Number Don't lie.... But?

[bedpan]

Hey Folks,

I am building out a small DC system with a 1000W inverter for a new trailer I am getting in a few weeks... I am building it all on a bench so it can be setup and ready to go. I won't get into the details of the whole system but I have a bit of a brain fart issue and I cannot get the numbers to line up. Maybe something stupid on my part, or maybe one of the meters are not accurate.. I have mathed hard and cannot see the answer though..

I broke the system down as small as I could when I found the "issue"
Right now its a single 100AH Renogy Lithium battery
Connected directly to a 1000W Motomaster Inverter.
I have a Kilowatt plugged into the Inverter.
I have a small 120V fridge plugged into the Kilowatt.

Fridge ----- Kilowatt ----- Inverter ---- 100AH 12V Battery

Nothing else connected.

With the compressor running Renogy is showing -5.1A at 13.2V on the LCD Display and the Bluetooth Dongle
The Kilowatt (with the fridge plugged into it) is showing .91A at 132V.

If the Fridge is drawing .91A at 132V =120.12W
120.12W/13.2V = 9.1A DC (Not accounting for loss in the inverter)

9.1A does not equal the 5.1A Renogy is showing me....

To try and confirm things I used my cheap AC clamp meter on the AC line and measured 0.75A AC or .75A x 132V = 99W

I don't have a DC Clamp to test the DC Side..

Going the Other way, 5.1A x 13.2V = 67W

I have almost 30 - 55W coming from the ether that I cannot account for and not considering loss in the inverter.

What am I missing...

Hmmm...



Edit
For those observant in the group you may notice the Renogy meter is showing 3 batteries connected. The photo is when I had 3 batteries in parallel. The numbers are more less the same when I drop to a single battery other then the hours remaining are 1/3.

 

[Bud Martin]

OP: The Kilowatt (with the fridge plugged into it) is showing .91A at 132V.
Are you sure your inverter really puts out 132Vac, that is awful high, that cannot be right.
The power input to the inverter will be higher than the output power due to conversion loss, but right now your numbers are not showing that, it looks to be measurement error.
Model of the Renogy that you are using to read the current draw and the wiring diagram?

 

[bedpan]

OP: The Kilowatt (with the fridge plugged into it) is showing .91A at 132V.
Are you sure your inverter really puts out 132Vac, that is awful high, that cannot be right.
The power input to the inverter will be higher than the output power due to conversion loss, but right now your numbers are not showing that, it looks to be measurement error.

Good call......
So I metered it out with a decent Klein meter, into and out of the kilowatt and I get 124V but the Kilowat show 130-132V

I plugged the kilowat into household wall and shows 120.. Klein show 120...

This got me thinking.. This older Inverter... I could not find any specs on... I am guessing its a modified sine way inverter and this is throwing numbers off maybe on the kilowatt?

 

[Bud Martin]

You may be right that the inverter is not pure sine wave inverter, that is why Kill-A-Watt is not showing correct reading, and it may damage the Kill-A-Watt internal power supply.
Can we see the picture of the inverter?

 

[bedpan]

Old'ee.. Built in 2010. I used if for a couple weeks last year to run the fridge.. So the fridge seems mostly happy with it.... Guess I should confirm if its Modified Sine.. I have a brand new 1000W on the bench as well. Another Motomaster but its a true sine wave with a remote. I was going to use it in the truck... Hmmm..

 

[bedpan]

The current version of it still being sold with the same part number is modified sine.. Guess it is true. I will need to think long and hard on this ;-)
Current Version

Thanks Bud for the question that pointed me in the right general direction