Multi RS Solar - VRM Power Reporting Inaccurate

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Rob Souto asked Feb 22, '23

Multi RS Solar - VRM Power Reporting Inaccurate

Hi All,

Just wondering if anyone else is seeing the same behaviour in VRM from their Multi RS?

It seems that whenever the Multi RS is charging the battery, from Solar or Mains or both, the charging power is being reported by both the Solar or Mains charger to VRM, but is also being shown as additional DC charging power, pressumably from the battery?

The figure seems to be consitently double the actual charging power, like VRM does not know how to subtract the power coming from the different elements of the Multi RS from the total power going to the battery, so is accounting for both as 'additional' DC charging power as well as individually.

System in question has a fairly large DC system so it is as important to account for that as the AC system, removing the DC system from VRM is not really practical.

Up to now the system had been getting limited Solar or AC charging because UK solar sucks in winter and Generator support has only recently been added, so I had been putting the discrepancy down to measurement tollerances to now.

Now @WKirby has helped out with the generator settings for the Multi RS, i am pretty certain that this must be some kind of reporting bug, interested if you have seen this with your system?

Batteries are Pylontech US5000 which are selected as the battery monitor, as they are pylons DVCC is automatically forced on with SVS & STS forced off, not really sure what else to try to get the reporting to be vaguely accurate, any suggestions welcome

VRM dc system Multi RS

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nesswill commented · Feb 23, 2023 at 07:25 AM

Hi, i have/had a similar issue, i too have seen the DC Power increase with solar power (not on the level you have) as JohnC answered below, mine now has gone back to normal'ish but i have noted over the last few days that DC Power varies with solar charge (double what i measure and expect) as its calculated i have not worried about it too much but maybe i should!.

This happened to me @2am then 3am (yes i was asleep) i was doing nothing to cause this, the only thing i noticed is i have fridge & freezers turning on & off normal cooling cycle (AC) roughly when it jumped back to normal.

I will be adding a Wind Turbine soon so it should be interesting to see what effect this has or doesn't have...

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Rob Souto nesswill commented · Feb 23, 2023 at 09:28 AM

@nesswill It will be interesting so see how it handles the wind turbine power in your system, as this would be the only source of charge not coming from the multi RS itself?

From previous projects, if the turbine is going to be an important producer for you, then might be best to have it connected to its own smart shunt so you can actually look at data from it etc, otherwise it can get lost in the DC power fluctuations (even without the MultiRS specific issues we are seeing)

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nesswill Rob Souto commented · Feb 24, 2023 at 05:49 AM

Hi yes it will be interesting...(would like to know all in one place what the WT is doing)

I have a lot of solar (been completely off-grid since 14th Jan 23 when i got my last set of batteries) so it will be a "top up" over night or when we have some overcast days (worst day has been 6kwh). Yes i intend to setup another SmartShunt like below, i do already have one Wind Turbine with some solar running a switch and some cameras at the top of my land where we have some barns and field shelters.

As for the problem it is strange, only seen the jump once but have noticed that DC Power varies with PV Output and settles down over night (but still about 20% high tho) so some sort of calculation or rounding issue maybe?

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JohnC answered · Feb 23, 2023 at 09:57 AM

@AlternativePowerProjects @nesswill

I've just been advised that this issue has been raised with the RS devs. If you've more info to offer, now's the time. Thanks for reporting it so well..

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Answer 1 · 2023-02-22T18:59:05Z

Alexandra answered · Feb 22, 2023 at 06:59 PM

@AlternativePowerProjects

Do you actually have a DC system, i assume that is why the tile is active since that is its use? What is measuring it?

If you dont have DC consumers/ chargers then deactivate the tile it does not apply to your system.

See VRM document for its use.

