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

[camdenlake]

Same here in Alaska - maybe even a bit worse for fogging up - auto OK until about 30F (0C)

Well this is not good . I have a new issue that started from these updates too. Randomly either ac or heat just does nothing. Not looking forward to this winter.

Sponsored

 

[AKgrampy]

Well this is not good . I have a new issue that started from these updates too. Randomly either ac or heat just does nothing. Not looking forward to this winter.

No issues like that thank goodness! I just do some manual switching and all is good.

 

[camdenlake]

No issues like that thank goodness! I just do some manual switching and all is good.

Yeah sometimes that works. But not always.

 

[One5ame]

Well this is not good . I have a new issue that started from these updates too. Randomly either ac or heat just does nothing. Not looking forward to this winter.

I had the same problem once or twice. Must be because of some update, because I never had them before.

 

[Mach-Lee]

Overnight Unplugged Test

Decided to test what happens to the battery temperature and heat if you park outside overnight in very cold conditions. Overnight temps were below 0ºF, but when I started the test everything had warmed up to about 0ºF/-18ºC.

Starting conditions:
Wind: NW 11 mph
Outdoor temp: 0ºF/-18ºC
Battery temp: 0ºF/-18ºC
Cabin temp: 14ºF/-10ºC

I manually started the car (no remote start) with my normal HVAC settings (68ºF/20ºC AUTO 2), disabled auto shutdown timer, and let it sit for 90 minutes to see how the cabin and battery would warm up.

The cabin reached set point after about 35 minutes. The heater throttled back at that point, afterwards using an average of about 2 kW. The battery was not heated whatsoever and remained at -18ºC with HVAC on. Vent temps were about 110ºF (warm).

Next I decided to drive the car to see if anything would happen to the battery temp. At -18ºC battery temp, the regen limit is 30 kW (less than half of normal), which is shockingly high. I'm surprised they even allow any regen at these extreme battery temps. It will use up the whole 30 kW and blend friction braking so you still stop at the same rate with 1PD. I saw some pretty crazy voltage drops, I got the battery all the way down to 300V under 400A load at 75% SoC. That's like a 50 volt drop. Battery isn't happy. The battery temp increased a couple degrees from ohmic heating, but again no battery heating was observed. There was a jump in regen limit of 43 kW once -15ºC was reached. I ended the drive with -14ºC battery temp.

As you can see at the top, cabin temp was maintained at 20ºC with ~100ºF vent temps. Heater output was close to full power (4-5 kW).

Next I parked the car and turned off HVAC, which finally allowed battery heating to initiate! That went for 35 mins, and battery heating was terminated at -7ºC. The battery eventually topped out at -5ºC, which brought the regen limit up to 68 kW.

Another interesting finding is the 12V battery only gained 3% SoC with the car on for an hour:

I decided to do another 75 MPH drive to see if the battery would cool off or heat more. In short, not much happened. Again, the battery was not heated and increased only a couple degrees from the amp draw. Went from -5ºC to -3ºC. Cabin temp was still good, heater operating at max 5 kW output, exterior temp still around 0ºF.

Now I haven't mentioned the fogging much, but it was mostly okay. Most of the fogging episodes resolved in less than a minute without user intervention. Which shows the HVAC strategy is conserving maximum heat. When I'm on the interstate at high speed I don't really get any fogging, it's all outside air. However when you slow down and exit the interstate or make a turn at an intersection, that's when you suddenly get fogging shortly afterwards. Clearly it's related to vehicle speed. But during one of these fogging episodes, something interesting happened and the battery actually heated for a short time:

The top green line is the coolant output temp before the heater core. You can see it was stable, but then started increasing, this was when the fresh air damper was closed (warmer return air allowed the loop temps to rise). When 64ºC was reached, the diverter valve opened to send coolant to the battery, but only for a brief moment. Coincidentally, at this same time I felt a sudden burst of cabin heat, which must have been because the outside air had closed. I also happened to place a phone call at this same time (17:22), which drops the blower speed. The coolant temp began to rise again, hit 64ºC, and the diverter valve opened again. This one lasted for a couple seconds and dropped the loop temp before switching back. The battery did not increase in temperature from these short bursts.

