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Encouraging frigid temperature results

Yesterday, when it was 0F, I attempted to pre-warm the battery by starting a charge about 2 hours before departure. The garage was about 38 degrees and the 60% full battery was very slow to accept a charge, maxing out at 4 of a possible 12 MPH. Driving to work, it took a good while for my energy usage to drop below 500 Wh/m though it eventually dropped to about 480 Wh/m after 10 miles, with regen limitations the entire way

So I decided to try a trickle charge technique where I charged at 8 MPH for the 14 hours before my morning departure. I also preheated the cabin about 15 minutes ahead of time. Mind you today it was -15F. There were no limits (dotted-line) on power output or regen. After 5 miles of driving, my average use was 206 Wh/m. I had the seat heat on, but climate off. It was at this point I needed to use the front defroster because it was fogging up, though comfortable. Over the next 5 miles, my avg consumption rose to 270 Wh/m. Because this commute involves about a 400 ft loss in altitude, it's not unusual to make it in under 200 Wh/m. Other confounding factors included icy buildup on the road that raised rolling resistance which also lowered the average speed by between 5 and 15 MPH.

I never considered charging while at work because I don't need the miles added, but considering the great loss in efficiency from a cold/unconditioned battery, it might be a good idea.

I am experimenting with precisely the same, that is, charging at the office, and have indications of the same results. Much better to have a long but slow charge prior to departure than a quick, "brutal" one. I would have posted this, but I didn't feel that I have enough data as yet.

Publish or perish:)

That looks like some promising data. Thanks for sharing.

Good to know. Thanks.

More info
Headed out to a concert tonight, -18F. Car had been in 37F garage, not charging. Regen was limited at 30 kW. This never showed any improvement over the course of a 25 mile roundtrip. Energy usage was 506 Wh/m. The tire pressure warning couldn't decide whether to stay on or off. Of note, I filled my tires to 46 PSI this week (ambient temp was in the 30s) and reset the TPMS for the 19" wheels. I measured the pressures tonight, which ranged between 41 and 42.5 PSI. Also the standard steering felt like sport, but more like standard when I changed it to comfort.

I also recognized a new breed of tailgater. In warmer weather, it's been boy racers generally. Now I'm seeing more jacked up pick-ups that seem challenged by the fact that the bad roads aren't slowing down the car much.

Since the battery didn't appear to be warmed much by driving, as evidenced by a constant regen limitation, I think that emphasizes how important the pre-conditioning charge will be. I wonder if a stop at a super charger will get the battery nice and toasty and running more efficiently. I guess many will get to add more to this collective knowledge as this weather heads east.

Air pressure at -18F is measurably lower than at 30F. The tires must start at 45 psi when cold. Adjust daily to suit.

Brian
I'm aware of the 1 PSI per 10deg loss rule. Easier said than done when it's cold as balls.

@Bighorn - Thanks for the updates. My MS generally finish charging 15 - 30 minutes before I drive off in the morning and haven't seen any regen limitations in the morning. But I would often get regen limitation for the evening commute since the car is not charged at work.

The tire pressure can wait. Keep the balls warm.

Good idea.

It makes sense to use the timed recharging so that there is activity in the battery pack in the 30-60 minutes prior to departure. Get that battery management system circulating and warming up in cold weather.

No need to recharge as soon as you get home in the evening. If your schedule is predictable, let it recharge in the hours right before you depart each day.

@ papa
When it's very cold, it takes a lot longer for the battery to begin accepting a charge. At least in my limited experience, I saw no appreciable warming in the first 1-2 hours which is why I lowered the amperage and extended the charge time. Last night I charged at 10A/ 240V and look forward to seeing what -22F will do today.

Wow, that is cold. My garage is around 40 F and once the car is outside it hits around 25-30 F this week. So I guess that is not comparable to your situation.

I wish we could schedule the climate temp also to start warming up the cabin about 15 minutes before my typical departure time. That would be a nice feature to have a scheduled timer to warm up the inside while still plugged.

Today, Stardate (I have no idea)
Wake up temps warmed to -11F for my commute. Despite being on charge for the previous 12 hours, I had a regen limit of 45kW today. I don't know if it is because I dropped my amperage from 12 to 10 or because I had been parked outside for a couple hours in -18F last night. Over the course of the drive, regen never improved and actually appeared to drop to 40 kW at one point. I was more frugal with the defroster as there seems to be a chronic band of frost by the driver's A pillar that wouldn't clear regardless. Door to door, I averaged 228Wh/m--not bad.

Bighorn, Wow! I would love to even see that number on a nice clear sunny warm day. The best number I have ever seen is 250. My trip this morning showed around 500. The battery was warming and it was only a 8 mile trip. It was 8 F when I left my unheated garage (probably around 35 F).

@Theresa
Don't feel bad, it's downhill and I see usage in the 190s on more temperate days. After completing a roundtrip, my usage is up near 300.

I think if you tried the overnight charging, you'd see that 500 figure drop precipitously. I also pre-warmed the cabin for 20 minutes and my app showed a temp of 86 despite a setting of 74.

Seems like a good feature for a future upgrade to figure all of this out automatically and do the optimal charging based on car temperature.

@Chunky - as a future owner in a cold climate, I'd say your suggest is a good one. The extended trickle charge suggested by the OP is a backdoor way to warm the battery for a long period of time.

I'm still surprised that the Tesla, once done charging, doesn't use shore power to warm the battery.

@Bighorn Thanks for the idea, I think you are on to something good! I charged all last night at a lower 18A and preheated for about 15 minutes in the morning while charging. I had way less regen limiting than the previous day and the regen limit went away during a 20 mile commute. Outside temp was around 0 F. Garage temp just above freezing.

