Tiny solar off grid cabin Northern Michigan

[tverdok]

Hello everyone, great forum and I have enjoyed reading it for system design info.
Let me start by saying that electric grid from the power company is simply not an option where I am located.
The system below will be full time use, connected to ultra efficient 200 sq ft cabin. Lights are LED, 24 Volt DC chest fridge, DC shower pressure pump, tiny AC washing machine with pulse motor, DC electric teapot, 2 laptops, wifi router and last mile internet equipment are pretty much all our electronics. In the fall we also run a Sedona dehydrator, and I plan to add movie projector in the future (most efficient I can find). Lets say total ~3000 watt hours per day of electric used.

Equipment:
12 x Canada Solar CS6P-235 235 Watt 24 Volt, Vmp 29.8. Imp 7.9A, Voc 36.9 Isc 8.46A
Outback MX60 CC
Outback FlexMax 80 CC
Magnum 4024 24 volt inverter (I know that 4000W is too big inverter for 24volt battery bank, don't plan to ever use it to it's full rating)
2 x Windmax 24v Y-400 Watt turbines, one on 20ft tower, one on 60ft tower
24 Volt forklift battery

I'm planning to set it up like this:
6 x 235 Panels on MX60 CC
6 x 235 Panels on FM80 CC
Both wind turbines connected directly to the battery with a MorningStar TS60 acting as a dump load controller + Dumpload heating element
I have no misconceptions about my wind generators, I know that the best I'll get out of them is couple amps, I plan to upgrade to a proper turbine in 3-5KW range once I can afford it.
I'm looking at couple lightly used Honda generators locally to connect one to my MS4024 to charge the batteries when it's cloudy for too long
My next steps are to get breakers, lightning arrestors, gen auto-start, combiners boxers, wiring and to start the assembly.

Couple questions to which I would appreciate an answer:
- Is there a better way to connect wind generators then directly to the battery + dump load? I know about Midnite Classic and Clipper, but it's not worth it for this toy turbine.
- For my 24 Volt DC loads, do I run those from the battery bank or is the inverter involved?
- Do I need lightning arrestor for each combiner box? What makes the combiner box compatible or incompatible with the Lightning arrestor?
- How do I size the generator for this system? I've seen a lot of generator info on this forum, but not much on sizing.
- Does sizing the battery differ in any way if I'm using a forklift battery since it has thicker plates and higher charger rate?

Looking forward to getting some input.

[Mike90250]

The generator size is supposed to be large enough to :
Run expected normal loads
Charge batteries at C/10 rate ( if its a 600ah battery, it needs to be able to drive the charger at 60A ) Some of the larger inverters have a mode where you can feed AC into them and they function as a battery charger, yours might have this feature,
Under both conditions above, still have about 30% reserve capacity at rated continuous load (not peak capacity)
****
Wind
very problematic, Wiring, Dump loads and Controller need to be really robust, they are the only failsafe against turbine overspeed and gernadeing, sending shards into your house
****
Combiners
Check the boxes made for combiners by Midnight Solar. Use DC breakers, not fuses.

[Sunking]

Couple questions to which I would appreciate an answer:
- Is there a better way to connect wind generators then directly to the battery + dump load? I know about Midnite Classic and Clipper, but it's not worth it for this toy turbine.
- For my 24 Volt DC loads, do I run those from the battery bank or is the inverter involved?
- Do I need lightning arrestor for each combiner box? What makes the combiner box compatible or incompatible with the Lightning arrestor?
- How do I size the generator for this system? I've seen a lot of generator info on this forum, but not much on sizing.
- Does sizing the battery differ in any way if I'm using a forklift battery since it has thicker plates and higher charger rate?

Looking forward to getting some input.

Tiny Off-Grid system my ass. 2820 watts is a monster sized system.

A1 NO. Forget the Wind Turds. A complete waste of money. They are not called Wind Turds for nothing.

A2. Last thing you want is 24 volts and is quite foolish. With 2820 watt sof panels would require two very expensive Charge Controllers. It also requires a lot larger more expensive wiring. At 2820 watts is a 48 volt Battery system with one single 60 Amp MPPT Charge Controller. Use the Morningstar TS-MPPT-60. I would even consider the Morningstar MPPT-600-60 a 600 volt controller. That will allow you to wire your panels 6S2P which means no requirement for expensive Fuses or Combiners, and nice and small inexpensive wiring between panel and controller. If you go with a 150 Voc controller like you have listed, you are looking at 3S4P panel configuration and a quite expensive Combiner, Fuses, and 1/0 feeder cable. That is a lot of money. At 600 volts no combiners or fuses, and using 8 or 10 AWg wire.

