Yes but only until the battery reaches the set charge limit, else 100% state of charge (SOC). If you plug in at 20% SOC and charge to 90% SOC using the 5A setting (assuming Level 1 at 120V) charging could take several days to reach 90%.
I agree with everything in your post. At these extremely cold temps, I would use a circuit/charger that could deliver at least 8KW. Then, enable Sentry mode so the car would wake to top off and warm the HV battery enough to allow this charging. Be interesting to see about how long and how much energy would be required to warm a cold soaked HV battery from say -45F to the point where charging could begin (maybe a SMT owner cold perform such a test). That said, if the HV battery cells were down to -45F they might already be damaged?
The risk to a lithium battery at temperatures below -23F (-31C) is that the electrolyte can freeze and damage the cell(s.) Charging (also adding energy to the battery via regenerative braking) would damage the battery whenever the battery temperature is below 32F (0C). The battery management system will always warm the batter, first, prior to charging (Recent information shows that the battery will be warmed to right around 39F (4C) before starting to charge.)
Brain teaser follows:
Converting 1kWh to BTU = 3412 BTU; 3.5kWh = 11943 BTU. Using the old definition, 1 BTU is the amount of heat energy required to raise 1 pound of water +1 degree F. (Disregarding that the battery cells are not made of water (but the coolant does contain water), 1000 BTU would be needed to raise the temperature of 1000 pounds of water +1F. 61000 BTU would be needed to raise the temperature of 1000 pounds of water by +61F.
So if I am reading your post correctly, the long range battery could be heated up by 61F in around 30 minutes and use less than 2KWH of juice? If true, all I can say is unbelievable to WOW!
Math was wrong; it would take 2.5 hours for a dual motor Model Y consuming 7kW for a total of 18kWh (18kWh is slightly more energy than is stored in 1/2 gallon of gasoline, so this seems crazy.) With a single motor stator generating half as much heat it would take 5 hours.
Glad you had a support truck with you, that would’ve been scary with kids. Aside from the louvre issue, I wonder how well the heat pump can perform that cold. I always thought that heat pumps were severely limited with air under 5F (-15C) due to the moisture content of the air. I have no idea how a heat pump actually works, or how it’s connected in the car. Maybe it would be different using recycled air from the car, ambient air warmed from the battery/motor/etc. Still think it would have been nice if they had left the resistive heater in there as well though.
I think even the best residential heat pumps run out of steam(pun intended) at around -10f. I can't imagine there's ANY harvestable power at -67f, but maybe the folks at Tesla slipped a resistive heater in there, or are doing some magic with waste heat from the drivetrain.
Heating the cabin is important but the bigger question is how much ENERGY would be required to warm and maintain the cell temps given the following three conditions. (Heating the battery via the motor stator windings has many none insulated surfaces, where the heat generated, will be lost, ie.. motor/inverter housings coolant lines, pumps, valves etc..)
Normal minisplits do run out at -15F or so. My Mitsubishi goes to -26F (although it struggles, of course) but it has other circuits to help it accomplish this.
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very very good point. I usually run my tires at 38psi for comfort but cranked em up recently due to low temps. my drive from the ski hill 45 minutes gives me an extra 3% with 43psi because of the extra roll out for downhill regen
I think that is all correct in the case where the car is not plugged in.
GM engineers for the Chevrolet Volt designed proactive heating of the Volt's battery pack into the battery management system as long as the Volt was plugged in. The Volt's battery was maintained between 32F and 40F when the Volt was plugged in. (Some of the original Chevrolet Volt team were from Detroit. The Volt team was well versed in winter driving considerations.
You’d be surprised how well most modern cars handle the extreme cold temps we can get in far northern climates. Most modern vehicles ICE and EV are daily drivers around here with little to no issues even being unplugged (block heater/EV charge) for your workday or overnight. The problems come from multiple days being parked outside unplugged and not driven or started. The ICE vehicles issues usually lie around the 12v battery becoming too cold to start the vehicle. A fix for this is to plug the vehicles block heater in a couple hours before you want to go or remove the battery and bring it inside to warm up then your good to go. And EV left outside in minus 40 for a few days is fine if it gets a precondition for an hour or to improve it a bit plug it in for a hour or two while preconditioning/warming up.
I think you a basically correct. If the car is plugged in, after the charge level drops around 3% below charge level set point, the car will wake up to bring the HV charge level back to the set point. If the battery is below around 39F, it will be heated to that point to allow L2 charging to begin. If it takes several days to drop that 3%, the battery could drop below the -22F danger point (depending on the ambient temp). If something keeps the car from sleeping, like Sentry, I think the car could top off as often as every 15 min? If true, the battery would not get much below 39F but the electric bill might be quite high. If temps were not in any danger of getting below -22f for any length of time and the car was going to be parked for several days, I would leave the car unplugged to not incur multiple battery heating operation for each top off; however, if the car was exposed to temps below -22f for an extended period, I would turn Sentry mode on so the car would wake up at least twice a day or possibly every 15 minutes to top off (and warm) the HV battery. In extreme cold conditions, refrain from charging to 90% charge level then dropping the set charge point back to 50% because, even if plugged in, it could take a few weeks to drop back to 50% set point. Sorry for the long rambling but hopefully you get the idea. Clear as mud, right!
