You are right, much much to be thankful for.
I am not far behind you though. PV only starts producing worthy to mention figures (650-800W) from about 10h00 these winter months. And I have to be done with significant loads at 14h30 - thereafter PV falls of the cliff.
See, a storm coming into Cpt … there goes the weekend … again!
Lelik TTT, lelik daai! Ek voel julle Capies se pyn.
Is waar … maar wag virrie somer … Cpt het meer irradiation per jaar, as julle … net Upington beat ons glo.
Why not just the panels?
If you are happy with the summer production and your existing MPPT is maxed out it will just clip around noon. You’ll still make more power in Summer either side of noon and your existing MPPt will be easily able to cope in Winter.
To demonstrate what Phil is talking about, why I got the 250/100, and the 350w panels.
You can do this … midday it clips about ±25amps “off” on max current at max temp, delivering 100amps IF I had use for it.
… but if Eskom gets really bad here in Cpt, different train of thought.
Can go 5S/4P too … but the calc cays 249.9v.
Currently on 4S/3P, 2 strings just asking to be connected. 
The itch … nope, enough! Beer …
I actually like the idea of having more amps on the MPPT than the inverter, that way you can charge your battery and max out the inverter. I have two 150/45s. Thinking of getting another one. But jeez, I’ve spent way too much money the last year… first I need to relax a bit…
Wish I had that view, I would make a chair deck and watch the panels!!! 
I am learning about my system, Have two identical String 2 x 450w in serial to a 8kw Sunsynk. One (1st) string constantly has 50 watts, 30 v higher even though they are in a row with no obstruction to the sun all day long. The only difference is the 2nd six string has a longer positive as its further from the inverter(Obviously) But I could not think it would affect 50watts all the time. I then cleaned only the lower six string panels with Soap and water, And … its now 50 watts more than the good string … Cleaning panels. Who knew it would help so much. Next , clean the other six, wonder if they will be 50watts more again?
How do I do this? Somewhere I have to make some change to the settings?
Please explain slowly, with pictures.
You add more and more panels till you have enough … me, I saw that if I want, using:
Aka a ton of extra power earlier and later every day … I’m at 12 panels already …maybe can squeeze 4 more in, then space becomes an aesthetic issue see.
With a 280ah 18cell bank, I will see if I can use 4 more panels …
Theoretical values are often aspirational. Your real-world measurements will tell you how much headroom you have with your MPPT’s.
The voltage limit is a hard input limit and you must never exceed this. The current limit however is an output limit self-imposed by the MPPT.
IOW, if you have the potential to exceed the input limit power, it will only output its current limit.
Thanks, I know about the input voltage that must never be exceeded. Victron does however specify max watts per MPPT as well and mine already exceeds this slightly.
But seeing as power is just v x a, and amps out is automatically clipped/limited by the MPPT, are you thus saying that I could just add further strings without having to worry something will pop?
I’m very slightly concerned by the watts limitation from Victron. Or maybe they just mean to say that you wont be able to get more watts than what MPPT is rated for? Same as the amps that is limited/clipped?
The Victron equipement does a great job of limiting the watts and amps for you (even the voltage to some degree) and that is why I like them and pay extra for them (dummy proof)
So you can add more panels and the MPPT will limit the current. The bigger models have a hardware current clamp, the cheaper one’s o it in software.
As long as you stay under the max voltage you will be fine.
Does it really?
Or are you saying that the panels on that MPPT theoretically exceed this slightly?
This isn’t the same thing.
To achieve that theoretical ideal, you need the planets to align whilst angels hum Barry Manilow. So work from your historical data.
What is 90% of the maximum power peak you have ever seen? Divide that by the number of panels you have and that will give you an indication of your minimum available headroom.
Expand to this size and you are not even clipping
This is the level I have taken it to so far, I have matched E,W & N arrays and achieved 60-100% over-panelling without clipping. I haven’t had to, I started out with 4 totally under-utilized (aka theoretically- panelled) MPPT’s.
Then you have to consider if you want to clip.
And this is where I am quite happy to venture in future expansions.
I don’t think there is any value to be had in extreme oversizing, in other words always clipping. But I do think, there is a reasonable compromise to be had considering your Winter and Summer production.
Maybe it’s better to waste a bit of power that you didn’t actually need in Summer to ensure you have enough in Winter? You’ll always have overcast days in Summer too where extra panels will serve you well.
I haven’t really decided on a practical fraction yet, but I do think there is a better answer than totally avoiding clipping.
The way I see it panels are a factor of production and MPPT’s are an overhead cost. I want maximum production with minimum overheads.
To answer this you will see that the same MPPT can feed a 12 & 24V bank but with proportionally lower power. That tells me that power is not the limiting factor, current is. This in turn means you gain efficiencies by having a higher voltage battery, but that is for another topic.
Yes, an MPPT will only take the power from the PV panels it needs to fulfil its maximum current limit.
MPPT’s in PV inverters are routinely over-panelled to the degree it is considered the norm in Australia.
I don’t know if you could add panels ad nauseum, but I understand it will handle clipping to a practical level.
This is from the manual. Maybe I understood it wrong but I thought that the watts also should not be exceeded. I have the 150|35 which is max 2000W at 48V
My one MPPT has 2460W worth of panels, and the other one has 2490W
I have at times seen up to 3,7Kw from my 5Kw array, but that includes some watts diverted to a low battery for charging. But the inverter is a 3Kva peak running at 2,6 - 2,7Kw mostly.
So that looks a lot like 35A in an 16-18 cell battery. Or basically 2000/35 = 57.2V. So that is a maximum amount of power the MPPT can deliver if your system’s voltage is high enough. On a Pylontech bank it would be around 52.4V, so 35 * 52.4 = 1,834W.
Basically, that figure has much less to do with the amount of current it will happily clip for you, but rather the system’s voltage and the current headroom in the MPPT.
Is there actually a limit to the amount of current it will clip? I mean, just because Eskom can deliver millions of amps to my house, the current through my circuits is determined by the appliances demanding it. So will the MPPT not just control its demand (or is it a bit more complicated than that)?
I have lead acids that sits at 54V when full.
Your max throughput power is 35A * your charging voltage.
Victron doesn’t know if that going to be 52V for your battery or 62V for mine, so a power input threshold can only ever be a very loose recommendation.
You have to be careful how you describe things. You don’t have a 5kW array you have two 2.5kWish arrays. That 3.7kW production total you describe may be severely weighted to a particular array. You want to find out how much available capacity you have on each array.
Tilt and direction, and to a degree shading can play a big role here with each array.
To discover where you have headroom you need to treat each MPPT separately because they will impose clipping independently.
The next thing is you are not looking to give yourself a pat on the back and say I peaked at 3.7kW on the best day of the year. You are looking for a peak value that will cover 90-95% of all peaks in a year, not just 10 freak days in a year.
Work with that value as a basis.
Indeed so.
So how would I determine this now? I’m able to switch each string of. So what if I wait for peak times at around 12h00, and switch off one MPPT and ensure that there is at least a 2,5 Kw load on (with full batteries)
Will this give me a fair idea of peak capacity/production? And then immediately do the same with the other MPPT.
On your GX you should be able to observe each MPPT separately. I haven’t yet tried to pull their data separately from VRM, not sure if it is recorded as such. Maybe @plonkster knows if it is possible to pull data from individual MPPTs.
