Avoid Automatic Temp Control to Minimize A/C Range Impact

[Ellsworth]

Our 2013 FFE apparently energizes its range-sapping cabin heater to modulate the A/C cooling whenever the cabin achieves the HVAC system's set target temperature. This imposes the load of both the A/C compressor and the heater on the main high-voltage battery pack.

I've written a long blog post about my experiments, observations and solutions regarding this EV-unfriendly aspect of our HVAC system.

 

[jmueller065]

Yeah 6kW is about what I estimated the heater uses by looking at the power consumption during preconditioning when it was <0F outside (and the car was sitting outside). Thus the 6kW figure was a worst case guess.

Reading further: I don't think I have seen that: The car cycling between A/C and heat to maintain the set point. When the outside temp is pretty mild to warm (e.g. mid-50s through 90s) I frequently set the HVAC to 72F and forget about it. The only time I see the climate gauge go to 5kW+ is when it should logically be heating the car (e.g. cold out, cold in cabin and heat called for). When driving around with it set to 72F (and outside is warmer) and it reaches the setpoint typically the fan slows and the climate gauge goes to zero..and stays there occasionally popping up to 1kW or less as the compressor kicks in.

You also have to keep in mind that all Focuses (not just the electric) use a new variable A/C compressor that Ford developed to increase efficiency. (Wow, perhaps they didn't: Been searching for a reference for this which I cannot find but I do remember reading it...somewhere! My Google Fu is failing me at the moment.)

This discussion also brings up another thing that seems apparent about the FFE: It appears that each FFE has its own "personality" per se. There are many threads on here describing some idiosyncrasy of their car to which the replies range from "nope mine doesn't do that" to "yup I get that and far worse". Almost as if the FFE wasn't a production car built on a line but hand built somewhere..!

 

[michael]

In moderate temperatures, I set the thermostat somewhat below ambient (like 65) turn the A/C off, and set the fan to maybe two bars. That provides vent, no heat, no A/C.

I'm generally willing to run the A/C if it's hot, but avoid running the heater unless really needed.

 

[WattsUp]

Our 2013 FFE apparently energizes its range-sapping cabin heater to modulate the A/C cooling whenever the cabin achieves the HVAC system's set target temperature. This imposes the load of both the A/C compressor and the heater on the main high-voltage battery pack.

Yes, I've seen this too. It's annoying.

 

[TexaCali]

Great write up. I had noticed the Climate load occasionally shoot way up (pegging the bar graph), but didn't realize it was the heater kicking in. Interesting. Fortunately around here I can often get away without any climate control, and I just turn it off (adding about 10-11 miles of range).

 

[unplugged]

Our 2013 FFE apparently energizes its range-sapping cabin heater to modulate the A/C cooling whenever the cabin achieves the HVAC system's set target temperature.

I have noticed this in situations where I was fooling around with the controls and, for instance, went from a automatic set temperature of 74 F and went past it to a 80 F. Then, the heat comes on to catch up. But i haven't noticed this when set at auto A//C for a longer period. I will have to be more alert and use my gauges to see if I can replicate this on a sustained auto A/C trip.

Are you certain that the A/C on auto does this under all conditions? From your blog, you state that the heater is essentially used to maintain A/C temperature at all times, rather than shifting the A/C compressor on and off. Have others kept an eye on their energy gauge and confirmed this to be the case? Why does my range only show a 6 or 7 mile hit when I turn on the A/C in 85 F conditions? You are stating that the heater would use far more than this in concert with the A/C on such a trip. I regularly travel to my folks' home 65 miles away by freeway with an elevation rise of about 1200 feet. Using the A/C does not appear to dramatically reduce range even though they live inland Riverside County.

Sorry to be skeptical without having any science to back up my questions. I just haven't seen the kind of effect you claim will result from using auto A/C. And I certainly don't feel like giving up my auto setting until I personally find I can't make a 65 mile freeway trip into Riverside County.

 

[v_traveller]

Our 2013 FFE apparently energizes its range-sapping cabin heater to modulate the A/C cooling whenever the cabin achieves the HVAC system's set target temperature. This imposes the load of both the A/C compressor and the heater on the main high-voltage battery pack.

Wow, I never noticed that. But that's because I've never used the auto temp control when I need the A/C. Prefer to set the fan speed and then punch the A/C button as needed. Good to know, thanks for the info!

So maybe now, thanks to your observation, I'm starting to understand why the Volt has a Comfort mode and Eco mode. And the RAV4 EV has a Normal, Eco Lo, and Eco Hi mode. Perhaps those modes use different logic to modulate the A/C and heater, depending on whether the priority is to maximize comfort (by overlapping A/C and heater activation) or maximize efficiency. Time for me to RTFM!

I've written a long blog post about my experiments, observations and solutions regarding this EV-unfriendly aspect of our HVAC system.

Excellent post, Ellsworth. I'll have to go though the rest of your blog tonight... looks like some great information and insight.