Saw the effects of a cold battery tonight. Lows to -24F with 30 mile average of 600 Wh/m. First time seeing no regen--seems significantly different than having as little as 5 kW. Almost feels like there's some residual power moving the car forward. Also funny to see 10 kW of output with foot off the accelerator due to battery warming and climate consumption. I'm glad this is freakish weather, but ultimately it's been extremely comfortable always having a warm car and the decreased efficiency is more an academic exercise as I have a short commute.

Glad you saw some benefit, MN.

I've been doing an eight hour charge for the last two weeks. I simply adjust the amperage so charging completes within an hour of leaving in the morning. Garage temp is in the 40s with outside in the 20-35' range. I preheat the cabin for about 20 minutes while plugged in.
For a 18 mile commute I typically consume only 15 miles of rated range all with the cabin and seat heaters running. Power consumption is about 265 kW which is less than what I see during the summer.
My return trip is with limited regen and consumption in the 350 range since I don't plug in at the office (yet).
Hope this helps!

panoz;
Would require scheduling your departure -- the car would have to know when you want to leave. Coming feature.

This is some great information Bighorn. Thank you for sharing what you have learned. Only once in my life I experienced -20F.
I found that the difference between -10F and -20F is astounding.

@Panoz, Chunky: I would think a bit of software for version 6 or so could add something that would handle this. A setting/control that would say, "Warm battery for..." coupled with a simple timer.

@Zap
It's been gratifying to get to see how the MS handles at the fringes--a trial by fire, so to speak, since one of the most common questions I got from my test-riders was "what about the winter?" I've only seen temps this cold here once in the last 17 winters and a neighbor pointed out that it's a few degrees cooler here (-27F this am) than Antarctica (Antartica, for you;)). I passed one of those friends in their Cayenne Turbo, bundled up as for an expedition while I can take off my coat at the outset of any journey courtesy of the climate app. Another friend was lamenting how their new Q7 TDI was dead in the water because of the cold.

These temps are crazy--they remind me of when I was a "yout" back in NY and we'd go skiing in Lake Placid. Your nose hairs freeze on first inspiration. You can't breathe through your mouth for the stinging in your lungs and the coughing fits. Have to breathe slowly through your nose, preferably through a scarf or neck of your jacket. Talking to friends in Alaska, I know there's a whole nother level there with temps 30 degrees colder where cars, if you can start them, can overheat because the antifreeze sludges.

I don't see letting a charge finish some time before you're ready to go as that gives the battery a chance to cool down. I've dispensed with completing a charge and arrange for the charging to be almost done for when I anticipate driving. I agree that future software will come in handy to achieve this battery warming without forethought. Perhaps some adjustments have been already been made for the cold weather package.

Everybody is misunderstanding my suggestion. My idea is that AFTER the battery is charged, shore power is used to keep the battery warm ALL THE TIME. Continual (but minimal) power draw. No timer. No having to know when I'll leave. Just plug the !?#!! car in at night, and in the morning the battery is charged AND WARM regardless of when I leave.

With my idea, you could leave your Tesla outside on a cold night and hop in at ANY TIME with a warm battery if you plugged it in. If it was sufficiently charged at your destination, then just 110v would keep the battery warm.

Another software design would be to use battery power to warm the battery if more than half-charged.

@Panoz
I hear what you're saying--I don't know how a minimal power draw could counteract really low temps, though. Options are always good.

@Bighorn

This event is a doozy. I read this at the NWS site:

"IF THE FORECAST LOW OF 18 AT SEA-TAC VERIFIES TONIGHT...IT WOULD BE THE COLDEST SINCE NOV 2010. OF COURSE...SEA-TAC TENDS TO BE ONE OF OUR WARMER REPORTING STATIONS ON CLEAR COLD NIGHTS."

The temperatures at SEA-TAC are some of the most moderate in the region. Everyone else can expect extremes. There was only one time in recorded history that SEA-TAC hit zero Fahrenheit.

Hello southerners, it's coming your way!

It was 20 F today and I got my first 12 volt low warning. Car started fine though and worked normally otherwise. Regen limited to 15 kW initially which was the lowest I have ever seen it. Battery warming alert on.

Is anyone else getting low 12 volt warnings due to cold weather?

@PapaSmurf

Is your car fairly new? Is there a chance that it may still have one of the inferior 12v batteries that are being replaced?

In any case, I'd call Ownership and select "questions about your car" and let them know, if I were you. I bet that they would diagnose while they had you on the line and be right on top of it if there is a problem.

What is really needed is a "Depart Soon" button. Pushing this button on the car or on the app would notify the car that you intend to start driving in 10-15 minutes. The car would then heat/cool the battery and cabin as appropriate using shore power if available. If you don't leave within 15 minutes the car goes back to sleep. But if you leave after 16 minutes the cabin and battery are still very near optimal temperatures.

We humans don't know all the parameters that go into preconditioning the car, nor should we have to. The climate control is already set to a reasonably appropriate cabin temp. The car knows what the battery temp should be. It knows the environmental temp. It can compute how fast it can heat/cool the battery and cabin to optimal temperature. The only thing it doesn't know is the target departure time. The "Depart Soon" button provides that. So the car has all the info it needs to prepare the car for departure.

The driver presses the "Depart Soon" button on the app. The car starts heat/cooling the cabin and battery using shore power. Fifteen minutes later the driver pulls away in a warm cabin with the battery at operating temperature. No big hits on range. No reductions in power or regen.

A timed departure, "Depart At" 7:43AM is a trivial addition.


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