Not sure I've got an inline ammeter hooked up correctly. Not getting the reading I wanted

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Blindowl1234
Blindowl1234 Registered Users Posts: 54 ✭✭
edited November 2023 in Solar Beginners Corner #1
I got one of those little cheap ammeters with built in shunt rated 20 Amps. Has connections for line and load. I hooked my incoming wires from the solar panels, to the line side of this little meter. The load side, I've got hooked to the solar input connections, on my charge controller. 300 watt 12 volt system and sun is full today. I'm showing 12.5 Amps and 20.6 volts using my regular vom meter. Figured it's getting about 257 watts give or take. This little inline meter on its display shows 20.6 volts, 0.65 amps, 12.4 W power. The last two numbers were bouncing around. So question is should this thing be showing the 12.5 amps I see at the wire from the panels? Not sure what the 12.4 number is ? Not my battery voltage, as batteries are fully charged. All I want it to do is have it to give me constant readings of what my panels are producing. Maybe this thing won't show me what I want. Thanks!
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,457 admin
    edited November 2023 #2
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    Can you give us a link to the shunt+meter you are using?
    Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • Blindowl1234
    Blindowl1234 Registered Users Posts: 54 ✭✭
    #3
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    BB. said:
    Can you give us a link to the shunt+meter you are using?
    Bill
    Thanks Bill. Here's the link and there's a bunch of these out there under various names. I got mine off Ebay. https://www.amazon.com/HiLetgo-6-5-100V-Voltmeter-Multimeter-Amperage/dp/B079JVGRSL/ref=asc_df_B079JVGRSL/?tag=hyprod-20&linkCode=df0&hvadid=366016835942&hvpos=&hvnetw=g&hvrand=13026962066921230902&hvpone=&hvptwo=&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=9015676&hvtargid=pla-791188452435&psc=1&tag=&ref=&adgrpid=80266838630&hvpone=&hvptwo=&hvadid=366016835942&hvpos=&hvnetw=g&hvrand=13026962066921230902&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=9015676&hvtargid=pla-791188452435
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  • Marc Kurth
    Marc Kurth Solar Expert Posts: 1,144 ✭✭✭✭
    edited November 2023 #4
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    Are you sure that there was a load when you saw that last reading, vs. when you read it with your VOM? Your batteries were fully charged, so there may have only been a 12.4 watt load on the charge controller.
    I always have more questions than answers. That's the nature of life.
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  • Blindowl1234
    Blindowl1234 Registered Users Posts: 54 ✭✭
    #5
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    Marc Kurth said:
    Are you sure that there was a load when you saw that last reading, vs. when you read it with your VOM? Your batteries were fully charged, so there may have only been a 12.4 watt load on the charge controller.
    I hadn't thought of that. Well then I don't think this is going to work like I thought it was lol. I was thinking it was going to give me a constant reading of volts and amps, from just the panels. That's what I was trying to do anyway. I can put my vom on the incoming wire from the panels and get volts and amps from the panels. I was hoping to have an easy way to do that, where the batteries/controller etc...are at. Oh well this isn't going to work. No big deal just an idea. Thanks
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,457 admin
    #6
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    Where are the + and - leads connected? To the panel wiring?
    And the load wiring to the charge controller input?
    Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • Blindowl1234
    Blindowl1234 Registered Users Posts: 54 ✭✭
    #7
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    BB. said:
    Where are the + and - leads connected? To the panel wiring?
    And the load wiring to the charge controller input?
    Bill
    Bill, The line side of ammeter is connected to plus and minus of wire coming from the solar panels. The load is connected to the solar panel input, on charge controller. I'm thinking this is only good for monitoring a 12 volt battery the more I look at it. Hopefully I'm wrong 
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,457 admin
    #8
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    I think you installed it correctly. The documentation is not clear on any limitations.
    Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • Horsefly
    Horsefly Registered Users Posts: 472 ✭✭✭✭
    #9
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    I've used a couple of those little meters previously. I got one from EBay and one from Amazon. They are all identical, rebranded by lots of companies.

    I never used the 20A internal shunt version, but rather the external 100A version. I found that they worked fine, but had a bit of an accuracy issue on the current (and therefore the watts and Wh). Based on comparison to the Schneider MPPT screen and my clamp meter (which were pretty close to each other), it seemed like the meter was off by 5% one way or the other, and could be off sometimes by as much as 10%.

    I've changed the system around and don't use the meters any more.
    Off-grid cabin: 6 x Canadian Solar CSK-280M PV panels, Schneider XW-MPPT60-150 Charge Controller, Schneider CSW4024 Inverter/Charger, Schneider SCP, 8S (25.6V), 230Ah Eve LiFePO4 battery in a custom insulated and heated case.
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  • WebPower
    WebPower Registered Users Posts: 73 ✭✭
    #10
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    I use one of those internal shunts on the wind turbine on my system. To check accuracy (assuming your voltmeter is accurate) put the volt meter in series with that meter on the panel side (Input) and compare the current readings. Do the same in parallel with the voltage measurement. See how far off they are. The ones I use give you instantaneous power as well as total power. I also have an AC version that I used for testing of the output of my Enphase microinverters when I was making my wind turbine interface. They are probably within about 10%. Good enough for me. Gives a ball park estimate of what's going on.
    9000+W grid tied IQ7 22 panel rooftop and 6 panel ground combination with 1 additional IQ7 connected to 500W wind turbine+200w solar+2 IQ7s with 300W+600W on the RV grid tied when it's in the driveway.
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