Farm workshop system

[kevinc_63366]

Ok folks, please rip this apart. Do note his is off-grid, must be off-grid, not-going-to-do-it grid tied. Please do NOT argue that point, but most everything else is fair game.

Parts (and why I like them):

Pallet of (20) Astronergy 305W panels (pallet discount, fewer panels to mount, competitive price when adjusted for fewer mounts)
Xantrex MPPT 80-660 Charge Controller (allows for 2 strings of 10 panels given my 20 panel supply)
MagnaSine MS-4448PAE/240 Inverter (like the inverter headroom for briefly running power tools in the shop - no worries, happens minutes a day)
Magnum Mini Panel breaker box
Magnum ME-ARC inverter remote (needed to control/program the inverter)
Magnum ME-BMK battery monitor (doublecheck the Xantrex numbers, but really for when the generator kicks in)
Magnum ME-CD Conduit Box (hey, its $74, not sure I'll need it but...)
Magnum ME-AGS-N auto gen start controller (for propane generator)
800 Ah battery bank - (16) Surrette 6V, 400 Ah S5320s flooded (really, REALLY open for comments here - would not mind more amperage, but don't want to go to 3 strings)
Mounting brackets, metal poles, concrete, etc. for a fixed tilt ground based mount, set at +15 of latitude to maximize winter power
Propane Generator set to kick in around 25% of discharge depth.

I've done the VOC math, the Xantrex should be fine: Each panel is rated at 45.29 VOC, temperature compensated for the coldest day in Missouri history makes that 55.06 VOC. (10) panels in a string will put the Xantrex well out of its MPPT range (195V - 510V), but keep it in its operating range of 550V on all but the record setting days. "I will die now" voltage on the Xantrex is 600 - so on record days it should be safe.

I'm a bit concerned about what happens when both the Xantrex is charging the batteries from the PV array and the MagnaSine is charging them from generator. Suspect there will be non-ideal conflicts, but hopefully it won't smoke anything.

Not happy with the batteries, they represent about a third of the system cost as is and I'd love more of them and potentially run the gen less, but they are SO expensive. Seeing flooded cells with 10 year warranties now, that should help if they don't cost 2X 5 year batteries...

Note that planning around 55 VOC means I could only use (2) panels in a string on most 150 VOC charge controllers (3 on the Classic 150 since they add the 48V system voltage in on top).

What am I missing? What is trash? Suggestion on who to buy from (if that doesn't violate forum rules)?

FYI: targeting about 8000 wH per day, winter usage, another 2500 wH/day in the summer. Some capacity exist in the array for recharging during normal load, but honestly, the array is only about 30% of the system cost, knocking off a few panels wouldn't affect much. Oh, I also figure panel requirements with 10 year old panels, e.g. 80%, to minimize surprises in my older age. I consider STC fiction and work with PTC numbers (and am not particularly happy with those). This workshop will be a good 500 feet from the house (and that is the closest grid AC), and will be using some wifi extenders which would really be convenient to leave on all the time - sometimes they are finicky establishing a connection, so... I'll probably have a small drain on the inverter 7x24 *sigh*. I know that is not ideal and will put it all on a power strip if it doesn't harass me with connection issues every morning, but my time is worth something too.

Thanks in advance!

Kevin

[Naptown]

Not to rain on your parade but Lowes sell 4/0 AL three wire direct burial cable for $1.89 a foot. Add a # 2 for ground and you could have about a 100 A service ( enough for all you want and then some but I have not calculated voltage drop to keep within 3% ) for about $1200
Plus whatever a trencher for a day or so would cost.
Now take all rhe cost of all that solar stuff you would have to buy.
Subtract say $2000 for running the service to the shop.
It will cost you about 5-8 times as much per KWH to run off an off grid system as buying from the Power company.
Get a standby generator for the critical loads like the freezers. You would need that anyway
Please do the math for yourself
Run the power line and install grid tie
Your wallet will thank me
Or you could just send the saved cash to me

[SunEagle]

But what good is a grid tie when the zombies come and eat the power generating station?

[kevinc_63366]

But what good is a grid tie when the zombies come and eat the power generating station?

