FE With The A/C

GaryG · #1 06-06-2006, 08:58 AM

Now that summer is here, the A/C is not an option after 11:30am here in So.FL. It would be nice if we all could put our heads together for the most FE possible while running the A/C. Since last year, I’ve learn a bit on how to push the FEH for mileage that I never thought possible, so my mileage should be much better with the A/C this summer.

The High Voltage (HV) Battery has now began to run the A/C compressor while ICE ON, so cabin A/C might as well run also. For the FEH, the ideal battery temp is 82F, the desired range is 77F - 100F and the trouble code range is below -40F and above 135F according to the shop manual. So like it or not, the compressor is coming on if the FEH is sitting in the sun for long and the temp is above the 82F range when the ICE is running. GPSman said the A/C runs at 92F and above, but I’ve notice condensation near the drivers side rear wheel at lower temps. Also, he says the ICE will start to run the compressor for cooling the HV battery, but I have not had that happen. Anyone that can confirm this either way, help us out here.

The tricks to hypermiling with the A/C should apply to all makes and models, so I think this thread should be in the general information forum.

This past week, I did some drafting between 55-60mph with short P&G behind this truck that was as tall as it was long. During the pulse back to a good draft, I was accelerating at around 28mpg and gliding in neutral at ~120mpg with the A/C on. This helped by average, but without the draft, I was averaging around 35-39mpg depending on my speed in a 70mph limit. It’s nice to go slow behind someone else for a change.

Around town, I was able to go EV with normal recirculating A/C and stay in the ~45mpg tank average, but it’s getting hotter every day. After parking for awhile, I would put the windows down till most of the build up heat cooled off. BTW, I would crack the windows while it was sitting. Planning on a trip to get my front windows tinted real soon.

Lets have some feedback on improving mileage with the A/C running. Tell us what you know!

GaryG

tbaleno · #2 06-06-2006, 09:46 AM

Don't forget to park in the shade.

Chuck · #3 06-06-2006, 10:15 AM

Between this Feb and the start of June, I was without A/C. Turns out it was a rat this winter that was nibbiling on my bird feed, then the A/C cable.

Turns out that parking under the shade at work and the garage at home was enough to cope with the Texas heat. Keep in mind that although some days were 95F, it will stay that warm longer and get past 100F

Since my workplace allows a golf shirt, it worked. Would not have held out this long if a shirt and tie was required.

I often toggle the A/C like it was the brakes.

tarabell · #4 06-06-2006, 10:55 AM

Quote:

Don't forget to park in the shade.

I second that, as a blinding hot parked car requires so much extra cooling -- the seats etc before the driver feels comfortable.

I haven't really used the A/C much to see what effect it has on FE. But have tried it once or twice, dialing the desired temp up to the high '70s and found that seemed to cool me off well enough in 5 minutes. Then I turned the compressor off and drove the rest of the way with just fan blowing on my face, outside vent closed and windows rolled up, so recirculating the cooled air long as possible.

But didn't like that the next day A/C AND FAN were both OFF, and the vent is expelling rather unpleasant warmish air. So I had to turn it on, dial the temp back down to the '60s and turn everything off again to have things back to normal.

Texashchman · #5 06-06-2006, 04:04 PM

Trouble is for like me the parking lot has NO trees or covers, uggh. kevin

GaryG · #6 06-07-2006, 05:01 PM

John, I should have said battery temp instead of refering to outside temp. Today, the ICE took awhile to shut down, and it appears to be because of the battery A/C running. I still am looking for a ICE start because of battery temp though.

From a cold start this morning till I reached my 20 mile commute, I averaged a little over 49mpg. Not sure how much the battery A/C ran, but that was with no cabin A/C. The return trip was hotter, and my average was 47-48mpg when I noticed the ICE not shutting down two times with all my tricks. It took about one minute of idle at a stop to shut down.

GaryG

VietVet'67 · #7 06-07-2006, 09:07 PM

Quote:

Originally Posted by GaryG

Today, the ICE took awhile to shut down, and it appears to be because of the battery A/C running. I still am looking for a ICE start because of battery temp though.

I noticed the ICE not shutting down two times with all my tricks. It took about one minute of idle at a stop to shut down.

