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[updated with *] P85D 691HP should have an asterisk * next to it.. "Up to 691HP"
- Thread starter krisg81
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- Driving Dynamics Model S
Yes, if there's literally no voltage sag @1500A, you get 600kw (804hp) peak. This is almost certainly not going to happen though.
The current P85D makes almost exactly 80% (416kW) of the 520kW theoretical peak @1300A.
If you believe voltage actually stays at 400, then the drop must come exclusively from setting a hard fuse limit at about 1050A (resulting in 420kW peak). That's a plausible fuse current limit I suppose on a 'dumb' 1300A fuse, but realistically, the voltage must sag somewhat at that current output.
I believe the current P85D makes closer to 1170A (a 10% gap on a 1300A fuse), meaning voltage is sagging to about 360V or so, making ~420kW.
Assuming the voltage sag is slightly more pronounced at higher current with the new 1500A smart fuse, maybe you end up at about 350V with the Ludicrous upgrade. If you assume that they tightened up the fuse gap with the 1500A fuse to say 15A (a tiny 1% gap), then you get 1485A @ 350V, making ~520kW (697hp).
Quick gut check on 1/4 mile horsepower calculators suggests that's not quite enough to break the 11 second barrier with a 5k lb car, so i guess the two possibilities are:
1. The 'L' won't break the 11 second barrier.
2. The voltage must not sag as much as I'm assuming. If so, that would imply that the current is hard limited perhaps closer to a 15% gap on the 1300A fuse.
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Updated calc:
If amps limited to 1100A on current fuse, that's 378V to achieve 416kw.
For 'L' If we figure slightly more sag, say 370V and 1% gap on 1500A smart fuse that's 1485A*370V = 550kW = 737hp
That's still not quite enough to achieve a 10.9 1/4 mile with a 5000 lb car.
I guess we'll see.
The number I posted was off the top of my head with rounded math, but it's probably close to the truth. There is definitely voltage sag. You can't just multiply things out to get a kW number. Doesn't work like that in the real world, especially when it comes to batteries.
The HV wiring is only 2/0 gauge. at 1500A or even 80% of that there is going to be significant sag there, plus more importantly the internal resistance of the cells under load. The internal resistance of the cells cause a significant voltage drop under load.
I've found the voltage drop under load, in testing, to be a hair better than the Panasonic NCR18650B, which has an internal resistance of about 55 miliohms in testing. I haven't made a definitive measure of the Model S cell internal resistance, but we'll be conservative and optimistic at the same time and say 40 miliohms.
So, at 1500A that is paralleled among 74 cells, so about 20.27A per cell. 85kWh pack is 96 sets in series of 74 cells in parallel. Remember amperage is constant across cells in series and split among cells in parallel.
Ohms law says that at 40 miliohms at 20.27A I would see a voltage drop of about 0.8108V. That would drop a fully charged pack's voltage from 403.2V down to 325.36V. 325.36 * 1500A = ~488kW.
For comparison, let's work the 1300A number from Elon. 1300A would be 17.57A per cell. Voltage drop of 0.7028V per cell @ 40 miliohms IR, so 335.73V. 335.73 * 1300A = ~436.5kW. Pretty close to reality considering this is optimistic and *only* accounts for internal resistance losses and not wiring, inverter, etc losses, which are bound to be appreciable.
So, being optimistic, I'm going to stick with saying about 500kW is the ceiling @ 1500A.
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Edit:
I'll go a little further and work the 420kW number (that we see currently from the P85D at full charge) backwards using the 1300A number from Elon and extrapolate.
420kW (~563HP) @ 1300A = 323.08V = 3.37V per cell after voltage drops (~0.8346V drop). That would give us 47.5 miliohms of resistance, which seems like a very reasonable full system number.
Using 47.5 miliohms at the 1500A level we get this:
0.96283V drop @ cell level, so 0.96283 * 96 = 92.43168V drop at the pack level = 310.76832V at the motor = ~466.1kW = about 625HP.
Basically there seems to be no way to spin this to look good.
The HV wiring is only 2/0 gauge. at 1500A or even 80% of that there is going to be significant sag there, plus more importantly the internal resistance of the cells under load. The internal resistance of the cells cause a significant voltage drop under load.
I've found the voltage drop under load, in testing, to be a hair better than the Panasonic NCR18650B, which has an internal resistance of about 55 miliohms in testing. I haven't made a definitive measure of the Model S cell internal resistance, but we'll be conservative and optimistic at the same time and say 40 miliohms.
So, at 1500A that is paralleled among 74 cells, so about 20.27A per cell. 85kWh pack is 96 sets in series of 74 cells in parallel. Remember amperage is constant across cells in series and split among cells in parallel.
