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75 and 75D variants increased performance from July 1st - software and hardware improvements?
- Thread starter Bluejuice
- Start date
clostridium
Member
The uncorking is definitely not in that version. The upgrade apparently has to be done at the SC and is separate from the software upgrades we get OTA. It's also completely unclear which vehicles will get the uncorking. From reading this thread it appears that some fairly recently built vehicles got the upgrade but the status of earlier 75's is not clear and I haven't seen anything about what will happen with 70's. That doesn't mean it won't happen of course. I'm still waiting on confirmation that it can be done with cars that don't have the new drive unit change. If it can be done on those vehicles that opens up a wide variety of eligible vehicles.
You can make an argument that the benefit of Tesla doing this is to further reinforce the differentiation between the Model 3's that are coming out first and the lower end Model S's that cost 40k more. Now that it's become clear that they can do this to at least some vehicles they could run the risk of some frustration from owners at a time when there will likely be some alternative EV options in the next year or two.
I've got a 75D 168xxx car and while I'd love to get this uncorking I am not going to lose lots of sleep over it.
clostridium
Member
That seems completely reasonable - we already know that the cars are software limited to some degree so having a software change to increase performance makes sense. What's not totally clear to me is how much of the motor power output difference between the 75 and 85's is due to the pack voltage difference (350 vs. 400) and how much is due to some sort of power limiting software. The motors are each rated for 264 hp or 518 hp total and even the 85D only gets 417 hp total out of them while the 75D (prior to the recent changes) gets I believe 329 hp or around that numbers. That leads me to believe that the pack voltage isn't the only limiting factor in the output.
Of course there are likely other potential limiting factors - does anyone else know what other powertrain components vary between the 75D and the 85D or 90D?
My guess is the inverter. This converts the DC battery voltage to A.C. to power the motors. Different inverters can produce more/less power .
I am pretty sure the small (front and rear) drive inverters were all the same as each other, only different from the large (rear) inverters which were all the same as each other - until the late June 2017 DU00 and DU01 units, which, besides being more efficient, probably have more performance headroom.
It makes sense that the firmware which limits performance (and hence differentiates horsepower between models) is more hardened than the general firmware. Hence no over the air updates.
All vehicles drive units and batteries are limited or governed. The high end ones for safety and then warranty purposes. The lower models for those reasons plus to differentiate them from the higher models.
I understand the thinking that Tesla might try to save a few dollars by building weaker components across model lines, mainly drive units and batteries, but the fact is we know that most of these components are the same across models, implying that it is cheaper to use one part that is over engineered than juggle supply chains, inventory and manufacturing for multiple parts.
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Tesla Model 3 exclusive leaked specs: 300kW+ inverter architecture putting its power capacity near Model S
“The power rating increases are largely enabled by better and better power electronics – transistors or IGBTs which is what we are using. As those improve, we can continue pushing up the current rating and continue increasing performance. If we can make the inverter just half a percent more efficient, that’s half a percent less battery pack that we have to put in the car or half a percent more range that the customer gets to have so it a very strong and virtuous feedback cycle with high efficiency.”
“The power rating increases are largely enabled by better and better power electronics – transistors or IGBTs which is what we are using. As those improve, we can continue pushing up the current rating and continue increasing performance. If we can make the inverter just half a percent more efficient, that’s half a percent less battery pack that we have to put in the car or half a percent more range that the customer gets to have so it a very strong and virtuous feedback cycle with high efficiency.”
Because the DC from the pack goes through the inverter, the pack voltage doesn't make much difference for driving performance. It does effect fast DC charging speed, but that's about it. The key is how much peak power the pack can produce (Voltage times current). Using the same cells, that is proportional to the number of cells in the pack.
The limit in performance on the small pack cars has largely been due to fewer cells in the pack, not the voltage. As the cells improved and the small packs got more cells, performance improved too. The old 60 had the original battery cell with fewer cells per module than the original 85 pack. The old 70 had the same number of cells as the 60, but with the new cells used in the 90 pack. The 75 standardized the module used between the 90 and smaller pack and that bumped the capacity up to 75. If you look at the 0-60 times for the old 60, 70, and 75 RWD cars (comparing apples to apples, the was no 60D until the software limited version came out), the time went down with each version.
