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All engineering topics (out of main)
- Thread starter Artful Dodger
- Start date
Just thinking about the endless rows of ID.3s sitting outside until this fall, unplugged, awaiting a software update:
Beyond the fact that I worry about their batteries (I seriously hope someone is recharging them occasionally!), it's got me thinking about the EU emissions credit scheme. Are compliance-related fees accrued on an annualized, quarterly, or monthly basis? Were ID.3 sales volumes intended to eliminate all of VW's noncompliance fines, or just a fraction? I'm curious as to whether this delay is a double whammy on this front, or whether the delay just means more fines upfront, less later in the year.
Beyond the fact that I worry about their batteries (I seriously hope someone is recharging them occasionally!), it's got me thinking about the EU emissions credit scheme. Are compliance-related fees accrued on an annualized, quarterly, or monthly basis? Were ID.3 sales volumes intended to eliminate all of VW's noncompliance fines, or just a fraction? I'm curious as to whether this delay is a double whammy on this front, or whether the delay just means more fines upfront, less later in the year.
Another note on platform management and design for parts commonality between diverse products.
A few people, not in this thread, have implied that common ‘skateboard’ and related design to accommodate widespread deployment of high capes items, like motors, necessarily implies that the resulting products will be somehow generic and characterless.
We surely all know that such an assertion is ridiculous and refutes now ubiquitous and basic engineering and production techniques. Obviously some do it much better than others.
When Tesla can adopt the fuse from SpaceX to provide more precise temperature control for batteries (P85D Ludicrous introduction) and the motor from the Plaid S to do steering fin control for Falcon 9:w are entering a new world of parts commonality. When Tesla/SpaceX can do that when others often stumble we should try to understand why, beyond my ‘inter disciplinary’ platitudes.
I suggest that the technical reasons stem from parts performance specifications, that do not specify the technology to be used to meet the performance. The specifications themselves seem often to be open in terms of goals, not so much in more details. Overall there have been a few that repeat consistently:
1. Safety- described is detail but seem to be ‘common sense’ rather than the traditional automotive/aerospace statistical probability of failure (POF) that has been so famously and disastrously manipulated so often.
2. Reliability- during the short life of Tesla and SpaceX they have been constantly reducing service needs and replacement needs, so allowing far lower service calls, in-service failures and predictive servicing. We see that most dramatically in SpaceX, least dramatically in the Difference between servicing needs for a 2012 Model S vs a current production one, and the uncanny absence of servicing and failures for Model 3. Not zero, but amazing advance. How about SpaceX progress?
3.Durability- First stage reuse, fairing reuse, million mile batteries . Nearly every manufacturer claims durability, but Tesla/SpaceX take cost reduction seriously. Reducing parts failure, production waste, durability all go together. Once reliability is established durability becomes axiomatic and ends out paying for itself very quickly.
4. Light weight- the lighter the weight the more of a virtuous circle becomes established. Every single component is easier to accomplish the first three goals if the weight is lighter.
5. Decrease parts count- That saves in every single component of cost except for initial parts production. Their things like new casting technologies and combining functions pays off. Of course this is only practical when you are devoutly dedicated to the first four priorities.
6. Reduce costs- that becomes pretty easy, in relative terms, when you have done the first five. However that one demands another two items;
7. Never design a new part if another one elsewhere can do all six of the above.
8. Always use the best solutions as widely as practically achievable.
These eight are all basic but often ignored. They skip explicit technological innovation because that is the means to several of these ends. Many companies treat technology as the end. Tesla does not, so use of advanced technology becomes far more robust at Tesla precisely because there are not compromises made to allow new technology. That said, we understand why gestation of Semi and Roaster have been so long, and why ramp up of Model X and Model 3 been unusually difficult.
Finally, failing to adhere to the principles for Model X proved to be an important lesson, as did Falcon introduction. Those were existence challenging lessons. Things like solar roof tiles seem only make it once the kinks are resolved, or so it seems to me.
Model 3, StarLink and certainly Model Y and GF 3 are proof that these principles are well established now.. They most likely are not stated in exactly this form but without question that is how so much new technology and new capability can be so consistently delivered: often late but delivered!
A few people, not in this thread, have implied that common ‘skateboard’ and related design to accommodate widespread deployment of high capes items, like motors, necessarily implies that the resulting products will be somehow generic and characterless.
We surely all know that such an assertion is ridiculous and refutes now ubiquitous and basic engineering and production techniques. Obviously some do it much better than others.
When Tesla can adopt the fuse from SpaceX to provide more precise temperature control for batteries (P85D Ludicrous introduction) and the motor from the Plaid S to do steering fin control for Falcon 9:w are entering a new world of parts commonality. When Tesla/SpaceX can do that when others often stumble we should try to understand why, beyond my ‘inter disciplinary’ platitudes.
