wiring for inverter and Watt's Up meter

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WYsolar
WYsolar Solar Expert Posts: 31 ✭
in Solar Beginners Corner #1
Sorry for yet another newbie question (I am learning though),

I have a small battery bank that I am going to use to power a small inverter. The inverter manual says to use #6 wiring between it and the batteries.

I want to put the watt's up in the circuit between the batteries and everything else so that I can monitor all power used.

Question: Obviously the wires for the Watt's up are nowhere near #6 (more like #12). How do I correctly wire the meter into the circuit?

I have read about "shunts" and I am wondering if this is what I need. If so, how do I use them?

Thanks again for all the advice. <sigh>
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  • solar_dave
    solar_dave Solar Expert Posts: 2,397 ✭✭✭✭
    #2
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    Re: wiring for inverter and Watt's Up meter

    Is the watts up a DC device or an AC device?
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  • WYsolar
    WYsolar Solar Expert Posts: 31 ✭
    #3
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    Re: wiring for inverter and Watt's Up meter

    DC.

    It is this one.

    http://www.amazon.com/Watts-Meter-Analyzer-WU100-Version/dp/B001B6N2WK/ref=sr_1_1?ie=UTF8&qid=1386599191&sr=8-1&keywords=watts+up+meter
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  • ILFE
    ILFE Solar Expert Posts: 364 ✭✭
    #4
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    Re: wiring for inverter and Watt's Up meter

    Forgive my ignorance if I am wrong here. But, couldn't it be wired up as in the first option on the following chart?

    Attachment not found.
    Paul
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  • WYsolar
    WYsolar Solar Expert Posts: 31 ✭
    #5
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    Re: wiring for inverter and Watt's Up meter

    Hmm. I don't know.

    I have my battery bank on one side and my inverter on the other. I also have one 12c DC "cigarette lighter" plug in the circuit just before the inverter for those types of loads. I will not be running the inverter and the 12v dc load at the same time. I do, however, want to be able to monitor either via the meter.

    So in wiring example one, I see the meter is utilizing the black (-) side of the circuit to the heavy load and is using that wiring, right? In my case that would still #6 (red and black) coming from the batteries, correct?

    This comes back to my original question: Is ok to connect the #6 (black) to the #12 (black) on the meter? Then I could use a #12 for the pos (red connection) to the other side of the meter?

    Sorry about all the questions. I am just having trouble physically understanding this. :/
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,447 admin
    #6
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    Re: wiring for inverter and Watt's Up meter

    A Watts Up type meter should be limited to around 15-20 amps continuous current (14 AWG wiring on unit).

    For example, a 300 watt AC inverter will use:

    300 watts * 1/0.85 inverter eff * 1/10.5 volts minimum = 34 amps

    And many AC inverters will support ~2x their rated output for a few minutes--or ~67 amps for this example.

    If you want to check the current once in a while, a DC Current Clamp Meter (this is an AC/DC with DMM type meter) would be easy and safe to use--And handy to debug your system, work on the car, etc...

    A shunt (precision resistor) with the appropriate meter, or a Battery Monitor (Victron is another good brand of monitor) would be very nice.

    A battery monitor is very nice, and just about mandatory for use with sealed/AGM type batteries. However, for smaller systems, battery monitors are not cheap and hard to justify the costs (Trimetric is around $155 + $30 for a shunt, plus shipping).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • vtmaps
    vtmaps Solar Expert Posts: 3,741 ✭✭✭✭
    #7
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    Re: wiring for inverter and Watt's Up meter
    WYsolar wrote: »
    I want to put the watt's up in the circuit between the batteries and everything else so that I can monitor all power used.

    Question: Obviously the wires for the Watt's up are nowhere near #6 (more like #12). How do I correctly wire the meter into the circuit?

    I have read about "shunts" and I am wondering if this is what I need.

    The Watts Up has its own built in shunt. Its rated 50 amps continuous (100 amps peak). Depending upon how small your "small inverter" is, it may be OK to wire the Watts UP into the circuit. There is a discussion of these issues on the Watts Up web site (read their FAQ). They also discuss how to use an external shunt with the Watts Up (voids the warranty).

    If you need an external shunt, I suggest you abandon the Watts Up and get a trimetric. The trimetric is a real battery monitor that can count the amps going into AND out of the battery.

    --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
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  • WYsolar
    WYsolar Solar Expert Posts: 31 ✭
    #8
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    Re: wiring for inverter and Watt's Up meter

    Thanks for all the replies.

    As I mentioned I am having trouble understanding how to put 50-70 DC amps through the little wiring of the meter. The one wiring diagram showed it physically connected to the (-) side, with a smaller gage wire connected to the (+) side. This still means a 14ga wire (of the meter) connected to a 6ga (-) cable running from the batteries. That just does not seem right in my limited electrical understanding.

