question

Minas Papageorgiou avatar image
Minas Papageorgiou asked

VRM : Discharge vs Load discapency , low loads, large cables.

I have 2 Multi Compact 2Kva/24v in parallel with a BlueSolar 150/70 connected to a 605A SOPZ bank.The cables to the bush bar are 50mm2 and from bar to inverters 35mm2 , distances matching to almost mm.

Since I have not received yet the VE.Direct 2 USB cable (for the smartshunt) I just connected the MK2 onto the Rasberry.

What is strange is that I have a big discrepancy between AC loads and discharging, meaning 76% efficiency.

Since the discharge measurement is also coming from the Multi, it cant be a matter of cabling, not to mention the load is so small to be affected by the cabling.

Any ideas??


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VRM
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1 Answer
JohnC avatar image
JohnC answered ·

Hi @Minas Papageorgiou

It's not your cabling, most likely Watts lost in running the Multis. These figures can jump around a lot too, with sample time variations, so a single sample isn't of much use. I like to use the MFD app, here's an excerpt from mine..

1657798184395.pngIt says 2 batts, but it means 2 readings from 1 batt. The dcA usually matches but the Multi is always 30-40 W lower than the shunt. Can't happen with dc, so the figures are fudged somehow to make presentable. But the W on the Multi closely matches the AC Loads W. The acA ends up wherever with a less than unity poiwer factor at play somewhere. I reckon I lose 30-40 W continuously, day and night. But it doesn't interrupt my sleep, hey. :)

The losses I see from IN vs OUT readings of my batts are far more substantial. I just wear it.




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