When they start using 14X modules from the 100 KWH pack (which they might be doing now, but we don't know), the total number of cells will be a little bit more (7224 cells) than the old 90 pack had (7104 cells). It will only be 350V, but with more cells in parallel than before. The reason I think the new 75 is a software limited larger pack is the performance numbers for the new 75 are pretty much identical to the old 90. The 100D got a tiny performance boost, but I think that is just from having more cells in the pack and the large pack non-performance car is close to maxed out due to the performance limits of the motor/inverter and not the pack.
clostridium
Member
So it's due to both voltage and current, just not clear to what degree each plays a part. There must also be something related to software limitations in output too because cars with different pack power outputs get similar performance - the 85D, 90D, and 100D.
@wdolson question
My S60 bought in late December 2016 and unlocked to a 75 in May 2017.
Do you think that unlocking the battery provided a performance boost? I could not feel it. My question is do you think the firmware or software involved with the DU needs to be flashed or tweaked to take advantage of the additional 15kW from the battery now? Thanks in advance. John
My S60 bought in late December 2016 and unlocked to a 75 in May 2017.
Do you think that unlocking the battery provided a performance boost? I could not feel it. My question is do you think the firmware or software involved with the DU needs to be flashed or tweaked to take advantage of the additional 15kW from the battery now? Thanks in advance. John
Performance is limited by whatever the weakest link in the chain is. The Performance cars are built to minimize the limits of every component and get as much power from the pack to the wheels as possible on launch. Limits could be wiring, the inverter, the motor, or the peak output capacity of the pack. With the non-performance 85D, 90D, and 100D, the key limit appears to be what the motors can handle. The rear motor is smaller than the rear motor on the Performance cars. I believe the inverter on all the cars is the same (or was before the latest change). The wiring is also probably the same on all cars.
On the small pack cars, the pack can't produce as much peak power as the larger packs could and this was the limiting factor. Take an old 70D or 75D and put a pack from a 90D in it, then change the firmware so it knows there is a larger pack, and you should have identical performance to a 90D.
How much current or how much voltage doesn't make much difference (within practical limits). The old 90D pack could produce 311 KW peak power (according to Wikipedia). That's 777.5 A at 400V. 888.57 A at 350V is also 311 KW. As far as the inverter is concerned, it makes no difference, the inverter will convert that to the AC needs of the motor.
Putting all the cells in parallel is impractical, that would result in a 4V battery pack with 77,750 A. That kind of current would be very hard on the wiring as power loss is I^2*R. The resistance of copper cabling is very low, but with that kind of current squared, the losses in the cabling will be huge.
Wiring all the cells in series to make a 28 KV battery pack with 10.9 A is also impractical. The higher the voltage the further it can jump from one point to another. In dry air 24 KV can jump about a 1 inch gap. The odds you're going to get unwanted arcing in the drive system is way too high.
But in the range of say 300-800V, you can make an inverter to take in any voltage in that range and the currents will be reasonable unless you have a massive battery pack. The semi will probably have an 800V pack to keep the currents down around where they are in the cars or maybe 2X (depending on how big the pack ends up being). The advantage of a higher voltage pack also means supercharging voltages can be higher too and that will help supercharging speeds. I expect the 350KW+ superchargers Elon has hinted at will be limited to the semi packs and any other very large battery packs.
The software locked battery still has the same number of cells as the 75, the software just won't allow them to charge more than 80%. So the peak power the pack can put out with a software limited 60 is the same as a 75. It just won't be able to put out power as long because the cells are charged up all the way when you start.
whitex
Well-Known Member
Battery "uncorking" was done to raise the peak current from the battery on P85D's to 1,500A. Before doing do, the new contactor had to be installed, hence the $5K price. Possibly the new cars are built with better contractors so the 75 battery peak current can be safely raised from whatever the current one is. With the higher peak current, the 75 can deliver the same power and a 90 at a proportionally (to the voltage) lower current.
turbosimon
Member
After the uncorking, 0 to 60 for my 75D (350V) is in low 4 seconds. For those who is interested in this....
turbosimon
Member
It's not based on your VIN. I believe it's based on your production date (Production date of 6/19/2017 or later).
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