All this tells me the PCM still wanted to heat the battery pack warmer than -3ºC while driving, but it couldn't because there wasn't enough heater output available.

At this point I ended my tests, and was greeted with some pretty hilarious efficiency displays for my trouble (the car sat a long time with the heater running):

Next key cycle the GOM tanked:

Findings:

• An extremely cold battery will not heat unplugged until HVAC is turned off (at least at these temps)
  • This may be a strategy change from last year, I saw more aggressive heating and loss of heat previously (currently 6.6.0 software)
  • Forced battery heating may still occur at colder temps if the battery is less than -20ºC
• Blended friction braking is used when the battery is too cold to support full regen, no noticeable difference in 1PD deceleration observed
• The regen limit is shockingly high for a cold battery. At -18ºC I would expect zero regen, but it still pumped 30 kW into the pack!
• Some crazy voltage drops happening due to the cold cells. The battery may become unstable at lower SoC with these voltage drops, with potential for severe power limits.
• -5ºC seems to be the minimum acceptable battery operating temperature.
• BlueCruise 1.0 really doesn't like random snow and salt covering the lines. Got several cancelled dings per minute.
• Heat levels were good still at 0ºF, but heater was pretty much maxed out. Will start to lose heat with colder temps.
• Some fogging but was manageable. Only one bad episode required defrost.
• 12V battery takes an extremely long time to gain charge in these temps.

Conclusions:

• Results reaffirm that a 5 kW PTC heater isn't enough, and is undersized for these temps. Much greater output (>10 kW) is required to keep both battery and cabin warm.
• Overall the thermal management of the battery in cold temps is still very poor, and there's not much you can do about it if you have to park outside unplugged.
  • If you have time, manually start the vehicle with HVAC off so the battery can heat up to -5ºC for 20 minutes. Then turn cabin heat on.
  • Unplugged departure time needs to exist for these situations.
• HVAC strategy is maintaining adequate heat down to 0ºF at the expense of battery temps. Fogging managed decently.
• I would like to see slightly more aggressive battery temperature management. There is some heater output being left on the table that still isn't being utilized. Perhaps a mode where the heater is locked into full output, blower speed reduced, and the battery heated until the cabin cools down a couple degrees.
• 12V BMS has some difficulties at low temperatures. Parking in a heated garage and using an external overnight battery charger may be required to reach SoC levels required for some OTAs.

 

[luckie]

Hmmm this reminds me, since LFP batteries need better BMS support than NCM batteries to perform optimally in cold weather, I am curious how well are they doing for new Mach-E owners?

 

[Murse-In-Airy]

@Mach-Lee Not sure how I missed this thread all this time but I was searching for the proper OBD parameters to monitor for preconditioning on the way to a DCFC. Good read through. My test at 30 degrees F, confirmed that I can either heat the battery or the cabin. And even if I forgo Cabin heat the battery won’t heat enough to make a real appreciable difference in how fast I can charge when I get there. Pretty much your numbers dead on a year later. Sigh.

 

[kltye]

@Mach-Lee Not sure how I missed this thread all this time but I was searching for the proper OBD parameters to monitor for preconditioning on the way to a DCFC. Good read through. My test at 30 degrees F, confirmed that I can either heat the battery or the cabin. And even if I forgo Cabin heat the battery won’t heat enough to make a real appreciable difference in how fast I can charge when I get there. Pretty much your numbers dead on a year later. Sigh.

I'd like to beg to differ. It enables the battery to reach proper much better charging temperatures much more quickly than if it only started the heating during charging. It might not hit 150+kW, but it certainly has helped it go >105kW during cold weather and a relatively low SoC when pulling into a DC charger.

 

[Mach-Lee]

I'd like to beg to differ. It enables the battery to reach proper much better charging temperatures much more quickly than if it only started the heating during charging. It might not hit 150+kW, but it certainly has helped it go >105kW during cold weather and a relatively low SoC when pulling into a DC charger.

It really depends on the battery, ambient temp, and how many miles in advance the charger is entered in the nav. If it's 30's or 40's outside, then yes the pack will probably warm up a decent amount before DCFC if it's still somewhat warm from a departure time. But if it's below zero, it just takes too much heat to even move the needle on the pack temp because of how much heat get sucked out the bottom while driving. It's like trying to fill a cup with holes in it.

