Article on cabin temperature (and traction battery temperature) when parked

http://www.racq.com.au/__data/assets/pdf_file/0007/48796/09_Temperature_in_Cars.pdf

interesting...there's no temperature difference in tinted and non tinted windows.

Interesting that car color did not make that much of a difference.

Here is how I read it. Tint slows down heat transfer. But utimately it reaches the equilibrium and the inside of the car gets to the same temperature. Tint is useful for driving, to reduce the heat influx, and reduce the load on the AC (better MPG), but does not do much for a parked car, if you leave it parked long enough.

I agree that this has got to be wrong. At this moment, the cabin temperature for our blue ribbon and gold Prii, sitting next to each other in our driveway, is 20 degrees different.

This is an incomplete study, beware of jumping to conclusions.

1. Air cabin temps were measured, but not heat accumulation
2. Windows were closed in all the tests except one.

How I read it is the dark tint actually absorbs heat and then radiates it into the vehicle. Air moving across the outside of the glass would have little effect compared to the air inside. Given the sunscreen test, reflective coating would seem to have no effect. Since the cooldown test seems to show that the tinted vehicle stays hot longer, higher mpg with tint seems unlikely(according to this test).

interesting, the test was done with coolers, not actual car interiors that might retain heat....

The 'glass sitting on cooler' test seemed the most debatable to me. I thought they measured the temperature on the ambient side of the glass. Finding that the glass heats up, and heats up more when tinted, is not surprising. The unanswered question is how much radiation passed into the cooler interior.

I would have liked to see a test of a white tinted car with a sunshade and windows down, compared to a dark car without tint or sunshade, and windows up. Is that too much to ask ?

In any case, we should remember this testing was only of cabin air temperature, not total heat accumulation.

I am usually very careful to put up a sunshade, but I forgot the other day. The car seat was too hot to sit on wearing shorts, and the steering wheel too hot to hold bare handed. I'm unlikely to forget again anytime soon.

No, you can see that the temp sensor in the tint test is mounted in the center of the cooler.

i wish there was a cabin temp sensor, i'm often curious as to the temp and if it's too hot for the battery.

I would say there would have to be a cabimn temp sensor for the HVAC system. It's just a matter of trying to access it's reading. Maybe through Scanguage.

Do your to Prii have the same interior color? Or is one dark and one light?

P.S. I didn't say I thought it was wrong. Just interesting. There's not really enough data.

I am using my ScanGuage to display cabin temp in my Prius v (wagon), but it should work on a Gen III too.

ScanGuage code can be found here: https://spreadsheets.google.com/spreadsheet/lv?key=0AiHL0r_2nhUEdF9lVVBxOVNoN3Zva3E0NmdZTUR1eVE&hl=en
See line 85

One thing that's worth keeping in mind with respect to the window tinting is that they're graded based on transmission of visible light. That only amounts to 45% of the total power from the sun. While one would hope that a tint manufacturer would design their product to block or reflect even higher amounts in the UV and IR regions of the spectrum, that's by no means guaranteed, unless the manufacturer advertises it. Given that you can't tell if a tint blocks IR or UV just by looking at it, I imagine there are plenty of manufacturers who have decided it's not worth the extra effort to do so...

Uh, I think it's time to rename this thread. There is NO correlation or data on "traction battery temperature".

Somebody leaping to conclusions?

Ergonomic mode
I have one of those reflective sunshades. It does keep the dashboard cooler which is important to me since I have two ScangaugeIIs sitting on top of the dashboard that I want to keep a tad cooler (to extend their lifespan). Since the Prius interior plastic is not padded vinyl - I'm not worried to much about the UV rays destroying the interior plastics (I've seen this happen on a Ford Fairlane) but I am concern about the UV rays fading the upholstery on the seats so this summer I'm covering the seats with a bed sheet when the Prius is parked in the sun for an extended time period. When I get a chance - I'm planning to tint the windows so I wont have to do this. Given how the reflective sunshade gets really hot after reflecting the sun off the dashboard, I'm not surprised either that the tinted glass absorbs a significant amount of UV heat. The other reason I want to get a tad more tinting is so I don't have to wear as much sunscreen. Hypermiling exposes the driver to more sunlight for longer periods of time - so I regularly put on Broad Spectrum Sunscreen when driving. It would be nice if I didn't have to do this all the time.

Scientific Mode
All the reports that I've seen says that regardless of color or window tinting that all vehicles eventually get equally as hot over time. Lighter colors and reflective window tinting can slow down the process of heat absorption but eventually the Second Law of Thermodynamics wins out ( Isolated systems spontaneously evolve towards thermal equilibrium -- the state of maximum entropy of the system -- in a process known as "thermalization"). However, from what I understand - the shell of a car (which has a higher mass density) and not its passenger cabin is holding most of the heat. Luckily when the car is moving the shell of the vehicle conducts/emits a great deal of this heat off.

Engineer Mode
The warmer temperature is a good thing for the ICE since the warmup penality is reduced.
However, hot temperatures are a very bad thing for the 110 pound NiMH battery in the rear.
The NiMh battery is air cooled and it draws its air from the passenger cabin - the ability to keep the HV battery from getting too hot is very important factor in extending its lifespan and reliability. When driving for an extended time period, I'm guessing that keeping the Prius' interior cabin temperature under 85 F degrees will help extend the HV battery's lifespan.

Commentary Mode
The study methodology is flawed - given the Second Law of Thermodynamics the data wrt to the cabin air and its basic conclusions are predictable and thus the study provides no new insight. More interesting study would have focus on the delta surface heat of each interior item via a non-contact laser thermometer.

I don't understand why. Could you elaborate?

You simply spend more time behind the wheel because one of the fundamental sprinciples of hypermiling is driving slower.

Ah. Got it. The assumption being that otherwise you would drive faster. I've never been a fast driver, so that's why I didn't get it. Thanks.

No problem.