GaryG

To be honest with all of you – I have not noticed, with the AC running, that the ICE runs any more than normal. What I have noticed is the rear battery powered AC coming on while I am in EV or while the ICE is completely shut down. I guess since on the FEH the auxiliary battery AC unit must be powered by the battery (don’t know if it is the 12V or 330V) it does run for a while after shut-down – at least until I open the door and shut the system down. This afternoon I noticed that it came on when I turned the key on (not starting it yet). I got out to make sure it was the rear AC and was correct. Guess it takes the coolant and cools the battery – ICE on or not. At first I thought the noise was coming from say an electric radiator cooling fan.

I’m with Gary on the not seeing the ICE come on for battery cooling. As said – if that is going to be the case, might as well just cut the thing on and keep me cool also. I see the coolant lines coming from the front and have noticed one line to be cooler, so that had to have come from the front AC unit (which is run off the ICE). So I guess the AC could have come on while in one of my short stints of the ICE running – but then the battery powered rear unit would have to be running the rest of the time. Think about it – if it is used to cool the battery during charging (heat build-up) and the main AC had to do all the work then the ICE would never shut down, but it does and the other takes over. I would also think that as long as that unit can do the job that is all that is necessary to keep the battery cool.

Don’t know if any of this makes sense but at least it is a shot in the dark.

VietVet'67 · #8 06-08-2006, 09:51 AM

Update –

OK this morning on my way to work I decided to see if I could tell if the A/C came on and ran - even though I had not turned it on.

When I parked at work I popped the hood and sure enough the high-pressure side coming out of the ICE A/C was cool and had condensation on it. Went to the rear to check the high-pressure line coming from the front to the auxiliary battery air conditioning cooling module - same thing.

So at some point the ICE A/C DID come on to assist in cooling the battery. So I guess our deduction that we might as well cool the cabin – and us – as long as the ICE A/C is going to be coming on anyway is correct. The MPG is going to take a hit anyway you go.

So I guess we are caught between a rock and a hard place.

In the winter we have to wait till all things heat-up to a point where we can go to EV and even then the ICE A/C also comes on to keep HV battery at its optimum temp.

In Summer, generally, it is going to be to hot for the HV battery – so keeping the cabin cool should keep the temp down and help the auxiliary unit. . If I am correct, and from other post, even parking in the shade with the outside temp over 77°F (the desired range is 77F - 100F), the A/C will turn on no matter what.

Wonder if taking off the carpet cover and letting the cool cabin air be in direct contact with the metal HV enclosure would help? The cover could be acting as a blanket and interrupting the dissipation of heat.

GaryG · #9 06-08-2006, 10:28 AM

Hey Phillip

Looking in the manual, the TBCM can send a message to the PCM to enable the A/C compressor. At what temp of the battery, if any, can the PCM start the ICE from EV mode to cool the battery is the question. There is no question that the PCM will never start the ICE in the Key-OFF position. My thinking is, if the battery temp is controlling the A/C compressor during ICE-ON because the outside temp will not provide any cooling effect, you might as well have the cabin A/C on normal recirc.

The TBCM determines if the outside vent door should close, and if the two battery fans should recirc air through the condenser to the battery compartment. There should not be much cooling effect to the battery without the compressor turning by the ICE. At best, the residual cool air may last a short time till the heat of the battery has warmed that air. This may be the point that the TBCM reopens the outside vent door till the ICE restarts.

It does appear that the addition of the cabin A/C on top of the battery A/C, does drop my mileage more in hot weather. This maybe because the PCM can automatically disengages the compressor clutch during battery cooling only. The A/C is manual in the cabin, so the compressor stays on as long the ICE is running. A light when the battery is cooled by the compressor would be nice and something to think about as a MOD.

GaryG

VietVet'67 · #10 06-08-2006, 11:09 AM

Quote:

Originally Posted by GaryG

Hey Phillip

A light when the battery is cooled by the compressor would be nice and something to think about as a MOD.

GaryG

Funny - I was just thinking about that same thing - say putting an LED inline so when the compressor is on for HV battery cooling you could turn on the cabin air, but as you stated - you would need to know that the PCM is calling for the compressor to come on - otherwise the LED would stay on because you are requesting the A/C to be on.

Does the ScanGuage read this type code being sent?

It would be nice to be able to have it set on 'standard – no A/C air flow' and when the PCM calls for the compressor for battery cooling, the air is circulated thru the cabin condenser for cooling at that time only, then the PCM is also controlling the cabin temp.