Cold Weather Observations

[larryh]

I estimate about 1.4 kWh of my commute to work is used to supply kinetic energy (for acceleration) to the car. 

 

Thus during the summer, of the 2.51 kWh used to propel the car, 2.51 - 1.4 = 1.11 kWh is used to overcome friction.  Of the 1.4 kWh used to supply kinetic energy, I get 0.75 kWh back during regen, i.e. 55%. 

 

During the winter, of the 2.84 kWh used to propel the car, 2.84 - 1.4 = 1.44 kWh is used to overcome friction.  Of the 1.4 kWh used to supply kinetic energy, I get 0.43 kWh back during regen, i.e. 30%.

 

The analysis in Post 348 is incorrect.  The plug-in energy consumed at 75 F is 1.76 kWh and at 0 F it is 2.42 kWh.  Thus 2.42 kWh / 1.76 kWh = 1.38 times as much plug-in energy is consumed in the winter vs. the summer, i.e. 38% more plug-in energy. 

 

At 0 F, the energy to overcome friction is 1.44 kWh / 1.11 kWh = 1.3 times the amount at 75 F.  So 30% of the 38% total additional plug-in energy results from increased friction.  The remaining 8% is due to less efficient regen (mostly from increased friction in the transmission).

 

Note that ICE cars do not have regen and are inherently much less efficient.  The effects of colder weather impact them less than a PHEV.  Not including regen, the increase in energy consumption is 2.84 kWh / 2.51 kWh = 1.13, i.e. 13% more.   Including regen, the increase in energy consumed is 2.41 kWh / 1.76 kWh = 1.38, i.e. 38% more.  Cold weather has a much greater impact on PHEVs.

Edited April 26, 2015 at 04:27 PM by larryh

[larryh]

To summarize my previous posts, it requires 1.76 kWh of plug-in energy for my 8 mile EV commute to work at 75 F vs. 2.41 kWh at 0 F, or a difference of 0.65 kWh.  I estimate that about 0.43 kWh of that difference is due to increased internal friction associated with cold drivetrain components (more viscous transmission fluid, stiffer bearings, more friction between gears, etc.).  This increases plug-in energy consumption by 0.43 / 1.76 = 25% .  The remaining 0.23 kWh is associated with denser air (aerodynamic drag) and tire rolling resistance.  This increases plug-in energy consumption by 0.23 / 1.76 = 13%.

 

Without the ICE running, it takes a very long time for the drivetrain components to warm up.   In a typical winter commute, the transmission fluid temperature starts at garage temperature (about 20 F) and only warms up to 50 F by the end of the commute.  At 50 F, there still is substantial increased internal friction.  If the ICE were running, the drivetrain components would heat up much more quickly from the waste heat generated by the ICE and the effects of a cold drivetrain would be less pronounced.

 

Whenever you read information about the effects of cold weather on mileage, they rarely mention increased internal friction.  Yet, at least in my case, this is the factor that has, by far, the greatest impact on mileage in the winter.  Now if rather than an engine block heater, they made a heater for the transmission instead.  That would be far more useful for improving EV mileage in the winter.

 

 

 

[larryh]

The following plot shows MPGe vs. Temperature for a longer 60 mile commute.   I start out with a fully charged battery and after that is consumed the car enters hybrid mode.  In the summer, at 75F, I average around 68 MPGe.  In the winter, at 0 F, I average 44 MPGe.  So it takes 68 / 44 = 1.55 times as much energy in the winter vs. the summer for my commute.  The main reason for the large difference in MPGe for summer vs. winter is that I get less plug-in EV miles during the commute.  Plug-in EV miles are approximately 2.8 times more efficient than ICE miles. In the winter, I have a larger proportion of less efficient ICE miles in the commute, which negatively impacts MPGe. 

 

Edited May 1, 2015 at 10:28 PM by larryh

[larryh]

In this plot, I have removed the plug-in EV miles from the commute.   These are the results I would expect to obtain if I made the trip entirely in hybrid mode and did not charge the HVB before each commute, i.e. I drove a Fusion Hybrid rather than a Fusion Energi.  In the summer, at 75 F, I would average 46 MPG.  In the winter, at 0 F, I would average 35 MPG.  This time, it requires 46 / 35 = 1.3 times as much energy in the winter vs. the summer.  This is far more than I would have expected due to the affects of increased air density and increased tire rolling resistance alone in the winter.   I would have expected the increase to be more like 15% rather than 30%.  I suspect the reason for the much higher than expected energy consumption in the winter is again significantly increased internal friction due to cold drivetrain components. 

