PlanB

No this will not work well for you. With 2 panels your 102.98V gives you 51.5V per panel and with 3 panels this will be 154.5V (will be even higher in winter). That is a bit too much over your limit. Your MPPT will shut down too much and you will loose production. I suggest you stay with 2 panels.

You loose very little. We are talking <5% so it is not worth buying an extra MPPT.
I have a MPPT where the one string face East and the other string West and this works great. All panels on the same string have to face the same direction though.
 
A assume this is 2S4P (4 strings of 2 panels in each string). You should be able to do 3 panels in each string (check your panel's spec for the Vmax). On paper your Vmax (the open circuit one) might be more than 50V which would limit your strings to 2 panels only, but in practice here in SA it is never so cold that you will get to that value. 
If you have been running your current install for more that 1 year you would have done a typical winter. So go check the stats on your MPPT in the Remote Console. Under Overall History you will see what the very max Voltage is your MPPT ever reached. If for 2 panels per string this is < 100V with some margin I will say it is safe to add a third panel to each string to get closer to the 150V
Here is my 100/20's history with 2x 425W panels per string.
The best thing is that even if you did go over the max for a little bit, your Victron SmartSolar has over voltage protection and will not break anything, but just shut down safely until the overvoltage has cleared. This is not true for all other manufacturer's MPPT though.

Technically you can just use 1 MPPT -- BUT this is not recomended as you will loose efficiency. Also consider if your panels are not identical, and you connect them to the same MPPT, the panels will basically only produce as much power as the lowest panel.

Firstly buy the exact same panels a stated above. Your 150/100 MPPT can take 5800w of solar = 14 x 420
Improtant just keep your 2 string configuration as to not exceed 150v

A few months ago I procured a Victron Backplate with a MultiPlus-II 48/5000/70-48 Inverter and a MPPT 150/100
I also managed to get my hands on 1x 4kw and 1x 8kw BlueNova Batteries and for my PV panels I got 8x 440w half-cut large wafer cell monocrystalline percium panels.
Today I saw a reading of 3712 W charging  on the monitor .. I was expecting at the very best conditions 3520W (8*440) , so I'm impressed and very happy.
Is it common / Ok for panels to produce more than what is specc'ed?
I believe ARTSolar is a South African Company, and I can so far recommend their service and the panels.

Yes, 4kWh (or 3.2kWh in reality) is way to small for your inverter size.
I know you may actually be able to get quite a bit more than the 'rated' energy from a new cell, but I still have to wonder about the fact that the manufacturer rates these as 60Ah cells. Surely they would rate them higher if they could. Here is a picture of a cell from a BlueNova 77Ah / 4kWh battery
There are 16 of these cells in the battery. Each cell is clearly printed as 60Ah / 198Wh. 198Wh x 16 = 3.168kWh
http://en.winston-battery.com/index.php/products/power-battery/item/wb-lyp60aha?category_id=176

A 4kWh Lithium Battery is undersized for a 5kW Inverter. Take a look at the Pylontech battery recommendations for example. You should also typically set your minimum SOC to around 30% - although this depends on how much battery reserve you need to keep for loadshedding.
I have a 12kWh BlueNova battery with a 3kW inverter so I generally only discharge to about 65% SOC overnight. My battery appears to have a larger capacity than advertised - cell voltages still looked okay when I once discharged it close to the full rated capacity (as measured by BMV712).    

Since that is supposedly a 4kWh battery, then to use 25% (down to 75% SOC) is only 1kWh. So if you use between 500W and 1kW then it will take 1 - 2Hours to go down to 75% SOC. Although in reality the "77Ah / 4kWh" BlueNova battery is actually a 60Ah 3.12kWh battery (You can open it up and check for yourself. The capacity of the cells is printed on them by the manufacturer). So 25% of the real capacity is actually only 0.78kWh

I suppose there are any number of devices capable of this, but it may be moot, if regulations dictate that the biggest system you are allowed is too small anyway.
Individual measurements are useful to discover your power guzzlers.
Reducing power usage is the first step.
ESKOM is adopting a new load-shedding approach, which they have stated will last eighteen months.
Which means five years. (Formula = times 2 add 1 and allow)
I'd be inclined to pull the trigger now, rather than just be ready to cope with load-shedding just about the time it is due to stop.
The Victron system is good, having inherited the "cheap and nasty" initially, I wouldn't go back. There may be other good brands, but I can personally vouch for Victron.
I consider solar panels to be cheap and a great investment that starts paying for itself from day one and carries on for 20 years +.
On the other hand, I think batteries are a hole in the pocket, but a necessary evil.
All aspects of batteries are often debated on this forum.
My opinion is, if I was intending to eventually go off grid, I'd go lithium from the outset, if not I think I'd go for a 48V bank of SAGM 06 375 Trojans and try and get 8 years out of them.
 
