At very cold temperatures it seems that internal resistance goes up considerably (just looked at a couple plots), so presumably that limits the energy that can be extracted, and when the voltage will drop out (too low for what it is driving, even though plenty of energy left)?
The internal resistance is higher the lower the cell temp. Even at normal or high temperature. This is why we precondition the battery before SuC to 48-50C.
But internal resistance do not affect the OVC at all, only when drawing current from the battery.
The general thesis about lithium ion is that the OVC reduce when the temperature increase. (This is mainly at high SOC, different types of cells have different temperature/voltage curves. I got the same voltage at +25C and -18C with one of my Panasonic 2170.
As a Tesla normally use like 0.15-0.25C (10-25kW) or so, it would not be any problem to drive even if the battery is very cold, and the car heats the battery to above freezing at latest when we start to drive.
So even though no change in voltage…there would be a change in voltage under load (which maybe what was meant but it is good to be precise about what is happening).
Yes, when driving the voltage drops more with a cold battery than with a warm.
More power = more voltage drop
Colder battery = more voltage drop
Lower SOC = more voltage drop for the same power.
The battery need to drop the voltage to be able to deliver power due to the internal resistance.
This is a question. I’ve always assumed that was the reason for the snowflake (which I have never seen of course).
In practice as long as you have high enough SOC presumably pack warms up and it is never an issue.
Car gets very upset if you park at low SOC in low temperatures so I assume this is an actual issue (for very low SOC).
The bold part is not really true, if you ask me.
There is no new warnings if you park in very cold weather with very low SOC, the warning is the same as in the summer.
Of course, parking with 0 or 1% in a very cold weather could mean that you have too little energy for the next drive.
But when the car sleeps with the battery disconnected it will not loose voltage due to the cold temperature. If the cells are at 3.00V, they will keep close to 3.00volt when the battery has colled down.
It is a common missconception that it is the voltage drop that cause the low SOC on the screen. It is not, and the BMS still reports the same SOC as when you parked but the screen show a lower number.
I would guess Tesla did it like this to adjust for the energey that will heat the battery (and maybe the car), so that we still can thrust the range number displayed (otherwise 100 miles maybe only get us 90 miles as 10 miles was needed top heat the battery etc.)