 

Edited May 1, 2015 at 10:37 PM by larryh

[larryh]

The following plot shows the Transmission Fluid Temperature (TFT) during two commutes.  The blue line is in the winter when the outside temperature is -5 F.  The red line is in the summer when the temperature is 68 F. 

 

In the winter, the TFT never rises above 100 F.  In post 350, you can see that there is significant power loss from increased friction when TFT is below 80 F.  During the winter, for more than 1/3 of the trip TFT is below 80 F.  TFT must be well above 100 F to minimize the power loss.  It never rises above 100 F in the winter.  In the summer, for more than 85% of the trip, TFT is above 100 F.  I suspect that 10% of the increase in gas consumption during the winter is from increased air density and tire rolling resistance (see previous post showing a total increase of 30%).  The remaining 20% is from increased friction resulting from cold powertrain components. 

 

Edited May 1, 2015 at 11:12 PM by larryh

[Russael]

Here's a link detailing ATF viscosity vs temperature.  It is WAY thicker at cold temperatures vs a 180 degree summer operating temperature.

 

http://www.viscopedia.com/viscosity-tables/substances/automatic-transmission-fluid-atf/

 

I thought most ATF was now synthetic, which I wouldn't expect to have as much variance.

[Hybridbear]

Because of this TFT temperature impact I would use the block heater in the winter to heat the transmission fluid. It isn't super effective at it, but it would get the TFT up to a starting temp of 100 F consistently with the car parked underground at our apartment. Then as we'd drive the TFT would hold steady in the cold weather even though we were driving and it should have been warming up.

[larryh]

The engine block heater does very little to warm the transmission fluid temperature in the winter.  The ICE needs to get a lot hotter than 100 F to warm the transmission fluid.   As an example, when the outside temperature was 3 F, the EBH heat the ICE to 72 F.  The TFT was still at 12.1 F.

Edited May 3, 2015 at 06:56 PM by larryh

[Hybridbear]

The engine block heater does very little to warm the transmission fluid temperature in the winter.  The ICE needs to get a lot hotter than 100 F to warm the transmission fluid.   As an example, when the outside temperature was 3 F, the EBH heat the ICE to 72 F.  The TFT was still at 12.1 F.

I imagine that outside this is the case, however, parking in a heated underground garage the TFT rises from an ambient temp of about 60 F to 100 F. The coolant gets up to 150 F.

[flyingcheesehead]

I imagine that outside this is the case, however, parking in a heated underground garage the TFT rises from an ambient temp of about 60 F to 100 F. The coolant gets up to 150 F.

 

The real question is, does the power consumption of the EBH reduce the energy loss in the transmission enough to make it worthwhile? And if so, under what conditions?

Edited May 4, 2015 at 06:07 PM by flyingcheesehead

[Hybridbear]

The real question is, does the power consumption of the EBH reduce the energy loss in the transmission enough to make it worthwhile? And if so, under what conditions?

The analysis has been done and I believe the answer was no. However, at our apartment the electricity in the underground garage is a shared resource that's used by maintenance and by owners who are vacuuming or doing other things to their cars. Management has said that they don't care if I plug in the block heater on the car.

[larryh]

The EBH consumes about 400 watts of power.  If you run it for 3 hours, that's about 1.2 kWh of electricity.  I estimate for my 8 mile commute to work, the additional power consumed due to a cold transmission is about 0.5 kWh of energy.  The commute requires about 2.4 kWh when it is below 0 F and about 1.7 kWh in the summer.  The remaining 0.2 kWh is mainly due to the denser air. 

 

However, the EBH does allow me to drive to work entirely in EV mode when it is below 0 F.  Without it, the ICE would come on.  The ICE would consume at least 0.07 gallons of gas.  That's about 2.4 kWh of energy.  So in this case, I am saving energy using the EBH.

[openair]

Today I am experiencing the ICE threshold on the empower screen fluctuate between 3.5 and its usual 4 bars depending on speed. Only reaching 4 bars at 60+kmh. There is 25% charge left on the ev range of the HVB and other demands such as climate settings or heated seats make no difference to this fluctuation of the ice threshold.

