Off-grid system sizing - Are these numbers correct?

[Trntemrnte]

CONSUMPTION
I checked my consumption in the apartment where I'm staying and for the last six-ish months it wasn't over 80kwh/month, which comes to 2,66kwh/day.
So just in case I've bumped that to 5kwh/day. Besides things I have now, that are using electricity, when I move off-grid I'll add to that a breadmaker(550w), which I'll use every 4-5 days, a water pump(some 400w), and a freezer(450w). Except for the freezer, the other two appliances will work rarely. The pump maybe for an hour a day, if that, and the breadmaker as said, a couple of hours every 4-5 days.

BATTERIES
So if I got it right, I'd need at least 10kwh of battery storage. I found LFP 51.2V batteries, 5120wh of capacity, that are produced in Europe, with a 10-year warranty. So it seems I'd need three of those if discharged up to 10% and to have some 2.5 days of backup for rainy days. In total some 15Kwh of capacity. An online calculator suggested I'd need 17.1kwh of storage, considering low(4C)winter temps. Is that correct?

PV PANELS
The calculator also suggested I need 2kw of PV panels at 4.1 hours of sunlight. I thought maybe I could add another 400w, as I'll probably have to go with three batteries.

INVERTER
I decided to buy all Victron devices, as I'm in Europe and they're a Dutch brand. So for the inverter, it seems MultiPlus 2 would work best. I'll have a generator connected to the inverter and MP2 has an integrated charger for this purpose.

MPPT CHARGER
The same calculator suggested I'd need 39amps for 2kw of panels. I saw Will saying it's always good to bump it up and also if I'd add that extra 400w for the total of 2.4kw of PV panels, then it comes to 50amps. I've found this Victron's MPPT 150/70. So that's 20amps more than needed, but according to specs it can charge up to 3440w, so I guess I could add more PV later on if needed, without having to upgrade the charger..?

GENERATOR
There's little info on this online, and I've been told many things that I've taken with a big grain of salt.
I know it can be automatic or manual, and that's about it.

QUESTIONS
Roughly, does 5kwh sounds enough?
Is battery sizing alright?
Is PV panels calculation correct? Should I add that extra 400w, for a total of 2.4kw?
Should I go with 3000VA or 5000VA MultiPlus2 for a system like this?
Is the calculation for the charger correct?
What generator would be the best bang for the buck? Auto vs manual pros and cons? I imagine those that have an auto-start option are more expensive.

Surely, any suggestions for further modifications are welcome as well.

 

[Steve_S]

I use on average 3.5-4.0kWh per day. (year round)
100% offgrid, with deep well pump.
Original Solar Array is 2080W that can provide up to 80A Charging
Second Solar Array is 2370W that can provide 92A Charge.
These are Fixed Ground Mount arrays @ 45 Degrees.

Now I run with a 45kWh bank because it's not unusual to be 10 days in the dark as it were... So I have chosen to have the bank be able to support that.

Lessons Learned Dept:
I started with a 3000W PureSine LF Inverter/Charger (Cheap Chinese One). Higher idle running watts (40W), it worked OK but was pretty featureless. Upgraded to a Samlex EVO 4000W Inverter/Charger with higher efficiency and low idle (17W) and Wonderfully programmable. I would have gone with Victron but it was not available in Canada at the time. I SUGGEST THE 5000KVA Multiplus because we ALL find after installation that we underestimated and sometimes we do need more than we accounted for... also we always buy more stuff & that increases our power needs. LESSON, Get the next bigger Inverter than you think you will need as long as it is as efficient if not better.

I installed the 2nd array to compensate for low generation times (Oct-Mar) the rest of the time the original array can keep things charged pretty well... again partly because I have over capacity & low usage.
LESSON: I should have run a larger OR second conduit (will pull strings) to pull the solar wire over from the 2nd array. "Dig the trench ONCE" I would have been far smarter to run a larger conduit OR wire in the extra wires in advance. SO when setting up make Provisions for Future expansion/change.

Product Lessons:
Mixing different products works BUT is also fraught with hair pulling complications. Stick to one product family/eco-system like "All Victron" and you'll be golden and with much less hassle & frustration. WARNING !! Victron is great and Several battery packs & their BMS (Battery Management Systems) support the Victron Protocol Stack. NOTE that NOT ALL BMS' DO ! A good "Closed Loop" system with smartBMS' that connect to Victron Gear can really make for a very manageable system.

GENERATOR: (back of envelope math here)
Boy this one gets messed up a lot...
Assuming a Multiplus 5KVA can output 70A @ 48VDC for charging. The genset needs to be able to provide enough for charging + passthrough overhead. 51.2Vx70A=3584W (*1), 58.4Vx70A=4088W (*2)
(*1) - (this is 3.2V per cell X 16 cells)
(*2) - (this is 3.650V per cell X 16 cells) Max Voltage that can be sent to LFP cells.
4500W÷230VAC = 19.6A
You would want a Genset that can handle a constant output of at least 4100W, preferably 4500W (20A) but that can handle surge to 230V/30A at least. Use a Proper Inverter Generator as that will provide clean qualified AC Power that the Inverter/Charger will accept. I would also suggest that you seriously consider a Dual Fuel (Gas/Propane) model so that you can ensure you will be able to run when needed. Gasoline goes sour in months but Propane lasts and won't sour, so you can always store a couple of tanks away for a "bad day". Given your location & what's going on around you, that makes more sense than ever.

I would recommend CHAMPION Generators because bang for buck they are really great BUT they have very limited offerings for Europe, I looked at their UK, Germany & Poland sites and they only have up to 3650W models there.

Hope it helps, Good Luck

 

[DIYrich]

You can add batteries and panels later, just plan for that (where to put, conduit, etc).

You calculated average energy per day. For inverter sizing, add up everything that can be on at the same time, plus the start amps of motors (pump, fridge).

For panels, on a good day, 2kw produces 8kwh. It would take 3 days to recharge a drained 15kwh battery. Do you want to plan for 3 rainy days followed by a nice day, followed by 3 more gloomy days? You can either add more panels, or use the generator.

Manual generator that can recharge the battery over 5-8 hour run. Since you have 3 days of battery, you can recharge at your leisure. 15kwh would be 2-3kw. Using 80% max running load, that would be 3-4kw. Assuming some conversion loss, that is 4-5kw. You could run for 1-2 hours to provide 1 day of power.

Note: if you have a hybrid car (toyota) you can use the car as a generator.

 

[Pi Curio]

Welcome to the forum @Trntemrnte

CONSUMPTION
I checked my consumption in the apartment where I'm staying and for the last six-ish months it wasn't over 80kwh/month, which comes to 2,66kwh/day.
So just in case I've bumped that to 5kwh/day. Besides things I have now, that are using electricity, when I move off-grid I'll add to that a breadmaker(550w), which I'll use every 4-5 days, a water pump(some 400w), and a freezer(450w). Except for the freezer, the other two appliances will work rarely. The pump maybe for an hour a day, if that, and the breadmaker as said, a couple of hours every 4-5 days.

What's your highest planned load?

As far as total consumed Wh/day vs a minimum of 5kWh capacity goes, looks good to me.

BATTERIES
So if I got it right, I'd need at least 10kwh of battery storage. I found LFP 51.2V batteries, 5120wh of capacity, that are produced in Europe, with a 10-year warranty. So it seems I'd need three of those if discharged up to 10% and to have some 2.5 days of backup for rainy days. In total some 15Kwh of capacity. An online calculator suggested I'd need 17.1kwh of storage, considering low(4C)winter temps. Is that correct?

Never heard of that brand, but the price looks ok. Would suggest doing your research on the company and the product, search forums, YT, etc.

If possible, contact their customer service and ask about the product/warranty in more detail. See how responsive is their customer service, to begin with.

There are many 48V server rack batteries priced in a similar range with a decent customer service reputation.

How long the warranty lasts doesn't mean much if you can't reach their customer service at all, or their support leaves much to be desired.

All in all, for your planned worst-case scenario of a 5kWh requirement per day, a 15kWh storage sounds good to me.

It's the winter that sucks the most, but, you can always double the solar Array size so it doesn't suck as much

With 15kWh LiFePO4 48V storage, you can pump some real solar numbers and still keep it gentle on the batteries.

PV PANELS
The calculator also suggested I need 2kw of PV panels at 4.1 hours of sunlight. I thought maybe I could add another 400w, as I'll probably have to go with three batteries.

I'd suggest going with 2,4kW of solar from the get-go. That's about 6x 400W panels, which will make things much easier to wire the array to begin with.

Plus, in general, you can expect about 85% of the STC(standard test condition) rating in the real world with some exceptions during colder clear sunny days.

