Question about heat

Well, the AC certainly has an effect. I wonder if tyre friction increases as the rubber gets hotter. That may have some impact. Also, I think the battery is less efficient when it's really hot. Still, it's really hard to say. Tracking all of the variables isn't possible and you're talking about a pretty small change in MPG. The sample set is too small I would think. Now if you're mileage had dropped by 10 MPG or more I think it'd be time to start looking at the possible causes. I wouldn't worry about it unless your mileage continues to drop.

 

I agree with Tripp. That is really too small a drop to be really significant. Here in Silver Spring the Outside Temperature read 111 degrees today when I got into the car! Of course it was sitting in the sun. When the air conditioning is on full blast the hybrid battery goes down pretty fast when you are sitting at stop lights but also recovers quickly when you are moving. So, the ICE does have to run longer when you are driving to help the battery recover SOC. There is probably a small mileage drop but when the outside temperature is that hot I'll live with it for the A/C.

<div class='quotetop'>QUOTE(efusco @ Jul 17 2006, 08:42 PM) [snapback]287840[/snapback]</div>

Doctor, I have never heard my battery fan come on, even when it is 99 outside. You think maybe the sound of the A/C fan blasting away covers up the battery fan, or is the battery fan really loud?

marjam

 

Over the weekend it was very hot, nearly 100. It was the second time I heard the fan go on. It stayed on for quite a while this time. I probably should have given the car a break but I had the AC on and drove up a hill. The battery stayed in the pink/purple 2 bar range and you could feel the car working hard. It recovered when we got to flatter surface and the climate equzlized more but it really kknocked my mileage down. I'm definitely going to try to park her in the shade as much as I can!

 

It was 105 today. The heat index is higher. On the way home I could here the tar from the roads being peeled away from the tires like it was bubble gum. Makes you wonder about the drag on the car from this. But, my mileage - at the moment - is better than it ever has been I've made 4 round trips to and from work and the MFD is showing a little over 61mpg. I only live 10 miles from work and when I leave work I go to the gym which is 2 miles. The short trips can't help due to ICE warmup energy.

 

When the battery gets too hot the car may protect it by using it less. Less use of the battery means the car is closer to a conventional car, and will get less mpg. A/C draws power, lowering the mpg, but it's the cooled air in the cab that is used to cool the battery, so refraining from using A/C could be counter-productive. Bottom line is extreme heat and extreme cold are both bad for mpg. That's the price we pay for living in the real world.

 

It's been hot here for a while now (95-104 degrees). My MPG (52-54 MPG) has not been effected at all, except for the occasional AC use.

When using the AC just make sure to use the Recirculation mode, as it is much more efficient to cool the already cool air inside your car rather then try to cool the hot air outside the car.

There are just too many variables when you are only talking about 2 MPG. You need to run a few more tanks to see the real results.

As far as the gas "pips", there his been a lot of discussion about the differences in these from car to car. You just have to get used to what your car does. My tank has never taken more then 10.1 gallons, even when that last pip is flashing. Normally, I get around 300 miles for the first half of the tank, and then around 230-240 more before I fill up again (within around 25 miles of when that last pip flashes). Although, some have reported running out of gas within a few miles of that last flashing pip, so be careful not to push it too far if you are not right near a gas station.

 

I went home the back route last night. At around 100 degrees here. Got my worst mpg of the summer at 38 mpg.
All due to AC. When it is hot it really helps to go faster, but the highway was having a traffic jam.

Noted my hybrid battery was at around 120 deg. or more.
AC ran on high till I was about 1 mile from home.

 

Another trick, if you can't park in shade, when you come back to the
car just open up ALL the doors and let all that hot accumulated air
escape. You can reach in and fire up to IG-ON and drop all the
windows, too. Let it sit that way for a bit. That way the A/C
only has to work against ambient, not all the extra heat, except
what's still retained in the seats and the dash plastic [if you
forgot to use your windshield shade]...
.
_H*

 

<div class='quotetop'>QUOTE(TonyPSchaefer @ Jul 18 2006, 08:24 AM) [snapback]288088[/snapback]</div>

Hmmm... that may not be your car.

 

I am experiencing 10mpg worse than usual. Normal 46 mpg, now that the heat is over 100 degrees, I get about 36 mpg. AC is set at 78. I often hear the battery fan running.

The hit in mileage percentage-wise is greater than any car I have owned. But it is still very good.

 

I just finished a weekend trip from Denver to Steamboat with a full car and temps from the low to high ninetys depending on my elevation. My MPG when I pulled back into town was at 49MPG. I'm happy with that. The Battery fan did come on about 4 or 5 times during the trip. It doesn't really come on that often in normal driving so my theory is that with a trunk full of stuff, the heat from the battery can't escape as easy and the fan is needed more.

From 5280 ft to almost 7000 ft with a couple hills that reach to almost 10,000 ft. Going up the engine works hard but coming down, it's all green.

Matt
Denver

 

<_< Dallas temps have been 0ver 100°F for the last week or so. My MPGs have dropped perhaps 2 MPG with constant use of the AC system. I can only park partially in the sun when working, so the temp at the Prius reads about 3° higher than the OAT until I drive about 5 miles by which time the AC system has substantially reduced the interior air temp. During the first mile or so, the traction (main) battery shows two purple bars but gets back to "blue normal" in about 3 miles or less.

Terrific AC system in my opinion... as is the rest of the Prius at 20,.000 miles on the clock.

 

<div class='quotetop'>QUOTE(TonyPSchaefer @ Jul 18 2006, 06:24 AM) [snapback]288088[/snapback]</div>

<div class='quotetop'>QUOTE(M. Oiseau @ Jul 18 2006, 06:41 AM) [snapback]288095[/snapback]</div>

yeah....considering the avatar I have wonder about the true source of the odor!

 

Here in Fla. temps have been 95 and above for the last month. 75 in the morning on the way to work (5am) 51-53 mpg. Afternoon above 95 same roads 44-46 mpg. In May when I first got the car it was 51-54 both ways. A/C is on but there is no difference in the afternoon with it off except the driver could go postal with no air. But even with the lower mpg it still beats the REAL MAN at work with his hummer. What an nice person. Told me couldnt take vacation this year because of the high gas prices. :blink: :blink: :blink: