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HPWC Phantom Load Measurements

Discussion in 'Model X: Battery & Charging' started by Solarman004, Jan 31, 2017.

  1. Solarman004

    Solarman004 Member

    Joined:
    Apr 27, 2016
    Messages:
    345
    Location:
    Colorado
    I was curious about the level of my Nov 2016 High Power Wall Charger (now called the Wall Connector) phantom power loads-- the power consumed that is not going toward charging the battery. Using a Hall effect clamp-on ammeter at the circuit breaker box, I took the following measurements:
    Conditions: Temp = 43 deg F, Range Mode= Off, Power Saving mode On, Always Connected= Off, HPWC on a 50 amp circuit and set to 40 amps max charging power
    Line voltage measured at 243 Volts

    1. HPWC connected to car, not charging, climate control off: 0.02 amps, 4.9 watts (42.9 kWh/year; 3.6 kWh/month)

    2. HPWC not connected: 0.02 amps, 4.9 watts (same energy consumption as above)

    3. Charging with climate control off. Car display indicating 40 A, 243 V charging: 40.3 amps, 9792.9 watts

    4. Charging with front and rear heaters set to 72 deg F, fan=3. Car display indicating 40 A: 40.7 amps, 9890.1 watts

    Observations:
    1. The background power consumption of the HPWC controller and relay is very small. To put the 3.6 kWh monthly energy consumption in perspective, the average American household consumes 920 kWh per month.
    2. Background consumption of the HPWC is the same whether or not the HPWC is plugged into the car.
    3. As would be expected, the HPWC maximum current set in the rotary dial is the maximum that is sent to the car regardless of whether or not the car is using auxiliary power for climate control. This makes sense so as to not overload the HPWC circuit. So when the car is charging and HVAC is on, the battery charging and HVAC will split the current being provided by the wall unit, in my case, 40 amps.
    4. I did not measure at the breaker box the HVAC power draw when HVAC is on, and the car is plugged in but not charging. But I have used the car display to get a rough idea of this consumption. With garage temps in the 40s, car plugged in but not charging, turning on either front or rear heater to 75 degrees (not at the same time), I have seen spikes of 3.6 kW power consumption before it settles to approximately 1.7 kW. This will vary greatly with specific conditions such as cabin temperature and the modulating of the heater or air conditioner as it tries to reach and maintain the thermostat set point.
     
    • Informative x 3
  2. Ampster

    Ampster Member

    Joined:
    Oct 5, 2012
    Messages:
    833
    Just a clarification about what is sent to the car. You mention that only 40Amps is sent based on the setting of the HPWC setting. What actually is sent from the HPWC is a message that tells the car how much to pull from the HPWC. My guess is the HVAC and heater run off the battery even when the car is plugged in and that is why you saw no current drawn through the HPWC. Others have observed that there is a trigger point when the battery management system sends a signal to the charger and it turns on.
     
  3. Solarman004

    Solarman004 Member

    Joined:
    Apr 27, 2016
    Messages:
    345
    Location:
    Colorado
    I agree... I've seen this also when the car is plugged in but not charging, and I turn on the heater. There is a fairly low threshhold where the power draw switches to the external HPWC. The charging display in the car goes from "0/0 Amps" to "xx/40 Amps" as the heating element kicks in. And, you can hear the relays in the car switchong on.
    At that point, given the high consumption indicated, it appears that all of the power running the heater is coming through the wall unit.
     
  4. Macgaver

    Macgaver Member

    Joined:
    Dec 6, 2014
    Messages:
    271
    Location:
    Montreal, Canada
    If the charger is still plugged and you have HPWC running, then the current come directly from the wall (and you see the charger flashing).
     

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