There are a number of reasons I don't want to be grid tied, fortunately zombies are not one of them (should I add that to the list?). Honestly, don't want to argue the point - please just accept my word that this will be off-grid or it won't be solar. I do want to invest in components that are most likely going to have the longest lifetime - so would spend more for 10 year batteries than 5 year ones, although not 2X - battery technology keeps evolving too.

Off subject: but I was very disappointed when VRB went bust. I had high hopes for them in this business. Imagine being able to disconnect charge rate & current draw from capacity... and to directly charge your battery with whatever voltage happened to be available (in roughly 1 volt steps). You could also draw off whatever voltage you wanted in similar step increments. Bit of switching technology required, but it was doable. They almost made it in the cell-tower UPS marketplace... almost.

[Sunking]

Ok folks, please rip this apart.

You asked for it. It is a lot more expensive than you think it is. Hope you got thick skin and have a really dumb rich client.

Pallet of (20) Astronergy 305W panels.

Keep it simple 6100 watts

Xantrex MPPT 80-660 Charge Controller

Bad news it can only take 4800 watts input @ 48 volt battery. With 6100 watts input @ 48 you need a 130 amps. Try again. Think 18 panels for 5400 watts using a Midnight Solar Classic 200 @ 48 volt battery. I just saved you $1000. FWIW you do not need that panel wattage for 8 Kwh/say in your location.

MagnaSine MS-4448PAE/240 Inverter (like the inverter headroom for briefly running power tools in the shop - no worries, happens minutes a day)
Magnum Mini Panel breaker box
Magnum ME-ARC inverter remote (needed to control/program the inverter)
Magnum ME-BMK battery monitor (doublecheck the Xantrex numbers, but really for when the generator kicks in)
Magnum ME-CD Conduit Box (hey, its $74, not sure I'll need it but...)
Magnum ME-AGS-N auto gen start controller (for propane generator)

No comment, will cost you $5000 for right answer.

800 Ah battery bank - (16) Surrette 6V, 400 Ah S5320s flooded (really, REALLY open for comments here - would not mind more amperage, but don't want to go to 3 strings)

Wrong battery selection. You want a single string. Not 2 or 3 in parallel. If you are looking at 8 Kwh per day usage you need a 40 Kwh battery @ 48 volts. In other words a 830 AH battery. In the Rolls line up a 4 to 6 year battery is a 6CS25P a 6 volt 820 AH battery (8 units) or a Rolls 8CS25P a 8 volt 820 AH battery (6 units). Either way about $10,000 to $12000 delivered.

[kevinc_63366]

You asked for it. It is a lot more expensive than you think it is. Hope you got thick skin and have a really dumb rich client.

Keep it simple 6100 watts


Bad news it can only take 4800 watts input @ 48 volt battery. With 6100 watts input @ 48 you need a 130 amps. Try again. Think 18 panels for 5400 watts using a Midnight Solar Classic 200 @ 48 volt battery. I just saved you $1000. FWIW you do not need that panel wattage for 8 Kwh/say in your location.

.

Yep... 6100 watts STC. PTC is 275w/panel, so now we are at 5500 watts.
5500 watts brand new. 10-25 year number is 80%, so now we are at 4400 watts.

Charge controller can eat 4800 REAL watts input. So why is 6100 marketing watts an issue?

[Sunking]

Do note his is off-grid, must be off-grid, not-going-to-do-it grid tied. Please do NOT argue that point, but most everything else is fair game.

Quit the BS Kevin. We have read all your post. This is not for a ignorant friend of yours. This system is 4 U.

You already owe me $5000 for saving you $10000. All you need is 3.75 Kw in panels, a simple Midnight Classic 150 charge controller, Rolls 6CS25P Battery (8 units). Generac 6 Kw Ecogen w LPG tank, and a 100 amp 48 volt battery charger.

[Naptown]

OK
Now that the baseball bat has been applied to your head to perhaps get the idea that you are wasting money ( unless you send it to me that is)
Now go off on another tack
Think hybrid systems.
With these you get the best of both worlds. A limited battery backup for the zombie apocalypse to keep the harvested wild game frozen and perhaps provide a bit of gaming on the computer.
You also get
A vastly lower electric bill as you will be able to utilize 100% of the power from the solar by feeding back to grid
Lower initial install costs for smaller batteries and no worries if the system produced 3 KWH today and you used 5
So as a suggestion only
Look at critical loads and Size for them
An energy star freezer uses about 1Kwh a day size your battery bank around those items
Run grid power to the new shop
Put in a system large enough ( perhaps split between grid tie and hybrid) to make a substantial dent in the purchased electric.
One thing that does not go over we'll here if you haven't already noticed is people wasting their money on things that will not provide a useful and cost effective solution.