 

[Ellsworth]

Our 2013 FFE apparently energizes its range-sapping cabin heater to modulate the A/C cooling whenever the cabin achieves the HVAC system's set target temperature.

I have noticed this in situations where I was fooling around with the controls and, for instance, went from a automatic set temperature of 74 F and went past it to a 80 F. Then, the heat comes on to catch up. But i haven't noticed this when set at auto A//C for a longer period. I will have to be more alert and use my gauges to see if I can replicate this on a sustained auto A/C trip.

Are you certain that the A/C on auto does this under all conditions? From your blog, you state that the heater is essentially used to maintain A/C temperature at all times, rather than shifting the A/C compressor on and off. Have others kept an eye on their energy gauge and confirmed this to be the case? Why does my range only show a 6 or 7 mile hit when I turn on the A/C in 85 F conditions? You are stating that the heater would use far more than this in concert with the A/C on such a trip. I regularly travel to my folks' home 65 miles away by freeway with an elevation rise of about 1200 feet. Using the A/C does not appear to dramatically reduce range even though they live inland Riverside County.

Sorry to be skeptical without having any science to back up my questions. I just haven't seen the kind of effect you claim will result from using auto A/C. And I certainly don't feel like giving up my auto setting until I personally find I can't make a 65 mile freeway trip into Riverside County.

I understand the skepticism, unplugged. The range of conditions under which the heater is energized is complicated to observe. If it's really hot, or I select a temperature that the system will never achieve, the heater won't energize. But it's completely repeatable - at warm to somewhat hot outdoor temps (78 to 84 degrees F observed so far), if I select 74 degrees F, the climate power will spike at 5+kW repeatedly.

I just added an addendum to the bottom of the blog post, with observations from a variety of conditions and user settings. -Ellsworth

 

[WattsUp]

at warm to somewhat hot outdoor temps (78 to 84 degrees F observed so far), if I select 74 degrees F, the climate power will spike at 5+kW repeatedly.

Yeah, the HVAC logic seems kinda dumb -- and especially in an EV with constrained energy reserves. If the ambient cabin temperature has dropped below the set temperature, rather than draw in warmer outside air (when available) it seems prefer to expensively heat the inside air.

You can cause this to occur manually (by raising the set temperature, obviously), but it can occur when the set temperature and ambient cabin temperature are very close. I've seen it. I drive around with the climate energy consumption graph in MyView all the time, so I've noticed when the unexpected heating occurs. I have to notch the set temperature down one or two degrees to get the heater to go back off, even when the outdoor temperature is warmer than the set temperature.

 

[dmen]

Yes I was just about to start a thread with this topic when I see you beat me to it.

I don't drive with the energy screen visible, but I came to the same conclusion observing the range estimate popping around wildly as climate control does its thing.
Scenario: Today it was 70F and car was parked in the sun. Climate off when I turn on the car, range is 80 miles. I turn on auto climate at 68 with A/C on, and range is 72 miles. I drive about 2 miles in 10 minutes in city traffic, and notice range is now 50 miles. What the heck? I toggle A/C off and on, but range remains 50. I turn off climate, and range returns to 80 miles. Then I turn on climate (range 50 miles) and turn the temp dial down to 66, and the range goes back to 80.
So it appears that the heater kicks in as soon as the car gets to goal cooler temp? That seems like a horrible design flaw! Maybe it doesn't actually run much, but why run at all?

Funny thing is I didn't notice this last summer, and I think I would have if it was happening. I wonder if something changed with the MFT update and/or SSN fix?

 

[sefs]

The range estimation is based on use of the climate control and what mode it is in. The various modes that it is in have historical estimates of energy usage. So when it is 70F and you have the HVAC set to 72F, you are in a mix of heat/AC. This mix isn't inherently terrible. The HVAC does not run the PTC heater at the full power blindly. As soon as it reaches set point, very quickly, it modulates the power back. If the last time you were in this mix mode was drawing a lot of power from the heater (for example, if it was cooler in the 50's), the estimation will be terrible. However, if you actually look at your consumption (Wh/mi), it will not be that bad at all. If you leave the HVAC in this mix mode for a good period of time, it will more accurately predict the range hit. For example, this morning it was 62F and I had the HVAC set to 72. It was only predicting a range hit of 11 miles (82 with HVAC on/93 with HVAC off) Keep in mind, though, the next time it gets cooler, the range estimation will most likely be reading high. There is also an AC only mode that the range estimator looks at. For instance, on that 70F day, put the HVAC down to LOW temperature. You should notice an increase in range due to it leaving mix mode. This also happens when it gets so hot out that you are only in AC mode (76+F). What you really need to look at is the Wh/mi. Mix mode (at least at a very mile 65-70F) doesn't affect the range that much at all, and the claims of horrible inefficiency of the PTC heater are exaggerated (not saying that it is as efficient as a heat pump, but it really isn't the end of the world). You are just seeing an artifact of the range estimator remembering that last time it was in mix mode for a prolonged period it used a lot of energy.

