Refrigerated Cybertruck Frunk?

[JBee]

True, but you did propose the problem in the context of a physical or mechanical issue that would require more than just a reboot.

I'm guessing these ac issues, aside from any software issues, are subjective as what I find cool and comfortable, most would find freezing, and vice versa, what most are comfortable with I find unbearably hot.

This argument is like an audio engineer complaining about the crap quality of a stock car stereo speaker system that 99% of owners think sounds great. Not much stock in subjective issues.

Heat subjectivity Is all in your feet. I joke not.

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[HaulingAss]

I can completely agree that the total heat load of any ICE would exceeed that of a comparable EV, but that conparison does not automatically mean that a EV has a adequately sized air conditioning system either.

Of course that is correct. Every EV must be considered for it's own capabilities. The engineers decide the design goal. Hopefully they consider all the factors and don't gloss over the effects of radiative heat from the catalytic converter and a heat-soaked engine compartment. In the end, you just have to live with eaach individual car model to know which works better in difficult conditions. My experience over the last 4 years with two Model 3's has told me, in no uncertain terms, the cooling of the Model 3 is far superior to the best ICE vehicles I have experienced, they tend to run out of capacity on hot days when stuck in traffic or doing multiple errands in a manner I have not experienced with either of our Model 3's.

In fact it seems common that EV's use much smaller air conditioning setups so they can save some energy for extra range. By doing that it can actually make them more sensitive to temperature extremes as they don't have enough power to do their job all the time. But like towing with an EV, more efficient is mostly good, but also makes it more sensitive to high demand.

If an EV used the same sized cooling system as an ICE car, it would be inappropriate. Under sizing the cooling system is not a good way to save battery power, owners would just run it harder. It's actually more efficient to oversize the cooling system components and run them at reduced speeds. Which is probably why the Model 3 is so efficient and has such a great A/C system.

If EV's had undersized cooling systems to save battery power, you would know it because they would be slow to cool and struggle to keep the cabin cool in hot weather. So, obviously, that is not the case.

 

[ajdelange]

If EV's had undersized cooling systems to save battery power, you would know it because they would be slow to cool and struggle to keep the cabin cool in hot weather. So, obviously, that is not the case.

That's exactly what they are complaining about.

 

[ajdelange]

Do you happen to know what the temperature delta is for battery and motor coolant?

Do you mean the difference between the battery and its coolant and motor and its coolant or the difference between battery coolant and motor coolant? Really doesn't matter as I don't know. If the former, it depends on a load of things of which coolant flow (lpm) is a major one.

How cool do you need to keep batteries, is ambient cool enough when it is >100F outside?

I don't think so. That's why the compressor is needed.

I know keeping them warm, when it's cool outside requires active heating of the cells, either resistive or through the heat pump, but I haven't really looked out the heat removal side, which is actually more relevant for my neck of the woods.

I'd expect most of the heat load to come from the motors and inverters. This heat will warm the batteries in the winter but also in hot weather. If the batteries are being kept at 90°F you have to pump the heat uphill 10 °F (at OAT 100 °F). That's not too far but obviously you need refrigeration that can handle that load plus the cabin.

 

[JBee]

Do you mean the difference between the battery and its coolant and motor and its coolant or the difference between battery coolant and motor coolant? Really doesn't matter as I don't know. If the former, it depends on a load of things of which coolant flow (lpm) is a major one.

I don't think so. That's why the compressor is needed.

I'd expect most of the heat load to come from the motors and inverters. This heat will warm the batteries in the winter but also in hot weather. If the batteries are being kept at 90°F you have to pump the heat uphill 10 °F (at OAT 100 °F). That's not too far but obviously you need refrigeration that can handle that load plus the cabin.

I meant the former. But thx anyway.

Is it worth pre-cooling the pack and try to use some of its thermal mass to reduce compressor cycling? I suppose the packs don't reaally like the cold either.

I"ve actually been thinking a lot more about EV cooling systems lately, ever since a roo took out my vans radiator pack last week. Wasn't much of a hit overall, but it took out the front grill, radiator, intercooler and condenser. Lkights and bumoer ok though. Now my option was $7500 for a new stack from VW Australia but ex Germany in 2 months or $1700 new from a German ebay store delvered in 2-3weeks. It really wasn't a hard choice, but it got me thinking that I'd really like that not to happen on my CT.