    BTW, VT...

    Could you give me the URL of the Watt's Up FAQ? For some reason my searches are not finding it. Thanks.
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,447 admin
    #9
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    Re: wiring for inverter and Watt's Up meter

    There are a bunch of helpful links under the main page:

    http://www.rc-electronics-usa.com/ammeters/dc-amp-meter.html

    The specs:

    http://www.rc-electronics-usa.com/ammeters/amp-meter-specs.html

    [h=2]WU100, Measurement Specifications[/h]


    [TH]Parameter[/TH]
    [TH="width: 150"]Range[/TH]
    [TH]Resolution[/TH]
    [TH]Accuracy
    (worst-case over temperature range)[/TH]


    Voltage

    0-60 Volts*

    0.01 V
    ± (1% + 0.035)


    Current

    0-100 Amps **

    0.01 A
    ± (2% + 0.06)


    Power

    0-6554 Watts

    0.1 W



    Charge

    0-65 Amp hours

    0.001 Ah



    Energy

    0-6554 Watthours

    0.1 Wh



    * Using auxiliary power/battery input. Minimum is ~4.0 V without it.
    ** 50 Amps continuous, 3-wire connection. Derate for wire temperatures next to case above 70 Deg C.


    With power systems--You should never run this meter at 50 amps continuous--It just is not safe with 14 awg wiring... Remember one of the power equations is P=I^2R... You double the current, you get 4x the waste heat.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • WYsolar
    WYsolar Solar Expert Posts: 31 ✭
    #10
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    Re: wiring for inverter and Watt's Up meter

    Understood.

    It makes sense that this meter (even though it says it can handle ~50A continuous) really should not be used in this way. Sounds like a clamp on DC ammeter would be the best option.

    Do all such clamp on meters require large current draws to read properly? I mean if I plug in a low wattage 12v device (like a AA battery charger) into my cigarette plug, will the meter be able to provide me useful information? My previous experience using them in lower current conditions has not been too good.

    Thanks again for the help everyone.
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,447 admin
    #11
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    Re: wiring for inverter and Watt's Up meter

    The meter I linked (Sears) has a 40 amp and 400 amp full scale reading.

    All DC clamp meters use a transistor sensitive to magnetic fields to read the current... And, as such, tend to drift over minutes/hours and are not a good way to measure long term current flow.

    A current shunt (resistor) is really the best way to go for long term measurements.

    For low current quick measurements--probably this one is OK down to 0.1 amps (accurately--just a guess).

    Lower than that, you need to measure with a shunt/Current Meter (problem with DMM's is they put a fair amount of resistance in-line to measure the current--Can affect the operation of some circuits if they are voltage sensitive).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • WYsolar
    WYsolar Solar Expert Posts: 31 ✭
    #12
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    Re: wiring for inverter and Watt's Up meter

    Thanks Bill.

    I will try out the clamp meter and report back.
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  • mtdoc
    mtdoc Solar Expert Posts: 600 ✭✭
    #13
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    Re: wiring for inverter and Watt's Up meter

    If you want to measure lower current with a clamp meter THIS works well and is accurate. You will pay more for this higher resolution. A review of this meter can be found HERE.

    I have one of these and it works as advertised.
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  • WYsolar
    WYsolar Solar Expert Posts: 31 ✭
    #14
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    Re: wiring for inverter and Watt's Up meter

    Thanks for the info, Doc.

    As I mentioned before my experience with clamp ammeters measuring less than 2-3A DC or so has not been very effective. I hope I can find a meter that will be reliable and provide decent service.
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  • mtdoc
    mtdoc Solar Expert Posts: 600 ✭✭
    #15
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    Re: wiring for inverter and Watt's Up meter

    Just keep in mind that the one I linked to does not have jaw openings large enough for large battery cables. I can't remember off hand how large it will go up to (spec says 12.5 mm) but I do know it is too small for my 2-0 inverter to battery cables. I have a traditional large jaw clamp meter for those. Obviously for large cables carrying large currents, milliamp current resolution is normally not important
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  • ILFE
    ILFE Solar Expert Posts: 364 ✭✭
    #16
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    Re: wiring for inverter and Watt's Up meter
    WYsolar wrote: »
    Thanks for all the replies.Could you give me the URL of the Watt's Up FAQ?

    Here is where they justify the wire size on the "Watts Up" meter.
    Paul
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  • mtdoc
    mtdoc Solar Expert Posts: 600 ✭✭
    #17
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    Re: wiring for inverter and Watt's Up meter

    I will say this about the Watts Up meter. I have one on my ebike wired with the "3 wire method" I have run 30-35 amps through it for 15 minutes continuously with no issue what so ever.
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