That said,

2400W(STC rating) solar *0.85(real-world performance) = 2040W of solar

2040W / 48V chargeV = 42.5A charging <--- This is a good starting point to start thinking about the SCC selection. More on that a bit later...

INVERTER
I decided to buy all Victron devices, as I'm in Europe and they're a Dutch brand. So for the inverter, it seems MultiPlus 2 would work best. I'll have a generator connected to the inverter and MP2 has an integrated charger for this purpose.

This is great to hear, Victron is the best possible choice in my honest opinion. And since recently, it's even more affordable. Either way, Victron will save you money and headaches in the long run, and Victron just works.

Let's go back to my previous question for a moment, what is your heaviest expected load?

Asking this because if you plan to cook food with an electric stove, in general, that's about 2000W-2200W load.

So if you plan to use only 2200W-ish tops at any given time from your system, there's a nice Victron Inverter/charger at a noticeable discount right now. Hence the reason why I'm asking the question.

Victron Energy PMP482305012 Multiplus II 48V - 3000VA - 35A - Multiplus - Inverter - ESS | NKON

.

eu.nkon.nl

It could save you a lot of money if your requirements do not exceed 2200W ish load at any given time.

MPPT CHARGER
The same calculator suggested I'd need 39amps for 2kw of panels. I saw Will saying it's always good to bump it up and also if I'd add that extra 400w for the total of 2.4kw of PV panels, then it comes to 50amps. I've found this Victron's MPPT 150/70. So that's 20amps more than needed, but according to specs it can charge up to 3440w, so I guess I could add more PV later on if needed, without having to upgrade the charger..?

Previously, I've done some napkin math on what you can expect to get from a 2400W solar array at peak sun hours on average.
About 2040W. 2040W/48V= 42,5A

In my opinion, Victron 150/45 SmartSolar SCC would do the job just fine, and depending on the panel you go with, it's Voc, a 3S2P solar array configuration could work just fine and would not require fuses, etc, on the PV side of things.

I don't want to overwhelm you with too much information at this point, but I believe it's important to mention that since your system will be an off-grid one IIRC, it would probably be wise to consider at least 2x SCC.

Instead of a single bigger SCC which tends to be expensive, you could go with two smaller ones and have redundancy in case if one of the controllers stops working. Plus, you would have more options for Solar expansion down the road without the introduction of more part counts like combiner boxes and whatnot.

Twin combo 2x (150/35 with 3x400W in series) is what I'm thinking.

And you are good up to 4000W actual solar(85% STC considered) if you want to upgrade one day, and still, no fuses or a combiner box messing up with efficiency and whatnot.

If that sounds interesting enough, I can expand more on that later. The math is in favor of twin SCC for sure.

GENERATOR
There's little info on this online, and I've been told many things that I've taken with a big grain of salt.
I know it can be automatic or manual, and that's about it.

I'm not an expert, but I think you should ask around about this in relation to the Victron Multiplus II Inverter/charger.

QUESTIONS
Roughly, does 5kwh sounds enough?

From what you've said about your requirements, to start with, yes.
For a few days of reserves, 15kWh sounds like a good point to get to eventually.

Is battery sizing alright?

5kWh to start with and 15kWh to end up with, for the 5kWh/day worst-case scenario requirement, it just may be.

Is PV panels calculation correct? Should I add that extra 400w, for a total of 2.4kw?

Yes, go with 2.4kW of solar from the get-go. It just makes sense all things considered.

Should I go with 3000VA or 5000VA MultiPlus2 for a system like this?

Comes back to, what's the heaviest load you plan to power on this system at any given time.

Do you use electricity to cook food, while watching TV with lights and AC on, or do you power only a thing or two at a time?

If you want the comfort of knowing you can cook and wash laundry, or in general power multiple devices at the same time, 5000VA would be better in my opinion.

Is the calculation for the charger correct?

Close enough to start with.

Surely, any suggestions for further modifications are welcome as well.

Would suggest triple-checking everything anyone says, including me.

Take everything with a pinch of salt

Good luck

 

[Trntemrnte]

Now I run with a 45kWh bank because it's not unusual to be 10 days in the dark as it were

Lessons Learned Dept:
LESSON, Get the next bigger Inverter than you think you will need as long as it is as efficient if not better.


GENERATOR

Hey @Steve_S , thanks!

