F-f-f-fluke.....

Even with accelerators it still needs a few days (usually about a week) to harden to 80% strength, and it will never be quite as strong as it would be without an accelerator.

I think that’s part of the reason we don’t use concrete pavement more often. It certainly lasts a lot longer, but laying it is way more time consuming. Asphalt is ready to go within a day, just needs to cool off.

Asphalt is laid somewhere around 300F, so if it truly got twice as hot it would melt the road and everyone’s tires.

When it is that hot I bring a pack with water and also take my dog, and or myself, swimming on the runs.

Yes, and it cools stuff to cooler than the outside air, right?

It makes more sense if you read the context. They're responding to a comment that said this:

I guess you don't understand active cooling then. If the coolest air in front of you is ~160⁰F, well that's the coolest your batteries are gonna get, at best. Which is way hotter than rated temperatures for lithium batteries...

A response that says "it's not X" can be interpreted as "it's not doing the thing you said it's doing". In this case, over_clox is saying that heat transfers directly from the battery to the air.

Did you even read the link you sent us?

Max 60°C: Continuous high temperature use will accelerate battery aging and capacity decay. If the temperature exceeds 70°C, the risk of thermal runaway will increase dramatically.

Yes, that's exactly my point. 160⁰F = 71.11⁰C

So let's just ignore the fact that the battery generates its own heat on top of the road its cooking on at 71⁰C..

'This is fine' meme vibes here...

You're ignoring that the pavement being that temperature doesn't mean that the battery will be that temperature. There's a layer of air between the road and the car, as well as other physical barriers. The battery is also actively cooled.

Last I checked, my fridge works even when the room is warmer than the fridge.

Topdon. I had Flir before and like this much better. For one thing, they don't watermark my images.

Active cooling means practically nothing at those temperatures, any cooling system is just a heat transfer device, that also generates heat itself. It just moves the heat elsewhere.

So sure, it'll help cool the battery, but what power it takes for the battery to cool itself comes from the battery itself, thereby heating it up even more as it fights to cool itself.

You don't know what the fuck you're talking about.

Active cooling means practically nothing at those temperatures,

What temperatures? The 71°C of the pavement? As I said, there's air and physical barriers that keep that temperature from reaching the battery.

any cooling system is just a heat transfer device, that also generates heat itself. It just moves the heat elsewhere.

Yeah. That's the whole point. It moves the heat from the battery to the outside air, keeping the battery from reaching that 70°C number you're worried about. Which, while I'm at it, is a change from the earlier 40°C number you claimed is a problem.

So sure, it'll help cool the battery, but what power it takes for the battery to cool itself comes from the battery itself, thereby heating it up even more as it fights to cool itself.

Are you fucking serious? Think for a moment. Do you really think that the cooling system, by drawing power from the battery, heats the battery up more than it cools it? That's ridiculous.

I bet you're fun to have a conversation with.

Used to be a paver and I can confirm that shit is HOT, only gets worse once you hit it with water. The steam will give you blisters as you work it

Depends on the type of cooling, but even the less efficient cooling systems will be using a tiny fraction of the battery output, like less than 1% for most. Passively cooled batteries are going to have problems for sure but even then I'm not convinced there would be enough heat transfer for long enough from a 70 degree road surface to actually be a serious problem. The road itself would be cooling and unless you're just sitting over it for a long time it's not likely to become a real problem. A somewhat pessimistic (for volume, not for actual capacity) estimate would be 300kg of battery mass for 100kwh. Assuming middle range lithium ion thermal capacity that's about 300kj per degree k. So for maths convenience let's assume the car is 10m^2 on the underside and that's all in contact with the battery, going by the previous estimates (again, worst case for battery overhead purposes) and assuming the air is moving and already preheated to 70 degrees c it would take around 5 minutes to heat the whole battery to 70. Thanks for the maths problem though, was interesting to look into this stuff, I've made some big assumptions but it's looking very unlikely you're realistically going to have big issues with overheating unless you spend an inordinate time with an EV sitting over hot asphalt, I didn't consider radiative heat transfer but I wouldn't think that would make a huge difference given the albedo of asphalt also the ambient air would probably help cool more than I considered. It would be neat if someone with more knowledge on the equations has input though.

Compressor heats up coolant, coolant exchanges heat with outside, cools down then evaporator cools it further, heat exchanges with cold loop then goes to be compressed again. It's the same principle that freezers and ac use, with the phase changes of the coolant you force them to move thermal energy in the desired direction.