 

Anyone else experienced similar? I don't recall the ice threshold ever behaving this way when there is any ev range left in the HVB. Even at sub zero temperatures. It's 12c today. I only recall seeing the ice threshold fluctuate with speed in ev later or hybrid driving.

 

Pretty sure it didn't fluctuate like this yesterday at 7c.

Edited October 4, 2015 at 05:11 PM by openair

[Hybridbear]

Today I am experiencing the ICE threshold on the empower screen fluctuate between 3.5 and its usual 4 bars depending on speed. Only reaching 4 bars at 60+kmh. There is 25% charge left on the ev range of the HVB and other demands such as climate settings or heated seats make no difference to this fluctuation of the ice threshold.

Do you have the instant MPG gauge turned on? Are you in EV Auto or EV Later?

[openair]

Do you have the instant MPG gauge turned on? Are you in EV Auto or EV Later?

Yes. Auto. The ice never actually engaged. Just the ice threshold behaving differently.

 

Edit: The ice threshold continued fluctuating between 3.5 and 4 bars for the remaining 25% of the ev range.  This morning, after charging last night, I'm back to a constant 4 bars at an even colder temp of 10c.

 

I think it must have been related to having driven the vehicle in ev later prior to this auto driving, the vehicle having not been charged for two days and the overnight drop in ambient temps all contributing to a variance in cell voltage that resulted in the drop of available ev power I experienced.

Edited October 5, 2015 at 10:12 PM by openair

[openair]

I am again experiencing a drop in available ev power in auto with the HVB at 71% and the climate control is off.

 

It was 7c inside the garage this morning. The vehicle was charged to 100% and precondition this morning. It was 5c outside the garage. I had a steady 4 bars of ice threshold omw to work.

 

Went to get lunch. It is now 15c and I am again seeing a fluctuation in the ice threshold while in auto. It starts at about 3.75 bars and climbs to 4 bars at 35km am hour.

 

It seems to me this is due to variation in cell voltage due to the changes in ambient temp. Anyone experience similar or have another explanation?

Edited October 15, 2015 at 04:22 PM by openair

[Hybridbear]

I am again experiencing a drop in available ev power in auto with the HVB at 71% and the climate control is off.

 

It was 7c inside the garage this morning. The vehicle was charged to 100% and precondition this morning. It was 5c outside the garage. I had a steady 4 bars of ice threshold omw to work.

 

Went to get lunch. It is now 15c and I am again seeing a fluctuation in the ice threshold while in auto. It starts at about 3.75 bars and climbs to 4 bars at 35km am hour.

 

It seems to me this is due to variation in cell voltage due to the changes in ambient temp. Anyone experience similar or have another explanation?

What happens if you put the car into EV Now and then increase the power demand above the threshold when in EV Auto?

[openair]

Idk. My guess is the enable ice pop up will appear as usual. Since it is only about 1/4 of a bar, not even, it may be difficult to get it exactly there.

 

(Tried. Since it fluctuates with speed, returning to 4 bars at 35km/h, I was unable to specifically sit inside that 1/4 of a bar before it raised to 4 bars)

 

Any reason to expect different?

Edited October 15, 2015 at 09:19 PM by openair

[rbort]

This is normal.  The colder it gets the less power you will see the battery able to provide.

 

Its a function of temperature as well as SOC of the HVB.  I see this with my Cmax, not to worry about it.

 

When you are moving the power comes up more as its easier for the battery to accelerate the car from moving than from a full stop.

 

You see this also with the hybrid battery when the HVB is empty, pretty much all the time.

 

-=>Raja.

[openair]

Just to be sure, you experience a drop of the ice threshold from 4 bars to between 3.5 and 3.8 bars at temps above 41F?

 

I know a much greater decrease in ev power is normal closer to 0F but not at 5+ "Celsius." That usually also occurs with a decrease in max range as well.

 

I also experience this problem or don't at the same temps.

