Refrigerated Cybertruck Frunk?

[JBee]

In cold weather, Tesla's use the waste heat from the computers and drive motors and inverters to warm the battery. If it's super frigid they will also use resistance to create additional warmth but it has to be pretty damn cold to need much of that. Even cars with heat pumps will use a bit of resistive heat in temps that cold.

I was asking about how it works when its warm outside not cold. Here in Australia warm is more dominant.

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[JBee]

Do you happen to know what the temperature delta is for battery and motor coolant? How cool do you need to keep batteries, is ambient cool enough when it is >100F outside? 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.

Ideal battery temperatures are 70-90 degrees F. Most of the heat produced by an EV is in the motors because they are only around 92% efficient. The batteries are over 99% efficient so, while they do produce a small amount of heat as they charge/discharge, it is a very small amount. When an ICE car idles it is 100% inefficient, ie, all the energy produced is wasted (except the small amount used to turn the compressor and alternator) and that energy manifests as heat that soaks the cabin and A/C system. In traffic this extreme heat can even backdraft right into the condenser that relies upon a flow of cooler ambient air to cool the cabin.

All this talk of heat blowing on the frunk is misguided. That's what insulation is for. True, you don't want to put ice directly in the uninsulated frunk liner unless you don't care if it rapidly melts. But that's what insulation is for. And a Tesla has much less waste heat than a Rivian because they are more efficient. I get very long life out of the ice packs I put in my frunk soft cooler. Over two days on a high speed trip to Montana through hot deserts and over multiple mountain ranges at high speeds in the late summer. The area surrounding my soft cooler was always cold when I would open the frunk because it was lined with a single thin layer of bubble/foil insulation.

Sorry that question was meant to be addressed to @ajdelange.

I'm trying to understand what makes up the heat in a Tesla/EV and which parts are temperature sensitive if its operated in ambient temperatures that are high.

 

[HaulingAss]

Dude whats the inlet air temperature difference between a condenser on a ICE and a EV?

The air inlet temperature on an ICE and EV is identical, assuming they are moving through the same air. I shouldn't have to tell you that. Of course, in isolation, that cannot define system performance without considering all relevant factors.

 

[HaulingAss]

I was asking about how it works when its warm outside not cold. Here in Australia warm is more dominant.

Obviously, in hot weather the system reverses and the cooling system is used to remove heat from the battery and motors. It caan do this passively (without the compressor) in milder conditions or actively (using the compressor) under more demanding conditions.

What gives EV's such a large edge over ICE when it comes to cooling in hot weather, and why they don't need a large front grill or huge radiator, is simply because they generate so little heat to begin with.

I'm having trouble understanding what it is you are having trouble understanding. This is all pretty basic stuff.

 

[ajdelange]

It's not technical FUD. Heat soaking the A/C components drastically reduces the amount of cooling that can be supplied to the cabin

This isn't really FUD as there is no Fear or Doubt nor Uncertaity. It's dead wrong. Rather than get technical (which wouldn't be understood anyway) I'll step back and look at the forest rather than the trees. If this were true would someone put the compressor (and all other components except the evaporator which, obviously, has to be in the cooled space) on the roof of a building in Bangkok rather than inside to protect it from this soaking?

 

[HaulingAss]

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.

Tesla uses a variable speed brushless dc motor for the cooling system. Like the motors that drive the wheels, they are small but very powerful for their size. I have no knowledge of the Rivian system but they are still learning and have very high cost of production so maybe they are trying to lower their bill of material costs.

When Tesla introduced Track Mode in the Model 3 they included the capability to overdrive the compressor for additional cooling capacity. That is very illustrative of just how versatile these electric compressors are in actual application.

 

[ajdelange]

The air inlet temperature on an ICE and EV is identical, assuming they are moving through the same air.

And this is where you reveal that you really don't understand how refrigeration systems work. It is the temperature of the condenser that determines head pressure and thus load (and efficiency) on the system. The compressor can be hot as hell (up to a point well beyond what is encountered in an ICE engine compartment) and that leaves the TXV and evaporator which obviously are inside. The gas going through the compressor goes through it so fast that the compression is considered isentropic.

 

[HaulingAss]

This isn't really FUD as there is no Fear or Doubt nor Uncertaity. It's dead wrong. Rather than get technical (which wouldn't be understood anyway) I'll step back and look at the forest rather than the trees. If this were true would someone put the compressor (and all other components except the evaporator which, obviously, has to be in the cooled space) on the roof of a building in Bangkok rather than inside to protect it from this soaking?

It's not dead wrong but your understanding of the conversation is.

Backing out by claiming you would explain why but it would fly over our heads is simply weaseling out of the actual truth of the matter. But that's what I have learned to expect from you.

 

[ajdelange]

Tesla uses a variable speed brushless dc motor for the cooling system. Like the motors that drive the wheels, they are small but very powerful for their size.

Probably not as that technology is pretty old being used mostly in applications like computer fans. I don't know that the compressor motors use the full up vector space control that the traction motors do but I wouldn't be too surprised,

 

[ajdelange]

Backing out by claiming you would explain why but it would fly over our heads is simply weaseling out of the actual truth of the matter. But that's what I have learned to expect from you.

It turns out I did wind up explaining it in the post just before the one you quoted. But explaining it in very simple terms should help people with limited understanding of technology to grasp the concept.

 

[JBee]

The air inlet temperature on an ICE and EV is identical, assuming they are moving through the same air. I shouldn't have to tell you that. Of course, in isolation, that cannot define system performance without considering all relevant factors.

Cool cool ?

I'm not trying to be provocative, or am I, I can tell anymore...anyways, engineering typically involves a whole bunch of work to make things work, (aha wow right? ) and I don't think anyone will think that engineers of a ICE are in any way inferior to a EV engineer.

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

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.

 

[Throwcomputer]

It is a problem nevertheless.

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

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.

 

[HaulingAss]

It turns out I did wind up explaining it in the post just before the one you quoted. But explaining it in very simple terms should help people with limited understanding of technology to grasp the concept.

Haha! That's the post where you demonstrate you don't understand what it is that is being discussed. As usual, you like to go off on tangents that are not particularly relevant to the discussion at hand (as if this will leave us in awe of your supposed knowledge).

 

[ajdelange]

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

And I really think it is an issue that requires more than just a reboot. I really think that it is what two of us have mentioned: an attempt to use a compressor that is not "big" enough for that 99th percentile load in order to extend range.

 

[ED_SFO]

?. Suppose the engine stalls and shuts off without any warning? Your dog would be cooked.?

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.

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