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Rob Souto commented · Feb 23, 2023 at 09:24 AM

Yes, as noted in the original question, the system has a DC system so turning it off not appropriate

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Answer 2 · 2023-02-23T06:51:17Z

JohnC answered · Feb 23, 2023 at 06:51 AM

Hi @AlternativePowerProjects

This looks similar to what's reported in this thread.. https://community.victronenergy.com/questions/185191/strange-dc-jump.html?childToView=187759#comment-187759

It's not solved either, and proving difficult to nail down. If this is the same (transient?) bug then Victron will want to know more so they can fix it.

Do you think yours might be the same thing?

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Rob Souto commented · Feb 23, 2023 at 09:17 AM

Hi @JohnC Thanks for having a look into this, as you say on the other thread, noone is hugely familiar with the Multi RS kit at the minute. I've got one running on a personal system to play with and evaluate, so far am very glad to be learning with my own kit before installing for a few projects later this year. Is definately a good product but guess some teething problems are always expected with brand new designs.

I believe the issues are both related yes, the DC power value in VRM is identical to that shown on the Cerbo GX itself in my case, and is consistently repeatable whenever any decent charge/discharge is happening. Whilst my question does say VRM reporting inacurate, potentially more accurate description is bad data from Cerbo being sent to VRM that is nowhere near the correct values, consistantly doubled.

In this screenshot below, the only DC loads running are the Cerbo, Wifi Router, and the Orions, few watts at most, plus the DC draw from the Multi RS itself, the 56w AC load is a Starlink Dish, which is pretty constant and doesnt fluctuate much (e.g. like a fridge would).

I am stuggling to understand where the Cerbo is getting the 'DC power' current measurement from, as Pylontech is reporting -0.5A, PV charger is sending +0.34A and AC loads are using roughly -1.25A

Even before charging starts, the numbers just dont add up, what are your thoughts on the issue being how the Multi RS DC Current is handled by Cerbo/VRM?

Would make sense as all the AC load pulled via the inverter, or put back in via the Solar or Mains charger elements, would count/report here, aswell as report a figure for the individual element, e.g. PV power in Below snip.

My system is very simply setup, Pylontech batteries, Multi RS & some mixed DC loads via Orion converters.

Here is the same snip from advanced with the Generator Charging the battery yesterday, roughly the same time as the homepage snip in the original question, the only theory I can come up with is that the Battery power figure and the DC current figure from the multi RS are being added together in some way, any thoughts?

@nesswill would be interested to see a similar snip from your system to see if this is unique to my setup or not

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wkirby ♦♦ Rob Souto commented · Feb 23, 2023 at 09:59 AM

An improvement was made in VenusOS v3.00~15 (beta versions), but I think it needs further refinement.

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Rob Souto wkirby ♦♦ commented · Feb 23, 2023 at 03:45 PM

@WKirby thanks for the headup, I had been reading beta notes for a clue to the issue but there is a lot going on in those to sift through! Will give V3.00~15 a try and see if it is any better

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Answer 3 · 2023-02-28T15:30:47Z

Rob Souto answered · Feb 28, 2023 at 03:30 PM

FYI to anyone who finds this thread, have loaded v3.00~20 (beta) and the reporting error with the DC power has mostly corrected itself

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nesswill commented · Mar 01, 2023 at 06:03 AM

agreed me to but i still see the DC Power increase with PV Charge, i guess the calculation's still need some refining.

Still no DC Charger (like the PV Charger) in the VRM Dashboard tho... (SmartShunt as a DC Source)

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Answer 4 · 2023-11-27T12:51:59Z

pierrick-ausseresse answered · Nov 27, 2023 at 12:51 PM

I happen to have the same issue and was planing to raise a ticket.

the DC power (I do have some DC loads) is always including the battery charging power but with different polarity : DC power = Solar power + realDC power - AC loads.

that means that DC power show positive when battery shows as "charging" from MPPT with AC load less than 5% of solar power and DC load around 10% of solar power

this is still present with the last update that enabled 3 phase power on the older SMPPT multi RS.

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