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Installed a Charger Meter for under $20

Discussion in 'Model S: Battery & Charging' started by brantse, Sep 27, 2015.

  1. brantse

    brantse Member

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    I want to be able to get a better idea of my "true" energy consumption and understand what really is the most efficient way to charge (ie. 40A max or something lower), so I picked up a very cheap meter on ebay. The meter comes with and only uses a single CT, so it assumes that the charger is balanced between each phase. So far that appears to be the case, as it is generally very accurate when compared with the display shown on the car. I'll update with some information after I've had several days/weeks to measure and calculate some efficiency results.

    IMG_20150926_125149637.jpg
     
  2. green1

    green1 Active Member

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    Neat idea, any more detail on which meter you got, how it's mounted, etc?
     
  3. FlasherZ

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

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    257V? That's running pretty hot!

    1 CT is fine, as the EVSE/car uses only 240V (L1+L2).
     
  4. brantse

    brantse Member

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    Here is the specific meter I used... http://www.ebay.com/itm/321789747389. There are many different sellers offering the same or very similar versions of this inexpensive meter. Just be sure that you get one that provides sufficient measurement and display capabilities (>50 Amp & >10 kW). I tried mounting it initially in a 2"x4" handy box, but it was just a little too snug. At the time I purchased, I was able to get this enclosure for under $5. I would look to find something similar, but be aware that you'll have to cut the opening for the meter yourself.

    Installation is a snap. You just need to disconnect one of the legs feeding the 1450 outlet and slide the CT over it. Then just land two small (18 gauge) wires on each of the 1450 supply terminations, to sense voltage. Of course, do all this after you've opened the circuit breaker and ensured that everything is safe.

    Yes, Flasher, my home's voltage has always been supplied hot. I contacted the utility about it years ago and they sent someone out to test it. He said it seemed fine to him and that I must have had a faulty reading with my multimeter. I have voltage displayed all the time now with three different devices and they all tend to read within 1 volt of each other, usually always 127-129 on each leg.
     
  5. mknox

    mknox Well-Known Member

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    That's a pretty inexpensive device. Any indication as to whether it is UL (or equivalent) approved? I might be inclined to install in-line fuses on the voltage reference lines (similar to fused leads on a multi-meter.
     
  6. FlasherZ

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

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    Wow, I'm amazed. Did he get a different reading? Or he just didn't want to go through the hassle of changing your transformer tap?

    I imagine you'd probably go through incandescent light bulbs at a rate nearly twice that of a normal person - unless you purchased the 130V ones.

    - - - Updated - - -

    #18 wires will act as an in-line fuse. :) Fusing current for #18 is about 80A or so at room temp.

    That said, just kidding, it's a good idea to add an in-line fuse holder to those wires.
     
  7. brantse

    brantse Member

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    Yes, I can't recall what reading he was getting at the time, but it was reasonable (122-124V) and said it wasn't high enough to cause a concern. I don't have too many incandescents left (most have been swapped to LED), but don't recall them going excessively quick. They probably were, I just didn't notice.



    Unfortunately, I'm a mech engineer and only know enough about electrical to get me in trouble. I know they are often installed that way, but what exactly is the purpose of fusing these voltage leads? It's not much of a loss if my meter happens to get toasted....just the pain of waiting for another one to be shipped from China.

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    I didn't look, but at that price and judging from the poorly translated manual, I would highly doubt it has any approvals/certifications.
     
  8. mknox

    mknox Well-Known Member

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    I was thinking that if the meter itself shorted out, the fuse would prevent the meter from potentially exploding. As @FlasherZ mentions, those small wires would probably burn clear anyway, but always better safe than sorry... especially for a device of dubious quality connected directly to 240 volts.
     
  9. FlasherZ

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

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    It will protect a board failure from generating intense amounts of heat that would not trip the 50A circuit breaker. Let's take the easiest case: that #18 wire becomes a dead short across the 240V. The #18 wires won't provide enough of a path for fault current to trip that 50A breaker. The wire will melt at about 80 amps or so, which means that you're somewhat protected and the circuit would be broken, but the 50A breaker simply won't trip. This means intense heat or fire could be generated.
     
  10. SabrToothSqrl

    SabrToothSqrl Active Member

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    With these things so cheap and only measuring 1/2 the circuit... you could buy two? Or the obvious, just double the reading...
     
  11. mknox

    mknox Well-Known Member

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    The Tesla UMC uses a 240 volt connection (not a 120/240 volt connection) so 1 CT is all that is required.
     
  12. Solarguy

    Solarguy Member

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    Here is another BUD enclosure that is pretty inexpensive that should work:
    http://www.ebay.com/itm/181663363418?_trksid=p2060353.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT
     
  13. brantse

    brantse Member

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    As I mentioned, I'm somewhat out of my element with this stuff. Can someone suggest a small fuse type and holder that would fit in such a small enclosure.
     
  14. brkaus

    brkaus Member

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    Sorry for the tangent - What is considered as an acceptable range for 240v?
     
  15. FlasherZ

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

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    ANSI standard is +/- 5%, so 228V to 252V.

    - - - Updated - - -

    There are a number of them. You'll want to use AGC fuses, they're the small glass tubes rated at 250V. A 1A fuse should be sufficient.

    Here's one of them:
    Amazon.com: PODOY In-line AGC Fuse Holder: Lamps Light Fixtures

    Any AGC fuse holder should work.
     
  16. mknox

    mknox Well-Known Member

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    In Canada, CSA Standard CAN3-C235-83 governs this.

    Normal Conditions are defined as 220 - 250 volts
    Extreme Conditions are defined as 212 - 254 volts

    Under extreme conditions, utilities are required to take corrective action on a "planned and programmed basis". Outside of extreme conditions, utilities are required to take corrective action as soon as practical.
     
  17. brkaus

    brkaus Member

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    Thanks. Mine is normally sitting at 247. Interesting that the face plate on my outdoor AC unit is listed as 208-230 1ph 60hz. I know this because of some arguments over warranty on a AC/DC inverter that went out in the unit... It has a variable speed DC compressor.
     
  18. FlasherZ

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

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    Appliances marked for 230V are expected to operate properly at 240V based on tolerance. My home voltage is right at 247-248V on a normal day.

    230V appliances are generally expected to have a tolerance that would work for 240V supplies. Once you start approaching 245V or so, the concern sets in.
     
  19. brucet999

    brucet999 Active Member

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    I'm confused. This device is simply a ring surrounding one of the 240V wires inductively reading amperage through the wire it is monitoring, isn't it? Presumably the 18ga wires are well back of the 50A terminal, so how can it be a short circuit hazard?
     
  20. FlasherZ

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

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    The voltage leads have to be connected to the 240V feed to sense. There are 4 wires... 2 to a CT, 2 to voltage sense.
     

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