Ohms law says that at 40 miliohms at 20.27A I would see a voltage drop of about 0.8108V. That would drop a fully charged pack's voltage from 403.2V down to 325.36V. 325.36 * 1500A = ~488kW.
For comparison, let's work the 1300A number from Elon. 1300A would be 17.57A per cell. Voltage drop of 0.7028V per cell @ 40 miliohms IR, so 335.73V. 335.73 * 1300A = ~436.5kW. Pretty close to reality considering this is optimistic and *only* accounts for internal resistance losses and not wiring, inverter, etc losses, which are bound to be appreciable.
So, being optimistic, I'm going to stick with saying about 500kW is the ceiling @ 1500A.
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Edit:
I'll go a little further and work the 420kW number (that we see currently from the P85D at full charge) backwards using the 1300A number from Elon and extrapolate.
420kW (~563HP) @ 1300A = 323.08V = 3.37V per cell after voltage drops (~0.8346V drop). That would give us 47.5 miliohms of resistance, which seems like a very reasonable full system number.
Using 47.5 miliohms at the 1500A level we get this:
0.96283V drop @ cell level, so 0.96283 * 96 = 92.43168V drop at the pack level = 310.76832V at the motor = ~466.1kW = about 625HP.
Basically there seems to be no way to spin this to look good.
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No reason to doubt your numbers, but neither 466kW nor 500kW are enough to propel a 5000 lb car to 10.9 seconds in the 1/4 mile.
According to several calculators I've tried online, you need 600hp to do a 11.7 1/4 mile and 750hp to do a 10.9. Of course, the current P85D has only 555hp and does an 11.7, so for some reason (less than expected drivetrain losses?) it's able to do the 1/4 mile with 45 less hp than it *should* take.
In any case, you need an extra 150hp or 110kW to fall from a 11.7 to 10.9 1/4 mile. If you simply take that at face value, then the 'L' upgrade will need 420 + 110 = 530kw. Don't know how they'll get it, but that's really the only way we'll see a P85D hitting a 10.9 1/4 mile.
The Inconel fuse could also have a lower safety margin, and the silicon battery a lower voltage drop. Could be the difference between 691 and 762 HP.
Edit: @wk057: I don't think you can just divide by 1300, the fuse also has some safety margin (or is it included in the 1300 number?). In that case the voltage drop should be less.
Edit: @wk057: I don't think you can just divide by 1300, the fuse also has some safety margin (or is it included in the 1300 number?). In that case the voltage drop should be less.
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Using the old cells, when calculating the horsepower of the car with the new cells (the upgrade only works with the new pack!) makes no sense.
1. We don't know the new pack voltage, it could be anywhere from 350 to 450 Volts.
2. We don't know how those cells behave under full power
3. We don't even know, if the P85D ever reached 1300 Amps. 1.3kA could have been the limit, but that doesn't necessarily mean it ever reached that limit.
(4. If you use a horsepower calculator for ICE cars, the result may not work for an electric car)
In the end the only thing that gives a hint, how much higher the hp are, is the 20% faster to top speed claim. It takes 25% more hp, to get to the same speed, with the same car, 20% faster, assuming that means it takes 80% of the time it took before. If the max power was 416kW before, I guess it would be 520 kW now. It could be even higher, because the first 1-2 seconds, both cars might accelerate the same, thats around 10% of the time it takes to 250.
1. We don't know the new pack voltage, it could be anywhere from 350 to 450 Volts.
2. We don't know how those cells behave under full power
3. We don't even know, if the P85D ever reached 1300 Amps. 1.3kA could have been the limit, but that doesn't necessarily mean it ever reached that limit.
(4. If you use a horsepower calculator for ICE cars, the result may not work for an electric car)
In the end the only thing that gives a hint, how much higher the hp are, is the 20% faster to top speed claim. It takes 25% more hp, to get to the same speed, with the same car, 20% faster, assuming that means it takes 80% of the time it took before. If the max power was 416kW before, I guess it would be 520 kW now. It could be even higher, because the first 1-2 seconds, both cars might accelerate the same, thats around 10% of the time it takes to 250.
Hi,
If someone can get a hold of some cells from the pack then I know someone how can test the cells. My father is actually involved in battery developement (based in Denmark), and he bought (and modified) a testing machine to this purpose.
They have some standard test that that is business wide standards, and he could simply modify the test bench to fit to 18650 cells instead of the smaller cells that they are developing (cr2032 and alike)
If someone can get some original Tesla cells - a handfull or 2, we could have the batteries tested and have the exact numbers. It is however important that the cells comes from a P85D pack, to ensure that the chemistry in the pack are the same. Tesla might have changed something over time.