Luckily, I am in southeast Europe, 10 days without any Sun doesn't happen here.

Ya, I've figured that out. I'll oversize everything, to leave room for the potential future upgrades.

Regarding 3000VA vs 5000VA; Is it possible to just go with 5000, without having a mismatch in the V, amp, W department?

Seems 5kwh will do. Gas generators are not common here, and a couple I've found are sucking so much gas that it isn't feasible to have one. Think I saw somewhere that diesel lasts longer than petrol, so I'll see if I can get one that runs on diesel. Brandwise, Honda. Tested, trusted, and easily available here. There's another Italian brand, Pramac, some people told me it's good. But I'd go with Honda.

Welcome to the forum @Trntemrnte

What's your highest planned load?


Never heard of that brand, but the price looks ok.


I'd suggest going with 2,4kW of solar from the get-go.


This is great to hear, Victron is the best possible choice in my honest opinion.


Asking this because if you plan to cook food with an electric stove, in general, that's about 2000W-2200W load.


Previously, I've done some napkin math on what you can expect to get from a 2400W solar array at peak sun hours on average.
About 2040W. 2040W/48V= 42,5A

Twin combo 2x (150/35 with 3x400W in series) is what I'm thinking.

If you want the comfort of knowing you can cook and wash laundry, or in general power multiple devices at the same time, 5000VA would be better in my opinion.

Would suggest triple-checking everything anyone says, including me.

Hey @Pi Curio, thank you!

Well, if I'd fire up every electrical device in my house-to-be, that would come up to some 3kwh. According to MP2 specs, if I got it right, it can go up to "Cont. output power at 25°C 2400 W", while 5000VA is rated at "Cont. output power at 25°C 4000 W". So does that mean I'll need the 5000VA model? Maybe I got it wrong...

Those batteries, it's a Slovenian brand, cells made in China with BMS made by that Slovenian company, TAB. They're compatible with Victron devices and the warranty is actually 5 years or 3000 cycles(80% discharge). Seems alright. Besides that, Slovenia is a neighboring country, they have an office in Croatia too, so warranty, servicing etc should be easy.

Ya, 2,4kw, definitely. Better have more than less in this case. Regarding Victron; I'll live there and it needs to work without any BS and last for a long time. No point in skimping there, just to have to spend more money later on(cos you bought a crappy device at first).

There won't be heavy suckers connected, like heating/cooling or water heating and cooking. Firewood and gas will do for that.

2x150/35 sounds good, for the wiggle room it gives.

Agreed. I'm asking around, to eventually get a clear picture. Can't go with just one opinion.


Another thing; some people go into a ton of details when doing sizing calculations; like temps, angle of panels, loss in the system and some other math/physics factors. Is that all really necessary or it simply helps with precision?

 

[Steve_S]

Another thing; some people go into a ton of details when doing sizing calculations; like temps, angle of panels, loss in the system and some other math/physics factors. Is that all really necessary or it simply helps with precision?

The small details & minutia may seem a waste but it really adds up fast & does indeed make a big difference.
Solar Panel Angles for instance. My panels are set @ 45 Degrees for best "Average Generation" (at my specific location) Below I am posting the Angles for ZAGREB

Note that a fixed array @ 44 DEG (Optimal in March & September) will produce the "best annual average" and just by shifting the angle, changes when you'll get optimal solar production. (This is assuming direct south orientation) A couple of degrees of angle can really change your production windows.

Direction (East/South/West) also has a mark impact on your production potential and that also has to be accounted for so you get the correct generation when you ca maximize it. Graphic below shows "Direct South" exposure which provides the best "daily average" generation. A few degrees shift in direction changed when (what time) the most optimal generation will occur, More East the earlier that Day Peak will be reached but the more west direction shifts Day Peak to later in the day.

 

[Pi Curio]

Hey @Pi Curio, thank you!

Nothing to it, happy to help if I can.

Also, it's great to see a fellow countryman here on this forum. Malo nas je, al nas ima!

Well, if I'd fire up every electrical device in my house-to-be, that would come up to some 3kwh.

Is that 3kW (power) or 3kWh(energy)?

According to MP2 specs, if I got it right, it can go up to "Cont. output power at 25°C 2400 W", while 5000VA is rated at "Cont. output power at 25°C 4000 W". So does that mean I'll need the 5000VA model? Maybe I got it wrong...

That's correct.

