Investor Engineering Discussions

[mongo]

I have little knowledge of this area but I’d like to learn. Would you explain some more please or link to where I can read? Why is the new radar higher resolution and more steerable and how do you know? What’s ARS4, Tx and Rx?

ARS4 is the Continental radar.
Tx : transmit antenna
Rx : recieve antenna
Resolution is dependent on antenna size(aperture) and frequency. Multi element antennas (ohased arrays) can approximate a single antenna of the overall size and are electronically steerable (like Dishy)
Both radars are in the 76 GHz range, but Phoenix (the new one) has wider bandwidth which can give more resolution in the range (away from radar) direction. It also has more elements which increases performance.

Old:

New:

 

[bkp_duke]

Sandy talks to people from Zeta Energy about their lithium sulfur battery.

Home

Zeta Energy's lithium-sulfur batteries offer unparalleled performance, stability, and affordability, and are sustainably manufactured.

zetaenergy.com

LiS has serious problems with longevity (i.e. relatively low cycle count to failure). Energy density is great at ~4X that of most Li-Ion. Just wish they held up better.

 

[JRP3]

LiS has serious problems with longevity (i.e. relatively low cycle count to failure). Energy density is great at ~4X that of most Li-Ion. Just wish they held up better.

Supposedly they've solved some of the issues, they spoke about it in the video.

 

[bkp_duke]

Supposedly they've solved some of the issues, they spoke about it in the video.

I watched the video, even before I posted. I would have preferred to have seen testing data for cycles, instead of them talking about it. I'll reserve judgement, but "show me the data!" is my mantra on new battery developments.

 

[JRP3]

I haven't looked too hard but supposedly there is some data out there:

Maslin explained that Zeta has succeeded in stabilizing the sulfur cathode and pointed to test results that show it can be cycled with minimal capacity loss over thousands of cycles.

Test results published in several scientific journals including Nature Magazine show that the Zeta battery has:

• Up to 3 times the energy storage capacity of lithium-ion batteries
• Faster charge time (minutes instead of hours)
• Lower battery temperature
• Little degradation over charge/recharge cycles

The Holy Grail Of Lithium Batteries

Better batteries are needed to economically smooth out the intermittency of renewables like wind and solar power. One company may have finally solved some of the most vexing problems facing lithium-based batteries.

www.forbes.com

 

[JRP3]

A close up look at the Optimus foot design, the "patient" had different feet than "doctors".

 

[MC3OZ]

The Gen3 Robotaxi model is chemistry agnostic. could that possibly extend to using Sodium batteries.

By this I mean that the drivetrain is efficient enough to use a Sodium battery, if that was necessary.

So Sodium is a contingency. The Jeff Dahn team was doing some research on Sodium, CATL is developing Sodium and some Chinese EVs are starting to use Sodium.

I was surprised that Sodium wasn't mentioned in passing on Investor Day. But Elon clearly thinks there is enough Lithium, and perhaps they didn't want to over complicate the message.

There is no other reason to mention chemistry agnostic, Model 3/Y already use LFP.

 

[JRP3]

By this I mean that the drivetrain is efficient enough to use a Sodium battery, if that was necessary.

Not sure what you mean by that.

There is no other reason to mention chemistry agnostic, Model 3/Y already use LFP.

I can't think of any reason to mention chemistry agnostic at all, every electric motor meets that criteria. The rebuilt forklift motor in my 6x6 worked fine with both the AGM lead pack and the LFP pack, as did the old Black and Decker push mower I got for free and upgraded to lithium this summer.

 

[MC3OZ]

Not sure what you mean by that.

The drivetrain needed to get to a certain level of efficiency before Tesla could replace NCA with LFP,

Essentially the aim is reasonable range for a vehicle with a reasonable weight.

Sodium is lower energy density, but when the drivetrain is efficient, fewer kWh are needed per 100 miles of range, so ultimately a sodium battery with the required amount of range isn't too heavy.

Obviously if Sodium gets a passing grade, LFP walks it in, and Nickel probably isn't required even for long range and performance versions. (Assuming that they make those versions.)

 

[JRP3]

The drivetrain needed to get to a certain level of efficiency before Tesla could replace NCA with LFP

Not really, we are talking low single digit percentage differences in drive train efficiencies, and any further improvements from the current 97% efficient motors are basically meaningless. Even an almost impossible 99% efficiency would only mean a 6 mile gain on a 300 mile pack.

 

[bkp_duke]

Not really, we are talking low single digit percentage differences in drive train efficiencies, and any further improvements from the current 97% efficient motors are basically meaningless. Even an almost impossible 99% efficiency would only mean a 6 mile gain on a 300 mile pack.

Reference for 97% please. I thought even the plaid motors were low to mid 90s from previous reading.

And remember, you have to double the losses for round trip efficiency (regen).

 

[MC3OZ]

Not really, we are talking low single digit percentage differences in drive train efficiencies, and any further improvements from the current 97% efficient motors are basically meaningless. Even an almost impossible 99% efficiency would only mean a 6 mile gain on a 300 mile pack.

