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Watt meter placement

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Kan2

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Sep 21, 2019
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Pardon my lack of knowledge but I have a question: I have a watt meter connected from the panel to my cheap PWM 30a charger controller, from my understanding that meter read I'm getting is not accurate it doesn't necessarily tell me how much power is going into my bank or how much power is being drawn by the inverter and what not. Where exactly should I place that meter to get the most accurate information?

Attached is a picture of my meter.
 

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Did it come with a shunt? You'll need a shunt to accurately read that.
 

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No it did not. Just positive and negative for both source and load, it does give me some useful information. But I don't know if this is the right equipment for it.
 
Well, I'm learning this as I go as well, but from what I gather a shunt (the item under the display panel in the picture) is necessary for **accurate** information. Here's a link to the one I just bought, but haven't had time to hook it up yet:

Amazon.com: MNJ MOTOR DC Multifunction Battery Monitor Meter, 0-200V 0-100A LCD Display Digital Current Multimeter Voltmeter Ammeter for Cars RV Solar System: Automotive

Buy MNJ MOTOR DC Multifunction Battery Monitor Meter, 0-200V 0-100A LCD Display Digital Current Multimeter Voltmeter Ammeter for Cars RV Solar System: Multimeters & Analyzers - Amazon.com ✓ FREE DELIVERY possible on eligible purchases
www.amazon.com
 
Wiring diagram:
 

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I just noticed mine is too small for my system so it's for sale cheap :LOL::poop:
 
Regarding placement of the shunt/meter you have to decide what information you want. That will determine where you want to put it. What you see done often is a meter/shunt is placed in each of the positions shown in my scribble. That way you know what's happening everywhere.

shunt-diagram.png

Also note that A is tracking current in both directions. The other two just need to track it in one direction. That means you'll need different capabilities in your different shunt/meter depending on where you put it.
 
I live in Mexico, one of my many issues with sourcing parts is just that, gotta do with what I got. This does measures: watts, wh, wpeak, amps, ah, lowest volts among other stuff.

For now I guess I'm mostly interested in finding out what's the pwm pumping out, kinda pointless to know what the panel is giving if the pwm won't take advantage of it.

I'll place it there, would be accurate for what I'm looking for?
 
Kan2 said:
I live in Mexico, one of my many issues with sourcing parts is just that, gotta do with what I got. This does measures: watts, wh, wpeak, amps, ah, lowest volts among other stuff.

For now I guess I'm mostly interested in finding out what's the pwm pumping out, kinda pointless to know what the panel is giving if the pwm won't take advantage of it.

I'll place it there, would be accurate for what I'm looking for?
Click to expand...
Yep, you want "B"
 
This meter has both a positive and negative on the source and load. From that sketch, I would literally plug it right after the pwm connecting to the battery bank right?
 
Yes, some want to be connected to the positive side, some to the negative. My diagram shows all the shunts on the negative conductor. If yours is designed for the positive wire just use that one instead.
 
Very good, I managed to get it working after the pwm and now I know how much power is truly being pumped into the bank/inverter load.

Thanks so much.
 
I think the device Kan2 has pictured is fine those drok ones are good as well but I wonder about their accuracy as well. Just because it has a 100amp shunt does not make it accurate. Dont get me wrong i have about 10 of those but if you put them all on same load they will all be a little different.
 
I saw where you could use just one of those meters Instead of two to display both in and out readings with the use of a DPDT switch connected. One position tells out other position will tell in. F4C0B318-328A-4D64-80C7-F5C7EC30D0F3.jpeg14CDC615-D504-449A-9016-FB04BF1E5B6F.png
 
For what it's worth, wattmeters are RMS, (root means squared), approximations and the most accurate way to measure the amount of flow of electricity is to know the amps and volts at your point of measurement then use the power formula to figure the wattage.
 
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