I see you've mentioned later in the post, that you will not use solar for cooking, heating, etc. With that said, If you previously meant to say 3kW, not kWh, then it's possible the 5000VA inverter would be better.

It depends on whether you plan to use more than 2400W AC at any given time or not.

While a 3000VA inverter could be sufficient for the job, if your current budget permits, going with a 5000VA inverter now will make your system more future-proof.

That is, if it ever comes to needing more power, the 5000VA will have you covered.

If you have a 3000VA, you will probably need to buy another inverter with more power.

Those batteries, it's a Slovenian brand, cells made in China with BMS made by that Slovenian company, TAB. They're compatible with Victron devices and the warranty is actually 5 years or 3000 cycles(80% discharge). Seems alright. Besides that, Slovenia is a neighboring country, they have an office in Croatia too, so warranty, servicing etc should be easy.

Hmm.. that's awesome that they have an office here. It makes it almost a no-brainer to get their product. Heck, even driving to Slovenia and visiting their HQ, is no biggy. Very convenient for sure.

Curious, is their office in Zagreb or somewhere else?

Ya, 2,4kw, definitely. Better have more than less in this case. Regarding Victron; I'll live there and it needs to work without any BS and last for a long time. No point in skimping there, just to have to spend more money later on(cos you bought a crappy device at first).

Exactly!

There won't be heavy suckers connected, like heating/cooling or water heating and cooking. Firewood and gas will do for that.

That makes for a night-and-day difference in terms of how powerful your system needs to be.

2x150/35 sounds good, for the wiggle room it gives.

Also, you can network them together for synchronized charging via the VictronConnect app on the phone.

Another thing; some people go into a ton of details when doing sizing calculations; like temps, angle of panels, loss in the system and some other math/physics factors. Is that all really necessary or it simply helps with precision?

I'd say, most of these are very necessary, mandatory even.

For example, when making the selection of solar panels for your SCC, it's essential to account for the panel temperature coefficient to ensure that the Array Voc does not exceed the SCC input voltage limit in colder weather. If it does, it will most likely fry your SCC.

This can be a very simple, but costly mistake.

If you have a solar panel in mind for the SCC you plan to go with, share it here and we can check the datasheet and see how well it fits within the SCC limits, be it Voc or Isc.

Also, Solar panel angle can make a lot of difference in terms of production.

@Steve_S shared some good info in his post.

 

[Trntemrnte]

The small details & minutia may seem a waste but it really adds up fast & does indeed make a big difference.
Solar Panel Angles for instance. My panels are set @ 45 Degrees for best "Average Generation" (at my specific location) Below I am posting the Angles for ZAGREB

Note that a fixed array @ 44 DEG (Optimal in March & September) will produce the "best annual average" and just by shifting the angle, changes when you'll get optimal solar production. (This is assuming direct south orientation) A couple of degrees of angle can really change your production windows.

Direction (East/South/West) also has a mark impact on your production potential and that also has to be accounted for so you get the correct generation when you ca maximize it. Graphic below shows "Direct South" exposure which provides the best "daily average" generation. A few degrees shift in direction changed when (what time) the most optimal generation will occur, More East the earlier that Day Peak will be reached but the more west direction shifts Day Peak to later in the day.

I get it. It's just that I have to take many deep-dives like this into different fields(like roofing etc), as I'll be doing the majority of work on my own. Gets overwhelming.

Is it possible to adjust the angle via PV panel holders? Orientation-wise, I'll build a workshop, with the panels on the roof. So I can go with 100% south orientation, or S-SW, S-SE.

Btw, thanks for those figures.



Đe me nađe!?

Is that 3kW (power) or 3kWh(energy)?

That's 3 kw max draw.

That is, if it ever comes to needing more power, the 5000VA will have you covered.


If you have a 3000VA, you will probably need to buy another inverter with more power.

Ya, what I said yesterday, it's better to oversize. 5000VA then...

Hmm.. that's awesome that they have an office here. It makes it almost a no-brainer to get their product. Heck, even driving to Slovenia and visiting their HQ, is no biggy. Very convenient for sure.

Curious, is their office in Zagreb or somewhere else?

https://tab.hr/

I'd say, most of these are very necessary, mandatory even.

For example, when making the selection of solar panels for your SCC, it's essential to account for the panel temperature coefficient to ensure that the Array Voc does not exceed the SCC input voltage limit in colder weather. If it does, it will most likely fry your SCC.

