higher or lower wattage panels

[Dex_]

Hi,

through all my research and (limited) understanding i am finding it hard to factor in my array. basically though in short i ask is there any reason not to go for the highest wattage panels available?

(i understand you get high voltage panels for larger arrays - i am specifically talking normal here)

eg, if you needed 500Watts to recharge your batteries and possible wanted to add more later would you go for 2 x 250's or would you stick in 2 x 350s now and have overhead?

[Guest]

Dex, the bottom lines are:
1) You first get the max ah of the battery bank you need which in turn dictates the amps the controller needs to push out to re-charge the bank.
2) From that you determine the array size, factoring in you want to recharge the batteries and power the load at the same time.
3) And that then determines the MPPT size you need as each make and model MPPT's has a max VOLTS and max AMPS it can take from the array, to recharge the batteries and power the load at the same time.

Or do it the easy way - work from inverter back:
1) Max inverter is say 3kva
2) So get a 3.5kw array (or 4kw) for winter and less opulent sunny days. 
3) On a 150/100 MPPT controller i.e. max 150v and 100amps charging ability - or a 150/45 or a 150/35 etc.

 

[georgelza]

if your array can do more that what your Inverter/Mppt can handle, does the balance just get thrown over board...

my thinking, over size array so that we closer to max needed in winter (with less solar/sunlight). and ye this means in summer we have wastage.

G

[Guest]

1 minute ago, georgelza said:

if your array can do more that what your Inverter/Mppt can handle, does the balance just get thrown over board...

my thinking, over size array so that we closer to max needed in winter (with less solar/sunlight). and ye this means in summer we have wastage.

Ditto. The power goes to where the socks and tupperware lids go - same place where the typing goes when you backspace on a computer.

Your array seldom preforms at peak, best case is on average 5.5. hours per day over a year period. So we all tend to to oversize for winters / cloudy days.

Just never exceed the max volts and max amps the MPPT can handle from the panels on a cold sunny day with cloud effect to boot - is a risk in buying a new MPPT. 

[georgelza]

... you still not going to like me much atm... still leaning towards a Axpert, can get a 5KVa unit at a great price, allowing me to spend more on batteries and panels now (suck up every bit of sun light, carry the house as close as possible during the day, and then carry load as long as possible during the night, will be shutting allot of non critical off using the ICC and sonof devices), carry most/all my load during the day, and night, and then look at a Inverter/MPPT upgrade year/2 down he line... and ye... most probably towards the Victron direction then.

So for me the MPPT is part of the Inverter. 

Rated Power	5000VA / 5000W
Maximum PV Array Power	4000W
MPPT Range @ Operating Voltage	60VDC~115VDC
Maximum PV Array Open Circuit Voltage	145VDC
Maximum Solar Charge Current	80A
Maximum AC Charge Current	60A
Maximum Charge Current	140A
Floating Charge Voltage	54VDC

So my understanding... the 3 panels in series must provide 60-115V for the Charge Controller to work (never more than 145VDC), and the amount of panels in series and parallel combination must not output together more than 80A (which should anyhow be protected by a fuse).

So time to read the Canadian panels and the Renewsys 330w panel specs. but thinking I'm in the right ball park.

G

[Guest]

16 minutes ago, georgelza said:

... you still not going to like me much atm...

By all means, we all started somewhere.  

Me, after having had to spend monies on replacing a battery bank the first time, I lost interest in powering loads using batteries. 

Grid tied with batteries as backup IF Eskom is off makes a lot more sense to me today.

Caveat: IF I was on a farm with very expensive Eskom connection THEN batteries make more sense because they are cheaper than fuel for a gennie. 

[georgelza]

The house is in Jeffreysbay, they getting 3am and 5am load shedding atm, 3-4 times a day, last one 7-10pm.

2 small kids and wife that side, and expensive electronics including a not so small media station/server thats currently taking a knock every day (we actually switched it off at the moment).

so a large solar (for day, pool pump, 2 geysers) / pv capability for night to run critical load at night is sort of important at the moment.

so saving money on inverter/mppt and spending on batteries is sort of ye... for batteries I pretty much made up mind, 2 x Pylontech US3000's + ICC stack/solution

Inverter is a pretty made up case,

Panels is the question now.

G

... I have a nice 7.5 KVa Geni, but it's noisy and we have some sensitive neighbours and damm petrol is also not cheap so thats a last resort/option.

Edited March 24, 2019 by georgelza

[Guest]

14 minutes ago, georgelza said:

The house is in Jeffreysbay, they getting 3am and 5am load shedding atm, 3-4 times a day, last one 7-10pm.

That is rough I get it. Nothing wrong to go with an Axpert.