 

[Murse-In-Airy]

I'd like to beg to differ. It enables the battery to reach proper much better charging temperatures much more quickly than if it only started the heating during charging. It might not hit 150+kW, but it certainly has helped it go >105kW during cold weather and a relatively low SoC when pulling into a DC charger.

That assumes a low State of charge and needing to charge up high. If you need to add less than 40% battery, even from a low state of charge, the difference between starting at 105KW speed versus starting at 72KW speed is going to be 10 minutes or so. I’m not sacrificing my cabin heat to save 10 minutes. It’s a judgement call for each of us to make independently and will require evaluating current SOC, Needed SOC, and ambient temps, as well as how well you dressed, and the comfort of anyone else in the vehicle with you.
When it gets down to it, Mach-Lee is correct, we shouldn’t have to choose between cabin heat and battery heat.

 

[kltye]

It really depends on the battery, ambient temp, and how many miles in advance the charger is entered in the nav. If it's 30's or 40's outside, then yes the pack will probably warm up a decent amount before DCFC if it's still somewhat warm from a departure time. But if it's below zero, it just takes too much heat to even move the needle on the pack temp because of how much heat get sucked out the bottom while driving. It's like trying to fill a cup with holes in it.

I was in Wisconsin during the cold snap, and preheating definitely helped a ton. Granted, I wasn't driving 80 mph, but it wasn't city driving either.

That assumes a low State of charge and needing to charge up high. If you need to add less than 40% battery, even from a low state of charge, the difference between starting at 105KW speed versus starting at 72KW speed is going to be 10 minutes or so. I’m not sacrificing my cabin heat to save 10 minutes. It’s a judgement call for each of us to make independently and will require evaluating current SOC, Needed SOC, and ambient temps, as well as how well you dressed, and the comfort of anyone else in the vehicle with you.
When it gets down to it, Mach-Lee is correct, we shouldn’t have to choose between cabin heat and battery heat.

I agree we shouldn't have to choose, because there's really no reason to most of the time. Setting the temp to 60F in the car is much warmer than needed most of the time, and I see the PTC heater only consuming 1-2kW for a minute or two before going to zero. During this time, the heater could be used to heat the battery, but it doesn't - which is stupid. I dress appropriately for the weather because... I dunno, I have to get out of the car and walk around outdoors in winter? I guess I'm just used to doing that since I've lived in a city forever and walking is just ingrained in me.

I guess I'm just saying preheating the battery is not as useless as some make it out to be. Saving 10 minutes per charging stop on a longer journey makes a huge difference, and saving 10 minutes at busy stations helps others get back on the road faster as well.

 

[Murse-In-Airy]

Tried again this morning on the way home. Surprised preconditioning still happened even at only 13% SOC. But still, only with the cabin heat off.

 

[21st Century Pony]

I was in Wisconsin during the cold snap, and preheating definitely helped a ton. Granted, I wasn't driving 80 mph, but it wasn't city driving either.


I agree we shouldn't have to choose, because there's really no reason to most of the time. Setting the temp to 60F in the car is much warmer than needed most of the time, and I see the PTC heater only consuming 1-2kW for a minute or two before going to zero. During this time, the heater could be used to heat the battery, but it doesn't - which is stupid. I dress appropriately for the weather because... I dunno, I have to get out of the car and walk around outdoors in winter? I guess I'm just used to doing that since I've lived in a city forever and walking is just ingrained in me.

I guess I'm just saying preheating the battery is not as useless as some make it out to be. Saving 10 minutes per charging stop on a longer journey makes a huge difference, and saving 10 minutes at busy stations helps others get back on the road faster as well.

Kitye, I fully agree with all your points based on my travels and experience with this car.

 

[ArthurDOB]

Tried again this morning on the way home. Surprised preconditioning still happened even at only 13% SOC. But still, only with the cabin heat off.

When it gets colder (which it will), I'm going to try pre-conditioning with no cabin heat. I don't "OBD," but I do experiment a bit with things. I don't feel like I need data to inform my observations.

Sponsored