question

Hi @codingparadox

'What gives' is that your formula, while suited to dc, is missing Power Factor when applied to ac. I'll let you google it for detail, but essentially the sine waves of V and I aren't in sync. And indeed some modern household appliances like power supplies, etc. probably make the wave form unrecognisable as true sine anyway.

So you end up with an Apparent vs True power (your differing W). I agree though that yours is at the high end, and you could try it with a resistive load (like say a toaster) to see what happens.

And to the observant many other wonders may also be visible. One I spotted a while back was when 'Weak AC' (a known and deliberate PF fiddler) is selected in my Multiplus. The Victron Voltage reading then was ~20V lower than that indicated by a cheap multimeter. I don't really know why, but I suspect the Multi is reading a RMS (root mean square) V, and the multimeter isn't. The capacitor-regulated genset I had there at the time probably had a nasty power quality as well.

The Victron kit doesn't claim the accuracy of a Fluke meter either, but once you get a little load on it's pretty good.

Best not to let this sort of thing consume you, but a base knowledge of it can't hurt.

Ah, very interesting. Most of my experience is with DC for sure. I was wondering if it was some sort of RMS issue, and the 3 amps was peak current load at some point in the curve, but not representative as an average. In any event, thanks for your experience here! I'll keep paying attention to watts. :)

I don't pretend to know about PF and the intricacies of sine waves...but I don't think this is a PF issue.

Sorry to resurrect an older thread...but I've been TEARING my hair out trying to solve this same issue:

AC-IN  L1                    210v     33.0A
                            4169w     50.1hz

AC-OUT  L1                  210v      36.5A
                           4890w      50.1hz

The keen observer would point out that I'm currently in assist mode, and you'd be correct. The math in this simply DOES NOT WORK.

ACIN  = 210v * 33.0A = 6930w (Showing 4169w)
ACOUT = 210v * 36.5A = 7665w (Showing 4890w)

I'm relatively certain based on what I know I'm pulling from shore power, and my usage, that the WATTS are the correct figure. I've tested it independently with a clamp, but it's been a while.

The real issue comes in because very few settings in the system are based on WATTS.

Input Current Limit:   41A

Strictly factually I'm connected to a 32amp 50hz shore power inlet at the dock. But because of the disparity in watts vs amps, I have to "massage" the shore power amps.

This has another gotcha. The calculation doesn't stay the same. Sometimes it's closer to 1.5, sometimes almost 2, sometimes it's almost correct at 1 to1.

System:

Quattro 12/5000 220 x 2 in Parallel configuration. If I remove the parallel config and shut one quattro off (but leave all the wiring the same) - the WATTS and AMPS calculation is correct. Then I can switch to the other one in single mode, and they are correct...then I can put it back in parallel and they are wrong again.

Anyone have ANY idea how to help me track this down? I'm quite technical and understand my system really well, but I've been fighting this for over 6 months.

Thanks ahead of time. I still wouldn't trade my Victron stuff for anything else out there!