I suggest that the technical reasons stem from parts performance specifications, that do not specify the technology to be used to meet the performance. The specifications themselves seem often to be open in terms of goals, not so much in more details. Overall there have been a few that repeat consistently:
1. Safety- described is detail but seem to be ‘common sense’ rather than the traditional automotive/aerospace statistical probability of failure (POF) that has been so famously and disastrously manipulated so often.
2. Reliability- during the short life of Tesla and SpaceX they have been constantly reducing service needs and replacement needs, so allowing far lower service calls, in-service failures and predictive servicing. We see that most dramatically in SpaceX, least dramatically in the Difference between servicing needs for a 2012 Model S vs a current production one, and the uncanny absence of servicing and failures for Model 3. Not zero, but amazing advance. How about SpaceX progress?
3.Durability- First stage reuse, fairing reuse, million mile batteries . Nearly every manufacturer claims durability, but Tesla/SpaceX take cost reduction seriously. Reducing parts failure, production waste, durability all go together. Once reliability is established durability becomes axiomatic and ends out paying for itself very quickly.
4. Light weight- the lighter the weight the more of a virtuous circle becomes established. Every single component is easier to accomplish the first three goals if the weight is lighter.
5. Decrease parts count- That saves in every single component of cost except for initial parts production. Their things like new casting technologies and combining functions pays off. Of course this is only practical when you are devoutly dedicated to the first four priorities.
6. Reduce costs- that becomes pretty easy, in relative terms, when you have done the first five. However that one demands another two items;
7. Never design a new part if another one elsewhere can do all six of the above.
8. Always use the best solutions as widely as practically achievable.
These eight are all basic but often ignored. They skip explicit technological innovation because that is the means to several of these ends. Many companies treat technology as the end. Tesla does not, so use of advanced technology becomes far more robust at Tesla precisely because there are not compromises made to allow new technology. That said, we understand why gestation of Semi and Roaster have been so long, and why ramp up of Model X and Model 3 been unusually difficult.
Finally, failing to adhere to the principles for Model X proved to be an important lesson, as did Falcon introduction. Those were existence challenging lessons. Things like solar roof tiles seem only make it once the kinks are resolved, or so it seems to me.
Model 3, StarLink and certainly Model Y and GF 3 are proof that these principles are well established now.. They most likely are not stated in exactly this form but without question that is how so much new technology and new capability can be so consistently delivered: often late but delivered!
Fact Checking
Well-Known Member
Not just recharging them, but keeping their temperature above freezing point is absolutely critical to battery pack longevity.
AFAIK freezing temperatures are the #1 most destructive condition to li-ion cells, followed by "too low voltage". This ID3 storage method seems to trigger both.
That is not the case. You can freeze batteries and store them. Jeff Dahn confirmed this too in his battery talk. As for voltage, as long as it's not too low it's fine. Also, below 4V per cell if possible.
What you are thinking of is heat which promotes metallization of lithium, especially when combined with high cell voltage.
But cold storing batteries is completely reversible.
JRP3
Hyperactive Member
If they aren't being charged freezing temperatures should have no effect. Cold is better than hot for inactive cells.
I think the bigger question is whether or not they have vampire drain, or if there is some sort of "complete power down" mode. We might find that come spring, half of them are bricks.
JRP3
Hyperactive Member
Just thinking about the endless rows of ID.3s sitting outside until this fall, unplugged, awaiting a software update:
Beyond the fact that I worry about their batteries (I seriously hope someone is recharging them occasionally!), it's got me thinking about the EU emissions credit scheme. Are compliance-related fees accrued on an annualized, quarterly, or monthly basis? Were ID.3 sales volumes intended to eliminate all of VW's noncompliance fines, or just a fraction? I'm curious as to whether this delay is a double whammy on this front, or whether the delay just means more fines upfront, less later in the year.
EU compliance penalties are "engineering topics out of main"? Seriously?
All batteries have set minimum and maximum charge, discharge, storage temperatures. Model 3 for example never lets its pack drop below something like -9°C in normal usage (so long as it has any charge left) in order to maintain sufficient operating (discharge) temperatures, but they can probably be safely up to stored when fully inactive 10-20 degrees colder than that. But there are limits. On the upper end as well.
Also, even with no vampire drain at all, there's always some self-discharge rate, which for li-ion is usually 1-5% per month. If there's any sort of vampire drain at all, it can be much faster. Fully discharging a li-ion battery is bad enough, but leaving it discharged for long periods is even worse.
A plugged-in EV is a happy EV.
JRP3
Hyperactive Member
The cell chemistry has almost no self discharge. I have bare cells sitting for many years, (5+), still sitting at 3.8V (LiCo) and 3.3V (LiFePO4).
The flat of A123 cells that was in a cabinet when I started a former job 10+ years ago are reportedly still juicy. Of course, they have no BMS hanging off them.