This can be a very simple, but costly mistake.

If you have a solar panel in mind for the SCC you plan to go with, share it here and we can check the datasheet and see how well it fits within the SCC limits, be it Voc or Isc.

@Steve_S shared some good info in his post.

That's where it seems to start to be complicated, with all those acronyms; SEC, VOC etc. Is there a calculator that can do the whole calculation? How the heck do I get it right, without a degree in electro engenieering?

 

[DIYrich]

That's where it seems to start to be complicated, with all those acronyms; SEC, VOC etc. Is there a calculator that can do the whole calculation? How the heck do I get it right, without a degree in electro engenieering?

MPPT Calculator - Victron Energy

MPPT Calculator - Victron Energy

www.victronenergy.com

 

[Steve_S]

Believe it or not, for a brand new person with minimal knowledge to get a real handle on this stuff takes about 1 year, 6 months if dedicated to learning... Overwhelming is something we hear a LOT ! It can be, if you let it. Even worse, people tend to fall over the differences between AC & DC Power, they are both electric but very different beasts. Just like the Computer World, there is a whole world terms to learn.

You are doing the SMART THING ! Researching, learning and starting to plan BEFORE Buying Anything ! NEVER EVER BUY ANYTHING TILL YOU HAVE PLAN ! That is the fastest way to dispose of cash ! So many show up saying "I bought A-B-C and now how do I put it together...."

You are building a shop, that can provide a LOT of optimizations.
1 Roof Face - facing due south OR dual arrays, 1 for East & 1 for West.
E & W will generate more kWh over the course of the day and provide Peak Power from each side at Mid Morning & Mid Afternoon and depending on your use pattern that could be far more beneficial as you have extended generation time.

As you are aware, Panel Angle makes a BIG difference, this is especially true the further North you go. My system is at 45 Degrees which is good for my location. Even @ 45 Degrees show will not shed quickly, I often have to go out and give the arrays a brush with my Foam Brush. Fortunately I can do that with a ground array... Had I done that on a roof, I'd have to wait for it to come off naturally and when it's frozen to the glass @ -30C it won;t slide off.

Something to consider:
My Panels are at 45 Degrees, that translates to a 12:12 Pitch Roof (pretty sharp)
44 Degrees is optimal for "Zagreb" and that translates to a 11.59:12 pitch (not that much difference eh).

Another Point because of New Build.
You have even more "free optimizations" that you can do to increase solar generation as well. If you use a White Metal/Tin Roof and install Bi-Facial Solar Panels the white background will increase the generation capacity & give you a lot more Watts per square meter. Bi-Facial panels have their own tricks and they do cost a little more but it increases your immediate energy supply and shortens the return on investment.

With the info you've provided here is my snapshot view.
- Stick with Victron Gear only.
- 5kva Multiplus-II (can be expanded with paralleling another)
- 2X Victron Solar Controllers (SCC's) 1 ea for East & West Roofs
- White Tin Roof with Bi-Facial Solar Panels
- Solar on Both Side of new building of course.
- 48V Battery Bank using LFP that supports Victron Comms for Closed Loop operations.

BATTERY NOTES: (LFP / LiFePo4 / Lithium Iron Phosphate)
- LFP is Millivolt & Milliohm sensitive... Accuracy is measurement is important.
- It cannot be charged below 0C Temp or above 55C
- You CAN add batteries over time without ANY issues !!!
- Battery Packs within a Bank do NOT have to be the same size (in Amp Hours) but should not be too divergent otherwise problems will occur. Greater than 100AH difference will require serious math and adjustments to prevent issues.
THERE ARE MANY VENDORS - Some BIG - Even with that not all are GOOD !
If you are DIY'ing your own battery packs, we have many Known Good Vendors to provide the required parts.
If you are buying Prebuilt Battery Packs - ASK Questions here about THE "Brand Name & Experiences" and check into them.
* Recently a Large Commercial company was exposed for some really awful & terribly dangerous things, Affected several "Rebranded Products"... so ASK !

IF considering DIY, there is the added costs of tools & equipment etc + even more learning curve albeit not too bad. You can look at this Guide I wrote a while ago to get an idea on it, download the PDF. Luyuan Tech Basic Lifepo4 Guide V1.0A

Hope it helps, Good Luck

 

[OzSolar]

Don't forget monitoring. Perhaps it was mentioned and I didn't see it.

