I'm finding something interesting when trying to START CHARGING from the iPhone App. Here is the scenario: The car is 30 RM below the DAILY LIMIT and I want to charge it to heat the battery. It's real cold. 10 degrees. So, the battery is real cold too. When I press the START CHARGING button on the app, the wheels spin and it tries, and then the screen re-appears with the START CHARGING button displayed again. At that point, the STOP CHARGING button should be appearing if the car is charging. So, it isn't charging. If I go out to the car and manually start the charging, once the battery gets up to temp and it starts charging, I can STOP it from the phone, and then START it from the phone. SO, my takeaway is that the app won't start charging the battery because it's too cold ... kind of defeats the purpose of having a remote charge option on the phone, when it's cold. The car is in my garage, with good Internet connectivity. It's plugged into a HPWC and I can pre-heat the cabin with the app. I've called Tesla and am waiting for their reply Your thoughts?
Here is what is happening. The reason that the bar looks to be lower then the daily limit, is because of the cold. The batteries cannot provide as much power when they are cold, especially cold soaked.
Now, hypothetically, for purpose of explanation, say out of nowhere your neighbors Hummer bursts into flames, and the million gallons of gasoline that is burning was enough to raise the ambient temperature to say, 80 degrees, and your pack warmed up, with no charging what so ever. You would then notice your charging bar (and range) increase to near what you had it originally charged to.
Due to the pack warming, it regains the ability to provide that power, and as such, goes back up. In the cold, the power is still in the battery, just "in-accessible". And as such, the car cannot dump more power into the pack. In this case, you would need to raise the slider slightly, maybe a few %, to give it enough headroom to start the cycle.
You may also notice, depending on the temperatures and pack temp, that charging may be extremely slow, or none at all, even though it says charging. in this case, the pack would be so cold (below 32*F or below 0*C) it would be unable to charge. In this case, the pack heater will be running. Via the app, pack heater consumption will not show. It will show on the charging screen though.
Once the pack is above the said temps, charging will start, first at slow pace then faster.
Lithium Ion batteries cannot be charged at or below freezing. Doing so will result in PERMANENT capacity loss. The Anode in the battery get electroplated. This is also why regen is disabled or severely reduced on a cold pack.