I'd expect the airflow requirements to be fairly low in comparison so I was hoping they could tuck the cooling in behind the more structural elements of the front end, and with that we could maybe avoid having to mount a roo bar to the front of the vehicle that would likely disrupt aerodynamics and reduce range.

 

[ajdelange]

Is it worth pre-cooling the pack and try to use some of its thermal mass to reduce compressor cycling?

I think it's always best to garage the vehicle in an environment at least close to the one in which it is to be operated as among other things it does reduce load on the vehicles battery (and cabin) conditioning system at startup.

The word "cycling" caught my eye here because modern heat pump/AC equipment doesn't seem to recycle that much. The inverter (VFD) compressors learn what speed to run at to hold temperature and may run for hours. They are very efficient. I've learned this from the two Mitsubishi split packs I just installed in my garage. They are amazing. As the compressors in the new Teslas do and the CT compressor doubtless will use this technology I think it may be possible to have A/C in the vehicles that will handle up into the higher percentiles without difficulty while still being pretty efficient in terms of Wh/mi under more nominal conditions.

I suppose the packs don't reaally like the cold either.

No they don't and using battery or shore power to "condition" them is a widely used technique in colder climes.

It's pretty clear that raising a battery soaked at 0°F up to near 90°F demands moving a lot more energy that moving one soaked at 100 °F to near 90 °F does so that's on your side.

I"ve actually been thinking a lot more about EV cooling systems lately, ever since a roo took out my vans radiator pack last week.

As I recall the fillets are pretty good.

Now my option was $7500 for a new stack from VW Australia but ex Germany in 2 months or $1700 new from a German ebay store delvered in 2-3weeks. It really wasn't a hard choice, but it got me thinking that I'd really like that not to happen on my CT.

Ouch! Maybe the stainless will offer more protection.

...mount a roo bar to the front of the vehicle that would likely disrupt aerodynamics and reduce range.

Yes, but think of the panache!

 

[Crissa]

Is it? Possibly on some days. But the pack charges more efficiently at a higher temperature and pre-heating heating or cooling while still plugged in (even from Level 1) is the way to go.

Always cheaper to keep a temperature than to try to change it.

-Crissa

 

[rr6013]

I meant the former. But thx anyway.

Is it worth pre-cooling the pack and try to use some of its thermal mass to reduce compressor cycling? I suppose the packs don't reaally like the cold either.

I"ve actually been thinking a lot more about EV cooling systems lately, ever since a roo took out my vans radiator pack last week. Wasn't much of a hit overall, but it took out the front grill, radiator, intercooler and condenser. Lkights and bumoer ok though. Now my option was $7500 for a new stack from VW Australia but ex Germany in 2 months or $1700 new from a German ebay store delvered in 2-3weeks. It really wasn't a hard choice, but it got me thinking that I'd really like that not to happen on my CT.

I'd expect the airflow requirements to be fairly low in comparison so I was hoping they could tuck the cooling in behind the more structural elements of the front end, and with that we could maybe avoid having to mount a roo bar to the front of the vehicle that would likely disrupt aerodynamics and reduce range.

Would a single bent bullbar, aka Brawler, kick a Roo over the roof?

W/O a full cowcatcher across the front, you’re asking for an integral crash bar embedded behind the Cybertruck front nose skin.
Is that enough? Your Roo look like our cows and moose in N.A. They takeout the entire FEA(Frontend Ass‘y).

 

[CyberGus]

"EV: Cooler than ICE"

 

[CyberGus]

Forget the frunk-fridge, I'm gonna tow this everywhere I go.

"There's never a wrong time to rock"

 

[Cybertruck Hawaii]

I live in sf which rarely gets above 65..usually 55 everyday where I live by the ocean lol...but yeah never had any of my cars stall while idling for 10 mins.

. While it may be cool outside, the inside of a vehicle can collect a lot of heat trapped inside like a greenhouse with the windows up. Thanks again!

 

[HaulingAss]

That's exactly what they are complaining about.

I was responding to @JBee who acted like weak A/C's were common in EV's to save electricity. I have no knowledge of whether the Rivian A/C is actually weak or if people are simply trying to discourage EV adoption, but I can tell you that modern Tesla do not have weak A/C, quite the opposite.

The idea that any EV manufacturer would undersize the A/C system to save electricity exposes a lack of knowledge because the cooling system will be more efficient if it is oversized. Using variable speed brushless motors and running them at a lower speed while having oversized condensers and evaporators, system efficiency is enhanced (as well as system capacity when the motor is run at moderate to high speed). Yes, oversized condenors and evaporators take up more room and cost more to purchase but they enhance efficiency.

