1 minute ago, Mstott said:

belive you have helped integrate with Victron ?

Well, I've been hinting at Kaloyan for a long time, but Andre also had a hand in it and they did most of the work themselves anyway.

Yip Kaloyan has been working hard on it . I'm sure he will help with any setup issues . I must admit I'm quite excited . 

This is the next job to do ! Lots to learn as I go .

@Mstott - Respect for that work of art DB. 

And congratulations on a very good choice in equipment, if I may say so publicly. 😁

8 minutes ago, The Terrible Triplett said:

Respect for that work of art DB. 

Thanks TTT much appreciated 

Ok @plonkster and @The Terrible Triplett I'm looking at panels and would like your opinion . I have MPPT 150-60 and only have space for 10 panels . 

Option 1 ) 10 panels.  2 series and 5 strings . 3500w 

Voc 49.6 x 2 = 99.2v

Isc 9.51A x 5 = 47.55A 

Max cable run would be 6m

Option 2) 9 panels 3 series and 3 strings . 3150w

Voc 49.6 x 3 = 148.8v

Isc 9.51 x 3 = 28.5A

Or I'm totally messing this up ?

Also not set on these panels

I have gone the "two in series" route.

Based on the feeling that there is not enough headroom in the Voc to go 3 in series.

1 hour ago, Mstott said:

Or I'm totally messing this up ?

Nope, not at all. 2 in series is good yes. I have 3 in series, never seen the 149v ... YET ... max so far is 137.84.

BUT it has not been through a winter yet and as Coulomb said, it takes one cool cloudy winters day with the clouds parting into a brilliant sunshine day to mess things up properly.

Note: From all I have blown up in solar, from the top - panels - to the bottom - batteries - I have not blown up a MPPT with volts too high ... yet.
Have burnt a few out because of supreme stupidity and once a Phocos 100/30 MPPT from over heating ... they don't like being in a cupboard.

Waiting on @plonkster to arrive safely in SA, having recovered, after he had all the time on the flight to think about the question, I asked him:
My logic says that - being grid tied:
1) We want spare for winter right? But, forget cloudy rainy days for no matter how much panels we have, it is just not going to be enough.
2) For the rest of the time, if the inverter can do max 3kva at room temp, what is the best balanced array for such a inverter?

I have 24v system, but same logic goes for all the 48v 3kva ranges, irrespective of make - can be extended to 5kva grid tied ranges too.

Option 1: 2800w on a 3kva with throttling on a cool day.

Option 2: 3500w with throttling on cool and hot days

1 hour ago, Mstott said:

Also not set on these panels

I like the Canadian ranges quite a bit. And the price is good, they've bee around a while and seem to really grow in SA.

So hopefully the warranty sticks around for 20 years - as to date I laugh at all warranties that claim 10-20-25 years. Most business failed before 10 years are over. 🙂 

I just installed a pallet of Artsolar 330W panels. And they feel as quality and perform as expected.

Pretty much the same as every other panel I've had any dealing with.

I am not pushing them, but I have no complaints and the price was reasonable.

 

2 hours ago, phil.g00 said:

I have gone the "two in series" route.

Based on the feeling that there is not enough headroom in the Voc to go 3 in series.

I have a feeling I might be doing the same , the factor that is worrying me now is the MPPT max Wattage is 3440w and I would like to install 10 350w = 3500w . I'm not sure if this is potentially damaging to the MPPT ? 

@The Terrible Triplett how dose power limiting work ? I have not come across this as yet . Are these MPPT calculators free for anyone to use ? Very useful indeed 

4 minutes ago, Mstott said:

I have a feeling I might be doing the same , the factor that is worrying me now is the MPPT max Wattage is 3440w and I would like to install 10 350w = 3500w . I'm not sure if this is potentially damaging to the MPPT ? 

@The Terrible Triplett how dose power limiting work ? I have not come across this as yet . Are these MPPT calculators free for anyone to use ? Very useful indeed 

It shouldn't be a problem. As long as the Voc and ICC isn't more than the MPPT's limits.

7 minutes ago, Mstott said:

... how dose power limiting work ?

It it exceeds the amps, MPPT stops working till the amps drop below what it can handle.
If it exceeds the volts, MPPT blows up. 🙂 

7 minutes ago, Mstott said:

Are these MPPT calculators free for anyone to use ?

Jip ... https://powerforum.co.za/topic/3303-starting-out-questions/?tab=comments#comment-50733

Think that one has the Canadian panels add. Adding your own panels, the temps are THE most important part, with the volts and amps.

Edited April 10, 20197 yr by Guest

3 hours ago, The Terrible Triplett said:

It it exceeds the amps, MPPT stops working till the amps drop below what it can handle.
If it exceeds the volts, MPPT blows up. 🙂 

Well, doesn't stop working exceeding Amps, just clips at the ceiling.

Exceeding the volts, seems to be permanently destructive.

Remember as well that power out is at charging voltage, which is closer to 56V for a 48V battery.

So yes you can, and in some/most instances it is best practice to exceed the power rating by a little bit.

Edited April 10, 20197 yr by phil.g00

24 minutes ago, phil.g00 said:

just clips at the ceiling.

Explain a wee bit more please?

If you set a charging current limit of say 30A on a 60A capable MPPT, it lets 30A through at the the set voltage.

Regardless of the available PV power.

If you set a 59A limit - same thing.