If someone can get a hold of some cells from the pack then I know someone how can test the cells. My father is actually involved in battery developement (based in Denmark), and he bought (and modified) a testing machine to this purpose.
They have some standard test that that is business wide standards, and he could simply modify the test bench to fit to 18650 cells instead of the smaller cells that they are developing (cr2032 and alike)
If someone can get some original Tesla cells - a handfull or 2, we could have the batteries tested and have the exact numbers. It is however important that the cells comes from a P85D pack, to ensure that the chemistry in the pack are the same. Tesla might have changed something over time.
I don't think any online calculators you're using are designed for EVs and take into consideration full torque available at 0 RPM.
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0) The Ludicrous upgrade is able to be implemented in the old packs, per Elon.
1) Voltage of the 90kWh pack, Yes we do know. It's the same as the 85kWh pack. Same physical setup, new cells.
2) The improvement is in energy density, so most likely close to the same internal resistance.
3) 1300A in short bursts fits perfectly with the performance data on the fuse from the 85kWh pack. (Dont have links handy)
4) Agree
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The new fuse isn't inconel, it's digital.
The time vs. amperage curve for the existing fuse is somewhere around here, but 1300A for a short period is within it's limits.
When you get the L uppgrade to P85D, cells don't change.
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Please see http://www.teslamotorsclub.com/show...olar-with-a-Model-S-battery-pack-at-the-heart
A normal ICE car does also have very good torque from a stand still. No one at the 1/4 mile does start from example 500rpm. Everyone revs the engine or use launch control to get the most torque before the car is limited by traction.
Tesla P85D with full torque from 0 RPM will be limited by traction.
This hp calculator is better because you can choose direct drive.
Acceleration simulator
It does show that about 530-550hp is enough for a 11.8 1/4 mile time using direct drive or wheel power, even the trap speed is almost correct.
To do a 10.9 1/4 mile is much harder and does require about 730hp when using that calculator.
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0: Oh, didn't know... I wonder if they will behave differently. You can only buy a P90DL now, so I thought the extra power might have something to do with the new cells. My mistake.
1: The pack voltage depends on the cells, if they were 3.6V and are 3.7V now, just to have an example, it changes the Packs voltage from 400V to 411V.
Knowing that the Voltage depends on the anode and cathode materials. So with changing the anode, the cell Voltage might have changed as well.
2: Could very well be, but just because it was a energy density improvement, does not imply that the rest stays the same.
3: I will have to take your word on that. But I would very much like to see the data, sounds interesting.
But, as I realize now, this is a topic about the P85D, not the P90D, so most of my arguments are irrelevant.
And as there is no reason in debating, if the P90Ds performance is different to the P85Ds, as long as nobody has ever driven one.
I would say the top HP of the P85DL, would be 15.4%(=1.5/1.3) higher than the P85D, around 485kW.
stopcrazypp
Well-Known Member
Here we go again. Tesla never claimed the motors put out 762hp together. They claimed the front motor can put out 259hp and rear motor 503 hp. They didn't make the same mistake of putting a combined number again.If I did the math right, the 1500A Elon referred to will get to the motor/inverter at the ~500-525kW level when the pack is full (ridiculous voltage drop at this amperage........) which is close to the original 691 HP number, but not quite the new 762 HP number. I'm starting to think they just make these numbers up.
Here's my two cents on the whole voltage sag power calculations in general (not to you specifically). I see a big flaw with how the math is being done in regards to 1300A vs 1500A. Elon had been clear that with the old fuse there is a bigger margin vs the new one. Thus it'll be something measurably less than 1300A vs 1500A.
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Andyw2100
Well-Known Member
I'm not on top of what Musk and Tesla have or haven't said this time with respect to the Ludicrous Mode and 762 HP. But assuming what you say is true, that's just more evidence for the fact that Tesla knows that what they did originally was wrong, and that they shouldn't have ever mentioned 691 HP and the P85D in the same breath, since the car never made 691 HP. A reasonable person might conclude that if Tesla knows it was wrong, and now has the ability to make it right (or at least a lot closer to right), why not do that?
Long story short, I don't think the P85D/P90D or the Ludicrous mode variants of the same will be capable of putting out even the originally advertised 691 HP.
The main issue, as is the topic of this thread, is that the P85D "Insane" version is *definitely* not capable of the advertised 691 HP.
The main issue, as is the topic of this thread, is that the P85D "Insane" version is *definitely* not capable of the advertised 691 HP.
thegruf
Active Member
Absolute power aside for a moment, there is another factor regarding times here.