Unless VW deenergizes the cell protection circuitry while the vehicle is in storage, I don't think the self discharge of individual bare cells is of particular relevance. To be fair, I have no idea what the the self-discharge rate of either Tesla or VW battery packs is; I just googled a handful random storage products and looked up their cited self-discharge rates when in storage from their spec sheets; typical numbers were in the 1-5%/mo range.
The minimum and maximum pack maintenance temperatures for the Model 3 however are known, however, as they're parameters visible in some of the factory mode leaks.
JRP3
Hyperactive Member
I believe that's exactly what Tesla does when the SOC gets low enough, and why it requires Tesla service to wake the car back up.
Have you been hangin' out in the Cybertruck thread?
We (I) welcome you contributions/cross-posts...
Cheers!
Brando
Active Member
Marketing/sales guy opinions talking to a Wall St. promoter. Interesting, but I'd prefer/suggest that engineers would be better trusted.
side note: I suspect Tesla break through in wiring may be "power only" to devices and perhaps wireless (radio) communications to the controlling computer system. Just consider how little actual wiring that would be - just 2 wires +/-.
Just me speculating. Inspired by Sandy Munro comments. But imagine the savings in wire/weight/assembly.
No need to point out what a drastic change this would be. Can safety and reliability be maintained or even improved ??
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I'm expecting Tesla to move to SS exoskeleton bodies, 48v architecture and robotic installed wiring for all vehicles including 2nd gen S / X / 3 / Y.
Based on CyberTruck pricing, this looks to be cheaper to build and last longer than the current, more traditional, build style.
It also gives Tesla a hell of a product roadmap for next 7 - 8 years.
Based on CyberTruck pricing, this looks to be cheaper to build and last longer than the current, more traditional, build style.
It also gives Tesla a hell of a product roadmap for next 7 - 8 years.
This has been discussed pretty extensively. Everything is optimized to its particular use case. There's under $2k manufacturing hardware depreciation per unit on Model 3 (we were told by Deepak it was under $2k nearly a year ago), so the potential capital savings are limited. You hurt your drag coefficient compared to current Teslas with the "cyber" approach. Musk thinks that with "great effort" Cybertruck might hit 0,30; by contrast, Model 3 is 0,23. So probably a bit over 0,30 - probably approaching a 50% worse Cd than Model 3. A "cyber-Model-3" would probably end up with ~30% more energy consumption at high speeds. Possibly worse, as it won't be able to have as long, shallow of a rear taper as Cybertruck to encourage flow reattachment, and/or a larger rear cross section after truncation (although the lack of the need for a bed may allow for some improvements on that end).
More energy consumption per unit distance equals a worse vehicle in so many different respects. Home charging cost, supercharging cost, supercharging infrastructure (less efficiency = more time charging = more stalls taken up), range (for a given battery size), mass (if battery size is increased to compensate), handling (if more weight, e.g. if more batteries), max production capacity (if battery size increased), # of cycles put on the packs per unit distance (if battery size not increased), depth of average daily cycle (if battery size not increased), charging taper hit at an earlier # of miles (if battery size not increased) and on and on.
The main thing that allows Tesla to make Cybertruck awesome for its price point is simply that it's two years off, and its batteries are priced at their estimated prices two years from now. Cybertruck's design is the result of relentlessly optimizing to a particular goal. They wanted to have it armoured. That means something heavy on the outside. Which you can't stamp. So, to keep it light: origami frame, which equals polygonal. And sure, sometimes things that are invented for one particular goal end up proving useful toward other goals. But it's not so simple. Efficiency matters a lot. Its importance decreases slowly with time as batteries get cheaper and more abundant and more energy dense, but at present it's still very important. By and large, it's Tesla's efficiency advantage that tends to give its vehicles so much better stats than everyone else, which in turn translates to its perception as an EV sector leader.
Also, for a truck, they're already pretty doomed when it comes to efficiency regardless. You could put them on low rolling resistance tires and give them a tapering tonneau and a beautiful aero profile, and your new owners will immediately put mud tires on them and draggy external accessories and drive around with the tonneau up and objects sticking out of it and tow a draggy trailer and on and on. Speaking of the latter: I haven't seen a simulation yet, but I have a strong suspicion that if you tow a tall trailer with the Cybertruck, the flow detachment at the pointed peak of the Cybertruck won't reattach, but will rather flow in a bubble over the trailer, and recirculate between the two (good for the combined drag coefficient of the truck-trailer system). If you tow with something like the Model X, you're basically trying to stick the flow to the back of a smooth, gentle rear taper only to ram it straight into a vertical wall that you're dragging behind it.
Back to cars: as discussed previously, if the goal is simply "cyber-aesthetics", you could create some rather interesting smooth-polygonal hybrids. Parts of the vehicle that already have flow detachment / turbulent flow face little impact from "cyberization", so you can keep the car smooth where important and "cyberize" other parts of it, and blend the two together, for what would probably be quite an interesting aesthetic.
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