I would be interested to know if the power that goes towards keeping battery pack temp up comes from the barttery or straight from the wall (bypassing battery)? The battery can't charge AND discharge at the same time right? So if heating power comes from the battery it self then current draw from the plug (charging) would be intermittent with periods of heating between? If heating energy comes dorectly from the outlet then draw would be continous, with some going to heating and some (obviously just a little) to charging.
I wonder which alternative is better For battery wear? If heating comes from pack it would probably be more efficient, since the discharge it self creates some heat, but it would also mean more charge/discharge cycles over time (without adding miles to the car) albeit without probably ever reaching lower SOCs.
I'll try to keep this basic. (Some times I have trouble with that
)
Whether its ICE cars, cell phones, AA's or your electric tooth brush, they all charge basically the same way.
I'll use cars and easy numbers (not exact)
When a 12v battery is charged it really reads 13v, and when dead it will have 10-11volts. 12 is the average so we call them 12 volt batteries.
If you want to charge a battery, you most apply a higher voltage to it in order to get current to flow in the proper direction. Also greater the voltage difference, the greater the current flows. This is why battery charge rates lower as the battery become closer to full charge.
So charging systems will run at 14 volts to charge the battery, this is slightly higher but not too great to damage the cells, So current flows into the battery. There are other systems down stream of the battery, head lights and fuel pumps will also draw current. They aren't discharging the battery, because the charging system is able to offer up more current then the battery can handle. Picture the system as being tied to a Tee, some current goes to the battery, some goes to other loads. In the case of a cell phone the wall charger has a higher output then the phone uses, so while you chat the extra current ends up in the battery.
So in the Model S, when you plug into the wall, some current goes to the battery pack, and some goes to other systems. It doesn't matter where this split happens, at the battery or up stream at the plug. In the OP'S case 2km's worth of energy was being added to the battery pack an hour, This was the available after all the other systems used what was needed. And was probably only for a few minutes, once less energy was needed for other systems (heating), the battery would have access to more.
This is why they use the term current draw, everything draws from the source, once the demand stops, the current stops. And that's why you set Amperage draw from the touch screen, your telling the car what to "ask" for.
Hope this helps