Edited October 18, 2015 at 06:50 PM by openair

[Hybridbear]

Our Energi is normally parked overnight in its nice, heated garage at home. The temperature in our underground parking at our apartment is heated to 55F minimum in the winter, but the temperature is usually 60-65 F in the winter. Right now, the temp underground is still around 70-75 F. This really helps us avoid a lot of the cold losses that Larry has described, due to a cold HVB, cold eCVT fluid causing more internal friction, etc. Over the weekend we visited some friends up north. The temperature on Sunday morning was about 35 F. The HVB temp had dropped, even while charging on 120V overnight, from ~83 F when we arrived to 45 F in the morning. The TFT temp was under 40 F. Our first trip that morning, near sunrise while everything was very cold only saw 135 MPGe (0.8 kWh in 3.5 miles according to MFM). The car then sat outside in the sun for about 3 hours, while the outside temp rose to about 55 F. Our next short city trip of 3.6 miles was 163 MPGe (only 0.7 kWh used according to MFM). This still is not as good as I would expect with higher TFT. The TFT was still only around ambient temp at the start of that second drive & only reached about 70F at the end of it.

 

It was very annoying to see this efficiency loss. It definitely makes me more appreciative of the heated garage.

[ebduda]

My car will be 2 years old in May and will be due for an oil change and tire rotation.  One thing I mentioned a while back is that when I do take it in, I want every computer module in that car flashed with the most recent software, but I don't believe a dealership will touch anything unless it's considered broken, or if a Ford TSB says to upgrade the software.  My computer gets a patch at least once a week for security, remove bugs, and improve performance.  Individual softwares get patches.  My car's software hasn't been touched since it rolled off of the assembly line, except for Sync, which allows users to upgrade.

 

I've been pretty lucky to have been virtually trouble-free all this time, sans a glitch here and there.

 

About 90% of you PC's updates are for security for the different Microsoft or other Vendor software.   I'm not surprised that the software running the car doesn't need to be updated unless their is a bug they find later.  In this instance, I would think the dealer would know the patch needs to be updated.   

[Russael]

About 90% of you PC's updates are for security for the different Microsoft or other Vendor software.   I'm not surprised that the software running the car doesn't need to be updated unless their is a bug they find later.  In this instance, I would think the dealer would know the patch needs to be updated.   

 

If the engineers find bugs, they do produce calibration updates.  Considering my car had updates for every single module, that is significant.  I personally did calibration updates to my girlfriend's 2012 Ford Focus (went to a local mechanic and borrowed his Rotunda programmer and laptop with the IDS software to patch the modules in her car).  Unlike mine, her's had 3 updates - one for the PCM/TCU, one for the audio system, and one for the instrument cluster.

 

After the PCM update, the car drove WAY better than it did before.  We were unaware of any bugs or updates for it.

 

After the audio update, we noticed several bugs were fixed, including no longer having the radio select random frequencies after switching sources, and no longer having the audio system come on at full volume with subwoofer rumble/MFT button push sounds when the car was unlocked.

 

After the instrument cluster update, we noticed that the turn signal sound had changed, the gear shift selector went to color (used to have a white outline instead), and she gained a new 4 quadrant trip summary screen.

 

Didn't know it, but her car had a recall for PCM reprogramming.  Dealership checked her car and found the software already installed, so they just closed it out.  Her car was in for a weather strip replacement on the passenger door.

 

Not sure which updated fixed this:  The rear defroster was supposed to automatically shut off after 10 minutes, but never did.  It now performs as it should.

 

As far as my Energi goes... I am much happier knowing that unseen bugs have been taken care of.  Did the software work before?  Yeah.  Did it work at its best?  Probably not.  Did it proactively fix potential issues down the road?  Most likely.

 

I actually took my car in yesterday to have all of the open recalls on the car fixed.  Door tabs, PCM reprogramming (turns out there's a new one for August of this year), steering bolt, and the replacement of the restraint control module with latest calibration.  I did not have them recheck the modules for updates again.  I'm not spending that insane amount of money anymore.  I can always borrow that programmer if I choose to do updates again.

[ebduda]

I would think that updating the software on anything would be part of the Maintenance warranty.  What did they charge you?  What does PCM stand for?

Edited November 19, 2015 at 01:38 PM by ebduda

[Russael]

It is if you want to spend time finding a TSB that impacts each module.  Turns out the Energi has 10, and I wasn't sure at the time how many modules it had that could take calibration updates... and I was lazy, and wound up paying 550 to have the updates, which I'm quite miffed about, but what's done is done.  The local mechanic charged me 80 - he did one update and misunderstood what I wanted, so I went back and he let me do the rest myself.  Far cry, and I know every module was updated on the Focus since I did it myself.

 

PCM - (P)owertrain ©ontrol (M)odule