There’s a faulty idea of how to ideally charge an Tesla with best efficiency in cold wx in Swedish Facebook forums. (Somehow the humbleness there is 0.0 for accepting new thoughts, dunno why).
A good thing that this is not how I experience it here.
Anyway, earlier without heat pump it maybe could have been an good idea to charge at arrival.
But with the function of the heat pump + octovalve and use if battery heat, the best way must be to charge late and at maximum possible power (preferable 11kW for AC). Having the car inside a garage if possible would also be good.
I havent kept track of the input energy lately, but fir the M3P it was a little more than 10% over the year. More wintertime with preheating etc, but charging late in a warm garage means the battery is warm enough not to need battery heat, and the heat generated is used by the heat pump in the morning drive to heat the cabin.
Not much losses.
The heat pump/octovalve/battery+Drive unit heats is fantastic. Understanding how these work together give us the opportunity to maximize the win from this system.
I have two examples that almost have to be told about, even if the post will be slightly long.
We did have extreme cold for one week.
Mostly -35 to -45C in the areas where I live and work.
I had to go to work 300 km away during this cold period. It was extremly cold both ways.
The home trip started after two days/nights with -40* to -41C, with MSP parked outside at work. Leaving work at official -35C I supercharged on the nearby SuC, and then drove 300 km home. It was -30C arriving home.
My MSP mostly use ~200Wh/km summertime when driving longer drives with the 21”. Wintertime on 20” plaid-arachnid look-alikes with studded tyres.
I had 220Wh/km when arriving home and the average temp during this drive must have been around -30C or so.
For the first ~ 2 hours when the battery still had heat energy to deliver to the heat pump, the consumption was about 210-215Wh/km, thats less than 10% extra consumption compared to summertime.
Cool (intended) to have a real range in extreme cold that is not much less than the summer range
View attachment 1008060
*The temperature indication is not correct on my MSP. Real temp -30C here, and it only showed -28C parking om an airport with the official temp -35C
How come it can be driven so efficiently in cold?
Well, the secret is that with the heatpump system with all things listed earlier, the heat pump prefers to use the battery heat energy before the outside air for heating.
Below ~ -10C the outside air can not be used efficiently at all.
So a freakin cold day, the car do not care much about this (the air resistance is higher, so slightly more consumption due to this).
But as long as the battery is warm and can deliver heat to the heat pump, the car will be very efficient.
Very efficient actually.
There was some comments of the heat pump being non efficient on short drives, so I made a few tests at home last weekend (at about -28C).
First test,
car in the warmed garage, heated the battery to +17- + 18C (to be warm but nit as warm as a home charge in my garage makes it. Preheated the cabin to have it heated already not to disturb the test.
The 7 minute 6km drive ended at 189Wh/km.
Second test,
Car outside, cold soaked to ambiemt with cell temp -4C (colder than planned, was aiming to have regen working):
The same drive but I started by driving around to get the cabin warmed up. Before the test, i parked abd briefly went outside to trigger a new trip measure of consumption.
The car did not actively heat the battery so it stayed below regen limit.
6km / 7 minute drive costed 363Wh/km. Regen seem to be about 10% of total energy so if we had the battery warm enough for regen we probably would be around 330Wh/km.
Last test, basically the same as test 2 but warm battery.
Car parked outside, cold soaked to about the same but the battery heated with dragstrip mode to +13- +14C (was to lazy to wait for same temps as test1. Also driven a little to make the cabin warm before the test. Consumption 214 Wh/km.
It’s a huge difference!
And this can come for free by charging late with high power (preferably in a warmed garage but not necessarily).
I know not all can use do this practically and in some cases only the first drive of the day will offer a warm battery, but at least knowing the tricks might be helpful the times it is possible.
Even if the car is outside, charging late with high power will make it possible to use the combination of the battery heating already paid for, plus the charging heat losses to heat the car, reducing consumption.
*) -40C = -40F
