Mach-Lee's Mach-E Cold Weather Testing [Taking Requests]

[stackcat]

It's -35F today, and still getting between 1.6-1.8mi/kWh. The heater can't keep up with the cold, but it's enough to prevent the windows and windshield from fogging.

Braking regen at 75kW is insane. I probably should make a cold specific profile to have the regen braking off (as much as it does be, with 1PD).

Other than this, the car is fine. Still only losing about 10-15% to outside temperatures. Biggest issue is my nose being cold, and I'm not about to start wearing a balaclava in my car. I might have to resort to a normal face mask with contacts on...

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[Womps]

Shoot, I’m bald and my windows fog up in the morning at these temperatures!

 

[mkhuffman]

@Mach-Lee , you previously posted that A/C doesn't work below 32 F. Did you confirm that in your testing?

Great thread, BTW. Starting with a warm car is really, really important. And it explains why I get decent range on cold days when I leave from home after parking in my 65 ish garage overnight. Not only is the battery warmer, meaning more capacity, but the cabin is already comfortable and the temperature only needs to be maintained rather than heated up.

 

[lightningandmache]

Regen
Is that full power going to battery or being partially pushed to say heater?

Cell Temps
Starting ~30F ending ~33F ... these are reported from some "pack avg" variable via OBD?
I would guess the cells near aluminum casted module end-caps are the outliers.

I don't understand why Ford doesn't valve in motor thermal loop which is providing ~1.5kW waste heat. E-gmp from Hyundai doesn't do this either and they aren't dummies. There /must/ be some reason.

Also, the PTC heater seems a touch undersized.

Will be interested to see your re-test with a fully conditioned battery, I think they preheat to near 60F?
Would also be interested to see more posts about battery temps from start->end at diff ambients.

Awesome post!

 

[Quartzo]

Regarding the humidity, there wasn't really any humidity purged. The relative humidity was tracking the temperature as you would expect and the total amount of moisture in the air of the car wasn't actually changing during the trip. The relative humidity decreased as the temperature increased because warmer air can hold more water, but the total amount of water in the air stayed relatively constant. The exception are the spikes in humidity when then fresh air damper closed. In those cases (relative humidity spike without a significant drop in cabin temperature) the humidity was increasing from your body in the car.

To put some numbers to it, at the start of the trip with 57% RH and at 29 F, the absolute humidity was about 2.4 g/m^3. When you heated the air to 64 F, if the absolute humidity remained constant at this value the relative humidity would be 16% and you were at 15%.

 

[Mach-Lee]

Wow, this topic was way more popular than I thought today! I charged back up from 8.5% to 50% and used 35.66 kWh from the wall. No battery heating was used during charging since the battery was above 32ºF. I get 91.5% charging efficiency to the pack, so doing some math that means the battery will hold 78.6 kWh at 100% while around 32ºF, a cold capacity loss of around 11% which is exactly what I would expect at those temps.

From your data looks like a good idea to precondition just because of the Regen issue while near freezing temps? I don't know even if 10-15 min of preconditioning will help?

FYI remote start doesn't heat the battery, only the cabin. So won't help unless you make a departure time.

Nice write up. I wonder why the humidity levels were so high early on, would have thought humidity would be low being so cold. Only thing I can think of is if the car was cold then brought into a warmer garage when parked prior to this and condensation formed on the colder surfaces?

Also surprised to see the temp delta between cells, would have thought they'd be much closer as they are probably all in a common cooling loop.

I think there was some moisture in the A/C core, but otherwise no condensation anywhere.

The cells are in a common cooling loop, but there is no flow so their temps vary. Circulating coolant periodically through the battery even if not heating or cooling would help even out the cell temps. I think a "pack thermal stir" when the deltas get too high is something that should be implemented.

I would love to see real charge data used. Calculations based on battery percentage or even using the BMS data were always off from that data. I will say, I think your 157 miles is spot on for a preconditioned battery and matches my data from last winter. If you did not precondition, that would have been 120-130 miles of range. If you could and test again, simply recharge to 100% after driving (starting at 100%) and calculate real efficiency based on Real miles driven to real kWh re-charged. You may be surprised it does not match the mi/kWh display, even after you deduct the 10% for charger losses. I think you may see that mi/kWh is actually about 15% less. Now, my data was measured in early 2022 on July 2021 software. I know Ford did some corrections and updates since I departed from my Mach E ownership, so that 1.9 mi/kWH may be spot on now (2.2*.85-1.9) but I would love to see a test on a 2022. You can only tell by charging back to 100% and reading what your charger puts back into the battery and deduct the 10% for losses. If you can do this and report back, that would be awesome and close a lot of questions. You may end up with the same result which will go along way in validating the BMS.

