question

Justin Tierney avatar image
Justin Tierney asked

Multiplus ii vs Converter Charging

passthru-converter.pnginverter-charger.png

This is in my RV. So the first picture is with charging of the multi disabled but the breaker for the converter on so it will do the charging. The multi ii 2x120 is newly added so I use to seeing the negative value when connected to grid power.

The second picture is with the converter breaker off and the multi set to do the charging.

Any thoughts as to why the converter shows negative (which I understand is providing power and I use to seeing) but the multi shows as consuming DC power when AC is connected? This seems like it'd be a loop. I know the DC power is a rough estimation, it just seems like a big difference.

Multiplus-II
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passthru-converter.png (47.7 KiB)
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1 Answer
snoobler avatar image
snoobler answered ·

DC power is the bucket of stuff that's leftover between known loads (inverter) and known inputs (MPPT, inverter charging, etc.).


DC Power reports those "leftover" loads as a positive consumption. Since you are charging from an "unknown" source, it shows up as a negative "load."


The Multiplus is reporting it's charging to the GX, so the GX knows that this is charging and reports it as such. The converter is just shoving current through the shunt, and the GX has no idea what's going on other than there is more DC current flowing INTO the battery than can be accounted for by AC loads, so it shows up as a negative load.

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Justin Tierney avatar image Justin Tierney commented ·
ok that makes sense. It was just a test honestly because with no load or in float charging mode the AC in will show a -10w or -1.1a and my dealer said they weren't sure what that was so I didn't know if maybe there was a tie into the above question. Thanks for the response.
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snoobler avatar image snoobler Justin Tierney commented ·

Just guessing...


That might be an issue with your shunt zero current calibration:


1640890686090.png


Additionally, if you have your converter and inverter floating at the same time, the converter might be at a slightly higher voltage and thus the inverter's float is not moving any current at all. 10W is a pretty common consumption for float, so I can't help but focus on that.

Since it's on the AC in, it might also be some sort of calibration issue with the inverter. You don't have back feed setup do you?


1640891385720.png

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Justin Tierney avatar image Justin Tierney snoobler commented ·

I don't have feedback setup. This is what I have. Also the converter is off via the breaker and will be removed shortly. I'll be cleaning up my wiring this weekend so while I'm doing that I'll disconnect everything and set the zero calibration and see if that changes anything.1640891656262.png

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snoobler avatar image snoobler Justin Tierney commented ·
Didn't think you would, but I had to ask. That's really weird.
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Justin Tierney avatar image Justin Tierney snoobler commented ·
do you think it's just noise? or actually back feeding?
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snoobler avatar image snoobler Justin Tierney commented ·
Almost certainly noise. Some appliances you're powering can cause momentary back feeding, but I doubt that's what's going on.



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Justin Tierney avatar image Justin Tierney snoobler commented ·
Ok. I only ask that because I'm going to have an electrician out to verify the RV and the house. When I plug the RV into a GFCI feed line, it will pop the GFCI at random times but mostly when the AC in is showing this negative. I'm 999% positive that I don't have any fault issues as I've checked all connection and cannot find any issues. No current flowing to ground any place I check. My dealer isn't sure whats going on either. The system worked fine until I installed this new inverter, still a mystery.
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snoobler avatar image snoobler Justin Tierney commented ·
Do you have any loads with variable speed motors or "inverter" type drives? I've seen soft start AC water pumps that will trip Class A GFCI (5mA) due to single digit milliamp ground fault. Solution was to replace with Class B GFCI outlet (20mA).


GFCI trip of inverter powered RVs seem to be just one of those things that happens. Every once in awhile, either of our 5th wheels will trip their GFCI for no known reason.

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