Since you're using Victon (smart move) you've got numerous options, I'd suggest at least Victron Smart Shunt and a Cerbo Gx. Or replacing Smart Shunt with the Lynx set up will allow for both monitoring and easier installation.

Either way this will allow you to see all of your equipment on one dashboard while you're home and away.

 

[Quattrohead]

Your calculations are good, but as others have said, you should size the inverter and MPPT for max size you could ever use but add more panels and batteries later on.

 

[wpns]

As others have said, while it's important to understand the engineering, and develop as close a model to reality as you can, there's a tradeoff between sizing the system to exactly what you need today, and having some margin for unexpected events. Once you've got the design, turn it around and see if there's a way to add more panels, batteries, parallel inverters, etc. The weather will change (it's already changing, getting crazy in places!), your loads will change, you'll replace some appliances, you'll add something you hadn't thought of (up to and including another member of your household), your solar hot water heater will fail and you'll run down to Home Depot and pick up a $100 water heater to tide you through the 6-month procurement process of the new one, etc. There's a tradeoff between overspending and adding margin, but chasing problems also has an opportunity cost. At least put the hooks in for more capacity later. For instance, the extra batteries will go here and connect up like this, the secondary array will go there on the roof and be wired through this installed but unused conduit, the parallel inverter will be mounted on the wall next to the primary and be connected to these spare connection points in the AC combiners, etc.

 

[Pi Curio]

Đe me nađe!?

That's where it seems to start to be complicated, with all those acronyms; SEC, VOC etc. Is there a calculator that can do the whole calculation? How the heck do I get it right, without a degree in electro engenieering?

Once you get used to the acronyms and do a few calculations here and there, you'll get a hang of it in no time. Practice makes perfect

Also, the link @DIYrich shared here is worth checking out.

 

[Trntemrnte]

Thank you guys, this was very helpful!

I found a big solar shop in Austria, Victron dealers, talked to them and they seemed decent at first. I'll be probably buying everything from them, so they're willing to work the numbers for me(based on the info from this thread) to come up with a setup. Of course, I'm not just gonna go with it instantly, I'll come back and check it with y'all. Triple-checking is the name of the game

 

[Trntemrnte]

@Pi Curio, @Steve_S, here's the reply I got from that solar shop.

Consumption

Let us use the worst-case value of 5kWh/day (so you will be better equipped for the future)

Batteries

Yes, approx. 3 days backup is what we aim to achieve for Off-Grid systems (period from April to October). Thus, we would need 3x 5kWh Modules, means 15 kWh!

PV Panels

With 2kWp of panel power you will yield ~5.4 kWh/day. This is an average value over the year -> in summer more and less in winter! This is definitively not enough for 15 kWh batteries and your consumption of 5 kWh/day mentioned above, especially between October and March! Since we have very low module prices it is wise to install as much as possible with respect to the given roof area. My suggestion is to install at least 5 kWp (better more) of module power, which would yield ~ 13,7 kWh/day (average value).

Inverter

Multiplus II 48/5000/70-50 would fit perfectly (up to 70A charging current). Furthermore, you can easily connect an ~230V emergency-power-generator to its AC-IN. In this case you would need a change-over switch for switching between the grid or emergency-power-generator. For sure you don’t need a change-over switch if you connect your generator/grid to the Multi permanently.

Charger

For the ~5 kWp module power (12x 405Wp) we would need a Smart MPPT 450/100 with two MPPTs, with 6 panels connected to each of them.

Generator

You can connect a common ~230V emergency-power-generator (usually 2.5 kW…5 kW) to the AC-IN of the Multi.

Stuff needed for the installation.

Will be provided by us.

Installation

We would support you with a schematic for the System.

Furthermore, I need some details for an offer:

• Details regarding your roof. How is the roof covered? -> Because of the installation material.
• Roof area -> length x width

While I get the more the marrier approach to this topic, I'm not sure is he just trying to upsell( 5kw of panels and an expensive MPPT charger, 450/100), or if bumping it up that much is really the best thing to do.
What do you think?

They seem to be a decent place to buy from, the reply was quick and the guy I talked with left an impression of a decent person. According to Google reviews, the owner is a bit of a solar geek and loves finding the best systems on a case-to-case basis. So in general, so far, the place seems to be alright, just not sure if their advice is spot on..?