Thanks, I posted the charging data above. If I use the energy numbers from the EVSE I get 1.85 mi/kWh which is basically exactly what the trip screen said. So maybe the BMS reading are just off compared to reality then.

Thanks for this @Mach-Lee, has you car received the GOM update OTA?

I'm sort of in-between there due to FDRS glitches, I have the BECM software from that OTA but not the rest of the powertrain modules. So maybe?

I feel like I've came across posts that say some updates have improved the heater performance. If I'm not making that up, would cars built in Oct '22 still benefit from updates to improve heater efficiency? Is the upcoming update to SYNC going to help?

Vehicles built after July 8th 2022 have it, so no.

The regen back is such a brief “transitory” instance that I wonder if it’s any harm true harm to the battery. Many Hyundais have no heating and I have not heard of any concerns…

That I don't know. I just know other EVs like Tesla severely limit regen at the same battery temps. If Tesla limits regen, it's probably a good idea for others to do the same. 75 kW is like 3 times what a Tesla with the same size pack would allow. A lot of heat was generated which tells me the cells aren't happy receiving it.

That’s about what I am getting here in Montana range wise right now with preconditioning. I am a little less, but I run studded tires in the winter. I am curious how that will change when our high is -23F this week. I know this sounds weird, but if my hair is wet in the mornings, it will fog my windows?.

Any extraneous moisture in the cabin will dramatically increase fogging in cold temps. I also get foggy windows in my ICE car with wet hair, so wet hair might be severe in the Mach-E.

@Mach-Lee , you previously posted that A/C doesn't work below 32 F. Did you confirm that in your testing?

Yeah, doesn't run. It was 38º a few days back and the compressor was running very slowly, so not much effect less than that temp.

Regen
Is that full power going to battery or being partially pushed to say heater?

Cell Temps
Starting ~30F ending ~33F ... these are reported from some "pack avg" variable via OBD?
I would guess the cells near aluminum casted module end-caps are the outliers.

I don't understand why Ford doesn't valve in motor thermal loop which is providing ~1.5kW waste heat. E-gmp from Hyundai doesn't do this either and they aren't dummies. There /must/ be some reason.

Also, the PTC heater seems a touch undersized.

Will be interested to see your re-test with a fully conditioned battery, I think they preheat to near 60F?
Would also be interested to see more posts about battery temps from start->end at diff ambients.

Awesome post!

Regen power can only go back into the pack since the heater is already maxed out. You can't send 75 kW to a 5 kW heater. But that would be an interesting extreme mod, add a 75 kW dump load to the back seat and send all the regen there. You'd get hot quick then!

The loops aren't connected because the temps are too different. You might be dumping 1.5 kW but the motor coolant might only warm up from -10 to 30ºF, which is still too cold to be useful for heating the pack. The second law of thermodynamics still applies, so that's why they make them separate. A heat pump would be required to transfer heat between the two loops, this is what Tesla does with a ton of complicated plumbing.

Regarding the humidity, there wasn't really any humidity purged. The relative humidity was tracking the temperature as you would expect and the total amount of moisture in the air of the car wasn't actually changing during the trip. The relative humidity decreased as the temperature increased because warmer air can hold more water, but the total amount of water in the air stayed relatively constant. The exception are the spikes in humidity when then fresh air damper closed. In those cases (relative humidity spike without a significant drop in cabin temperature) the humidity was increasing from your body in the car.

To put some numbers to it, at the start of the trip with 57% RH and at 29 F, the absolute humidity was about 2.4 g/m^3. When you heated the air to 64 F, if the absolute humidity remained constant at this value the relative humidity would be 16% and you were at 15%.

I realize what you're saying and understand % humidity is relative to temperature, but there was still an absolute humidity drop. The dew point went from about 15ºF to 10ºF in those 30 minutes (my sensor also records dew point but doesn't export it unfortunately), so some moisture was purged. Not a ton, but measurable. But yes, most of the % drop was due to temp increase.