"Ludicrous improves acceleration from 60-155mph by 20%"
So the existing power taper with speed is less severe with Ludicrous.
This is somewhat difficult to estimate using calculators, however if Tesla are claiming a 10 second time, this is one claim I think they will have to deliver on.
Now going back to absolute power - why are Tesla claiming the motor power increased?
Surely if they are talking "motor power" then this is the max hp the standalone motor can deliver given a sufficient supply.
"Ludicrous improves acceleration from 60-155mph by 20%"
So the existing power taper with speed is less severe with Ludicrous.
This is somewhat difficult to estimate using calculators, however if Tesla are claiming a 10 second time, this is one claim I think they will have to deliver on.
Now going back to absolute power - why are Tesla claiming the motor power increased?
Surely if they are talking "motor power" then this is the max hp the standalone motor can deliver given a sufficient supply.
+1
I am afraid that Tesla do not think 'they have to deliver on any thing'. I know this thread is about the power shortcoming, a thing that Tesla has chosen to ignore is a way that is starting to become a farce. I also know there is a thread about the shortcoming of the acceleration time from 0-60 mph, but given your statement that they have to deliver on the 10s claim, I think you are going to be very disappointed. I have not heard of any P85D's that can meet the 3.1s 0-60 mph claim since they upgraded the sw from .188 and do not start with the 1-foot rollout, the claim is ZERO to sixty.
So yes, the car is fast and it is going to become faster, but it will not meet the claims that it was originally sold on when looking at power, however the new fuse is diffidently an improvement, so +1 for Andyw2100
The 1/4 mile is a bit different as it depends on sustained power far more than the 0-60 does where early power before most ICEs hit their power band can change the 0-60 game a lot. There's no way the a 5000 lb car can go from an 11.7 to 10.9 second without producing a lot more power than just a 0.8 * 1300 to 0.8 * 1500 amps = 64 KW * 1.34 (kw / hp) = 85.82 hp. Either the power will be a lot more than that or it won't really hit 10.9 seconds.
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The only thing the 90 kWh pack implies is that after x number of miles a fully charged 85 vs 90 pack, the 90 pack will have a slightly higher voltage because it will not be as far along in it's discharge curve. i.e it's % discharge after x miles will be less than the 85 pack. I suspect this is where the "almost" comes from. Nothing about Silicon lowers the internal resistance. In fact, chemistry changes that typically increase capacity typically decrease peak current capacity as a trade off. I don't know for a fact that this is the case with the new 90 pack nobody should assume the new pack will put out higher voltage since the number cells is the same.
So maybe VT is off or something, but under WOT acceleration runs, the voltage is only dropping a few volts. The 1300 amp fuse, since it's the type that melts must use a pretty big margin. Typically, devices are rated for 80% of the fuse rating. 80% of 400v * 1300 = 416KW. Coincidentally, the maximum REST api reading ever seen at 100% SOC was 415KW.
If the voltage drop was really significant, like down to 325, then the 1300 amp fuse is NOT a 1300 amp fuse but instead a 1600 amp fuse. That's the only way you get 416KW out of 325 volts with a 20% margin on the fuse.
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It doesn't matter what they claim the hp is which they still of course are not. But they are claiming a 10.9 second 1/4 mile which will require a LOT more hp than whatever the P85D is making now.....a lot more.
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Um, I've done this with my vbox repeatedly. In fact, even at an SOC of 60% I'm still able to hit 3.2.
Interesting, and I'm not being sarcastic . Was this with the 1-foot rollout off or on? Which conditions do you find optimal for reaching those times?
Could I ask you to do a 0-60 run with the 1-foot rollout off and state under which conditions the run was made and SW and maybe rest data? I am being genuine, because I hear a lot of owners saying their car does not meet the numbers.
Car and Driver also have trouble meeting the 3.1s - Tesla Announces 762-hp Model S, "Ludicrous" Mode, New Base Model – News – Car and Driver | Car and Driver Blog
'It should be noted that we’ve been unable to match Tesla’s claim, with our quickest zero-to-60-mph time for the P85D landing at 3.3 seconds.'
ERP
Ludicrous Member
The lack of detailed information is leading to a lot of conjecture. With what little info we have, I don't think the actual fuse limit matters for this discussion. The original message from Tesla regarding this upgrade states: "The net result is that we can safely increase the max pack output from 1300 to 1500 Amps."
To me, it would be odd for Tesla to give the actual fuse limit in a PR statement and then leave us guessing to the actual usable current. So it doesn't matter if the 'old' fuses melt at 1600 amps and the new ones disconnect at 1700 amps, or what factor of safety is added to the fuses. I read it as stating the upgrade increases normal maximum current by 200 amps.
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