A3. Surge arrestor is optional. TVSS is a Passive device and does not interact with anything.

A4. Generator has to be sized to operate all loads plus charge the battery as fast as possible at C/6 to minimize fuel burn. With 2820 watts of panels suggest your battery capacity is 28 Kwh and peak load is 2 Kw which works out to about a 8 Kva genny. Again this is where 24 volts is not possible. With your panel wattage of 2820 watts minimum battery AH capacity is around 1000 AH which would need a 175 to 200 Amp 24 volt Battery Charger. Good luck finding one. They do exist in the Telecom market. At 48 volts you are looking at 75 to 100 amps, a whole lot less expensive. Dump the 24 volt battery idea.

A5. Battery capacity is determined by your daily Kwh load for 5 day reserve capacity giving you 3 days autonomy. It is also has to meet minimum and maximum charge current requirements of no greater than C/6 in your case with Forklift batteries and no less than C/12. With a 48 volt battery means they must be no smaller than 450 AH and no larger than 900 AH. If you use 24 volts, foolish, double those capacities from 900 to 1800 AH. Last word on batteries DO NOT USE PARALLEL CONFIGURATION. Since you are willing to spend the bucks on Fork Lift Batteries, there is a better option which is slightly less expensive and will last longer than FL batteries, Trojan makes an Industrial Line, no better battery can be found. Cell capacities are perfectly aligned so you WOULD NOT have to use PARALLEL configuration. Capacity starts at 454 AH up to 1850 AH. Take care of them and you are looking at a 10 to 15 year battery. Fork lift and you may get 5 to 7 years.. What is not to like? Less expensive and last longer.

Follow my advice and you save $10,000 to $15,000 and will work a lot better than your plan. I only charge 15% for the money I save you.

[extrafu]

A2. Last thing you want is 24 volts and is quite foolish. With 2820 watt sof panels would require two very expensive Charge Controllers. It also requires a lot larger more expensive wiring. At 2820 watts is a 48 volt Battery system with one single 60 Amp MPPT Charge Controller. Use the Morningstar TS-MPPT-60. I would even consider the Morningstar MPPT-600-60 a 600 volt controller. That will allow you to wire your panels 6S2P which means no requirement for expensive Fuses or Combiners, and nice and small inexpensive wiring between panel and controller. If you go with a 150 Voc controller like you have listed, you are looking at 3S4P panel configuration and a quite expensive Combiner, Fuses, and 1/0 feeder cable. That is a lot of money. At 600 volts no combiners or fuses, and using 8 or 10 AWg wire.

Hey Sunking - wouldn't even a 6S2P require a combiner box? I am asking because I consider 24 panels, and I had in mind 2 ground mounts of 12 panels - all in series with each a Conext MPPT 600-80. But having 12 panel in series can be slightly problematic with shading thus the 6S2P is interesting for me also, but not necessarily having a combiner box.

Thanks!

[tverdok]

Sunking - Thank you for the advise. I probably should have mentioned that I already have the Outback CCs + Mate and MS4024 inverter: both of which I got very very cheap. I also have the panels themselves. I've accepted the fact that I will likely have to sell the MS4024 and get a 48 volt inverter, so thus my main question: what about all my 24 volt equipment? I know about DC-DC step down converters to step down 48v to 24v but from what I've read they are cheaply made, not long lasting, prone to fire and generally inefficient do to converting DC-AC-DC. Is there a better way to get 24 volt usable DC inside the cabin?

A1. My plan was to wire the setup for the small turbine as if it's a 5KW unit, see how much wind I can get on the 60ft tower. This way I could swap out the unit for a larger turbine next year when I can afford it. I already have 2 wind turds, got them as part of barter. I don't want to spend on Wind CC + Clipper + 3KW turbine and find I don't get enough wind to make it worth it.