It is often stated that Drivetrain efficiency impacts on the set of battery chemistries that are viable,

It is probably a simplification, in that the total car design is a factor.

Nothing stopping anyone putting an LFP battery pack into a Hummer, just don't expect decent range.

 

[Oil4AsphaultOnly]

Reference for 97% please. I thought even the plaid motors were low to mid 90s from previous reading.

And remember, you have to double the losses for round trip efficiency (regen).

I couldn't find a source, but did find a 2019 C&D article that quoted Tesla claiming the model S (non-plaid) had average efficiency of 80-90%, with a peak of 94% during the EPA test cycle. So with the use of PSMR motors in the plaid, and a higher claimed EPA range than the 2019's, the efficiency can only be better than 94% right?

 

[transpondster]

LFP were introduced at the same time as heat pump refresh, so it helped offset increased weight

 

[JRP3]

Reference for 97% please. I thought even the plaid motors were low to mid 90s from previous reading.

And remember, you have to double the losses for round trip efficiency (regen).

I thought that was Tesla's number when the introduced the new PMSRM motor. Tesla claims the entire operating efficiency of the drive unit is greater than 93% so the motor alone would have to be higher. (I'm not sure what regen has to do with it since only a tiny portion of drive time would be utilizing it.)

All Model S and X vehicles now benefit from Tesla’s latest generation of drive unit technology, which combines an optimized permanent magnet synchronous reluctance motor, silicon carbide power electronics, and improved lubrication, cooling, bearings, and gear designs to achieve greater than 93% efficiency.

The Longest-Range Electric Vehicle Now Goes Even Farther | Tesla

www.tesla.com

 

[JRP3]

It is often stated that Drivetrain efficiency impacts on the set of battery chemistries that are viable,

I've never seen that stated. Even if you went from an 85% efficient drive train to a 95% efficient drive train that's only 30 extra miles for a 300 mile pack and only 20 for a 200 mile pack. That's not a game changing difference that suddenly allows a lower density cell chemistry to be used and the differences we are actually dealing with are even smaller as I've explained.

 

[bkp_duke]

I thought that was Tesla's number when the introduced the new PMSRM motor. Tesla claims the entire operating efficiency of the drive unit is greater than 93% so the motor alone would have to be higher. (I'm not sure what regen has to do with it since only a tiny portion of drive time would be utilizing it.)

The Longest-Range Electric Vehicle Now Goes Even Farther | Tesla

www.tesla.com

We were told on the Semi introduction that round-trip motor efficiency was critical, because it kept heat low. That drive system uses the same motors as the plaid, that's why I was asking. For the Semi (and while tracking S/X) round-trip efficiency is the sum of losses in both acceleration and regenerative braking. I believe Jordan on TLF postulated that is why the Semi wasn't introduced earlier, because round-trip efficiency was too low. Losses to heat are 1/2 in acceleration and 1/2 during regen. I believe it was in his video that I saw the reference for roundtrip efficiency.

Anyway, it's a tangent.

 

[bkp_duke]

I've never seen that stated. Even if you went from an 85% efficient drive train to a 95% efficient drive train that's only 30 extra miles for a 300 mile pack and only 20 for a 200 mile pack. That's not a game changing difference that suddenly allows a lower density cell chemistry to be used and the differences we are actually dealing with are even smaller as I've explained.

It's much more than that. It's a LOT less heat needing to be dissipated during both acceleration and regen, and heat dissipation affects range much more than just the efficiency number.

 

[JRP3]

It's much more than that. It's a LOT less heat needing to be dissipated during both acceleration and regen, and heat dissipation affects range much more than just the efficiency number.

Unless you are racing I'd think heat dissipation is minimal in a 90%+ system. How much power is required to keep a vehicle moving at say 65 mph? Low speed stop and go will not be creating that much heat either. And how does any of this change the small single digit potential efficiency improvements which could in no way magically allow a poor battery density chemistry to be applied?

 

[mongo]

We were told on the Semi introduction that round-trip motor efficiency was critical, because it kept heat low. That drive system uses the same motors as the plaid, that's why I was asking. For the Semi (and while tracking S/X) round-trip efficiency is the sum of losses in both acceleration and regenerative braking. I believe Jordan on TLF postulated that is why the Semi wasn't introduced earlier, because round-trip efficiency was too low. Losses to heat are 1/2 in acceleration and 1/2 during regen. I believe it was in his video that I saw the reference for roundtrip efficiency.

Anyway, it's a tangent.

I just reviewed the transcripts. Semi reveal spoke of drag coefficient, semi delivery spoke of efficiency everywhere, and TLF spoke of triple motor for max regen.

Loss to heat is proportional to the square of current in the stator and roughly linear to current in the inverter. Since acceleration can use more power than regen, it will likely have more losses.

It's much more than that. It's a LOT less heat needing to be dissipated during both acceleration and regen, and heat dissipation affects range much more than just the efficiency number.

Acceleration is a time limited event and thus energy (heat) limited. Why would that impact range?