Victron "quirk" in VRM

[wildebus]

This is possibly only relevant for those who use the Victron VRM system to look at their setup, but others may be interested?

The VRM has lots of performance data & information available on the various devices that are connected to the system.
This includes for solar the following:
PV Yield as denoted by the "System" (the "System" is the Victron GX Device that gathers the info, be it a CCGX, Venus GX, Cerbo GX, Raspberry Pi, etc.)

It also has PV Yield info for the Controller ...

Now what is the difference? Well, I have never quite known TBH when you have one controller and when I have compared them in the past the numbers have been nearly identical, so I thought it might have been a timing thing to poll/accumulate the data.
One thing I was sure of was that the "System" PV Yield would have been the total PV Yield for all Solar Controllers, as that would make sense to get the overall picture?
And as I do have two PV Controllers now, it would be useful

(when I actually have a panel on the 2nd one!)

I noticed a fairly large discrepancy here though ....

System Yield is 269W (which is pretty good from a 270W Array), but the Controller Yield is only 255W? where did either the extra 14W come from? or the missing 14W go? (depending which way round you look).

Well, the answer is as follows and was revealed with a negative Harvest!

I am getting a -14W Yield from the Solar Array? how is that possible? People talk about the battery backfeeding into the panels at night, or fitting bypass diodes to avoid a shading panel taking power, etc etc. But no, none of that nonsense, it is just a quirk of the way the data is collated and presented - but it is important to know if you are analysing solar performance over time as the Devices PV Yield is misrepresented IMO.

The full picture can be seen when you look at the Controllers Load Output chart as well

I am drawing around 1A from the load (e.g. around 14W).

If I look at the Controller using VE Direct, that tells me what the Load output is as well at the time

I have a pretty constant overhead of c 14W give or take a Watt or two connected to the Controllers Load Terminal (I have all the original Habitation electrics going through the Solar Controllers Load).

So to summerise ...

The Controller PV Yield is a net value of power from Controller to Battery (what Victron refer to as "Battery Watts") - so the Solar Array Harvesting is a contribution, and the Controller Load is a debit and the difference added together is the "Yield"
However the System PV Yield is the Solar Array Harvesting without any deduction for any Load connected to the Load Output.

It may be important to you to know the difference, but from the Titles, they would appear to mean the same

 

[PeteS]

Its more apparent when you disable the solar charger as the load output is still enbled, took me a while too to work out how i got a -ve yield. In my case the debit is the Ablemail vehicle charger which only takes gulps of current at irregular intervals once the starter battery max voltage is reached

 

[wildebus]

Its more apparent when you disable the solar charger as the load output is still enbled, took me a while too to work out how i got a -ve yield. In my case the debit is the Ablemail vehicle charger which only takes gulps of current at irregular intervals once the starter battery max voltage is reached

Yup, I had the AMT on the load as well, which is handy for monitoring it, but the draw is so low, never really picked up this oddity.
Only really noticed when I moved the standard Autotrail habitation power line from the battery to the Load to allow me to log it and really saw it then as the load is a lot more constant and larger (that is fused to allow up to 20A, so the 20A maximum on the controller is just enough to be ok).

I am slightly annoyed about this as I bought a 2nd controller for the portable panels and instead of another 100/20, went for the smaller/cheaper 75/15 which is fine for them, but the Load output is only 15A, so too small for the Habitation connection, otherwise I could have split the main solar from the hab easily to make the info more meaningful. (Another 100/20 would have been better for potential redundancy as well in fact for not that great an amount more. My bad )

 

[Nabsim]

I may decide to go with a 75/15 instead of doing what I was thinking Dave. I have been seeing low 270W coming off my Votronic 250 Duo so worse case I am losing less than 30W in ideal conditions and not the 50 I was thinking it would be. Not certain yet though

 

[wildebus]

My harvesting has been surprisingly good recently and I have seen over 100% of the rated capacity a couple of times (276W from a 270W array)
I think this could be a consequence of the temperatures being unseasonly cool for the time of year in the UK - so getting good sunlight levels overhead without the warmer weather to go with it means more efficiency (we are after all less than a month away from the longest day of the year).

the times an array produces better than say 80% of the rated wattage is a tiny percentage - and usually in the summer when you likely have excess power anyway, so I don't think undersizing a controller is a bad idea if it is a big money saver (£10-£15 not worth it, £50 or more starts to get more interesting).

 

[Nabsim]

I think it is about £50 difference between the 75/15 and the 100/20 isn’t it? Will try and take more notice of peak harvesting but it mean I need to be looking at the Votronic solar computer display at the time. Good point about cooler ambient temperature with strong sun, hadn’t thought about that.

 

[wildebus]

I think it is about £50 difference between the 75/15 and the 100/20 isn’t it? Will try and take more notice of peak harvesting but it mean I need to be looking at the Votronic solar computer display at the time. Good point about cooler ambient temperature with strong sun, hadn’t thought about that.

It's about £40 retail, so maybe £30 after discounts?
the 75/15 is good for 290W so with a 300W array I would go for that over the 100/20 for sure.
If you wanted a SmartSolar 75/15 you could have mine at the Photonic trade price as I have decided to get a 100/20 instead to match the other 100/20. It has never actually been connected to anything other than the battery even!

Just for info, this is the kind of info you can see with the SmartSolar to check out the last 30 days of harvesting

I am especially impressed with "4 days ago" and "20 days ago" - Peak Power of 276W and 275W respectively. That is pretty sweet for a 270W Array

 

[Nabsim]

Good job I posted on here as it thought you had said it was the 100/20 that was good for 290w panels lol. Yes I will definitely have the 75/15 off you then Dave, I am fairly sure I will be at Kelso meet so no need to bother with posting. Pm me how and what you want paying

 

[wildebus]

Ah. I think I have messed up. Doh!
it IS the 100/20 that is 290W (that is what I am using on my 270W Array.
the 75/15 is for 220W.
Sorry.
I can get you a 100/20 on the same 'terms' - Trade price (let me know and I will order 2 (one each) to come to me at the same time and save on combined post as well )

 

[xsilvergs]

Bit late to this thread, poor signal were I've been recently. This is a snap from this morning, 2 x 100/30 Victron MPPT, these have no Load output.

My AMT isn't fitted at the moment as it's back with Ablemail for reprogramming to work with LiFePo4's only.