht Batteriezellen vom Typ 18650 her - manager magazin
PSA: you'll have to have your browser translate....
stopcrazypp
Well-Known Member
Cathode or anode? Tesla did not indicate they are moving away from NCA for the cathode. For anode they have already switched to a partial silicon anode in the 90kWh packs. Maybe they will have more silicon on the Model 3 cells, but that will only improve volumetric energy density (not gravimetric significantly). That means they can cram more energy into a given volume, but the weight will not improve.
To go to the next step they have to develop high voltage electrolyte to push the nominal voltage higher.
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If translation is correct, it says the cells will use similar chemistry to Tesla's existing cells but will have 30-40% higher energy density than competitors. It is not saying they will have 40% higher energy density than Tesla's existing cells.
ModelNforNerd
Active Member
I'm not guaranteeing that's the article being referenced, but it's probably close
Let's look at it this way:
Model S60 is rated at 208 miles EPA. This implies an EPA rating of 3.47miles/kWh. So, if the Model S hypothetically had an S55 variant, then the EPA range would be around 191 miles (ignoring the lower weight of a smaller pack).
Now, the S60 has a Cd of 0.24, CdA of 6.2 sq ft, and a curb weight of 4,600 lbs. So, if we assume (from the rumors floating around) that Model ☰ does have a Cd of 0.2 and CdA = 6.2*0.8 = 4.96. Let's also assume curb weight = 4600*0.8 = 3,680 lbs. Coeff of rolling resistance is assumed at 0.008, since 17" low-rolling-resistance tires average around that.
Now, plug in the numbers to calculate drag & rolling threshold forces, then use EPA combination to get the average energy consumption... blah blah blah... I just used a Matlab program that churns out the results. The effective range of a Model ☰ 55 would be around 228 miles. I've been predicting 240 miles EPA, because the result of 228 miles is based on the assumption that the battery and drivetrain technologies are the same as in current Model S. We know the Model ☰ will be getting a new generation drivetrain, and the new 26650 cells with 40% higher energy density. That alone should add a few more miles to the estimate. I was being conservative and rounded it up to 240 miles.
So, there you have it! Hope that clarifies how I ended up with the 240 mile estimate.
McHoffa
CyberOwners
We'll definitely see over 200. With the Bolt coming out THIS YEAR with >200 mile range (though probably 205 or something), a car coming more than 12 months later, and from Tesla using batteries from their gigafactory, HAS to get more than 200 or they'd be thelaughing stock after years of promises from Musk of over 200 miles real world. Imagine Chevy outdoing Tesla, and a year early? They won't let that happen.
I'd guess 240 up to 300, and the S will get bumped so that 90 kWh will be the low end, with up to 120 kWh or so and over 400 mile range at the top end.
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Also think the low end M3 will be a 60, not 55. The Bolt uses a 60.
I'd guess 240 up to 300, and the S will get bumped so that 90 kWh will be the low end, with up to 120 kWh or so and over 400 mile range at the top end.
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Also think the low end M3 will be a 60, not 55. The Bolt uses a 60.
Bolt might be a heavier car due to steel construction and lower energy density batteries; not to forget the inherently crappier aerodynamics of the econobox design. Model 3 might not need the same battery size to get similar range. Again, just speculation.
That was the article. LOL. I had difficulty finding it yesterday. Thanks Nerd, for finding it. I remembered the 40% higher energy density remark as a comparison with their own batteries, for some reason. I take that back. It does say it's against competition. But, still, I'm sure if a model S can squeeze 191 miles out of a 55kWh pack, it shouldn't be that improbable to get a model 3 over that 240 mile marker with the same pack.
Don't get me wrong, guys. If they do go with 60kWh pack as base, I'd actually be happier. More the merrier.
ModelNforNerd
Active Member
Cool. wasn't sure if it was the one. But there weren't many that referenced the specific battery packs.
I'm thinking that from a PR perspective, if they don't go with a 60 pack as the base...it's still going to have more range that the Bolt, due to better aerodynamics and other efficiencies. This is Tesla's 3rd go-round at EV design from the ground up, whereas this is Chevy's first full-time EV.
I think that we're all too caught up on the KWH numbers (even me sometimes). Though, I generally don't care about the KWH, because I care more about the driving range and charging time. However, just for fun....
But a bit of basic math:
Model S has a 70 and a 90 KWH pack currently:
Model ≡ is 20% smaller?
Model ≡ batteries are 10% taller?
Model ≡ batteries are 30%-40% more efficient?
70*.8*1.1*1.3= 80.08KWH
70*.8*1.1*1.4= 86.24KWH
90*.8*1.1*1.3= 102.96KWH
90*.8*1.1*1.4= 110.88KWH
The KWH COULD be very high...
But we still cannot figure out the most important part (driving range) from that.
But a bit of basic math:
Model S has a 70 and a 90 KWH pack currently:
Model ≡ is 20% smaller?
Model ≡ batteries are 10% taller?
Model ≡ batteries are 30%-40% more efficient?
70*.8*1.1*1.3= 80.08KWH
70*.8*1.1*1.4= 86.24KWH
90*.8*1.1*1.3= 102.96KWH
90*.8*1.1*1.4= 110.88KWH
The KWH COULD be very high...
But we still cannot figure out the most important part (driving range) from that.
Not true, GM has done at least three full-time EVs: EV1, S-10 Electric, and Spark EV. So you could look at the Bolt as a 3rd or 4th go-round since the EV1 and S-20 essentially shared the same drive train. (And I'm sure they gained a lot of experience with the Volt as well.)
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