Charger powering car systems

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Burnchar

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#1
Does a charging cable for the Model 3 charger power systems directly or through the battery?
For example, if I run the heater while connected to a SuperCharger, does the heater draw power directly from the SuperCharger, or does it draw from the battery as the SuperCharger charges that battery?
 

Ed Woodrick

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Atlanta, GA
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#4
All car power comes from the charger while plugged in.
Are you really sure about this? If this was the case, then the internal systems would have to be switched between the different sources.

I'm pretty sure that the charging cable is connected to the up inverter, which is then connected to the battery, the down converter, that most other things are connected to is also connected to the battery.
 

garsh

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#5
Does a charging cable for the Model 3 charger power systems directly or through the battery?
For example, if I run the heater while connected to a SuperCharger, does the heater draw power directly from the SuperCharger, or does it draw from the battery as the SuperCharger charges that battery?
TLDR version: it's going to come from the charger.

Longer version:

When charging, the PCS is going to supply a voltage to the battery that is slightly higher than the battery's voltage. This is how you charge a battery.

The HVC is going to take whatever voltage it finds on the battery's terminals and use it to run the car's systems. As long as the charger (and PCS) can supply enough power to keep the voltage higher than the battery voltage, then any power the HVC takes from the battery's terminals will actually be coming from the charger, and the battery will continue to charge as well. The voltage that the PCS presents will necessarily drop a little, and the battery will then charge a bit more slowly.

Now, if you're using your Mobile Connector to charge from a 120v 15 amp outlet, and you turn on the car's heater, you'll find that the heater requires more power than what the charger (and therefore the PCS) can supply. In this case, the PCS will no longer be able to maintain a battery-side voltage higher than the battery pack's current voltage. At that point, any power that the HVC tries to draw from the battery terminals is going to come from both the charger (via PCS) as well as additional current from the battery.
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This description is all based on what I learned while studying Electrical Engineering 25 years ago (as well as guesses as to what exactly each system in this diagram is doing). Feel free to correct me if I got something wrong. :)
 
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