 

[JohnFoxeSheets]

I'm curious to know at roughly how cold it needs to be for the regen-causing-battery-plating issue to become a real concern? While our temperatures on the Pacific coast are rarely truly cold, it does get cold in the mountains, which is precisely the kind of place where a long period of regen is feasible/likely.

 

[HGxxx]

I understand just thinking of setting departure time in fordpass, 15 min before I leave , I don't know if it will work ?

 

[Mach-Lee]

I'm curious to know at roughly how cold it needs to be for the regen-causing-battery-plating issue to become a real concern? While our temperatures on the Pacific coast are rarely truly cold, it does get cold in the mountains, which is precisely the kind of place where a long period of regen is feasible/likely.

Well anytime the pack is below about 0ºC/32ºF. You would have to park it for hours in temps below about 30ºF for it to cool off. So parking overnight (8 hours) in freezing weather?

This is a good reason why we should have a battery temp gauge...

 

[JohnFoxeSheets]

Well anytime the pack is below about 0ºC/32ºF. You would have to park it for hours in temps below about 30ºF for it to cool off. So parking overnight (8 hours) in freezing weather?

This is a good reason why we should have a battery temp gauge...

Thanks. Generally not a huge concern for me, but good to know. And if I recall correctly, the car won't precondition when plugged into 120V, right?

 

[AKgrampy]

It's -35F today, and still getting between 1.6-1.8mi/kWh. The heater can't keep up with the cold, but it's enough to prevent the windows and windshield from fogging.

Braking regen at 75kW is insane. I probably should make a cold specific profile to have the regen braking off (as much as it does be, with 1PD).

Other than this, the car is fine. Still only losing about 10-15% to outside temperatures. Biggest issue is my nose being cold, and I'm not about to start wearing a balaclava in my car. I might have to resort to a normal face mask with contacts on...

Woo - hoo! Can’t wait to give mine a try.

 

[RedRocker]

I understand just thinking of setting departure time in fordpass, 15 min before I leave , I don't know if it will work ?

I recall someone reporting to fully pre-condition the battery was ~5kwh, so given a ~5kw PTC, you need 1hr to fully pre-condition the battery + ~10min for the cabin. That said if you keep it on plug, I think it keeps it above 32F, so any amount of pre-condition will bump you over 32F if you are concerned.

 

[HGxxx]

I usually leave it plugged in and usually sits in a non heated garage.

 

[21st Century Pony]

One picayune caveat from my decades-old Geographic Meteorology class (or whatever its name was - can't remember): air does not hold water (as in "H2O in a liquid state"), even in droplets. Air does hold water vapor which is H2O in a gaseous state. Condensation results when air cannot hold water vapor gas and the water vapor precipitates out as... liquid water droplets, for example fog or rain. The riddle our prof used to hammer this concept into our heads was "which cubic meter of air holds more water vapor - the one on a clear July day in the Sahara, or the one during a January blizzard in Alaska?" Of course, the answer is "the July Sahara cubic meter of air" because the higher the temperature, the exponentially more water vapor the air can hold in a dissolved (gaseous) state.

I note this here because, with condensation on a glass windshield surface that divides cold outside and warm(er) inside air, the water vapor (gas) which precipitates out of the cabin air forms into liquid water droplets right there across the cabin, maybe too tiny to spot but they are there... and liquid water will right away make our skin feel colder. And when we subjectively feel colder on our skin surface, we think we are cold, even if our body core remains at the same temperature. Whereas water vapor as a gas, our bodies cannot sense.

 

[lightningandmache]

The loops aren't connected because the temps are too different. You might be dumping 1.5 kW but the motor coolant might only warm up from -10 to 30ºF, which is still too cold to be useful for heating the pack. The second law of thermodynamics still applies, so that's why they make them separate. A heat pump would be required to transfer heat between the two loops, this is what Tesla does with a ton of complicated plumbing.

Far out of my depth here... but batteries in the 1000J/kgK territory + ~350kg of cells, doesn't 1.5kW make sense if coolant loops in series?

You can't send 75 kW to a 5 kW heater.

Yeah, was thinking more along the lines of 5kW heater momentarily powered from regen, not battery, then delta battery couldn't handle sent to be "inefficiently" run through motor to generate waste heat. Seems possible?

I can't imagine they would have a BMS taking current @ 32F it couldn't handle. 0.75C pulse.

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