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how to best capture charging electricity usage data?

Discussion in 'Model X: Battery & Charging' started by carteriii, Jan 19, 2017.

  1. carteriii

    carteriii Member

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    I have a HPWC hooked to a 50 amp breaker and I'd like to capture the true amount of electricity that my MX uses, including charging, the amount of electricity used to pre-heat or pre-cool the vehicle, etc. Has anyone used a device like a clamp-on amp meter, either near their breaker panel or near the wall charger itself, that continually gathers that data either for download or pushes it to a service that can report on it?
     
  2. carteriii

    carteriii Member

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    This morning I found something that looks good enough that I just ordered it. It's the Efergy product(s), Efergy USA - Home power monitors and wireless electricity monitors. You need the hub to transmit to their website and allow you to download the data (rather than only the standalone display). The very bottom of the website has a link to an accessories page that will let you buy a secondary transmitter and current sensors (connects to the same hub) so you can have one transmitter for the entire house and a separate one monitoring only the circuit to your charging point (HPWC or NEMA 14-50, etc.).
     
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  3. aesculus

    aesculus Still Trying to Figure this All Out

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  4. AB4EJ

    AB4EJ Member

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    Depends on how high-tech you want to go. A number of people have gotten a surplus electric meter (like power company uses), and simply wired in series with the 220v line going to your charging station/outlet. Low tech, but is said to be effective.
     
  5. carteriii

    carteriii Member

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    I received & installed my Efergy monitor last night, using one set of clamps on my house main lines and one set on just the lines going to my HPWC. I then did a simple experiment and turned on preheating, letting it run until it stopped on its own. My Model X 90D was already charged to the limit I set (70%) and was consuming nothing prior to the preheating. The ambient temperature in my garage was about 40F, car interior showed 42F and I pre-heated to 66F. Efergy says I used 0.57 kWh in total. The first two minutes each used significantly more (2866 Wm == ~0.05 kWh) before things settled down to a range of 900-1200 Wm (~0.015-0.02 kWh). It's obviously just one random data point, so your "mileage"/energy usage may vary.
     
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  6. scsmx

    scsmx Member

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    I use the TeslaFi service. It provides the input kWh used, as well as the raw data if you want to make your own calculation. Since the car captures the input voltage and amps, I am not sure why you would need to monitor at the panel. Unless I am missing something.
     
  7. carteriii

    carteriii Member

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    I was under the impression the data you're getting with TeslaFi is related to charging but doesn't necessarily show energy which goes directly to preheating, and it certainly wouldn't show the (minimal, HPWC Phantom Load Measurements) energy used by the HPWC which doesn't even go to the car (e.g. the green LED). If you believe TeslaFi includes preheating (unrelated to charging), please let me know.
     
  8. SDRick

    SDRick Member

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    The simplest, cheapest and quite accurate method incorporates a relatively inexpensive ammeter. I believe they are around $15.

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  9. scsmx

    scsmx Member

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    Interesting point on the HPWC phantom load. The raw data that I download from TeslaFi has a heater data field, mine is set to False during charging and None or blank otherwise. When it is set to None, I see some valuse between -.1 and -.4 from the battery current when the car is plugged in, but the actual input current is always 0. I think this is telling me that the temp in my garage has not been cold enough to warrant pre heating, but I have no idea what the threshold is for the batter heater to engage. I will post a question to the TeslaFi developer.
     

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