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Effects of charging on home service voltage

Discussion in 'Charging Standards and Infrastructure' started by FlasherZ, May 19, 2016.

  1. FlasherZ

    FlasherZ Sig Model S + Sig Model X + Model 3 Resv

    Jun 21, 2012
    #1 FlasherZ, May 19, 2016
    Last edited: May 19, 2016
    While doing some of my investigation work behind the HPWC failure, I pulled my data records for voltage as seen on my 6 kVA UPS, and it turns out that things have been running "hot" enough (voltage-wise) to put the UPS's into "trim" mode, where they're cutting down the voltage. This may be a contributing cause to the failure of the HPWC.

    I sample my voltage at the UPS inputs once per minute, so I have a fairly granular record of what my home voltage looks like. More importantly, I can show you what happens to the service voltage as heavy loads are put onto the system.

    Here's a graph of the voltage as seen over the past 18 hours or so, along with a 3-hour moving average (in orange) - unfortunately, the granularity of my UPS measurement is limited by the UPS communications protocol in use. As you can see, we're running pretty hot - averaging between 251 and 254V when the cars aren't charging; the power company is coming out today to take a look. My home load really isn't changing overnight, but you can see the effects that other places around me (a good chunk of them farms) have, beginning at 4 am or so.

    You can see that charging the Model X (69-70A) tends to drop the voltage from just over 252 down to 250 or so, and adding the Model S load to that (another 80A) drops it to around 246.5 or so.


    I have 400A service, with 2 independent HPWC's. One is attached via a separate 100A connection to lugs in the base of the meter, one is attached as a 100A feeder from my 200A grid-only service panel that feeds various non-critical loads in my home. Transformer is approximately 75 feet from the service entrance, using 350 kcmil compact conductors.

    (Yes, I know you can calculate this fairly easily with Ohm's law and some approximations of ohms per foot given your service conductor size and distance from transformer, but I figured some empirical evidence would be interesting.)
    • Informative x 2

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