There exists stop signs, red lights, traffic, and trains..

Never assume you won't be parked for more than 5 minutes...

Ofc but I made some big assumptions with regards to ambient temperature, battery mass and lack of functional cooling. 5 minutes is absolute worst case with 70 degree ambient air.

Air only flows significantly when you're driving. Have you ever heard of stop signs, red lights, traffic, and trains? You assume the vehicle is always in motion, which isn't always the case.

The better option would have been if the road crew didn't open the road to traffic until the asphalt cooled closer to regular road temperatures.

Also, look up Peltier cooling, even those generate heat from the power source. So even then, the battery is using energy to cool itself, thereby using more energy and warming itself while delivering energy to cool itself. Catch 22, at those temps, the battery is fighting itself.

Only 5 minutes? Our trains have us parked for like 20 minutes, I posted about this a few weeks ago.

Oh, I should also add, that I have real world experience working with hot asphalt. That shit indeed will melt your tires and other plastic parts on your vehicle, such as mirror shells, and also burn the paint off your vehicle.

Yes, I have experience. Yes, I know what the fuck I'm talking about.

By your logic, home air conditioning can't work because the condenser is stationary.

A quick lesson on logical reasoning:

If you want to show that a piece of technology A is inefficient and you know that another piece of tech B is more efficient, then you can use the inefficiency of B as evidence for the inefficiencies of A. Basically, for some inefficiency threshold T where any value above T is poor efficiency, then A>B and B>T means that A>T.

Here, we're comparing vapour-compression (A) and solid state (B) heat pumps. Solid states are much more inefficient. So you have AT. You can't use this to make any claims about the relationship between A and T.

what is this in normal units

If the ambient temperature is 71⁰C, then no, air conditioning will not work, at least not sufficiently to sustain life or protect batteries.

Fuck, you do realize that 71⁰C is enough to melt your shoes to the pavement right?

We're talking about an edge case here, there should never be a vehicle driving over roads that fucking hot. The road crew should have never opened the road for driving until it cooled down closer to 120⁰F or so, 160⁰F is still too fucking hot.

Which is a fair claim to make. I don't know why you went with "EV batteries aren’t safe over 40⁰C", which is clearly False based on the source you cited, then went on a whole roundabout talking about how it's not safe at 45C, then 70C, then how active cooling is inefficient while citing the efficiency of Peltier devices. Your top-level comment was fine. Nothing else you said after that made any sense.

My bad, I meant 50⁰C, when it starts to become a concern. My bad, typo, road trip be bumpy yo.

7 beansontoast

Almost 74C!

i gave only the basics. From those I could explain the pattern or someone could think about it very hard and understand how the pattern is created.

Oof you are very sure of yourself.

Regarding the asphalt:
If there is a delta in energy level in matter then it will even our until an equilibrium is reached.

How could this apply here?
When a car tire rolls over the fresh asphalt it wouldn't rest a long time in one spot but it would definitely absorb some energy during contact. Since it is rotating and contacting the road it is reasonable to assume that there is would be a decent amount of heat transfer. Wind or air cooling of the tire doesn't seem like a significant factor here. But that doesn't really matter here anyways.

A long stretch of hot asphalt gives us a equally long distance of a tire surface area contacting the ground.

This gives us some heat transfer from the road into the tires.

The car drives in and takes the heat with it.

Many cars equals a decent amount of heat.

That could explain the pattern.

It is smart to think about alternatives to your own opinion when you don't know all the facts.

Did I think about it very hard enough?

Why would you want to think about it that much ?
There is a lot of heat escaping from the truck while it is waiting to be dumped and this creates temperature gradient inside the load.
I didn't have to think about it that much because I worked for many years in asphalt surveillance.
Normally we don't use infrared cameras but we do have infrared heat guns and much more sophisticated devices.

Well, 0 is arbitrary in Celsius and especially Farenheit, so doubling that temperature isn't really doubling the heat.

Kelvin has its scale actually designed around how heat energy works. 160F is 344K. Double that and you've got 688K. Convert that back to stupid-units and you have 779°F

I think I did that right, at least. If nothing else it shows how whacky temperature math can be when doubling units gets wildly different results!

Hey, hey, that’s freedom-units to you.

That said, the difference in scales when it comes to doubling is something I never really considered. Very informative!

If you think about it very hard you can figure it out

Don't think about it so hard

Make up your mind. Either you are a socially inept person, a kid, a troll or all of the above.

Bye.

I don't think the UK gets to be part of the "normal units" gang with this hodgepodge they have going on