 

[DIYrich]

Use Pvwatts to estimate production during the worst time of the year. 5kw of panels seems reasonable to charge 15kwh of batteries during the worst time of year.

Your choice on mppt. Note: you can "overpanel" the mppt as long as it has enough capacity for worst time of year. Let's say the 5kw of panels produce 3kw in winter. Then you want at least a 3kw mppt.

 

[Pi Curio]

While I get the more the marrier approach to this topic, I'm not sure is he just trying to upsell( 5kw of panels and an expensive MPPT charger, 450/100), or if bumping it up that much is really the best thing to do.
What do you think?

While I have no insight into the information exchanged between you and the seller, based on the information you've shared alone and your requirements, he's doing his job.

He's upselling as far as the SCC goes, while at the same time, he's offering you a super 'Safe option' that will work for you in the future, no matter what, In terms of your solar requirements or whatnot.


My preference would be as previously said, a Twin combo composed of two separate SCC+panels.

You want 5kWp? No biggy.

There's a way cheaper but better option that can get you there, imo.

At not even half the cost of the 450/100, a Twin SCC setup. A Twin combo, 2x (150/45 with 6x400W panels in 3S2P Array configuration) and you are good for up to 5.2kWp as far SCCs go. If you ever need to expand later for more power, just add another 150/45/Array combo.

And guess what, no fuses or combiner box is needed, and depending on the panel specs, you can go with regular PV 6mm2-AWG10 cables and MC4s between SCC-Solar. However, you'll want to have at least the main fuse, SPD, and PV isolator switch between solar and SCCs.

Your SCCs will start to do their job with only battery Voltage +5V, plus your Array Vmp of 120V Ish is just about the sweet spot for a 48V system.

Just my 2 cents.

They seem to be a decent place to buy from, the reply was quick and the guy I talked with left an impression of a decent person. According to Google reviews, the owner is a bit of a solar geek and loves finding the best systems on a case-to-case basis. So in general, so far, the place seems to be alright, just not sure if their advice is spot on..?

I see nothing out of place in terms of what he offered.

It's just my opinion, that there's a cheaper and better design as far as the solar side of things goes for your stated requirements.

In his defense, as previously stated, he offered something that will work for you in the future, no matter what. Plus, there might be some features on the 450/100 I'm not aware of.

I assume you have no shading issues on the planned solar installation site.

 

[Trntemrnte]

While I have no insight into the information exchanged between you and the sellers, based on the information you've shared alone and your requirements, he's doing his job.

He's upselling as far as the SCC goes, while at the same time, he's offering you a super 'Safe option' that will work for you in the future, no matter what, In terms of your solar requirements or whatnot.

It's literally a copy-paste of my initial post, with a couple of tweaks, like two mppt's like you suggested. Ya, seems the SSC part is not really necessary, that's the upsell, rather than 5kw of panels. Initially, it is more expensive, but then I guess the generator won't have to run that often, saving on fuel in the long run. Kind of a tradeoff.

My preference would be as previously said, a Twin combo composed of two separate SCC+panels.

You want 5kWp? No biggy.

There's a way cheaper but better option that can get you there, imo.

At not even half the cost of the 450/100, a Twin SCC setup. A Twin combo of 2x (150/45 with 6x400W panels in 3S2P Array configuration) and you are good for up to 5.2kWp as far SCCs go. If you ever need to expand later for more power, just add another 150/45/Array combo.

And guess what, no fuses or combiner box is needed, and depending on the panel specs, you can go with regular PV 6mm2-AWG10 cables and MC4s.

That makes sense, I'll tell them to include those two in the offer.

I assume you have no shading issues on the planned solar installation site.

No, I'll build a shed, so it can be placed at the best possible place.

 

[Pi Curio]

It's literally a copy-paste of my initial post, with a couple of tweaks, like two mppt's like you suggested. Ya, seems the SSC part is not really necessary, that's the upsell, rather than 5kw of panels. Initially, it is more expensive, but then I guess the generator won't have to run that often, saving on fuel in the long run. Kind of a tradeoff.



That makes sense, I'll tell them to include those two in the offer.



No, I'll build a shed, so it can be placed at the best possible place.

I've added it to my previous post so I'll share it here too.

Despite the fact you don't need fuses or combiner boxes, and I'm not the expert, but you might still want to have at least the main fuse, SPD, and PV isolator switch between solar <-> SCCs.

Ask them about that too.