A2. I would go with Midnite or Morningstar MPPT CC, but I already have 2 Outback CCs which cost me less together then a single PWM CC I planned to buy to dump load from wind. Also my property is forest and I'm sure I will have shading problems, so if I understand correctly I should try to stick to 2 or 3 panels per string so in case one panel gets in a shade I don't loose that entire string.

A3. I live in an area especially prone to high winds, thunderstorms and lightning. Could I fit a surge arrestor into any combiner box? Is installing a surge arrestor and proper grounding the system all I can do to protect against lightning or is there something I'm missing?

A4. If magnum inverter can act as a charger for batteries from AC load wouldn't that be enough, or would I still need a separate charger for the battery bank?

A5. I looked at Trojans, but I can get a new forklift battery much much cheaper from my business client so even if the life time would only be 5 years it would still be worth it. The IND17-6V would cost $1,375.00 each + shipping and I would need at least 4 for 24 volt bank, or 8 for 48volt bank. Forklift batteries are considerably cheaper for the same capacity.

Lets say I buy a combiner box for 4 strings, could I use that box for two controller with each CC getting 2 strings?

Thank you again for the input

[jflorey2]

I have no misconceptions about my wind generators, I know that the best I'll get out of them is couple amps, I plan to upgrade to a proper turbine in 3-5KW range once I can afford it.

Remember that tower height is the #1 issue with low production. The rule of thumb is that the bottom edge of the rotor should be 30 feet above the highest obstacle within 500 feet - and that's the _minimum_. For good performance you're going to want to go much higher.

- For my 24 Volt DC loads, do I run those from the battery bank or is the inverter involved?

Inverter not involved. Make SURE they are fused to protect the wiring. Also an LVD is a good idea (like a C40.)

- How do I size the generator for this system? I've seen a lot of generator info on this forum, but not much on sizing.

Size for C/4 to C/8.

[tverdok]

@ jflorey2: I think I got that covered, the 60ft tower will be mounted on the hill overlooking the forest, and it's at least 40ft or more from the bottom of the rotor to tallest tree. The wind broke couple of the tallest trees tops last year so now it looks oddly even in height when you look at the forest.

- So I run 24volt from the battery to the breaker box and from there to the cabin with some type of LVD device in between? Or do I use Outbacks CC output port and program LVD via it?

The DC portion of the project is most confusing to me.

[Sunking]

[B]Hey Sunking - wouldn't even a 6S2P require a combiner box? I am asking because I consider 24 panels, and I had in mind 2 ground mounts of 12 panels - all in series with each a Conext MPPT 600-80. But having 12 panel in series can be slightly problematic with shading thus the 6S2P is interesting for me also, but not necessarily having a combiner box.

No not really, just a standard Junction Box to splice the two strings and feeder cable together.

[tverdok]

If I go with 48volt battery bank, can I run 24 volt equipment off it without stepdown DC-AC-DC converters?

My current 24volt inverter is capable of 105 amp charging according to the specs, does it mean it that the max battery capacity it can handle is 1050AH? Would it even be able to charge forklift battery? I have two answers that differ, could someone clarify?

If I read @Mike90250 post correctly I can use my current 105 amp inverter to charge a 1000AH 24v battery
If I read @Sunking post correctly then I can't use the 105 charger for 1000AH 24 volt battery

Sorry about redundant questions, feel like I'm missing some piece of information.

[Logan5]

Your refrigerator is going to need a carefully selected 48 to 24v stepdown, check with the manufacture of the refrigerator for their recommendation. the rest of them you select for the device or devices. I would have a 12 and a 19v stepdown sized for laptops and TV, you can easily run 12 or 24v lighting. Just make sure all stepdowns have a breaker/fuse as well as a courtesy switch. since you already have a mostly DC system I would only run the inverter for special loads.

[Mike90250]

Generator & Battery charging.
There is a LOT to be understood about charging batteries. in a post not too long ago

https://www.solarpaneltalk.com/forum/off-grid-solar/off-grid-solar-panel-systems/349207-generator-sizing-to-handle-equalization-for-fla-bank

I covered some about chargers, efficiency, power factor, loads and schemes to intelligently use a smallish generator to maintain a larger bank, You have to understand that batteries take a long time to charge, and you can shorten that by using higher charging voltage to pump amps into it faster, but there is still a minimum amount of time that is required to accomplish a full charge.
Too small of genset, you will burn it up, and take a long time to charge batteries
Too large and you waste fuel running below capacity.
you have some guides now from sunking and i on how to start calculating YOUR needed size, remember to calc this out for your 48V expansion too, and you may resize the genset to match both systems, although I do recommend you have a backup genset (I only have 3), or enough cash in the bank to purchase a new battery set when you kill it from deeply discharging it.