[cjb80]

Yep... 6100 watts STC. PTC is 275w/panel, so now we are at 5500 watts.
5500 watts brand new. 10-25 year number is 80%, so now we are at 4400 watts.

Charge controller can eat 4800 REAL watts input. So why is 6100 marketing watts an issue?

This question/comment has not been answered. I am curious to see what others thing about this. I have spoken to Schneider Electric and they has mentioned that if you feed in more wattage than the charger can handle, then the charge controller will simply not use it. Furthermore, they recommend putting 115% of maximum wattage (nameplate) because of the fact that the solar panels does not achieve their nameplate wattage under nearly all circumstances.

Oversizing the wattage for a charge controller is an interesting idea for areas where the insolation is very low in the winter months and the extra power is not needed in the summer months (e.g., Pacific Northwest).

Chris

[Sunking]

This question/comment has not been answered.

Well if you read through all the threads he opened on the subject He only needs a 3.75 Kw system, and a standard 200 volt 80 amp controller. Otherwise he just ends up spending $10,000 more than needed.

[kevinc_63366]

Well if you read through all the threads he opened on the subject He only needs a 3.75 Kw system, and a standard 200 volt 80 amp controller. Otherwise he just ends up spending $10,000 more than needed.

Per SunKing's opinion... anyhow...

To answer your question, presuming they don't delete this post of mine as well: If you look at the MidNite Charge Controller sizing calculator, they are perfectly good with you having up to 20% more PV array than the charger can handle. I suspect that is for the reasons you stated. Personally, I felt that charger input amperage should be about 2% higher than output to compensate for charger losses, and should be REAL amps coming in, not STC nameplate sales amps.

[Naptown]

Do you think the engineers at Schneider Et al haven't taken that into account?
Almost every panel I have ever looked at has a PTC rating between 89 and 91% of STC
They also have a positive power tolerance so that 250W panel may very well be a 255.
You are over thinking this whole thing. And applying different parameters of your own choosing which may or may not be accurate.
So put some diet on your collectors pit them through the burn in process. Buy about 100K worth of testing equipment and then engineer your own system.
The standards are there for a purpose. It is to allow for consistent design parameters that work in real life.
Trying to tweak things for perhaps a 1% increase in harvest doesn't make sense.

[Sunking]

Personally, I felt that charger input amperage should be about 2% higher than output to compensate for charger losses, and should be REAL amps coming in, not STC nameplate sales amps.

Wrong completely wrong. The amps input to a MPPT controller will be significantly lower than output amps.

For example lets say You have a input of 150 volts @ 4000 watts from the panels the input current = 27 amps. Output current assuming 48 volt battery is 80 amps.

With a MPPT controller the current rating is for the output and Output Current = = Panel Wattage / Battery Voltage. But there is limit. For example on the MS Classic 150 @ 48 volt battery the limit is 120 Vmp panel voltage, 4438 watts(37 amps input). At output 76 amps on 48 volt battery. Anything above 4438 is just clipped off and wasted by operating the panels above MPPT voltage.

[kevinc_63366]

You are correct, I got sloppy with my terms. I should have said 2% "power", since nothing can convert at 100% efficiency.

[cjb80]

Wrong completely wrong. The amps input to a MPPT controller will be significantly lower than output amps.

For example lets say You have a input of 150 volts @ 4000 watts from the panels the input current = 27 amps. Output current assuming 48 volt battery is 80 amps.

With a MPPT controller the current rating is for the output and Output Current = = Panel Wattage / Battery Voltage. But there is limit. For example on the MS Classic 150 @ 48 volt battery the limit is 120 Vmp panel voltage, 4438 watts(37 amps input). At output 76 amps on 48 volt battery. Anything above 4438 is just clipped off and wasted by operating the panels above MPPT voltage.

So, I think what you're saying is in agreement with what Schneider was saying. It sounds like your objection to putting more wattage on a charge controller is that the power is wasted assuming that the system is within the voltage limits (including extreme temperature ranges).