I just don't like the fact that Voltronic does not help, firmware bugs are not sorted, bar from the great guys in Australia like Coulomb and Weber and I have noticed that the last few months that there has been a few posts asking for help on unforeseen repairs needed on a Axperts and the copies.

Yes, Victron can also pop but you have suppliers all over that can repair them in a jiffy, in PE and George.

BUT money is a huge factor in the decision, and whatever you buy, it is not a lifelong decision either. Equipment last X years. Victron at least 5 years as per their warranty.

Go with a Axpert because you are making an informed decision, having read the forum AND debated the pro's and con's of Victron prices.

[georgelza]

As you say, not a for life decision, what we have now... will have changed night and day in 5 years... make that prob 3 years, so spending roughly 3rd on the Axpert now, using funds for  battery and panels which cost bigger % of solution and then in 2-3 years can relook at the inverter and technology out there.

G

[Coulomb]

14 hours ago, georgelza said:

So my understanding... the 3 panels in series must provide 60-115V for the Charge Controller to work (never more than 145VDC), and the amount of panels in series and parallel combination must not output together more than 80A (which should anyhow be protected by a fuse).

Actually, the 80 A is on the battery side. So it's best to work with nominal (close to maximum you'll see in practice) power, and don't exceed 120-125% of the rated power of the solar charge controller (or the real maximum PV power, in the rare case that Voltronic Power provides this number). You quote a maximum of 4000 W of PV power, but that's just 80 A x 50 V, with no margin for oversupply. So I'd work on a maximum of 4000 x 125% = 5000 W (nominal).

I note that three 72-cell panels in series is a little too much in cold areas; I use 2S myself. But if you stick to the 60 cell panels (these are usually around 250 Wp), then 3S is fine. I find that the 300+ watt panels are a beast to lug around unless you have two people to handle them.

[georgelza]

hmmm, ok, only response i ca give is "huh"...

I'm still waiting for a installer/supplier to actually deem my questions worthy of their attention and actually bloody respond, show interest to supply/install this for me. Seems to be a tad of a problem with a over supply of customers wanting this at the moment. Never mind finding stock of everything.

As for the 300W being big/heavy, thats a once of problem for installer... not going to make design decisions around that. do it once, swear once, get it up there, get it over with, use the extra Wattage they give.

G

[Guest]

54 minutes ago, georgelza said:

As for the 300W being big/heavy, thats a once of problem for installer... not going to make design decisions around that. do it once, swear once, get it up there, get it over with, use the extra Wattage they give.

With my 350w panels, not an issue at all. The installers have knacks and tricks to make it look easy after having done a few installs themselves, and they tend to work in pairs.  

54 minutes ago, georgelza said:

hmmm, ok, only response i ca give is "huh"...

What Coulomb is saying, if you use the big Canadians, and boy can they produce (seen 2.7kw out of my 2.1kw array at times), is that you are running on the brink of dangerous on a cold sunny day with cloud effect with them on a Axpert. If you exceed the volts (or the amps) the MPPT will pop.

2S is 2 in series.

Edited March 25, 2019 by Guest

[georgelza]

problem, so all we saying rather connect them Canadians as 2s and not 3S... to keep Volate/Ampage safe.

G

[Guest]

11 minutes ago, georgelza said:

problem, so all we saying rather connect them Canadians as 2s and not 3S... to keep Volate/Ampage safe.

Correct. 

The thing is that panels are a 20 year install, not so much inverter and batteries, right?

So if you have plans to change one day, you want the panels ready for the next device. So you may decided on say 350w Canadians, 2S, 3P, and then one day you have another type of MPPT, and you simply change the wiring to 3S, 2P or whatever. All that is required is a rewiring.

Edited March 25, 2019 by Guest

[georgelza]

... agree, might make me do 5p x 2s now, or maybe 6px2s.

looking at either the 330w Canadian's, or if price allow maybe the 350w's

G

[georgelza]

... bummer, just discovered the ICC solution currently only support 4 x Sonof's. so all else will need to be done by myself, would have liked to see it being able to manage more.

they do however come with light, medium or heavy load options.

light = 4 x sonof 10amp

medium = 2 10, 2 x 16 amp

heavy = 4 x 16 amp,

G

[georgelza]

@PaulF007 .... might be pressing on that button to get some flashed FW units via you.

G

[georgelza]

... MY thinking at the moment, considering I only have 4 sonof devices 2 x 10Amp, 2 x 16 Amp.

Anyone know of a make/model contactor/relay switch that can use to drive the non critical load, to be commanded from a sonof.

The sonof on the NAS / (it's a critical load for me), but when the batteries get low I want to remotely switch it off (init 0) (thinking their R2 sonof so that i can confirm load is 0, or retry)

G