Only difference is 60A is the highest you can set, the rest gets gets clipped just the same as if you imposed the limitation yourself.

The MPPT can present a variable impedance to the PV side, that's how it does what it does.

Edited April 11, 20197 yr by phil.g00

8 hours ago, phil.g00 said:

Only difference is 60A is the highest you can set, the rest gets gets clipped just the same as if you imposed the limitation yourself.

Let me ask it from the other side: 
If the MPPT can do say max 60amps and I left the setting at that. 
On a cool sunny day the panels easily exceed the max the MPPT can handle ito amps AND the load at that time is maxed.

Same as limiting the charging amps, the MPPT will keep on providing the max of 60amps if the load demands it, correct?
It won't "switch off" or some such, running at the max?

In other words, this warning is pure information only, to advise that the clipping will be applied if conditions are met?
You still get the 100.0 Amps.

Edited April 11, 20197 yr by Guest

13 hours ago, The Terrible Triplett said:

2) For the rest of the time, if the inverter can do max 3kva at room temp, what is the best balanced array for such a inverter?

Well, I have a 3KVA inverter too, with a 2.6kwh (for now) total solar array. For me the battery size (7kwh) is the limiting factor. Only on a Tuesday (washing day) do I use almost all my power directly. Every other day I need around 3kwh-4kwh storage in the battery otherwise I run out of places to sink the PV into (aka a DoD of around 40%-45%). At the moment I'm okay with this distribution, but if I had a but more battery I could probably stretch the PV a bit more. In any case, to me the best balance for a 3kva inverter is a 3kwp solar array IF you have a battery bank that can store some of the excess, otherwise I'll go with a 2kwp solar array. That is assuming that your day-time loads is mostly like mine (one load of washing, one load in the tumble dryer, fridge, freezer, and some computers).

In short: I think making the PV array larger than the inverter's peak is mostly a waste, unless you have a large battery. The bulk of the energy is always harvested between 12PM and 3PM and your loads are always lower even if you do lunch at home.

Re the 2-series vs 3-series question. If you're pushing over 149V on a 150V controller at 0°C that's simply too close. That is less than 1%. And 0°C is a real possibility even in the warm Western Cape. I have 3-series arrays (two of them!) but I only reach >149V at -4°C. That is a lot more defensible 🙂

 

2 minutes ago, plonkster said:

... the best balance for a 3kva inverter is a 3kwp solar array IF you have a battery bank that can store some of the excess, otherwise I'll go with a 2kwp solar array.
... I think making the PV array larger than the inverter's peak is mostly a waste, unless you have a large battery. 

I can attest to 2.1kw array with a battery bank that does not count that I have surplus and the dishwasher / geyser scheduled in 2 homes being fed grid tied and I work for home and all that.

My gut told me that 3kw array is a good fit - caveat now added - if you have a battery bank that can use it.

So thanks @plonkster - seems that my question to you, 2.8kw or 3.5kw array, that until I get a real battery bank I must not go 3.5kw array ... IF I power loads at night.

I must sit on my hands ... this sitting on hands ... BORING!!! ... but wise.

My hope is that @Energy 's new lithium batteries are the answer with a price tag I can "afford" (read will 🙂 at), for I am NOT going 48v just for blerrie batts.

For I swear, the day I go 48v with a new bank, few years down the track it will bite me in the ar_e when I could have bought 2 x 12v cheap Royals (in a pinch) but are forced to then buy 48v bank ... pinch the day the dog needs medical treatment and the wife said I cannot put it down and the batts failed. 🤣

14 minutes ago, The Terrible Triplett said:

I am NOT going 48v just for blerrie batts

Other good news for you is that a 24V version of the Multiplus-II will probably show up some time.

29 minutes ago, plonkster said:

Other good news for you is that a 24V version of the Multiplus-II will probably show up some time.

O my word!!! Did you HAVE to tell me that!

You know that if it arrives, is on the list, I will itch and scratch and what what.

Dammit! 😜

(Gumtree users will see a 24v Multigrid still under warranty for sale ... at a price that makes it fly off the wall)

No no no ... sit on your hands TTT - if it works, don't fix it!

Edited April 11, 20197 yr by Guest

14 hours ago, Mstott said:

I have a feeling I might be doing the same , the factor that is worrying me now is the MPPT max Wattage is 3440w and I would like to install 10 350w = 3500w . I'm not sure if this is potentially damaging to the MPPT ? 

I have 3kW of panels so was initially planning on the MPPT 150/60. I eventually decided to go with the MPPT 150/70 (capable of 4000W @ 48V) so that I could make use of the extra power from the solar panels when you have light/scattered clouds. My 3kW panels routinely go above 3kW, one time even recording a peak close to 3900W.  I also prefer to run the MPPT at less than the maximum rating to ensure overall long-term reliability.

An MPPT offers a variable impedance to the PV panels.

Taken to extremes, this could mean that it could present as either a short circuit (V=0V; I=Isc) or an open circuit. (V=Voc; I=0A)

In both these instances power (VxI) = 0 watts.

If you have more available power than is required, the MPPT just adapts its apparent impedance to suit.

It isn't being over-powered, it will just present an impedance that moves the power point to a different operating point on the VI curve, which could anywhere from max capability/limitation down to 0 watts.

One of the main reasons I have been looking at 10 x 350w and 5 strings is to try get the best output with partial shading . So if 2 panels get shaded the remaining 8 will be unaffected? 

Thanks for the input guys much appreciated