I've read that a somewhat typical specific heat capacity for EV battery packs is in the range of 800 - 850 J/K*Kg
Your number is about in that range
My M3P 2021 heats the pack with more or less 1C/ minute using 6KW of motors heat. This is during the rapid heating.
(I have very exact data of this logged)
This tell us each minute is 0.1 kWh worth of energy 6 kW x 1/60= 0.1)
It takes 30 minutes to increase the temperature 30egrees.
Combined, we see that per each Centigrade we store 0.1kWh in the battery.
In (really) cold weather when the heat pump cannot use ambient outside air to excess heat, the heatpump use the battery heat down to 11-12C, if there is any heat to use.
End temp of a (correctly performed) supercharging session is about 58C so we have (58-12)x 0.1 = 4.6 kWh of heat to use.
A heatpump/octovalve car will not dispose this heat outside but use this to heat the cabin. This reduce the consumption quite much.
I have lot of logged examples and even a fresh example of this from yesterday.
After supercharging from 30-80% I drove 77km starting at -21C(-6F) and ending at -18C (0F), at an average speed of 86 km/h.
The consumption was 191 Wh/km, and the battery temp decreased steadily from about 50C to about 20C (I will supply better data in a while).
At location I had the car connected to a free AC-charger, that kept the tempersture in the battery to around 10-12C.
No battery heating was needed on the return drive as the battery was not cold.
The starting temp was -18C and when passing the Supercharger on the way home it was again -21C.
So the temperature was more or less exactly the same and there was absolutely no winds (we ”always” have inversion when cold, so all wind will stay higher up in the atmosphere and it will be no wind at ground level. All smoke goes straight up at least to 1000 feet.
The return drive, at same speed/temp and same road consumed 260Wh/km when I passed the Supercharging station.
As the battery was not hot enough it was passively heated by the rest heat of the motors and heat loss of the battery, sloooowly heating from about 10C to 15C.
On a longer drive, the battery would reach about 17-18C and then the heat pump would suck the energy of it down to 11-12C, then this repeats.
I think it is ballpark correct to say that after Supercharging, the car wants to reduce pack temperature about 15C quickly (say, within 20 minutes). If the heat can be utilized or stored elsewhere -- great. If not, it gets expelled to ambient.
Not in heat pump cars, see the answer above. For pre hestpump cars, I think you are right.
I will supply good data of this after building the IKEA warderobes we got yesterday.
A 15 C drop in pack temperature using 825 J/K*Kg in an 80 kWh pack (Model Y LR) calculates out to 1.8 kWh, or about 5.4 kW over 20 minutes. After that heat dump, the pack has another 10C or so to 'spend' before the next Supercharger stop. Unless ambient is **really** code, I have read that a COP of ~ 2.0 is realized, which implies another 2.4 kWh of heat into the cabin.
The COP ~ 2 refers to a specific temperature of the hest source we are taking energy from, like outside air and 0C or so.
Fir at least other heatpumps, increasing the source temperature by 3C increase the COP by about 10%. (I have data on this as well.
When the battery is 30C or more, there would not need to be any heat ”pumped”, just heat exchanged so the losses or need for extra energy added would be transfer pumps and fans only. The octovalve should be able to supply heat directly from the battery to the cabin.
When the batt temp goes below ~25C or so, whe need to ”heat pump” to increase the temperature, but still with a source temperature at 12C or above the COP should be very good. Even in a smaller/cheaper heat pump.