If your claim is that people are complaining about the A/C cooling capacity in Rivian's first vehicle, a truck made in very low numbers, I would suggest you are changing the subject (and I have no idea of whether Rivian's A/C system is strong or weak). Somehow I doubt it's weak unless it's just poorly designed. You can be confident the Cybertruck will have a powerful A/C system.

 

[Crissa]

The Leaf and early BMWs did have weak AC, as did several of the compliance cars.

But they skimped on lots of things. There's no particular reason for the AC to be undersized, as you point out, that makes it inefficient.

-Crissa

 

[charliemagpie]

It is a problem nevertheless.

Most problems can be resolved eventually. Some take nothing more than a reboot. Some require redesign and ultimately recall.

I'm just noting people complaining about inadequacy in the R1T A/C and note that the first thing Sandy Munro said when he took the frunk tub out of one was that the compressor looked very small. It seems these BEV use as small a compressor as they think they can get away with to save Wh thus extending range.

The fact that it looks very small doesn't mean it's not capable of adequately cooling a car. It is an incorrect summation. From something as simple as that, legs grow and threads are made that Tesla can't cool its cars. And here we are.

 

[ajdelange]

I was responding to @JBee who acted like weak A/C's were common in EV's to save electricity. I have no knowledge...

But he does and that's why he made the very reasonable suggestion, as have I, that the Tesla (and maybe Rivian too) made the design trade of using a smaller capacity air compressor than one that would cover 99.9999% of loads.

...of whether the Rivian A/C is actually weak

How do you define weak? I think your problem here stems from naivete about how engineers size equipment against requirements. You cannot say weather an A/C system is "weak" or not until you define what "weak" and "strong" mean. For example in housing codes a landlord might be required to maintain 80° whenever it is 95° or less outdoors with a humidity of less than X %.

or if people are simply trying to discourage EV adoption,

Hey, I'm sure that's it!

...but I can tell you that modern Tesla do not have weak A/C, quite the opposite.

No you can't because you haven't defined what weak means. In your naive way of thinking it's not weak because you have never observed it to be so. But have you driven it in Death Valley in mid summer and found it adequate? Or out where JBee lives where it's even hotter and found it adequate?

Actually I was referring to the posts like this one...

I live in L.A. and had to drive out the valley today. It was warm today. That said - I'm not sure my air conditioning is working correctly. Yeah, it blows cold air but just not enough. If the car is hot - hotter inside than out - I put all the windows down to get a quick, fresh cool air reboot for a minute. But today it never really got cool enough in the car. Not sure if this is my car or if others in warm climate are having the same experience.

...that I used to see quite frequently when I checked the Tesla forums and just noted that I'm starting to see them on the Rivian forum now too.

The idea that any EV manufacturer would undersize the A/C system to save electricity exposes a lack of knowledge

You are displaying a lack of knowledge about how design tradeoffs are done.

because the cooling system will be more efficient if it is oversized.

Now that's a good one.

Using variable speed brushless motors and running them at a lower speed[/QUOTE]Now I love HVAC systems using VFD AC motors and sang their praises in No. 56 but I have never, in 60 years of engineering experiencencountered a system in which putting in a bigger machine and running it at reduced capacity increased its efficiency. VFD compressors are a new thing to me, however, and perhaps they are the exception.

In any case, if it is discovered that the current A/C design does not span a wide enough portion of the load space (evidenced by too many complaints about A/C performance that do in fact turn out to be cased on insufficient capacity) then the only option to reducing this "weak" performance is to increase capacity and run at fraction capacity for the majority of the time. This, of course, decreases system efficiency and increases overall consumption (Wh/mi) this decreasing range a bit. Depending on how much load space to be serviced is increased, the impact on range may be larger or smaller.

It is probable that Tesla has been through one or more design iterations of this type.

If your claim is that people are complaining about the A/C cooling capacity in Rivian's first vehicle,

I make no claim of any sort. I am simply observing that complaints about Rivian's A/C are starting to show u on their forum.

You can be confident the Cybertruck will have a powerful A/C system.

How do you define "powerfull"? Question is will it be powerfull enough for JBee? That's what he is worried about and his concern is certainly justified, Apparently Tesla did not hit it on the first go with the other models, Why would we think it would for the CT? PossibIle answer: they have more experience now than they did 8 years ago.

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