 

[dmen]

Sefs, thanks but I understand how the range estimate works. I was just using its behavior as an indicator of when the heater was engaging.
Yes, I could leave the climate control at the desired set temp and hopefully see that the heater turns itself off after a short period of time, and after some days of accepting this probably small energy waste the resulting range hit might be softened. But it's hard to ignore an obvious waste of energy in a car with such a small amount of stored energy to begin with. So instead I'll fiddle with my HVAC system more than I should have to, and hope it doesn't distract me from the road. For what it's worth, during the few minutes that my range was showing a big drop, my Wh/mi was rapidly climbing just like it does on a winter day when I actually want cabin heating.
I don't want my cabin to cool constantly on a day in the 70s so setting it to LO is not an ideal solution.
My point was that there is not a good reason for the cabin heater to engage when the HVAC system has been called on to cool down the car and cabin temp arrives at the desired temperature. My home HVAC certainly doesn't do this. The fan continues to blow and the A/C compressor turns off. In time when my home warms again, the compressor turns back on. It's not complicated.
As far as the FFE's heater efficiency, I guess it's all relative. All I know is that my range- real, not just estimate- is half as far when I use the heater as when I don't. To me that's terrible.

 

[sefs]

Sefs, thanks but I understand how the range estimate works. I was just using its behavior as an indicator of when the heater was engaging.
Yes, I could leave the climate control at the desired set temp and hopefully see that the heater turns itself off after a short period of time, and after some days of accepting this probably small energy waste the resulting range hit might be softened. But it's hard to ignore an obvious waste of energy in a car with such a small amount of stored energy to begin with. So instead I'll fiddle with my HVAC system more than I should have to, and hope it doesn't distract me from the road. For what it's worth, during the few minutes that my range was showing a big drop, my Wh/mi was rapidly climbing just like it does on a winter day when I actually want cabin heating.
I don't want my cabin to cool constantly on a day in the 70s so setting it to LO is not an ideal solution.
My point was that there is not a good reason for the cabin heater to engage when the HVAC system has been called on to cool down the car and cabin temp arrives at the desired temperature. My home HVAC certainly doesn't do this. The fan continues to blow and the A/C compressor turns off. In time when my home warms again, the compressor turns back on. It's not complicated.
As far as the FFE's heater efficiency, I guess it's all relative. All I know is that my range- real, not just estimate- is half as far when I use the heater as when I don't. To me that's terrible.

I do agree, that I wish it could be inhibited completely. However, pull up the MyView screen and put the accessory consumption display up. When your range drops to 50 miles, note that the Climate bar will peak to max, but less than a minute later it will go back to nothing. My point being is that while it does constitute an unnecessary drop in range, it really isn't enough to worry about. Perhaps 8 miles on a full charge. Sometimes those 8 miles really do count, I understand. I, myself, will drive with no climate control if it is really about pushing the range to the max. Have you tried LO but with the fan manually controlled to the lowest setting? This will keep it in AC only mode, but with the fan at low it will be unable to reach that temperature, and if it gets too cold you can toggle the AC off. To get to half range resulting from heat, I would have to be in the single digits of temperature. But to be fair, that is a result of a cold battery and heater energy usage. And in the single digits, a heat pump would be no more efficient than a PTC heater. An ECO mode would be nice, though. Perhaps this mode could inhibit heat entirely in warmer weather, accepting the possibility of not perfect temperatures; and just use the a 1 kW max setting on the PTC heater with a low fan in the winter to extend range.

 

[hybridbear]

It appears that the Focus Electric isn't the only Ford to do this. The C-Max Energi & Fusion Energi will also energize their electric heater when the climate is set to Auto & the A/C is on. The Fusion Hybrid will send hot coolant through the heater core and blow hot air into the cabin. We have often found in our Fusion Hybrid that one temp is too cold & one is too hot. Often this breaking point is about 73 or 74 F. If the HVAC is set to 73 F on Auto it blows too much cold air. If it is set to 74 F on Auto it begins blowing hot air and is too hot. So we end up turning off Auto and controlling the fan speed manually. The issue seems to stem from the way that Auto likes to use high fan speeds. Quite often we will leave the temp on 73 but turn the fan to the lowest speed and then we're comfortable for long trips.

 

[unplugged]

I've been running with the climate energy usage in the MyView display for several days trying to observe this behavior, and I have not seen this happen yet on my new 2014 FFE.

It has been in the upper 70s and low 80s here. I have noticed no use of the heater in my energy use display. Perhaps the heater only runs when it is below 76? I have a 2013.

Is it remotely possible that Ford snuck in some minor improvements to the 2014 climate control without any mention of a change from earlier years?

No. But there may be differences from car to car. I guess we will have to take a poll.