DC Power + AC Load not equaling Battery Discharge rate

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zac asked Jun 20, '21

DC Power + AC Load not equaling Battery Discharge rate

Hi all,

I am hoping to get some help debugging this issue. I recently connected my new victron quattro and im having an issue with DC Power read out. I havent been able to update the Quattro firmware yet (still on 413) so im hoping its just out of date. I'm pretty sure the discrepancy is the inverter losses not being taken into account by the DC power but im not 100% sure. My system comprises of a Cerbo GX, BMV-712, two MPPT smart charge controllers and the Quattro. Any Ideas what it could be? Would updating the firmware and enabling DVCC help? Anytips would be much appreciated.

Thanks

MultiPlus Quattro Inverter Charger inverter current draw dc system

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Answer 1 · 2021-06-20T11:43:49Z

bonie-wanda answered · Jun 20, 2021 at 11:43 AM

yeah it never really adds up, sometimes it’s close. I believe there’s the inverter portion and other losses.

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Answer 2 · 2021-06-20T12:45:16Z

JohnC answered · Jun 20, 2021 at 12:45 PM

Hi @Zac

You'll drive yourself crazy trying to work it out. A good place to watch it is on the MFD app. A snip from that on my system..

Solar feed and DC loads both off, so only ac through the Multi happening here. The shunt I consider 'gospel', the Multi's input usually shows ~30-40W less (self-consumption?). AC Load W usually close to the Multi input.

But look at the ac Amps.. they don't ever match the W. Power Factor? I assume, from a laptop, tv and heater fan.

These figures flick about a bit, possibly due to varying sampling times, but the trend is there. Not that this helps you much, but you're not alone wondering..

One other thing I notice when running a genset with 'Weak AC' selected (a known Power Factor fiddler), is that the AC Volts shown is ~20V less than that shown on my (cheap) multimeter. And I don't really know which one to believe..

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zac commented · Jun 20, 2021 at 10:08 PM

Thanks for the reply @JohnC and @Bonie Wanda. Your data is looking much closer, and the power consumption of your multi seems really low which is great.

I figured the DC Power calculation would simply be: Discharge Current - AC Load Current = DC Power?

I'm confused as the Quattro is reporting a current draw of 2.10 amps to power a 76W AC load (indicating inverter loss of ~33W, which seems a little low, I would expect 60W) but the DC Power for the rest of the system is showing as 68W which is way higher than it should be. I'm only running a Cerbo, BMV and some MPPT's which basically switch off after dark.... This leads me to believe that the DC Power figure is taking into account the inverter losses but only a portion of them... weird.

It seems that the Quattro 10kva under low load has a self consumption of around 100w. Does that sound right? If so that's a shame as my previous inverter (now the back up) was only 35W. I'm really hoping the BMV is reading incorrectly for some reason, I will need to measure.

Thanks, Zac

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