 

Hi,
I have 255W art solar panels and is working fantastic.
Definitely can recommend them.
They can give you the ATP results of each panel you buy.
Regards

I've just bought 28 x 280 watt panels from ART solar. So far so good

If it comes to Infinisolar, I would think again. ABB is in a bit of a different league though. In many cases Infinisolar has advantages over Goodwe. For one, the backup power is not limited to 2.3Kw or 4.6Kw, but limited to how much PV / battery power is available. And it can run off Lead Acid batteries, which Goodwe prefer not to.

I will try and answer as much as I can, and others have given some responses already
Simple. You might start out with a 5Kw today but decide to upgrade in future. Everyone doesn't want 10Kw so 5Kw is sufficient. Or you might want a 5KW on each phase of a 3phase setup. With a 3phase 10Kw you essentially have 3.3Kw per phase.
The Goodwe's can't stack.
This is quite handy if your roof isn't north facing and you need to install an East and West facing PV array. And also handy if there's bound to be some shade at some stage during the day - then only one string gets affected.
As the name, Open Circuit, implies, this is the voltage that could potensially be reached when there's no load. Others have explained this in details as well. Both are important when calculating a system size.
In simple terms, on a clear sky, cool / cold morning, the system voltages can reach higher levels than what the MPPT can handle. This could happen at 7am when it's -2 degrees outside.
As above.
Voltronics is the manufacture. Though MPPSolar also claim to be the manufacturere. Mustek, one of the big IT importers, re-brand most of their equipment and sell them under the Mecer (or Mustek) brand. Pinnacle rebrand their equipment under the Proline brand,hence having proline inverters in the market as well. It's still an Axpert or Infinisolar though. And I think Rectron sells it as RCT, which was the original brand of the first UPS' that Voltronics made, and can still be brought as RCT.
Polycrystalline tend to work better in the warmer areas of the country. Thin Film work even better with lower light so they produce a bit more power, earlier in the mornings and later in the afternoons / early evenings.
Putting all your essential loads onto, say, the red phase and the non essentials split equally between yellow and blue is not that difficult. Just make sure the neutrals are split properly, and as far as possible that the loads are still balanced between the 3 phases.
I have not dealt with Eskom directly yet, so not sure what is involved.
Feel free to ask Perhaps open a new topic per question, as different people monitor different topics and will respond accordingly.
 
 

Those are pretty neat chargers!

Hey, don't be too quick. I believe Ctek might make one. But I might be mistaken. They definitely have a model that takes power from a PV panel as well as from your alternator, for 4x4/camping type people. You could theoretically use one of those and feed it with a mains transformer... but they are not cheap. You might be better off just using two separate chargers.

Sure, generally. But the sun could burst out from behind thick cloud, and the panels could give a burst of power, enough to blow up the solar controller. It only takes once.

Welcome Great post! I promoted it. J

Mainly for expansion; you buy the 5 kW model now, and buy another 5 kW later when you can afford it.
But there is also the idle power drain; you can switch off one inverter at night (possibly automatically), and save the idle power load, if you don't need it. Our patched firmware (for Axpert off-grid models, not the hybrids you are considering) even has a facility called Dynamic Load Control, which allows you to turn on and off some of your paralleled inverters with a command over the RS232 port.

Really, it's Voc, since that determines the maximum number of panels in a string. But Vmppt tells you if that number of panels will be efficiently handled by the inverter. For example, many Axpert models have a maximum PV voltage of 145 V, but the MPPT range is stated as 60-115 V. So if you squeak under the absolute maximum voltage, but your string's highest power voltage exceeds 115 V, then you know that you won't be getting the most out of your panels, as the MPPT is only at its most efficient up to 115 V. (Turns out the real figure for Axperts is 130 V).
I don't know what you're referring to with the "operating voltage"; perhaps you mean the nominal panel voltage (the vast majority are "24 V", but some smaller panels are "12 V"). These are for directly connecting panels to batteries, usually via a PWM controller. Ignore those specifications; they mean little in the context of a home energy system.