[bberry]

Don't buy anything until you know what you are doing (and you don't know what you are doing).

As other have said, forget wind. Since you have a large budget, look at higher end equipment. Pay for a professional design from someone experienced with higher end off grid systems.

[Sunking]

If I go with 48volt battery bank, can I run 24 volt equipment off it without stepdown DC-AC-DC converters?

Noi

My current 24volt inverter is capable of 105 amp charging according to the specs, does it mean it that the max battery capacity it can handle is 1050AH? Would it even be able to charge forklift battery? I have two answers that differ, could someone clarify?

If I read If I read @Sunking post correctly then I can't use the 105 charger for 1000AH 24 volt battery.

I never said or implied any such thing. I said Lead Acid Batteries have minimum and maximum charge and discharge currents. Depend son manufacture and model but rule of thumb is C/12 to C/8. A 1000 AH battery would be 80 to 125 amps. Fork Lift batteries are a Hybrid and can easily go up to C/4 or even C/2 currents. That would be 250 to 500 amps on 1000 AH.

You realy need to stop and rethink things. First step is thrown the wind turds away and switch to 48 volts.

[tverdok]

Thank you everyone for input:

Sunking I've followed your advice and switched my design to 48 volts. A follow up question on a concept I knew nothing about 2 days ago - connecting panels without combiner box.

According to your post here: https://www.solarpaneltalk.com/forum...a-combiner-box

Arrange your panels 2 x 3 and there is no requirement for fuses and combiners. Your way is just a waste of money, time, material, and labor.

Q: Considering I already have two outback controllers (MX60 + FM80) without an option to return them and 12 solar panels (CS6P-235) It seems to me it would make sense to wire 6 panels per CC with 2 strings of 3 each and skip on combiners. I can also combine the two CC into common wiring when coming into the battery. Do you see anything wrong with either of this?

Q. On the wind turds, since I already have them and my consciousness won't let me sell them to someone else I'd like to put them up on short towers (20ft) and wire them up to the battery with a duimp load charger. I now understand the difference between DC and AC turbines and why it would be a bad idea and waste of money to put them up on my 60ft tower, which I will save for 3-5KW AC turbine. The two wind turds I currently have are 24 volts, 400 watts, "low wind" 5 blade units, they come with their own 24 volt CCs with a build-in dump load, but the CC are not adjustable to 48 vots as far as I can see. Could the two 24 volt wind turbines in parallel to charge 48 volt battery bank? like in the attached picture (the info I got from this link http://www.hydrogenappliances.com/Parallelcharging.html )

Mike90250 Thank you for that link, it and you other answers helped my understanding of this subject. Here's an odd question on the generators setup, I know that the Outbacks CC dry contact works for the two wire generators and the Magnum MS4444 PAE AUX input + Gen Start module works with three wire. Would there be any benefit having two generators hooked up similtaniosly, so in case one fails the other one would take it's role, or maybe even having two generators work at the same time? Maybe having a smaller DC generator on the Outback, and larger AC generator on the Magnum

[tverdok]

So I wrote this very long post and the forum ate it. Here's the short version:

I will follow good advise on this forum and go with 48volt system, so four questions arise from this:

Q1. Considering I already have and won't be able to return my two Outback CCs, does it make more sense to hook up 6 panels per each controller, in configuration of 3 panels, in two strings, thus skipping the combiner box?
Q2. Would it also be make sense to combine the wiring from the controllers to the battery bank or are there benefits to keeping them separate?
Q3. Considering I have two wind turds and won't sell them to some unknown fool on principle. Is it possible to wire two 24 volt 400 watt DC turbines in parallel to get 48 volt to the battery bank? And Would that be enough voltage to charge 48volt bank?
Q4. I know that Outback CC support two wire start generators, while the Magnum 4440 PAE support three start generators. Is it theoretically possible to take two generators, and connect them both to the system: a DC generator to the Outback CC and AC to the Magnum Inverter? Does it make sense to do so?

I understand a great deal more then I did couple days ago. I thank you all.