Controlling/Monitoring battery temperature.

<div class='quotetop'>QUOTE(Malarkey @ Jul 25 2007, 07:59 PM) [snapback]485225[/snapback]</div>

Interresting question! I have often wondered myself if I am shooting myself in the foot by not running my Air Conditioning to save feul as I sit there sweating in stop and go traffic. I have not heard the battery fan coming on, but I listen to the radio, and the windows are down, so I don't know if I would hear it. I guess it would be a great experiment to buy a Radio Shack remote temperature sensor and maybe an idiot light that comes on when the battery cooling fan comes on and gather some data.

What will make this hard is all the other variables. Here in Portland area, one day is 85 and the next is 60. Traffic is stop and go one day, and slow and go the next.

 

I'm hoping that hypermilers around here will correct me if I'm wrong, but it is my understanding that hypermilers attempt to use the battery as little as possible, so they aren't likely to get a significant benifit from carefully controlling the battery temperature.

Driving with the windows down at any speed above a crawl will certainly reduce your MPG. If you enjoy driving with the windows down, then simply accept the reduced efficiency as the cost of the pleasure. On the other hand, if you are sweating, and keeping the windows down in an attempt to improve MPG, you are probably making a mistake, especially after the 2004 model year.

I wouldn't think that cooling off the batteries with the A/C would make a huge difference in your MPG unless you have driving conditions that require extensive use of the battery (regen, stealth, etc). However I'd expect that reducing the aerodynamic drag by putting up the windows would have a noticable affect.

 

Yaah, this is what I have been wondering. I have no doubt that cruzing along at 35 or more MPH, that using the very efficeint Prius electrically driven AC would be much better than adding the drag of the open windows, but I have heard some say that in stop and go type traffic conditions, the AC really hurts the MPG. And when I am alternating between 0-15 MPH, that is when I think the open windows are better.

<div class='quotetop'>QUOTE(Danny Hamilton @ Jul 25 2007, 08:33 PM) [snapback]485244[/snapback]</div>

 

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<div class='quotetop'>QUOTE(NoMoShocks @ Jul 25 2007, 10:19 PM) [snapback]485236[/snapback]</div>

You indeed might not hear the battery fan straining to keep the system cool under those conditions, and there's a good chance that you *are* reducing your battery system efficiency. There's a reason why the battery gets its cooling air from the cabin and not directly from the outside.

 

The car will use fuel to keep the cat warm when in "ready". The engine must also be kept warm, but the cat requirement, in my experience, keeps the engine warm. Probably will run for 30 sec. every 10 min. or so to keep the cat up to temp. though I haven't tested this myself. I would expect the A/C would be first in fuel use requirement, then cat, then engine.

 

Well, I am convinced to start enjoying my AC, but I think I will follow the plan of cycling it on and off myself. To be honest, I have not figured out all the conditions that will cause the AC to go to Auto mode on its own. I know hitting defrost will do this, but I think there are others, perhaps tied to specific days of the week or cycles of the moon. Like I said, have not figured it out, other than to keep checking to make sure it hasn't set itself to Auto on its own.

It is just So Hard to be near the 50 MPG threashold, and I would imagine being at the 60 MPG threshold is worse that 50. Why is it that 49.9 can make you feel so blue, while 50.5 begins to make you feel elated. I have been taught this works in the stock market. Stocks will rise to 49.90 and then stall for a while before the pop out of it and spring past 50 to 52.

Right now, my average is about 51.8. Today, I got 58.7, but I have a confession. I an not apposed to reseting the computer mid tank if it somehow gets below 50. And what's worse, "You put Nala in danger!" No, I mean, what's worse, I reset it after my five minute warm up, so the 58.7 is not a real average. My game is to see if I can keep it in the 50s for for or five days.

Todays trick, I am going to try a surface street route home, but I do worry a little that this is not as safe. In five years of driving across town on surface streets vs. five years of commuting on the Interstates, there is a much higher probability of getting into a fender bender on the surface streets.

 

<div class='quotetop'>QUOTE(catgic @ Jul 26 2007, 05:32 AM) [snapback]485321[/snapback]</div>

Actually quite the opposite. The '04-'07 Prius has an initial warm-up cycle of 57 seconds where you are running almost all on the battery unless you accelerate and make power demands that exceed the battery alone, then both work together. After the first stage is complete, the battery will always be available and used when the hybrid ECU decides to do so. Perhaps you are confusing the Classic Prius warm-up cycle which can be as long as 5-8 minutes because of the HC adsorber.

Wayne