There is electronics that is always connected to the PV input. On some models, like the Axperts, there is no relay to disconnect this voltage. So there will be MOSFETs, electrolytic capacitors, and other devices that have absolute maximum voltage ratings. Operating above these limits means you're operating beyond the design limits. In the case of MOSFETs, even a few percent above the design limit can mean catastrophic failure, like a bang and a bad smell, not working after that. For electrolytic capacitors, the limit is more rubbery, usually causing the life of the capacitor to be reduced. However, they can also go out with a bang, and a different bad smell.
The panel voltage will be highest on clear cold mornings. So you work out your likely coldest temperature, and what panel voltage you will likely see at that temperature (usually around 10% more than the string's Voc), and make sure that this is under the maximum permitted panel voltage for your inverter.

I don't know specifically about South Africa, but in most areas, this is never allowed. It's equivalent of paying the full retail price for your exported power. They'll only want to pay you (if they pay you anything at all) for the wholesale cost of generated power, which is roughly a third of the retail price. I get the impression that in many parts of SA, you aren't even allowed to export power at all, and if it's detected, the meter might cut your power.

Pardon me addressing just a few questions.
Yes, the branding is confusing. Voltronic Power are the manufacturers, but they don't want to hand hold the customers. So they leave all that to the resellers, who get their own brand name on the box. I haven't seen an actual Voltronic branding, but I could be wrong. The problem is that the resellers can also change the model name, sometimes slightly, sometimes a lot, sometimes with overlaps (one model name could refer to two different actual models, for example).
The best you can do is to carefully read the specifications of the model(s) you are considering buying, so that you are getting what you expect, and can meaningfully compare them.
[ Edit: it's Mecer, not Mercer, no "r". Mercer made computers back in the day, I'm told. ]
It's to cater for the situation where you have dissimilar panel orientation and/or shading. The classic case is where you have no north facing roof, so you split the panels east and west. These will have very different insolation at different times of the day, so the MPPTs can optimise each better than if the strings were paralleled.
Similarly with shading. If you have one string that is prone to shading, and one that is not, or is subject to different shading, the independent MPPTs can get the most from the two strings.
All panels have a negative voltage-temperature coefficient, something like -0.4%/°C. That means you get higher voltage at lower temperatures. Less than half a percent doesn't sound like much, but a cold morning can be 25°C or more colder than the 25°C that the panel has its voltages specified at, so that's some 0.4 x 25 = 10% difference. In deciding how many panels you can connect in a series string, that 10% can put the open circuit voltage over the edge, possibly damaging the inverter's solar charge controller.
I note that as the temperature goes up, the current goes up, but the voltage goes down faster, so you end up with less power when the panels heat up. It's just a fact about silicon, though monocrystalline and pollycrystalline panels have slightly different coefficients, and they can vary slightly from manufacturer to manufacturer.

Hi @PlanB
Here is a thread I started when I installed my Infinisolar which highlights some of the questions I had when starting off with it and some answers. Infinisolar install
Here is also a thread where I provided some feedback later. Comment
I'm very happy with the Infini considering how much it cost, and with ICC running on Pi it give me most functions of much more expensive inverters.
I now also have it running with a Pylontech battery and very happy, using for backup and cycling it in the early hours of the morning.
When I bought my inverter I bought two as my neighbour was also interested, but then changed his mind, so I kept the second one as backup "in case", but it has run very well for the past 15 months with absolutely no issues, so will probably look to sell the second unopened one.
There is a lot of valuable information on the forum and most of what I learned came from here.
If there are specific Infini questions about running it in Off-grid mode I'll try to answer.
Good luck!

Hi PanB, i´ll tell you my PlanA for this kind of installs. Here, in Spain, is a very repetitive case when someone who has a house and some trees, need a borehole to water. 
We are going to suppose your pump is a 1.5 kW 3X400 VAC motor. In that case, peak start current would be 6 or 8 times nominal current, so you would need a very powerful low frecuency, which use to be not cheap. SMA, Schneider...
What I ussually do is to install an isolated transformer, which rises voltage from monophase inverter to 380-400 V, which feed a VFD, driver, which obtains 3x400 VAC from 1x400 Vac, that comes from the output of transformer. This scheme allows you to reduce start current to 1.5-2.0 nominal current.
Also, it allows you to modify the frecuency of pump motor, in order to adjust solar power to pump power. As example, if your pump is taking 2 Kw at 50 Hz, and you modify frequency via VFD to 45 Hz, the power needed would reduce to (45/50)x(45/50)*(45/50)x2 Kw = 1.45 Kw. 
 
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