What stage is this?

What stage is this and how do I get out of it?

It is 108 degrees outside, I have been driving for 40+ minutes, the A/C is on "LO" (and Recirc) and the battery is showing 3/4ths full (~2 bars from green), then all of the sudden everytime I stop at a red light, the ICE runs sending the energy directly to the battery for about 10-20 seconds. If the light turns green and I just take my foot off the brake, the ICE kicks in and I am getting 2 MPG. Sunday it did this for about 20 minutes (until I got home). Luckily, yesterday I was close to home when it started happening. This phenomenon has just started happening the last two days....It is frustrating, on Sunday, I was at 57 MPG average for the tank when it started happening, by the time I got home my average MPG was at 56 (I have been able to recover since then back to 56.5 @ 400 miles on the tank so far).

Since I am mostly by myself in the car, I have all the vents in the front turned off except the ones in front of the driver seat. I find that I can feel more comfortable at a lower fan speed like this. Is this more efficient? When I start the car, I put the air conditioning on "M" let the hot air blow out of the system for about 3 min, and then gradually go down to "LO" as I feel more comfortable. I would say it takes about 20 minutes into my commute before I get it in "LO."

Thanks,
M

 

So to avoid this, should I cool the interior of my car more by either opening the passenger side vents, running the A/C at a higher fan speed, or both?

I did notice on Sunday that the battery fan in the back was running near the end of my drive. So the batteries are definitely getting hot, but I don't see why they ICE would need to run to cool down the batteries, especially since my batteries are almost in the green.

M

 

So if I am understanding the replies correctly, the ICE is running so that the A/C can operate off of the ICE instead of the batteries because the batteries are too hot to operate efficiently.

Since I am going to be filling up my tank today, I will run the next tank using the Auto setting at 80F for the whole tank and post how it affects my MPG. I will open the passenger side vents so that there is an even distribution of cool air.

The comparison won't tell me if running the A/C more is better than letting the battery heat up since the hot battery problem has only been on the last 70 miles of this tank, but it will help me quantify how much I am paying in MPG for a little more comfortable ride.

Bottom line, if I choose to keep running the A/C on "LO" and the battery problem only comes up on the last five minutes of my commute- will I do permanent damage to the batteries in the long run? I would think the answer is no because the ICE is running to prevent damage to the batteries.

Thank you for your help,
M

 

"It's just that you can improve overall efficiency by judiciously and appropriately using the AC."

That's the tricky part!

Thanks for everybody's responses. I just got back from the gas station, the tank came in at 54.1 MPG. I will post my results in about 3 weeks (the car is going to sit in the driveway for about a week during 4th of July week). We will see how A/C Auto in 108F weather will affect my gas mileage. If what seasalsa is saying is correct, I will be getting about the same gas mileage as I got in the dead of winter (50F ambient for the Phoenix area).

Thanks again,
M

 

Thanks Bob,

So it looks like the sweet spot for cabin temperature is somewhere between 80F and 90F (depending on your comfort level, of course). It looks like any cabin temp under 80F does not give you any benefit from a battery standpoint. Even on the 0C test, the batteries still got up to 50C, it doesn't look like the fan kicked in until the batteries reached 45C. The setpoint looks like an average battery temperature of 40-45C.

M